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Using Light (Sunlight, Blue Light & Red Light) to Optimize Health | Huberman Lab Podcast #68



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Welcome to the Huberman Lab Podcast,
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where we discuss science and science-based tools
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for everyday life.
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I'm Andrew Huberman,
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and I'm a professor of neurobiology and ophthalmology
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at Stanford School of Medicine.
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Today, we are going to discuss light
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and the many powerful uses of light to optimize our health.
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We're going to discuss the use of light
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for optimizing skin health, appearance, and longevity,
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for wound healing, for optimizing hormone balance,
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and for regulating sleep, alertness, mood,
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and even for offsetting dementia.
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One of the reasons why light has such powerful effects
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on so many different aspects of our biology
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is that it can be translated into electrical signals
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in our brain and body,
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into hormone signals in our brain and body,
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and indeed into what we call
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cascades of biological pathways,
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meaning light can actually change the genes
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that the cells of your bodies express,
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and that is true throughout the lifespan.
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Today, I will discuss the mechanisms
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by which all of that occurs.
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I promise to make it clear for those of you
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that don't have a biology background,
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and if you do have a biology background,
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I'll try and provide sufficient depth
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so that it's still of interest to you,
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and I promise to give you tools,
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very specific protocols that are extracted
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from the peer review literature
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that will allow you to use different so-called wavelengths,
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which most of us think of as colors of light,
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in order to modulate your health
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in the ways that are most important to you.
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For those of you that are thinking
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that the use of light to modulate health
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falls under the category of woo science,
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pseudoscience, or biohacking,
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well, nothing could be further from the truth.
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In fact, in 1903, the Nobel Prize was given
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to Niels Vinson, he was Icelandic, he lived in Denmark,
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for the use of phototherapy for the treatment of lupus.
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So there's more than 100 years of quality science
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emphasizing the use of light,
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and as you'll soon see,
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the use of particular wavelengths or colors of light
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in order to modulate the activity of cells
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in the brain and body.
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So while it is the case that many places
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and companies are selling therapies and products
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related to the use of flashing lights and colored lights,
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promising specific outcomes
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from everything from stem cell renewal
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to improvement of brain function,
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and some of those don't have any basis in science,
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there are phototherapies
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that do have a strong foundation in quality science,
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and those are the studies and the protocols
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that we are going to discuss today.
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But I thought that people might appreciate knowing
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that over 100 years ago,
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people were thinking about the use of light
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for the treatment of various diseases
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and for improving health,
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and indeed, many of those therapies are used today
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in high quality hospitals and research institutions,
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and of course, clinics and homes around the world.
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One of the more exciting examples of phototherapy
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in the last few years is the beautiful work
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of Dr. Glenn Jeffrey at University College London.
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The Jeffrey Lab is known for doing pioneering
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and very rigorous research
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in the realm of visual neuroscience.
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And in the last decade or so,
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they turned their attention to exploring the role
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of red light therapy for offsetting age-related vision loss.
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What they discovered is that just brief exposures
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to red light early in the day
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can offset much of the vision loss
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that occurs in people 40 years or older.
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And what's remarkable about these studies
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is that the entire duration of the therapy
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is just one to three minutes done
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just a few times per week.
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What's even more exciting
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is that they understand the mechanism by which this occurred.
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The cells in the back of the eye
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that convert light information into electrical signals
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that the rest of the brain can understand
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and create visual images from,
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well, those cells are extremely metabolically active.
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They need a lot of ATP or energy.
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And as we age, those cells get less efficient
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at creating that ATP and energy.
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Exposure to red light early in the day,
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and it does have to be early in the day,
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allowed those cells to replenish the mechanisms
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by which they create ATP.
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I'll talk about these experiments
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in more detail later in the episode and the protocols
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so that you can apply those protocols should you choose.
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But I use this as an example of our growing understanding
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of not just that phototherapies work, but how they work.
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And it is through the linking of protocols and mechanism
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that we, meaning all of us,
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can start to apply phototherapies
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in a rational, safe, and powerful way.
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I'm pleased to announce
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that I'm hosting two live events this May.
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The first live event will be hosted
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in Seattle, Washington on May 17th.
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The second live event will be hosted
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in Portland, Oregon on May 18th.
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Both are part of a lecture series
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entitled The Brain-Body Contract,
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during which I will discuss science
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and science-based tools for mental health,
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physical health, and performance.
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I should point out that while some of the material
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I'll cover will overlap with information covered here
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on the Huberman Lab podcast
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and on various social media posts,
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most of the information I will cover is going to be distinct
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from information covered on the podcast or elsewhere.
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So once again, it's Seattle on May 17th,
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Portland on May 18th.
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You can access tickets by going to HubermanLab.com slash tour
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and I hope to see you there.
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Before we begin, I'd like to emphasize
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that this podcast is separate
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from my teaching and research roles at Stanford.
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It is, however, part of my desire and effort
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to bring zero cost to consumer information about science
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and science-related tools to the general public.
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In keeping with that theme,
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I'd like to thank the sponsors of today's podcast.
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Our first sponsor is Athletic Greens, also called AG1.
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I started taking AG1 way back in 2012,
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so I'm delighted that they're sponsoring the podcast.
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The reason I started taking AG1
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and the reason I still take AG1 once or twice a day
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is that it covers my foundational vitamin,
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mineral, and probiotic needs.
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It also has adaptogens and things like zinc
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for immune system function,
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but the probiotics are one of the key features in there.
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I've done several podcasts on the gut microbiome,
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which are these trillions of microbiota
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that live in our digestive tract
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and that are crucial for our immune system,
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brain function, and so on.
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One way to enhance our gut microbiome
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to ensure that it's healthy
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is to make sure that we get the correct probiotics.
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And Athletic Greens has the correct prebiotics
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If you'd like to try Athletic Greens,
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They'll give you five free travel packs
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I mix mine with some water
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Many of us who get sunlight get enough vitamin D3.
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Many of us, even if we do get sunlight,
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do not get enough vitamin D3.
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So the year supply of vitamin D3 also has K2,
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which is important for cardiovascular function,
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Again, go to athleticgreens.com slash Huberman
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to get the five free travel packs
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and the year supply of vitamin D3K2.
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Today's episode is also brought to us by Thesis.
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Thesis makes custom nootropics.
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Nootropic is a smart drug.
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And personally, I'm not a big fan
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of the concept of a smart drug,
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at least not the way that most people talk about smart drugs
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or nootropics, for the following reason.
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Being smart involves various things.
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There is creativity, there's focus,
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there's task switching, and so on.
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And each one of those involves different operations
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in the brain, different neural circuits,
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different neurochemicals have to be deployed
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in order for us to, for instance, be very focused
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I've been using thesis nootropics for over six months now.
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And I have to say, it's been a total game changer
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and very unique from the experience
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So with thesis, it's really directed
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toward particular brain body states.
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I should also mention
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that they tailor those custom blends to you.
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So by taking a quiz on their site,
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So if you want to try
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you can go online to takethesis.com slash Huberman.
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You'll take a three minute quiz
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Today's episode is also brought to us by Element.
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Element is a properly balanced electrolyte drink
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that has no sugar.
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When we get our electrolytes in the proper ratios,
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the cells of our brain and body can function optimally.
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Many people are surprised to find
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that when they increase their sodium intake,
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provided that it is in proper balance
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with potassium and magnesium,
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they can think more clearly.
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They recover from exercise better and they have more energy.
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There is no surprise as to how that all works.
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However, every cell of your body
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requires the electrolytes to function.
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And in particular, the neurons of your brain and body
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require sodium in order to function.
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So while people with pre-hypertension and hypertension
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definitely need to be careful about increasing
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their sodium intake,
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many people do well to increase their sodium intake,
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again, provided it's in the proper balance
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with potassium and magnesium.
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Element provides that proper balance.
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If you'd like to try Element, you can go to Drink Element,
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Again, that's Drink Element lmnt.com slash Huberman
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to claim a free sample pack.
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Okay, let's talk about light.
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First, I want to talk about the physics of light.
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And I promise to make that very clear,
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even if you don't have a background in physics.
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And then I want to talk about the biology of light,
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meaning how light is converted into signals
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that your brain and body can use
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to impact things like organ health or disease,
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or how you can use light in order to repair
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particular organs like your skin,
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your eyes, your brain, et cetera.
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The physics of light can be made very simple
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by just illustrating a few key bullet points.
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The first bullet point is that
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light is electromagnetic energy.
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If the word electromagnetic feels daunting to you,
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well then just discard that
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and just think of light as energy.
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And think of energy as something that can impact
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other things in its environment.
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Now, the way to imagine light
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or to conceptualize light as energy
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is that all around you,
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light is traveling in these little wavelengths.
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And the reason for those of you that are watching,
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I'm making a little wavy motion with my hand
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is that's actually the way that light energy moves
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in little waves,
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just like sound waves are coming at you
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and impinging on your ears.
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If you can hear me talking right now, that is happening.
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Those are sound waves,
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meaning the movement of air particles out there
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impacting your eardrum.
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Well, light energy is just little bits
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of electromagnetic energy traveling
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through your environment all the time in these little waves
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and impinging on your brain and body and eyes, et cetera.
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And as I mentioned before,
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energy can change the way that other things behave.
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It can cause reactions in cells of your body.
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It can cause reactions in fruit, for instance, right?
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You see a piece of fruit and it's not ripe,
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but it gets a lot of sunlight and it ripens.
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That's because the electromagnetic energy of sunlight
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had an impact on that plant or that tree,
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or even on the fruit directly.
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As a parallel example of energy
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and its ability to impact other things,
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we are all familiar with food
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and the fact that food has calories.
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Calorie is a measure of energy.
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It has everything to do with how much heat is generated
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when you burn a particular article of food,
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believe it or not.
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And it turns out that how hot a given article of food burns
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gives you a sense of how much energy
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it can provide your body in terms of your body's ability
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to store or use that energy.
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So again, think of light as electromagnetic energy,
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but really put that word energy into capital letters,
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embed that in your mind going forward,
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and you'll understand most of the first bullet point
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of what light is in terms of the physics of light.
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Now, the second thing that you need to understand
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about the physics of light
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is that light has many different wavelengths.
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And the simplest way to conceptualize this
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is to imagine that cover of that Pink Floyd album
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where there's a prism,
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you have a white beam of light going into that prism,
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and then the prism splits that beam of light
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into what looks like a rainbow.
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So you've got your red, your orange, your greens,
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your blues, your purples, et cetera.
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Anytime we have light in our environment
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that is so-called white light,
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it includes all those wavelengths,
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but sunlight and other forms of light
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also have other wavelengths of light that we can't see.
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So when we think about the rainbow,
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that's just the visible spectrum of light.
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There are also wavelengths of light
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that are not visible to us,
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but that are visible to some other animals
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and that can still impact your brain and body
link |
00:13:19.140
because there is still energy at those wavelengths.
link |
00:13:22.900
I'll give a few examples of this.
link |
00:13:24.940
Humans are not a species that can see
link |
00:13:27.420
into the infrared realm of the spectrum.
link |
00:13:31.380
A pit viper, meaning a snake that has infrared sensors,
link |
00:13:35.960
however, can sense in the infrared.
link |
00:13:38.900
So if you were to walk through a jungle
link |
00:13:40.980
and there's a pit viper there,
link |
00:13:42.640
it sees you as a cloud of heat emission
link |
00:13:46.340
because your body is emitting infrared energy all the time.
link |
00:13:51.180
You're casting off infrared energy.
link |
00:13:53.740
The snake can see it, you can't.
link |
00:13:55.780
If you were to put on a particular set of goggles
link |
00:13:58.700
that were infrared goggles,
link |
00:14:01.220
well, then you would be able to see the heat emissions
link |
00:14:03.580
of any organism, human or otherwise,
link |
00:14:06.020
that could emit infrared energy.
link |
00:14:09.740
Let's take the opposite end of the spectrum.
link |
00:14:11.940
We are familiar with seeing things that are blue or green
link |
00:14:14.660
or very pale blue, but as we say below that,
link |
00:14:18.740
meaning even shorter wavelength light is out there.
link |
00:14:21.440
Ultraviolet light is a really good example
link |
00:14:23.960
of light energy that's coming from the sun
link |
00:14:26.240
and is in our environment
link |
00:14:27.280
and is being reflected off surfaces all the time.
link |
00:14:29.700
We don't see it and yet if it's very bright outside,
link |
00:14:33.380
that ultraviolet light can burn our skin.
link |
00:14:36.280
As you'll learn in today's episode,
link |
00:14:38.100
ultraviolet light can also positively impact us.
link |
00:14:42.760
In fact, I will describe a particular set of new results
link |
00:14:45.860
that show that ultraviolet light
link |
00:14:48.220
viewed for just a few minutes each day
link |
00:14:51.160
or landing on the skin for just a few minutes each day
link |
00:14:53.580
can actually offset a lot of pain.
link |
00:14:56.460
It actually has the ability to reduce the amount of pain
link |
00:14:59.980
sensed by your body and we now understand
link |
00:15:01.940
the specific circuits in the brain and body
link |
00:15:03.740
that allow that to happen.
link |
00:15:05.180
I'll talk about that
link |
00:15:06.020
and the related protocols a little bit later.
link |
00:15:08.340
So the important thing to understand
link |
00:15:09.540
about the physics of light is that there's energy
link |
00:15:11.860
at all these different wavelengths.
link |
00:15:13.300
We only see some of those wavelengths,
link |
00:15:15.620
which basically is to say that light impacts us
link |
00:15:19.020
at many different levels and the so-called levels
link |
00:15:23.100
that I'm referring to are the different wavelengths of light
link |
00:15:26.080
and you're welcome to think of the different wavelengths
link |
00:15:28.140
of light as different colors,
link |
00:15:29.740
but do understand that there are truly colors of light
link |
00:15:33.240
that you and I can't see and yet that have powerful impact
link |
00:15:37.380
on your brain and body.
link |
00:15:38.440
Now, the third bullet point to understand
link |
00:15:40.460
about the physics of light
link |
00:15:41.880
is that different wavelengths of light
link |
00:15:44.220
because of the way that their wave travels
link |
00:15:47.900
can penetrate tissues to different depths.
link |
00:15:51.780
This is very, very important.
link |
00:15:53.980
Today, we're going to talk a lot about red light therapies
link |
00:15:56.380
and near infrared light therapies.
link |
00:15:59.940
Those are so-called longer wavelengths.
link |
00:16:02.300
Longer wavelength, just think of a bigger, longer wave,
link |
00:16:06.340
a bigger curve, as opposed to short wavelength light,
link |
00:16:08.660
which is going to be shorter.
link |
00:16:10.780
A short wavelength light would be something like blue
link |
00:16:12.780
or green light or ultraviolet light.
link |
00:16:15.620
Blue, green and ultraviolet light,
link |
00:16:17.860
because it's short wavelength light,
link |
00:16:19.640
doesn't tend to penetrate tissues very easily.
link |
00:16:23.620
It has to do with the way that the physics of light
link |
00:16:25.520
interacts with the physical properties of your skin
link |
00:16:27.780
and other tissues of your body.
link |
00:16:29.220
But basically, if you were to shine UV light
link |
00:16:31.260
onto your arm, for instance,
link |
00:16:33.000
it could impact the skin on the surface of the arm
link |
00:16:35.180
and maybe some of the cells
link |
00:16:36.860
just beneath the top layer of skin,
link |
00:16:38.980
but it wouldn't penetrate much deeper.
link |
00:16:41.860
Long wavelength light like red light and near infrared light
link |
00:16:45.940
has this amazing ability to penetrate through tissues,
link |
00:16:49.960
including your skin.
link |
00:16:51.300
And so if we were to shine red light
link |
00:16:53.440
or near infrared light onto your arm,
link |
00:16:57.100
it would pass through that top layer of skin.
link |
00:16:59.900
It might impact it a little bit,
link |
00:17:01.460
but it could penetrate deeper into your skin,
link |
00:17:04.780
not just to the skin layers,
link |
00:17:05.980
but maybe even down to the bone,
link |
00:17:07.660
maybe even down to the bone marrow.
link |
00:17:09.540
And for many people, this will be hard to conceptualize.
link |
00:17:11.820
You think, well, wait, I've got a skin there.
link |
00:17:13.360
Doesn't the light just bounce off?
link |
00:17:14.780
And the answer is no,
link |
00:17:15.940
because of the way that long wavelength light
link |
00:17:19.540
interacts with the absorbance properties of your skin.
link |
00:17:22.500
Absorbance properties is just the way
link |
00:17:24.040
that the skin takes light energy
link |
00:17:26.180
and converts it into a different form of energy.
link |
00:17:29.300
And your skin is not able to take long wavelength light
link |
00:17:32.780
like red light and near infrared light and absorb it,
link |
00:17:36.340
but the tissues deeper in your body can.
link |
00:17:39.620
So if you shine red light or near infrared light
link |
00:17:42.180
onto the surface of your skin,
link |
00:17:43.500
you'll see a red glow there as a reflectance
link |
00:17:46.060
on the surface of your skin.
link |
00:17:47.420
But a lot of the photon energy,
link |
00:17:49.700
the light energy in those longer wavelengths
link |
00:17:51.980
is indeed passing through those top layers of skin
link |
00:17:54.860
into the deeper layers of skin
link |
00:17:56.380
and can even make it into the deep layers of your arm.
link |
00:17:59.620
And as we start to transition from the physics of light
link |
00:18:01.900
to the biological impacts of light,
link |
00:18:04.820
just understanding that the different wavelengths of light
link |
00:18:07.380
impact our tissues at different levels,
link |
00:18:09.260
literally at different depths,
link |
00:18:10.940
will help you better understand
link |
00:18:12.860
how light of different colors, of different intensities,
link |
00:18:16.200
and how long you are exposed to those colors
link |
00:18:19.620
and intensities of light can change the way
link |
00:18:22.340
that the cells and the organs of your body work.
link |
00:18:25.700
And if it didn't sound weird enough
link |
00:18:27.060
that you can pass light through particular tissues
link |
00:18:29.840
and have them land and be absorbed
link |
00:18:31.780
at tissues deeper in your body,
link |
00:18:34.500
well, it turns out that different wavelengths of light
link |
00:18:37.560
are also best absorbed by particular
link |
00:18:40.940
so-called organelles within your cells.
link |
00:18:43.560
What are organelles?
link |
00:18:44.400
Organelles are the different compartments
link |
00:18:46.280
and different functions within a given cell.
link |
00:18:48.940
So for instance, your mitochondria,
link |
00:18:50.460
which are responsible for generating ATP
link |
00:18:52.540
and energy in your cells,
link |
00:18:53.900
those exist at a particular depth,
link |
00:18:56.980
at a particular location within a cell.
link |
00:18:58.580
They're not all at the cell surface.
link |
00:18:59.920
They sit somewhat deeper in the cell.
link |
00:19:01.780
The nucleus of your individual cells contains DNA,
link |
00:19:05.140
and that sits at a particular depth
link |
00:19:06.620
or location within your cell.
link |
00:19:09.220
Different wavelengths of light
link |
00:19:10.700
not only can penetrate down into different tissues
link |
00:19:13.480
and into different cells of your body,
link |
00:19:15.600
but they can also penetrate and access particular organelles,
link |
00:19:19.540
meaning mitochondria or the nucleus
link |
00:19:22.180
or the different aspects of your cells
link |
00:19:24.020
that are responsible for different functions.
link |
00:19:26.400
This is exquisitely important,
link |
00:19:29.240
and it's exquisitely powerful
link |
00:19:31.340
because as you'll learn today,
link |
00:19:32.780
particular wavelengths of light
link |
00:19:34.180
can be used to stimulate the function
link |
00:19:35.980
of particular organelles within particular cells
link |
00:19:39.000
within particular organs of your body.
link |
00:19:41.540
I can think of no other form of energy,
link |
00:19:43.780
not sound, not chemical energy, so not drugs,
link |
00:19:47.820
not food, not touch,
link |
00:19:51.720
no form of energy that can target the particular locations
link |
00:19:55.700
in our cells, in our organelles, in our organs,
link |
00:19:59.660
and in our body to the extent that light can.
link |
00:20:02.420
In other words,
link |
00:20:03.420
if you had to imagine a real world surgical tool
link |
00:20:07.260
by which to modulate our biology,
link |
00:20:09.940
light would be the sharpest
link |
00:20:11.620
and the most precise of those tools.
link |
00:20:13.820
Now let's talk about how light is converted
link |
00:20:15.280
into biological signals.
link |
00:20:17.060
There are several ways in which that is accomplished,
link |
00:20:19.620
but the fundamental thing to understand
link |
00:20:22.180
is this notion of absorption of light energy.
link |
00:20:26.920
Certain pigments or colors
link |
00:20:30.440
in the thing that is receiving the light energy,
link |
00:20:33.780
meaning the thing that the light energy lands on
link |
00:20:37.360
are going to absorb particular wavelengths of light.
link |
00:20:40.460
Now, I promise you that you already intuitively know
link |
00:20:43.340
how this works.
link |
00:20:44.700
For instance, if you were to sit outside
link |
00:20:47.260
on a very bright sunny day
link |
00:20:49.060
and you had a table in front of you that was metal,
link |
00:20:52.520
you might find it hard to look down at that metal table
link |
00:20:54.980
because it's reflecting a lot of light
link |
00:20:56.900
of particular wavelengths.
link |
00:20:59.220
If that table were pitch black, however,
link |
00:21:01.980
it wouldn't reflect quite as much
link |
00:21:04.540
and you would be able to comfortably look at it.
link |
00:21:07.980
If that table were red, it might be somewhere in between.
link |
00:21:10.860
If that table were green,
link |
00:21:12.820
it would be also somewhere in between,
link |
00:21:14.700
but let's say it were very light blue,
link |
00:21:16.540
well, then it might reflect almost as much
link |
00:21:18.980
as a table that were just metal or a white table surface.
link |
00:21:23.380
So the absorbance properties of a given surface
link |
00:21:26.420
will determine whether or not light energy goes
link |
00:21:28.620
and stays at that location
link |
00:21:31.100
and has an impact on that location
link |
00:21:33.260
or whether or not it bounces off.
link |
00:21:36.340
Every biological function of light
link |
00:21:38.720
has to do with the absorbance or the reflectance of light
link |
00:21:43.040
or light passing through that particular thing,
link |
00:21:46.780
meaning that particular cell or compartment within a cell.
link |
00:21:51.880
I'd like to make it clear how this works
link |
00:21:53.520
by using the three primary examples
link |
00:21:55.820
of how you take light in your environment
link |
00:21:58.920
and convert it into biological events.
link |
00:22:03.040
We have photoreceptors in the back of our eyes.
link |
00:22:05.940
These photoreceptors come in two major types,
link |
00:22:08.660
the so-called rods and the cones.
link |
00:22:10.340
The rods are very elongated, they look like rods,
link |
00:22:13.060
and the cones look like little triangles.
link |
00:22:15.980
Rods and cones have within them photo pigment.
link |
00:22:20.800
They have dark stuff that's stacked up in little layers.
link |
00:22:24.300
Rods absorb light of essentially any wavelength.
link |
00:22:27.380
There's some variation to that,
link |
00:22:28.740
but let's just say rods don't care
link |
00:22:32.020
about the different colors of light.
link |
00:22:34.900
They will absorb light energy, photon energy.
link |
00:22:37.700
If it's red, if it's green, if it's blue, if it's yellow,
link |
00:22:41.320
doesn't matter as long as that light is bright enough.
link |
00:22:44.160
And it turns out that rods are very, very sensitive.
link |
00:22:46.500
They can detect very, very small numbers of photons.
link |
00:22:50.820
And rods are essentially what you use
link |
00:22:53.180
to see in very low light conditions.
link |
00:22:55.420
We'll return more to vision later.
link |
00:22:57.460
The cones come in three major varieties.
link |
00:23:00.940
At least for most people who aren't colorblind,
link |
00:23:02.980
you have so-called red cones, green cones, and blue cones,
link |
00:23:05.340
but they're not really red, green, and blue
link |
00:23:06.840
in the back of your eye.
link |
00:23:07.940
They are cones that either absorb long wavelength light,
link |
00:23:11.720
red, that absorb medium wavelength light,
link |
00:23:15.300
green, or short wavelength light, blue.
link |
00:23:19.680
The reason that they can absorb different wavelengths
link |
00:23:22.260
of light is they have different photo pigments.
link |
00:23:24.740
So much as the example I gave before,
link |
00:23:26.900
where you have different tables outside
link |
00:23:29.580
in the sunny environment,
link |
00:23:30.740
and some are reflecting light more than others,
link |
00:23:32.660
others are absorbing light more than others.
link |
00:23:35.460
Well, so too the photoreceptors,
link |
00:23:38.100
meaning the cones are absorbing light of different
link |
00:23:41.700
wavelengths to different extents.
link |
00:23:43.700
And in a absolutely incredible way,
link |
00:23:46.560
your brain is actually able to take that information
link |
00:23:48.980
and create this perception that we have of color.
link |
00:23:51.380
But that's another story altogether that we'll just touch
link |
00:23:53.540
on a little bit more later,
link |
00:23:55.500
but that if you want to learn all about,
link |
00:23:57.040
you can go to our episode on vision.
link |
00:24:01.140
So that's photoreceptors in the back of your eye,
link |
00:24:03.760
absorbing light of different wavelengths, rods and cones.
link |
00:24:07.100
The other place of course,
link |
00:24:08.180
where light can impact our body is on our surface,
link |
00:24:11.180
on our skin and skin has pigment too.
link |
00:24:14.640
We call that pigment melanin.
link |
00:24:16.960
We have within our skin multiple cell types,
link |
00:24:19.840
but in the top layer of skin,
link |
00:24:21.180
which is called the epidermis,
link |
00:24:23.060
we have keratinocytes and we have melanocytes.
link |
00:24:27.380
And the melanocytes are the cells that create pigmentation
link |
00:24:30.900
of the skin.
link |
00:24:31.740
And of course there is wide variation in the degree to which
link |
00:24:35.180
there's pigmentation of the skin,
link |
00:24:37.160
which has to do with genetics,
link |
00:24:38.580
also has to do with where you were born and raised,
link |
00:24:41.100
how much light exposure you have throughout the year, right?
link |
00:24:43.720
So people toward the equator tend to have more melanocyte
link |
00:24:46.200
activity than people who are located at the North pole.
link |
00:24:49.380
And of course people live at different locations
link |
00:24:51.260
throughout the earth,
link |
00:24:52.100
regardless of their genetic background
link |
00:24:53.920
or where they were born.
link |
00:24:54.860
And so, as you all know, with light exposure,
link |
00:24:58.380
those melanocytes will turn on genetic programs
link |
00:25:02.560
and other biological programs that lead to enhanced
link |
00:25:05.780
pigmentation on the skin, which we call tanning.
link |
00:25:08.700
The way they do that is by absorbing UV light specifically.
link |
00:25:12.700
So with melanocytes,
link |
00:25:14.180
we have a very specific example of how a pigment absorbs
link |
00:25:19.140
light of a particular length, in this case,
link |
00:25:20.980
ultraviolet short wavelength light,
link |
00:25:23.200
which in turn creates a set of biological signals within
link |
00:25:27.100
those cells that in turn creates changes in our skin
link |
00:25:30.060
pigmentation.
link |
00:25:31.000
So we have photoreceptors,
link |
00:25:32.140
we have melanocytes and the third example I'd like to
link |
00:25:34.420
provide is that of every cell of your body.
link |
00:25:37.620
And what I mean by that is that every cell of your body,
link |
00:25:40.340
meaning a cell that is part of your bone tissue or your bone
link |
00:25:45.140
marrow or heart tissue or liver or spleen,
link |
00:25:48.760
if light can access those cells,
link |
00:25:51.520
it will change the way that those cells function for better
link |
00:25:54.300
or for worse.
link |
00:25:56.500
For many organs within our body that reside deep to our
link |
00:26:01.180
skin, light never arrives at those cells.
link |
00:26:05.300
A really good example of this that we'll touch on later is
link |
00:26:07.980
the spleen.
link |
00:26:09.400
Unless you have massive damage to your body surface,
link |
00:26:12.580
unless you literally have a hole in your body,
link |
00:26:14.740
light will never land directly on your spleen,
link |
00:26:18.060
but the spleen still responds to light information through
link |
00:26:22.460
indirect pathways.
link |
00:26:24.100
And those indirect pathways arise through light arriving on
link |
00:26:27.500
the skin and light arriving on the eyes.
link |
00:26:30.600
So a key principle that I'm going to return to again and
link |
00:26:33.420
again today is that the ways in which light can impact the
link |
00:26:37.940
biology of your organelles, your cells,
link |
00:26:40.600
your organs and the tissues,
link |
00:26:41.960
and indeed your whole body can either be direct.
link |
00:26:45.380
So for instance,
link |
00:26:46.220
light onto your skin impacting skin or light onto your
link |
00:26:48.900
photoreceptors impacting the photoreceptors of your eye,
link |
00:26:52.060
or it can be indirect.
link |
00:26:53.880
It can be light arriving on your photoreceptors,
link |
00:26:56.900
the photoreceptors then informing another cell type,
link |
00:26:59.880
which informs another cell type,
link |
00:27:01.740
which then relays a signal and kind of a bucket brigade
link |
00:27:04.900
manner off to the spleen and says to the spleen,
link |
00:27:07.620
Hey, there's a lot of UV light out here.
link |
00:27:10.380
We're actually under stress.
link |
00:27:12.060
In fact,
link |
00:27:12.900
there's so much UV light that you need to activate an immune
link |
00:27:15.860
program to protect the skin.
link |
00:27:18.100
And in response to that,
link |
00:27:19.180
the spleen can deploy certain signals and certain cell types
link |
00:27:21.920
to go out and start repairing skin that's being damaged by
link |
00:27:24.500
UV light.
link |
00:27:25.420
So we have direct signals and we have indirect signals,
link |
00:27:28.380
but in every case,
link |
00:27:30.940
it starts with light,
link |
00:27:32.140
a particular wavelengths being absorbed by particular
link |
00:27:36.220
pigments or properties of the surfaces that those light
link |
00:27:40.620
waves land on.
link |
00:27:42.300
And as you recall from our discussion about the physics of
link |
00:27:44.620
light, remember,
link |
00:27:45.580
it's not just about light impinging on the surface of your
link |
00:27:48.260
body.
link |
00:27:49.080
Light can actually penetrate deep to the skin and access at
link |
00:27:53.080
least certain tissues and cells of your body.
link |
00:27:55.800
Even though you can't see those wavelengths of light,
link |
00:27:58.380
they are getting into you all the time.
link |
00:28:00.980
So perhaps the best way to wrap this discussion about the
link |
00:28:04.420
physics and the biology of light with a bit of a bow is to
link |
00:28:08.780
think about light as a transducer,
link |
00:28:11.220
meaning a communicator of what's going on in the environment
link |
00:28:14.660
around you.
link |
00:28:15.720
And that some of those signals are arriving at the surface
link |
00:28:19.120
and impacting the surface of your body.
link |
00:28:21.220
But many of those signals are being taken by cells at the
link |
00:28:24.200
surface of your body,
link |
00:28:25.800
meaning your melanocytes in your skin and the
link |
00:28:27.860
photoreceptors of your eyes,
link |
00:28:29.460
and then being passed off as a set of instructions to the
link |
00:28:33.600
other organs and tissues of your body.
link |
00:28:35.740
Light can impact our biology in very fast,
link |
00:28:38.940
moderately fast and slow ways.
link |
00:28:41.500
But even the slow ways in which light can impact our biology
link |
00:28:45.180
can be very powerful and very long lasting.
link |
00:28:48.340
Just as a quick example of the rapid effects of light on our
link |
00:28:52.400
biology, if you were to go from a room that is dimly lit,
link |
00:28:57.340
or dark into a very brightly lit room,
link |
00:29:01.060
you would immediately feel very alert.
link |
00:29:04.540
You might say, no, that's not true.
link |
00:29:05.940
Sometimes I wake up and it's dark and I kind of stumble out
link |
00:29:09.040
and it's lighter out in the next room.
link |
00:29:10.980
And it takes me a while to wake up.
link |
00:29:13.000
But if we were to move you from a room that was very dark to
link |
00:29:15.980
very bright,
link |
00:29:17.060
a signal conveyed from your eyes to an area of your brain
link |
00:29:20.820
stem called the locus coeruleus would cause the release of
link |
00:29:24.320
adrenaline similar to the release of adrenaline.
link |
00:29:27.480
If you were to be dropped into very,
link |
00:29:29.140
very cold water, all of a sudden,
link |
00:29:30.820
you just an immediate wake up signal to your brain and body.
link |
00:29:33.500
So that's an example of a rapid effect of light on your
link |
00:29:36.680
biology, not a very typical one,
link |
00:29:38.720
but nonetheless one that has a hardwired biological
link |
00:29:41.780
mechanism at the other end of the spectrum or what we call
link |
00:29:46.180
slow integrating effects of light on our biology.
link |
00:29:49.940
So what I mean by that are ways in which your body is taking
link |
00:29:53.860
information about light in the environment,
link |
00:29:56.620
not in the sort of snapshot acute sense,
link |
00:29:59.720
but averaging the amount of light in your environment.
link |
00:30:02.500
And that average light information is changing the way that
link |
00:30:06.360
your biology works.
link |
00:30:07.940
But even though this is a slow process,
link |
00:30:10.620
as I mentioned before, it's a very powerful one.
link |
00:30:13.460
The primary example of this are so-called
link |
00:30:16.140
circannual rhythms, circannual rhythms are literally a
link |
00:30:20.740
calendar that exists within your body that uses not numbers,
link |
00:30:26.420
but amounts of hormone that are released into your brain and
link |
00:30:29.580
body each day and each night as a way of knowing where you
link |
00:30:33.700
are in the 365 day calendar year.
link |
00:30:37.520
Now that might seem kind of crazy, but it's not crazy.
link |
00:30:40.900
The earth travels around the sun once every 365 days.
link |
00:30:45.020
And depending on where you are on the earth, where you live,
link |
00:30:50.220
you are going to get more or less light each day on average,
link |
00:30:54.880
depending on the time of year.
link |
00:30:56.520
So if you're in the Northern hemisphere in the winter months,
link |
00:30:59.680
days are shorter, nights are longer.
link |
00:31:02.900
In the summer months, days are longer, nights are shorter.
link |
00:31:05.980
And of course things change whether or not you're in the
link |
00:31:09.260
Northern hemisphere or the Southern hemisphere.
link |
00:31:11.660
But nonetheless, in short days,
link |
00:31:15.140
you have more darkness that's obvious.
link |
00:31:17.840
And if you understand that light arriving on the eyes is
link |
00:31:24.060
absorbed by a particular cell type called the intrinsically
link |
00:31:27.120
photosensitive ganglion cell, it's just a name.
link |
00:31:29.700
You don't need to know the name,
link |
00:31:30.620
but if you want it's the so-called intrinsically
link |
00:31:32.300
photosensitive ganglion cell also called the
link |
00:31:33.940
melanopsin cell, because it contains an opsin,
link |
00:31:36.780
a photo pigment that absorbs short wavelength light that
link |
00:31:42.100
arrives through sunlight,
link |
00:31:43.700
those cells communicate to particular stations in the brain
link |
00:31:47.460
that in turn connect to your so-called pineal gland,
link |
00:31:51.660
which is this little pea-sized gland in the middle of your
link |
00:31:53.940
brain that releases a hormone called melatonin.
link |
00:31:57.620
And the only thing you need to know is that light activates
link |
00:32:01.020
these particular cells,
link |
00:32:02.160
the intrinsically photosensitive melanopsin cells,
link |
00:32:04.500
which in turn shuts down the production of melatonin from
link |
00:32:08.580
the pineal gland.
link |
00:32:10.980
If you think about this in terms of the travel of the earth
link |
00:32:14.500
around the sun across the year,
link |
00:32:16.940
what it means is that in short days,
link |
00:32:19.560
because there's very little light on average landing on
link |
00:32:22.860
these cells,
link |
00:32:24.700
the duration of melatonin release will be much longer
link |
00:32:28.140
because as I mentioned before light inhibits,
link |
00:32:30.820
it shuts down melatonin.
link |
00:32:32.540
Whereas in the summer months,
link |
00:32:34.340
much more light on average will land on your eyes, right?
link |
00:32:37.540
Because days are longer.
link |
00:32:38.960
Even if you're spending more time indoors on average,
link |
00:32:41.100
you're going to get more light to activate these cells.
link |
00:32:45.140
And because light shuts down melatonin production,
link |
00:32:48.600
what you'll find is that the duration of melatonin release
link |
00:32:51.280
for the pineal is much shorter.
link |
00:32:54.380
So melatonin is a transducer.
link |
00:32:57.460
It's a communicator of how much light on average is in your
link |
00:33:01.060
physical environment.
link |
00:33:02.960
What this means is for people living in the Northern
link |
00:33:06.380
hemisphere,
link |
00:33:07.420
you're getting more melatonin release in the winter months
link |
00:33:10.540
than you are in the summer months.
link |
00:33:12.640
So you have a calendar system that is based in a hormone.
link |
00:33:18.540
And that hormone is using light in order to determine where
link |
00:33:22.860
you are in that journey around the sun.
link |
00:33:26.160
Now this is beautiful.
link |
00:33:27.060
At least to me, it's beautiful because what it means is that
link |
00:33:30.380
the environment around us is converted into a signal that
link |
00:33:34.060
changes the environment within us.
link |
00:33:36.860
That signal is melatonin and melatonin is well-known for its
link |
00:33:40.900
role in making us sleepy each night and allowing us to fall
link |
00:33:43.740
asleep.
link |
00:33:44.760
Many of you have probably heard before,
link |
00:33:46.200
I am not a big fan of melatonin supplementation for a number
link |
00:33:49.380
of reasons, but just as a quick aside,
link |
00:33:52.160
the levels of melatonin that are in most supplements are far
link |
00:33:54.700
too high to really be considered physiological.
link |
00:33:57.480
They are indeed super physiological in most cases.
link |
00:34:00.180
And melatonin can have a number of different effects,
link |
00:34:02.900
not just related to sleep, but that's supplemented melatonin.
link |
00:34:07.680
Here I'm talking about our natural production and release of
link |
00:34:10.820
melatonin,
link |
00:34:11.660
according to where we are in the 365 day calendar year.
link |
00:34:17.100
Indogenous melatonin,
link |
00:34:18.220
meaning the melatonin that we make within our bodies
link |
00:34:20.380
naturally, not melatonin that's supplemented,
link |
00:34:23.560
has two general categories of effects.
link |
00:34:26.760
The first set of effects are so-called regulatory effects,
link |
00:34:29.140
and the others are protective effects.
link |
00:34:30.900
The regulatory effects are for instance,
link |
00:34:32.780
that melatonin can positively impact bone mass.
link |
00:34:37.540
So melatonin can, for instance,
link |
00:34:39.300
turn on the production of osteoblasts,
link |
00:34:41.820
which are essentially stem cells that make more bone for us
link |
00:34:45.820
that make our bones stronger,
link |
00:34:47.420
and that can replace damaged aspects of our bone.
link |
00:34:51.060
Melatonin is also involved in maturation of the gonads
link |
00:34:53.940
during puberty, the ovaries and the testes.
link |
00:34:56.860
Although there, the effects of melatonin tend to be
link |
00:34:59.100
suppressive on maturation of the ovaries and testes,
link |
00:35:02.780
meaning high levels of melatonin tend to reduce testicle
link |
00:35:06.820
volume and reduce certain functions within the testes,
link |
00:35:10.880
including sperm production and testosterone production.
link |
00:35:13.580
And within the ovaries,
link |
00:35:15.420
melatonin can suppress the maturation of eggs, et cetera.
link |
00:35:18.580
Now, I don't want anyone to get scared
link |
00:35:20.020
if you've been taking melatonin,
link |
00:35:21.540
mostly effects of melatonin on those functions
link |
00:35:23.880
are reversible,
link |
00:35:25.180
but I should point out that one of the reasons
link |
00:35:27.280
why children don't go into puberty until a particular age
link |
00:35:30.640
is that young children tend to have
link |
00:35:32.540
chronically high endogenous melatonin,
link |
00:35:34.760
and that is healthy to keep them out of puberty
link |
00:35:37.380
until it's the right time for puberty to happen.
link |
00:35:40.700
So melatonin can increase bone mass,
link |
00:35:43.400
but reduces gonad mass, so to speak.
link |
00:35:46.860
It's going to have varying effects
link |
00:35:48.740
depending on the ratios and levels of other hormones
link |
00:35:51.460
and other biological events in the body.
link |
00:35:53.220
But as you can see, melatonin has these powerful
link |
00:35:55.420
regulatory effects on other tissues.
link |
00:35:57.540
I should also mention that melatonin
link |
00:35:59.140
is a powerful modulator of placental development.
link |
00:36:02.120
So for anyone that's pregnant,
link |
00:36:03.500
if you're considering melatonin supplementation,
link |
00:36:05.860
please, please, please talk to your OBGYN,
link |
00:36:08.540
talk to your other doctor as well.
link |
00:36:10.980
You want to be very, very cautious
link |
00:36:12.380
because of the powerful effects that melatonin can have
link |
00:36:14.660
on the developing fetus and placenta.
link |
00:36:16.900
For people that are not pregnant, in fact, all people,
link |
00:36:20.020
melatonin has a powerful effect on the central nervous
link |
00:36:23.780
system as a whole.
link |
00:36:24.980
Your brain and spinal cord are the major components
link |
00:36:26.980
of your central nervous system.
link |
00:36:28.460
And melatonin, because it's associated with darkness,
link |
00:36:33.020
which is just another way of saying that
link |
00:36:34.340
light suppresses melatonin, melatonin is thereby associated
link |
00:36:38.020
with the dark phase of each 24 hour cycle,
link |
00:36:41.800
it can have a number of different effects
link |
00:36:44.700
in terms of waking up or making our body feel more sleepy.
link |
00:36:48.340
And it does that by way of impacting cells
link |
00:36:50.420
within our nervous system,
link |
00:36:51.460
literally turning on certain brain areas,
link |
00:36:54.040
turning off other brain areas.
link |
00:36:55.580
And it does that through a whole cascade
link |
00:36:57.060
of biological mechanisms,
link |
00:36:58.460
a bit too detailed to get into today.
link |
00:37:00.460
So melatonin is regulating how awake or asleep we are.
link |
00:37:03.000
It tends to make us more asleep, incidentally.
link |
00:37:05.940
It's regulating our timing of puberty
link |
00:37:08.860
and it's regulating how our gonads,
link |
00:37:11.300
the testes and ovaries function,
link |
00:37:12.900
even in adulthood to some extent,
link |
00:37:14.780
and it's regulating bone mass.
link |
00:37:17.420
As I mentioned before, melatonin also has protective effects.
link |
00:37:20.480
It can activate our immune system.
link |
00:37:22.160
It is among the most potent antioxidants.
link |
00:37:25.500
So it is known to have certain anti-cancer properties
link |
00:37:28.140
and things of that sort,
link |
00:37:29.620
which is not to say that you simply want more melatonin.
link |
00:37:32.120
I think a lot of people get misled
link |
00:37:33.860
when they hear something like melatonin
link |
00:37:36.100
has anti-cancer properties.
link |
00:37:37.960
That doesn't mean that just cranking up
link |
00:37:39.580
the levels of melatonin by supplementing it
link |
00:37:42.060
or by spending time in darkness and not getting any light,
link |
00:37:44.540
which would of course inhibit melatonin
link |
00:37:46.140
is going to be beneficial for combating cancer.
link |
00:37:48.500
That's not the way it works.
link |
00:37:50.540
It is actually the rise and fall of melatonin
link |
00:37:53.980
every 24 hour cycle and the changes in the duration
link |
00:37:57.420
of that melatonin signal throughout the seasons
link |
00:37:59.820
that has these anti-cancer and antioxidant effects.
link |
00:38:03.300
So when we think about light impacting our biology,
link |
00:38:07.100
the reason I bring up melatonin
link |
00:38:08.660
as the primary example of that is A,
link |
00:38:10.740
because melatonin impacts so many important functions
link |
00:38:13.220
within our brain and body,
link |
00:38:14.420
but also because hormones in general, not always,
link |
00:38:17.840
but in general are responsible
link |
00:38:19.240
for the slow modulatory effects on our biology.
link |
00:38:22.660
And so I'm using this as an example
link |
00:38:24.780
of how light throughout the year is changing the way
link |
00:38:27.820
that the different cells and tissues
link |
00:38:29.660
and organs of your body are working
link |
00:38:31.060
and that melatonin is the transducer of that signal.
link |
00:38:34.300
So at this point we can say
link |
00:38:35.940
light powerfully modulates melatonin,
link |
00:38:38.060
meaning it shuts down melatonin.
link |
00:38:39.700
Melatonin is both beneficial for certain tissues
link |
00:38:42.420
and suppressive for other tissues and functions.
link |
00:38:46.220
What should we do with this information?
link |
00:38:47.780
Well, it's very well established now
link |
00:38:50.860
that one of the best things that we can all do
link |
00:38:53.100
is to get the proper amount of sunlight each day.
link |
00:38:56.580
And by proper, I mean appropriate for that time of year.
link |
00:39:00.340
So in the summer months where the days are longer
link |
00:39:03.540
and nights are shorter,
link |
00:39:04.780
we would all do well to get more sunlight in our eyes.
link |
00:39:08.220
And again, it's going to be to our eyes
link |
00:39:10.100
because as you recall, the pineal sits deep in the brain
link |
00:39:14.220
and light can't access the pineal directly,
link |
00:39:16.300
at least not in humans.
link |
00:39:17.820
So in order to get light information to the pineal
link |
00:39:22.620
and thereby get the proper levels of melatonin,
link |
00:39:26.100
according to the time of year,
link |
00:39:27.560
we should all try and get outside as much as possible
link |
00:39:30.900
during the long days of summer and spring.
link |
00:39:34.140
And in the winter months,
link |
00:39:35.340
it makes sense to spend more time indoors.
link |
00:39:37.700
For those of you that suffer
link |
00:39:38.820
from seasonal affective disorder,
link |
00:39:40.180
which is a seasonal depression
link |
00:39:41.460
or feel low during the fall and winter months,
link |
00:39:44.180
there are ways to offset this.
link |
00:39:45.300
We did an entire episode on mood and circadian rhythms
link |
00:39:47.860
where we describe this.
link |
00:39:49.100
So it does make sense for some people
link |
00:39:50.480
to get more bright light in their eyes early in the morning
link |
00:39:52.920
and throughout the day during the winter months as well.
link |
00:39:56.020
But nonetheless, changes in melatonin,
link |
00:39:59.380
meaning changes in the duration of melatonin release
link |
00:40:02.060
across the year are normal and healthy.
link |
00:40:04.080
So provided that you're not suffering from depression,
link |
00:40:06.760
it's going to be healthy to somewhat modulate your amount
link |
00:40:09.540
of indoor and outdoor time across the year.
link |
00:40:12.260
The other thing to understand
link |
00:40:13.240
is this very firmly established fact,
link |
00:40:15.040
which is light powerfully inhibits melatonin.
link |
00:40:19.260
If you wake up in the middle of the night
link |
00:40:20.980
and you go into the bathroom and you flip on the lights,
link |
00:40:23.320
and those are very bright overhead fluorescent lights,
link |
00:40:26.500
your melatonin levels,
link |
00:40:28.060
which would ordinarily be quite high
link |
00:40:30.180
in the middle of the night,
link |
00:40:31.020
because you've been eyes closed in the dark presumably,
link |
00:40:33.820
will immediately plummet to near zero or zero.
link |
00:40:37.000
We would all do well, regardless of time of year,
link |
00:40:40.020
to not destroy our melatonin
link |
00:40:43.540
in the middle of the night in this way.
link |
00:40:45.380
So if you need to get up in the middle of the night
link |
00:40:46.940
and use the restroom,
link |
00:40:47.780
which is a perfectly normal behavior for many people,
link |
00:40:50.860
use the minimum amount of light required
link |
00:40:53.940
in order to safely move through the environment
link |
00:40:57.080
that you need to move through.
link |
00:40:59.720
Melatonin needs to come on early in the night.
link |
00:41:02.440
It actually starts rising in the evening and towards sleep.
link |
00:41:06.300
But then as you close your eyes and you go to sleep,
link |
00:41:08.220
melatonin levels are going to continue to rise,
link |
00:41:10.680
at least for several hours into the night.
link |
00:41:13.580
Again, if you get up in the middle of the night,
link |
00:41:15.220
really try hard not to flip on a lot of bright lights.
link |
00:41:17.920
If you do that every once in a while,
link |
00:41:19.460
it's not going to be a problem.
link |
00:41:21.020
But if you're doing that night after night,
link |
00:41:22.980
you are really disrupting this fundamental signal
link |
00:41:27.440
that occurs every night,
link |
00:41:28.980
regardless of winter, spring, summer, et cetera,
link |
00:41:31.100
and that is communicating information
link |
00:41:33.500
about where your brain and body should be in time.
link |
00:41:37.060
And I know that's a little bit of a tricky concept,
link |
00:41:38.900
but really our body is not meant to function
link |
00:41:41.860
in the same way during the winter months
link |
00:41:43.340
as the summer months.
link |
00:41:44.540
There are functions that are specifically optimal
link |
00:41:48.020
for the shorter days of winter.
link |
00:41:49.620
And there are functions that are specifically optimal
link |
00:41:51.780
for the longer days of summer.
link |
00:41:53.780
So again, try to avoid bright light exposure to your eyes
link |
00:41:58.520
in the middle of the night.
link |
00:41:59.560
And for those of you that are doing shift work,
link |
00:42:01.580
what I can say is try and avoid getting bright light
link |
00:42:04.100
in your eyes in the middle of your sleep cycle.
link |
00:42:06.060
So even if you're sleeping in the middle of the day,
link |
00:42:07.440
because you have to work at night,
link |
00:42:08.740
if you wake up during that bout of sleep,
link |
00:42:11.160
really try hard to limit the amount of light,
link |
00:42:13.360
which is going to be harder for shift workers, right?
link |
00:42:15.580
Because there are generally a lot more lights on
link |
00:42:17.420
and bright lights outside too.
link |
00:42:18.620
You would want to close the blinds
link |
00:42:20.060
and limit artificial light inside.
link |
00:42:22.380
One way to bypass some of the inhibitory effects
link |
00:42:25.940
of light on melatonin
link |
00:42:27.420
is to change your physical environment
link |
00:42:29.980
by for instance, dimming the lights.
link |
00:42:32.000
That's one simple way, very low cost way.
link |
00:42:34.000
In fact, you'll save money by dimming the lights
link |
00:42:35.780
or turning them off.
link |
00:42:36.700
The other is if you are going to use light
link |
00:42:39.140
using long wavelength light,
link |
00:42:40.700
because as you recall these intrinsically
link |
00:42:42.540
photosensitive melanopsin cells within your retina
link |
00:42:45.020
that convey the signal about bright light
link |
00:42:48.220
in your environment to impact melatonin,
link |
00:42:50.420
to shut down melatonin,
link |
00:42:51.740
respond to short wavelengths of light.
link |
00:42:53.840
So red light is long wavelength light.
link |
00:42:55.860
You now understand that from our discussion
link |
00:42:57.760
about the physics of light.
link |
00:42:59.620
And if you were to use amber colored light or red light,
link |
00:43:03.420
and even better dim amber or dim red light
link |
00:43:06.700
in the middle of the night,
link |
00:43:07.540
well then you would probably not reduce melatonin at all,
link |
00:43:11.100
unless those red lights and amber lights
link |
00:43:13.040
are very, very bright.
link |
00:43:14.080
Any light provided it's bright enough
link |
00:43:16.260
will shut down melatonin production.
link |
00:43:18.860
One final point about melatonin,
link |
00:43:20.900
and this relates to melatonin supplementation as well,
link |
00:43:23.980
is that now that you understand how potently melatonin
link |
00:43:27.340
can impact things like cardiovascular function,
link |
00:43:29.220
immune function, anticancer properties,
link |
00:43:31.160
bone mass, gonad function, et cetera,
link |
00:43:34.340
you can understand why it would make sense to be cautious
link |
00:43:37.500
about melatonin supplementation,
link |
00:43:38.980
because supplementation tends to be pretty static.
link |
00:43:41.480
It's X number of milligrams per night.
link |
00:43:44.460
Whereas normally endogenously,
link |
00:43:47.220
the amount of melatonin that you're releasing each night
link |
00:43:49.420
is changing according to time of year,
link |
00:43:52.140
or if you happen to live in an area
link |
00:43:54.340
where there isn't much change in day length across the year.
link |
00:43:56.940
So for instance, if you live near the equator,
link |
00:43:59.140
well, then your body is accustomed
link |
00:44:00.920
to having regular amounts of melatonin each night.
link |
00:44:04.020
When you start supplementing melatonin,
link |
00:44:06.180
you start changing the total amount of melatonin obviously,
link |
00:44:09.260
but you're also changing the normal rhythms
link |
00:44:12.240
in how much melatonin is being released
link |
00:44:14.980
into your brain and body across the 365 day calendar year.
link |
00:44:19.020
So while I'm somebody who readily embraces supplementation
link |
00:44:22.940
in various forms for things like sleep and focus, et cetera,
link |
00:44:26.380
when it comes to melatonin, I'm extremely cautious.
link |
00:44:30.100
And I think it's also one of the few examples
link |
00:44:32.580
where a hormone is available without prescription
link |
00:44:35.820
over the counter.
link |
00:44:36.660
You can just go into a pharmacy or drug store,
link |
00:44:38.020
order online this hormone,
link |
00:44:39.620
which is known to have all these powerful effects.
link |
00:44:41.880
So I get very, very concerned
link |
00:44:43.620
when I hear about people taking melatonin,
link |
00:44:45.740
especially at the levels that are present
link |
00:44:47.380
in most supplements.
link |
00:44:48.560
It's been recognized for a very long time.
link |
00:44:50.580
And in fact, there are now data to support the fact
link |
00:44:53.540
that animals of all kinds, including humans,
link |
00:44:56.580
will seek out mates and engage in mating behavior
link |
00:44:59.860
more frequently during the long days of spring and summer.
link |
00:45:04.140
That's right, in seasonally breeding animals,
link |
00:45:06.820
of course, this is the case, but in humans as well,
link |
00:45:10.860
there is more seeking out of mates and mating behavior
link |
00:45:13.780
in longer day times of year.
link |
00:45:16.820
Now you could imagine at least two mechanisms
link |
00:45:19.540
by which this occurs.
link |
00:45:21.520
The first mechanism we could easily map to melatonin
link |
00:45:25.380
and the fact that melatonin is suppressive
link |
00:45:28.000
to various aspects of the so-called gonadal axis,
link |
00:45:31.440
which is basically a fancy way of saying
link |
00:45:34.020
that melatonin inhibits testosterone and estrogen output
link |
00:45:37.700
from the testes and from the ovaries.
link |
00:45:40.100
I just want to remind people that both males and females
link |
00:45:42.280
make testosterone and estrogen,
link |
00:45:44.680
although in different ratios typically in males versus
link |
00:45:47.060
females, and that both testosterone and estrogen
link |
00:45:50.560
are critical for the desire to mate
link |
00:45:54.020
and for mating behavior.
link |
00:45:55.860
There's a broad misconception that testosterone
link |
00:45:58.860
is involved in mating behavior and estrogen is involved
link |
00:46:01.300
in other behaviors, but having enough estrogen is critical
link |
00:46:04.640
for both males and females in order to maintain the desire
link |
00:46:07.660
to mate and indeed the ability to mate.
link |
00:46:10.160
I discussed this on the episode on optimizing testosterone
link |
00:46:13.740
and estrogen, so if you'd like more details on that,
link |
00:46:15.940
please see that episode of the Huberman Lab Podcast.
link |
00:46:19.300
Okay, so if melatonin is suppressive
link |
00:46:22.840
to the so-called gonadal axis and reduces overall levels
link |
00:46:27.380
of testosterone and estrogen in males and females,
link |
00:46:30.020
and the light inhibits melatonin,
link |
00:46:33.500
then when there's more light, then there's less melatonin
link |
00:46:36.720
and a more hormone output from the gonads.
link |
00:46:39.540
And indeed that's how the system works,
link |
00:46:41.700
but that's not the entire story.
link |
00:46:43.700
It turns out that there is a second so-called parallel
link |
00:46:47.280
pathway, meaning a different biological pathway that operates
link |
00:46:51.180
in parallel to the light suppression of melatonin pathway
link |
00:46:55.460
that provides a basis for longer days,
link |
00:46:58.700
inspiring more desire to mate and more mating behavior.
link |
00:47:02.040
So if we think of the first pathway involving melatonin
link |
00:47:05.220
as sort of a break on these reproductive hormones,
link |
00:47:08.480
the second mechanism is more like an accelerator
link |
00:47:11.100
on those hormones, and yet it still involves light.
link |
00:47:15.060
As I'm about to tell you, in animals such as mice,
link |
00:47:18.740
but also in humans, exposure to light,
link |
00:47:22.340
in particular UV blue light, so short wavelengths of light,
link |
00:47:26.120
can trigger increases in testosterone and estrogen
link |
00:47:29.180
and the desire to mate.
link |
00:47:30.780
Now what's especially important about this accelerator
link |
00:47:33.660
on the desire to mate and mating behavior and hormones
link |
00:47:36.820
is that it is driven by exposure to light,
link |
00:47:40.900
but it is not the exposure of light to the eyes.
link |
00:47:44.740
It turns out that it is the exposure of your skin
link |
00:47:48.120
to particular wavelengths of light that is triggering
link |
00:47:51.020
increases in the hormones, testosterone and estrogen,
link |
00:47:54.460
leading to increased desire to mate.
link |
00:47:57.020
As it turns out, your skin, which most of us just think of
link |
00:48:00.860
as a way to protect the organs of our body
link |
00:48:03.340
or something to hang clothes on or ornaments on,
link |
00:48:06.300
if you're somebody who has earrings and so forth,
link |
00:48:09.440
your skin is actually an endocrine organ,
link |
00:48:12.340
meaning it is a hormone producing
link |
00:48:15.180
and hormone influencing organ.
link |
00:48:18.200
I promise what I'm about to tell you next
link |
00:48:19.660
will forever change the way that you think about your skin
link |
00:48:22.580
and light and the desire to mate
link |
00:48:25.760
and indeed even mating behavior.
link |
00:48:28.380
I think the results are best understood
link |
00:48:30.580
by simply going through the primary data,
link |
00:48:32.980
meaning the actual research on this topic.
link |
00:48:35.340
And to do so, I'm going to review a recent paper
link |
00:48:37.560
that was published in the journal Cell Reports,
link |
00:48:39.980
Cell Press Journal, excellent journal.
link |
00:48:42.080
This is a paper that came out in 2021,
link |
00:48:45.380
entitled Skin Exposure to UVB Light
link |
00:48:48.660
Induces a Skin Brain Gonad Axis and Sexual Behavior.
link |
00:48:53.100
And I want to emphasize that this was a paper
link |
00:48:55.780
that focused on mice in order to address specific mechanisms
link |
00:49:00.560
because in mice, you can so-called knock out
link |
00:49:03.420
particular genes, you can remove particular genes
link |
00:49:05.540
to understand mechanism.
link |
00:49:06.620
You just can't do that in humans
link |
00:49:08.140
in any kind of controlled way,
link |
00:49:09.980
at least not at this point in time.
link |
00:49:12.420
And this study also explores humans
link |
00:49:15.380
and looked at human subjects, both men and women.
link |
00:49:19.340
The basic finding of this study was that
link |
00:49:22.380
when mice or humans were exposed to UVB,
link |
00:49:26.300
meaning ultraviolet blue light,
link |
00:49:27.580
so short wavelength light of the sort
link |
00:49:29.140
that comes through in sunshine,
link |
00:49:30.980
but is also available through various artificial sources.
link |
00:49:34.300
If they received enough exposure of that light
link |
00:49:39.180
to their skin, there were increases in testosterone
link |
00:49:44.100
that were observed within a very brief period of time,
link |
00:49:46.980
also increases in the hormone estrogen.
link |
00:49:50.060
And I should point out that the proper ratios
link |
00:49:52.140
of estrogen and testosterone were maintained
link |
00:49:54.500
in both males and females,
link |
00:49:55.820
at least as far as these data indicate.
link |
00:49:58.740
And mice tended to seek out mating more and mate more.
link |
00:50:04.460
There were also increases in gonadal weight,
link |
00:50:07.580
literally increases in testes size and in ovarian size
link |
00:50:11.260
when mice were exposed to this UVB light
link |
00:50:14.040
past a certain threshold.
link |
00:50:15.500
Now, as I mentioned before, the study also looked at humans.
link |
00:50:18.180
They did not look at testes size or ovarian size
link |
00:50:21.940
in the human subjects.
link |
00:50:23.260
However, because they are humans,
link |
00:50:25.240
they did address the psychology of these human beings
link |
00:50:28.940
and address whether or not they had increases in,
link |
00:50:31.700
for instance, aggressiveness or in passionate feelings
link |
00:50:34.800
and how their perception of other people changed
link |
00:50:38.660
when they were getting a lot of UVB light exposure
link |
00:50:42.340
to the skin.
link |
00:50:43.200
So before I get into some of the more important details
link |
00:50:45.340
of the study and how it was done
link |
00:50:47.040
and how you can leverage this information for yourself,
link |
00:50:49.760
if you desire, I just want to highlight
link |
00:50:52.780
some of the basic findings overall.
link |
00:50:55.620
UVB exposure increased these so-called sex steroid levels
link |
00:50:59.380
in mice and humans.
link |
00:51:00.680
The sex steroid hormones, when we say steroids,
link |
00:51:03.780
we don't mean anabolic steroids taken exogenously.
link |
00:51:06.480
I think when people hear the word steroids,
link |
00:51:07.880
they always think steroid abuse or use.
link |
00:51:10.640
Rather steroid hormones such as testosterone and estrogen
link |
00:51:13.900
went up when mice or humans had a lot of UVB exposure
link |
00:51:18.300
to their skin.
link |
00:51:19.220
Second of all, UVB light exposure to the skin,
link |
00:51:22.780
enhanced female attractiveness,
link |
00:51:24.620
so the perceived attractiveness of females by males
link |
00:51:27.780
and increase the receptiveness or the desire to mate
link |
00:51:31.900
in both sexes.
link |
00:51:33.340
UVB light exposure also changed various aspects
link |
00:51:36.620
of female biology related to fertility,
link |
00:51:39.020
in particular, follicle growth.
link |
00:51:41.500
Follicle and egg maturation are well-known indices
link |
00:51:45.820
of fertility and of course correlate
link |
00:51:48.540
with the menstrual cycle in adult humans
link |
00:51:51.220
and is related overall to the propensity to become pregnant.
link |
00:51:56.220
UVB light exposure enhanced maturation of the follicle
link |
00:51:59.340
which just meant that more healthy eggs were being produced.
link |
00:52:02.540
These are impressive effects.
link |
00:52:03.900
First of all, they looked at a large number of variables
link |
00:52:06.420
in the study and the fact that they looked at mice
link |
00:52:08.500
and humans is terrific.
link |
00:52:10.140
I think that oftentimes we find it hard to translate data
link |
00:52:13.060
from mice to humans.
link |
00:52:13.900
So the fact that they looked at both in parallel
link |
00:52:16.260
is wonderful.
link |
00:52:17.160
In the mice and in the humans,
link |
00:52:20.260
they established a protocol that essentially involved
link |
00:52:24.500
exposing the skin to UV light that was equivalent
link |
00:52:27.820
to about 20 to 30 minutes of midday sun exposure.
link |
00:52:31.340
Now, of course, where you live in the world
link |
00:52:33.060
will dictate whether or not that midday sun
link |
00:52:34.700
is very, very bright and intense,
link |
00:52:36.460
or is less bright, maybe there's cloud cover, et cetera.
link |
00:52:39.360
But since I'm imagining that most people are interested
link |
00:52:43.100
in the ways to increase testosterone
link |
00:52:45.700
and or estrogen in humans and are not so much interested
link |
00:52:48.840
in increasing testosterone in mice,
link |
00:52:51.060
I'm going to just review what they did
link |
00:52:52.800
in the human population or the human subjects.
link |
00:52:55.900
What they did is they had people,
link |
00:52:58.220
first of all, establish a baseline.
link |
00:53:00.020
And the way they establish a baseline
link |
00:53:01.340
was a little bit unusual,
link |
00:53:02.640
but it will make perfect sense to you.
link |
00:53:04.520
They had people wear long sleeves and essentially cover up
link |
00:53:06.940
and avoid sunlight for a few days
link |
00:53:08.780
so they could measure their baseline hormones
link |
00:53:10.720
in the absence of getting a lot of UVB light exposure
link |
00:53:14.700
from the sun or from other sources.
link |
00:53:16.620
Now, of course, these people had access
link |
00:53:18.860
to artificial lights,
link |
00:53:19.980
but as I've pointed out on this podcast before,
link |
00:53:22.020
it's pretty unusual that you'll get enough UVB exposure
link |
00:53:25.420
from artificial lights throughout the day.
link |
00:53:27.980
And in the morning, you need a lot of UVB exposure,
link |
00:53:30.660
or we should be getting a lot of UVB exposure to our eyes
link |
00:53:34.060
and to our face and to our skin throughout the day,
link |
00:53:36.020
provided we're not getting sunburned.
link |
00:53:37.700
This is actually a healthy thing for mood
link |
00:53:39.580
and for energy throughout the day.
link |
00:53:41.180
It's only at night, basically between the hours
link |
00:53:43.900
of about 10 p.m. and 4 a.m.
link |
00:53:46.280
that even a tiny bit of UVB exposure from artificial sources
link |
00:53:49.700
can mess us up in terms of our sleep
link |
00:53:51.860
and our energy levels and so on.
link |
00:53:53.420
And that's because of the potent effect of UVB
link |
00:53:55.860
on suppressing melatonin.
link |
00:53:58.040
So the point here is that they establish a baseline
link |
00:54:01.180
whereby people were getting some artificial light exposure
link |
00:54:04.180
throughout the day, but they weren't getting outside a lot.
link |
00:54:06.660
They weren't getting a lot of sunlight.
link |
00:54:08.340
And then they had people receive a dose
link |
00:54:11.700
of UVB light exposure that was about 20 to 30 minutes
link |
00:54:16.180
outdoors.
link |
00:54:17.020
They had people wear short sleeves, no hat, no sunglasses.
link |
00:54:20.320
Some people wore sleeveless shirts.
link |
00:54:21.900
They encouraged people to wear shorts.
link |
00:54:23.560
So they were indeed wearing clothing.
link |
00:54:25.960
They were not naked and they were wearing clothing
link |
00:54:28.900
that was culturally and situationally appropriate,
link |
00:54:31.420
at least for the part of the world where this study was done
link |
00:54:34.340
and they had people do that two or three times a week.
link |
00:54:37.100
So in terms of a protocol that you might export
link |
00:54:39.120
from this study, basically getting outside
link |
00:54:40.980
for about 30 minutes, two or three times a week
link |
00:54:43.320
in a minimum of clothing and yet still
link |
00:54:46.260
wearing enough clothing that is culturally appropriate.
link |
00:54:48.940
They were outside, they weren't sunbathing,
link |
00:54:51.180
flipping over on their back and front.
link |
00:54:52.540
They were just moving about doing things they could read.
link |
00:54:54.720
They could talk, they could go about other activities,
link |
00:54:57.540
but they weren't wearing a broad brim hat
link |
00:54:59.540
or a hat of any kind.
link |
00:55:00.540
They're just getting a lot of sun exposure to their skin.
link |
00:55:03.700
They did this for a total of 10 to 12 UVB treatments.
link |
00:55:07.940
So this took several weeks, right?
link |
00:55:10.060
It took about a month if you think about it,
link |
00:55:11.420
two or three times per week for a total
link |
00:55:12.780
of 10 to 12 UVB treatments.
link |
00:55:15.780
These treatments, of course,
link |
00:55:16.620
are just being outside in the sun.
link |
00:55:18.380
And then they measured hormones
link |
00:55:20.860
and they measured the psychology of these male
link |
00:55:23.180
and female adult subjects.
link |
00:55:24.920
Let's first look at the psychological changes
link |
00:55:27.060
that these human subjects experienced
link |
00:55:28.940
after getting 10 to 12 of these UVB light exposure,
link |
00:55:33.060
outdoor and sunlight type treatments.
link |
00:55:35.380
They did this by collecting blood samples
link |
00:55:37.080
throughout the study.
link |
00:55:38.380
And they saw significant increases
link |
00:55:40.940
in the hormones beta estradiol,
link |
00:55:42.700
which is one of the major forms of estrogen,
link |
00:55:45.220
progesterone, another important steroid hormone,
link |
00:55:48.420
and testosterone in both men and women.
link |
00:55:51.700
Now, an important point is that the testosterone increases
link |
00:55:55.180
were significantly higher in men that happened
link |
00:55:58.660
to originate from countries that had low UV exposure
link |
00:56:04.040
compared to individuals from countries
link |
00:56:05.520
with high UV exposure.
link |
00:56:07.940
Now, this ought to make sense if we understand
link |
00:56:10.820
a little bit about how the skin functions
link |
00:56:12.660
as an endocrine organ.
link |
00:56:13.980
Many of you have probably heard of vitamin D3,
link |
00:56:17.040
which is a vitamin that we all make.
link |
00:56:19.680
Many people supplement it as well
link |
00:56:21.180
if they need additional vitamin D3.
link |
00:56:24.260
We all require sunlight in order to allow vitamin D3
link |
00:56:28.800
to be synthesized and perform its roles in the body.
link |
00:56:32.180
And it turns out that people who have darker skin
link |
00:56:35.100
actually need more vitamin D3 and or more sunlight exposure
link |
00:56:39.700
in order to activate that D3 pathway
link |
00:56:42.180
than do people with paler skin.
link |
00:56:45.260
And this should make sense to all of you,
link |
00:56:47.460
given what you now understand about melanocytes,
link |
00:56:50.140
that cell type that we discussed earlier,
link |
00:56:51.700
because melanocytes have pigment within them.
link |
00:56:54.800
And if you have darker skin,
link |
00:56:56.640
it means that you have more melanocytes
link |
00:56:59.260
or that you have melanocytes
link |
00:57:00.540
that are more efficient at creating pigment.
link |
00:57:03.940
And as a consequence, the light that lands on your skin
link |
00:57:07.680
will be absorbed by those melanocytes
link |
00:57:09.380
and less of it is able to impact the D3 pathway.
link |
00:57:12.700
Whereas if you have pale skin,
link |
00:57:14.020
more of the light that lands on your skin
link |
00:57:16.080
can trigger the synthesis
link |
00:57:18.140
and assist the actions of vitamin D3.
link |
00:57:22.340
Similarly, in this study,
link |
00:57:23.560
they found that people who had paler skin
link |
00:57:25.740
and or who originated from countries
link |
00:57:28.180
where they had less UVB light exposure across the year
link |
00:57:32.260
had greater, meaning more significant increases
link |
00:57:35.500
in testosterone overall than did people
link |
00:57:37.900
who already were getting a lot of UVB exposure.
link |
00:57:41.080
This led them to explore so-called seasonal changes
link |
00:57:43.820
in testosterone that occurred normally
link |
00:57:46.400
in the absence of any light exposure treatment.
link |
00:57:49.660
So up until now, I've been talking about
link |
00:57:52.020
the aspects of this study involving people getting outside
link |
00:57:55.140
for about 20 to 30 minutes per day in sunlight
link |
00:57:57.960
in a minimum of clothing.
link |
00:57:59.420
There was an increase in testosterone observed
link |
00:58:01.820
in both men and women.
link |
00:58:03.260
The increases in testosterone were greater for people
link |
00:58:05.820
that had paler skin than darker skin.
link |
00:58:08.520
So the data I'm about to describe
link |
00:58:10.220
also come from this same paper,
link |
00:58:11.900
but do not involve 20 to 30 minute
link |
00:58:14.360
daily sun exposure protocols.
link |
00:58:16.100
It's simply addressing whether or not
link |
00:58:18.220
testosterone levels change as a function of time of year.
link |
00:58:23.980
They measure testosterone across the 12 month calendar.
link |
00:58:27.820
This study was done on subjects living
link |
00:58:29.660
in the Northern hemisphere for the entire year.
link |
00:58:32.180
And so in the months of January, February, and March,
link |
00:58:35.500
of course, the length of days is shortest
link |
00:58:38.620
and the length of nights is longest.
link |
00:58:41.060
And of course, in the spring and summer months,
link |
00:58:43.620
June, July, August, September, and so on,
link |
00:58:45.700
the days are much longer and the nights are shorter.
link |
00:58:47.660
And what they observed was very obvious.
link |
00:58:51.580
They observed that testosterone levels were lowest
link |
00:58:55.380
in the winter months and were highest
link |
00:58:57.780
in the months of June, July, August, and September.
link |
00:59:01.260
Now, these are very important data.
link |
00:59:03.060
At least to my knowledge,
link |
00:59:03.900
these are the first data systematically exploring
link |
00:59:06.840
the levels of sex steroid hormones in humans
link |
00:59:09.960
as a function of time of year and thereby as a function
link |
00:59:13.420
of how much sunlight exposure they're getting.
link |
00:59:15.960
And what's remarkable about these data
link |
00:59:17.900
is that they map very well to the data in mice
link |
00:59:20.640
and the other data in this paper on humans,
link |
00:59:23.560
which illustrate that if you're getting more UVB exposure,
link |
00:59:28.000
your testosterone levels are higher.
link |
00:59:29.780
This study went a step further
link |
00:59:31.060
and explored whether or not the amount of sunlight exposure
link |
00:59:33.740
that one is getting to their skin influences
link |
00:59:36.060
their psychology in terms of whether
link |
00:59:38.740
or not they have increased desire to mate and so on.
link |
00:59:41.560
It's well known that sunlight exposure
link |
00:59:43.940
to the eyes can increase mood.
link |
00:59:46.760
And I talked about this in the podcast episode
link |
00:59:49.040
with my guest, Dr. Samir Hatar,
link |
00:59:50.980
who's the director of the Chronobiology Unit
link |
00:59:52.740
at the National Institutes of Mental Health.
link |
00:59:54.380
And Samir's recommendation is that people get
link |
00:59:56.260
as much bright light exposure as they safely can
link |
00:59:58.800
in the morning and throughout the day
link |
01:00:00.180
for sake of both sleep and energy,
link |
01:00:02.420
but also for enhancing mood and regulating appetite.
link |
01:00:06.860
In this study, it was found that both males and females
link |
01:00:11.040
had higher levels of romantic passion
link |
01:00:13.340
after getting the UV treatment.
link |
01:00:16.140
In fact, some of them reported increases in romantic passion
link |
01:00:18.740
from just one or two of these UV treatments.
link |
01:00:21.500
So they didn't have to go through all 10 or 12
link |
01:00:24.160
in order to get a statistically significant increase
link |
01:00:26.960
in passion.
link |
01:00:28.400
Now, when we talk about passion,
link |
01:00:30.020
as the authors of this paper acknowledge,
link |
01:00:31.980
there's really two forms.
link |
01:00:32.940
There is emotional and sexual,
link |
01:00:34.640
and they parse this pretty finely.
link |
01:00:36.380
I don't want to go into all the details
link |
01:00:37.900
and we can provide a reference and link to this study
link |
01:00:39.740
if you'd like to look at those details.
link |
01:00:41.740
But what they found was that women receiving
link |
01:00:45.100
this UVB light exposure focused more on increases
link |
01:00:49.500
in physical arousal and sexual passion.
link |
01:00:51.740
Whereas the men actually scored higher
link |
01:00:53.700
on the cognitive dimensions of passion,
link |
01:00:55.580
such as obsessive thoughts about their partner and so on.
link |
01:00:58.220
Regardless, both males and females experienced
link |
01:01:02.220
and reported a increase in sexual passion
link |
01:01:05.420
and desire to mate.
link |
01:01:06.880
And we now know there were increases
link |
01:01:08.620
in testosterone and estrogen,
link |
01:01:10.500
which of course could be driving the psychological changes.
link |
01:01:13.180
Although I'm sure that those interact in both directions,
link |
01:01:15.820
meaning the hormones no doubt affect psychology
link |
01:01:19.380
and no doubt the psychology,
link |
01:01:21.200
these changes in passionate feelings,
link |
01:01:22.940
no doubt also increased or changed
link |
01:01:25.420
the hormone levels as well.
link |
01:01:26.920
And I want to reemphasize that there was a component
link |
01:01:30.620
of the study that had no deliberate daylight,
link |
01:01:33.620
sunlight exposure for 20 or 30 minutes,
link |
01:01:36.340
but rather just looked at hormone levels
link |
01:01:38.500
throughout the year and found that the increase
link |
01:01:42.420
in day length correlated with increases
link |
01:01:45.420
in testosterone and sexual passion.
link |
01:01:47.420
Now, my opinion, this is a very noteworthy study
link |
01:01:50.140
because it really illustrates that sunlight
link |
01:01:53.740
and day length can impact the melatonin pathway
link |
01:01:56.420
and thereby take the foot off the brake, so to speak,
link |
01:02:00.580
on testosterone, estrogen, and the desire to mate.
link |
01:02:03.980
It also emphasizes that sunlight, UVB light,
link |
01:02:08.220
can directly trigger hormone pathways
link |
01:02:11.360
and desire to mate and mating behavior.
link |
01:02:14.100
Now, the study went a step further
link |
01:02:15.480
in defining the precise mechanism
link |
01:02:17.500
by which light can impact all these hormones
link |
01:02:19.740
and this desire to mate.
link |
01:02:21.540
And here, understanding the mechanism is key
link |
01:02:23.660
if you want to export a particular protocol
link |
01:02:26.140
or tool that you might apply.
link |
01:02:29.300
We talked earlier about how UVB light exposure
link |
01:02:31.720
to the eyes triggers activation
link |
01:02:33.360
of these particular neurons within the eye
link |
01:02:35.620
and then with centers deeper in the brain
link |
01:02:37.940
and eventually the pineal gland
link |
01:02:39.780
to suppress the output of melatonin
link |
01:02:42.140
and thereby to allow testosterone and estrogen
link |
01:02:45.040
to exist at higher levels
link |
01:02:46.180
because melatonin can inhibit testosterone and estrogen.
link |
01:02:50.580
In this study, they were able to very clearly establish
link |
01:02:54.100
that it is sunlight exposure to our skin
link |
01:02:57.460
that is causing these hormone increases
link |
01:02:59.440
that they observed in mice and humans.
link |
01:03:02.120
And the way they did that
link |
01:03:03.580
was to use the so-called knockout technology,
link |
01:03:06.640
the ability to remove specific genes
link |
01:03:08.700
within specific tissues of the body.
link |
01:03:11.100
And what they found is that UVB light,
link |
01:03:13.620
meaning sunlight exposed skin upregulated,
link |
01:03:18.000
meaning increased the activity of something called P53,
link |
01:03:20.980
which is involved in the maturation of cells
link |
01:03:24.020
and various aspects of cellular function.
link |
01:03:25.980
And the cells they were focused on were the keratinocytes,
link |
01:03:29.840
which you are now familiar with from our earlier discussion
link |
01:03:32.540
about the fact that the epidermis of your skin
link |
01:03:35.100
contains mainly keratinocytes and melanocytes.
link |
01:03:38.900
Sunlight exposure increased P53 activity in the skin
link |
01:03:43.020
and P53 activity was required
link |
01:03:46.220
for the downstream increases in ovarian size,
link |
01:03:49.420
in testicular size, in testosterone increases,
link |
01:03:53.660
in the estrogen increases
link |
01:03:55.540
and the various other changes that they observed
link |
01:03:58.460
at the physiological level
link |
01:03:59.980
when animals or humans were exposed to sunlight.
link |
01:04:03.060
So these data are important
link |
01:04:04.060
because what they mean is that not only is it important
link |
01:04:06.920
that we get sunlight exposure early in the day
link |
01:04:09.820
and throughout the day to our eyes,
link |
01:04:11.660
at least as much as is safely possible,
link |
01:04:14.000
but that we also need to get UVB sunlight exposure
link |
01:04:16.700
onto our skin if we want to activate this P53 pathway
link |
01:04:21.020
in keratinocytes and the testosterone and estrogen increases
link |
01:04:25.660
that are downstream of that P53 pathway.
link |
01:04:28.380
So even though the gene knockout studies were done on mice,
link |
01:04:33.220
they clearly show that if you remove P53 from the skin,
link |
01:04:36.580
that these effects simply do not occur.
link |
01:04:39.220
So in terms of thinking about a protocol
link |
01:04:41.620
to increase testosterone and estrogen,
link |
01:04:43.540
mood and feelings of passion,
link |
01:04:45.860
the idea is that you would want to get
link |
01:04:48.420
this two to three exposures per week minimum
link |
01:04:52.620
of 20 to 30 minutes of sunlight exposure
link |
01:04:55.460
onto as much of your body
link |
01:04:57.440
as you can reasonably expose it to.
link |
01:05:00.380
And when I say reasonably, I mean,
link |
01:05:02.020
of course you have to obey cultural constraints,
link |
01:05:04.360
decency constraints,
link |
01:05:06.260
and of course you have to also obey the fact
link |
01:05:08.660
that sunlight can burn your skin.
link |
01:05:10.620
So many people are probably going to ask
link |
01:05:13.020
what happens if you wear sunscreen?
link |
01:05:15.980
In theory, because sunscreen has UV protection,
link |
01:05:19.700
it would block some of these effects.
link |
01:05:21.860
Now I'm not suggesting that people
link |
01:05:23.060
do away with sunscreen entirely.
link |
01:05:24.540
I do hope to do an episode all about sunscreen
link |
01:05:27.140
in the future because sunscreen
link |
01:05:29.000
is a bit of a controversial topic.
link |
01:05:30.960
Skin cancers are a real thing
link |
01:05:32.700
and many people are especially prone to skin cancer.
link |
01:05:35.620
So you need to take that seriously.
link |
01:05:37.540
Some people are not very prone to skin cancers
link |
01:05:39.800
and can tolerate much more sun exposure.
link |
01:05:42.620
You're probably familiar with the simple fact
link |
01:05:44.460
that if you've gone outside on the beach with friends,
link |
01:05:47.900
some people get burned very easily, others don't.
link |
01:05:49.940
So you really should prioritize the health
link |
01:05:52.440
and the avoidance of sunburn on your skin.
link |
01:05:54.820
However, these data and other data point to the fact
link |
01:05:58.740
that we should all probably be striving
link |
01:06:01.500
to get more sunlight exposure onto our skin
link |
01:06:04.180
during the winter months
link |
01:06:05.660
and still getting sunlight exposure onto our skin
link |
01:06:08.940
in the summer months,
link |
01:06:10.020
provided we can do that without damaging our skin.
link |
01:06:12.740
Another set of very impressive effects of UVB light,
link |
01:06:15.660
whether or not it comes from sunlight
link |
01:06:16.740
or from an artificial source is the effect of UVB light
link |
01:06:20.660
on our tolerance for pain.
link |
01:06:22.400
It turns out that our tolerance for pain
link |
01:06:24.320
varies across the year and that our pain tolerance
link |
01:06:27.900
is increased in longer day conditions.
link |
01:06:32.140
And as we saw with the effects of UVB on hormones
link |
01:06:35.660
and mating, again, this is occurring via UVB exposure
link |
01:06:41.340
to the skin and UVB exposure to the eyes.
link |
01:06:45.120
I want to just describe two studies
link |
01:06:46.700
that really capture the essence of these results.
link |
01:06:49.500
I'm going to discuss these in kind of a top contour fashion.
link |
01:06:52.500
I won't go into it as quite as much depth
link |
01:06:54.220
as I did the last study,
link |
01:06:55.420
but I will provide links to these studies as well.
link |
01:06:58.980
The first study is entitled skin exposure to ultraviolet B
link |
01:07:03.540
rapidly activate systemic neuroendocrine
link |
01:07:05.800
and immunosuppressive responses.
link |
01:07:07.500
And you might hear that and think,
link |
01:07:08.400
oh, immunosuppressive, that's bad.
link |
01:07:09.860
But basically what they observed is that
link |
01:07:12.860
even one exposure to UVB light
link |
01:07:16.200
changed the output of particular hormones
link |
01:07:18.440
and neurochemicals in the body,
link |
01:07:20.060
such as corticotropin hormone and beta endorphins,
link |
01:07:23.620
which are these endogenous opioids.
link |
01:07:25.700
We've all heard of the opioid crisis,
link |
01:07:27.300
which is people getting addicted to opioids
link |
01:07:29.460
that they are taking in drug form, pharmaceuticals.
link |
01:07:32.780
But here I'm referring to endorphins
link |
01:07:35.040
that our body naturally manufactures and releases
link |
01:07:37.520
in order to counter pain
link |
01:07:39.100
and act as a somewhat of a psychological soother also,
link |
01:07:44.080
because of course, physical pain and emotional pain
link |
01:07:46.360
are intimately linked in the brain and body.
link |
01:07:48.700
What they found was that exposure to UVB light
link |
01:07:51.940
increased the release of these beta endorphins.
link |
01:07:55.040
It caused essentially the release
link |
01:07:56.600
of an endogenous pain killer.
link |
01:07:59.380
Now, a second study that came out very recently,
link |
01:08:03.000
just this last week, in fact,
link |
01:08:04.780
published in the journal Neuron,
link |
01:08:06.020
cell press journal, excellent journal,
link |
01:08:08.260
is entitled a visual circuit related
link |
01:08:10.240
to the periaqueductal gray area
link |
01:08:12.380
for the anti-nociceptive effects of bright light treatment.
link |
01:08:15.300
I'll translate a little bit of that for you.
link |
01:08:17.980
The periaqueductal gray is a region of the midbrain
link |
01:08:21.620
that contains a lot of neurons
link |
01:08:24.140
that can release endogenous opioids,
link |
01:08:26.840
things like beta enkephalin,
link |
01:08:28.940
things like enkephalin, things like mu opioid.
link |
01:08:32.220
These are all names of chemicals
link |
01:08:34.320
that your body can manufacture
link |
01:08:35.640
that act as endogenous painkillers
link |
01:08:37.620
and increase your tolerance for pain.
link |
01:08:39.480
They actually make you feel less pain overall
link |
01:08:41.900
by shutting down some of the neurons that perceive pain
link |
01:08:45.360
or by reducing their activity, not to a dangerous level.
link |
01:08:48.660
They're not going to block the pain response
link |
01:08:50.140
so that you burn yourself unnecessarily
link |
01:08:52.620
or harm yourself unnecessarily,
link |
01:08:54.140
but they act as a bit of a painkiller from the inside.
link |
01:08:58.980
If you heard the word anti-nociceptive,
link |
01:09:01.260
nociception is basically the perception
link |
01:09:05.180
or the way in which neurons respond to painful stimuli.
link |
01:09:09.420
So you can think of nociceptive events
link |
01:09:11.700
in your nervous system as painful events.
link |
01:09:14.060
And there I'm using a broad brush.
link |
01:09:15.720
I realized that the experts in pain will say,
link |
01:09:17.620
oh, it's not a really a pain circuit, et cetera, et cetera.
link |
01:09:20.460
But for sake of today's discussion,
link |
01:09:22.860
it's fair to say that nociception is the perception of pain.
link |
01:09:26.500
So if this title is a visual circuit
link |
01:09:29.140
related to the periaqueductal gray,
link |
01:09:31.340
which is this area that releases these endogenous opioids
link |
01:09:34.220
for the anti-nociceptive,
link |
01:09:35.580
the anti-pain effects of bright light treatment.
link |
01:09:40.140
The key finding of this study
link |
01:09:41.540
is that it is light landing on the eyes
link |
01:09:45.220
and captured by the specific cells
link |
01:09:48.080
I was talking about earlier,
link |
01:09:48.980
those intrinsically photosensitive melanopsin ganglion cells
link |
01:09:52.220
is the long name for them,
link |
01:09:53.060
but these particular neurons in your eye
link |
01:09:54.920
and in my eye incidentally,
link |
01:09:57.280
that communicate with particular brain areas.
link |
01:10:00.580
These brain areas have names.
link |
01:10:01.720
If you want to know them for you aficionados
link |
01:10:04.220
or for you ultra curious folks,
link |
01:10:05.740
they have names like the ventrolateral geniculate nucleus
link |
01:10:08.100
and the inter geniculate leaflet.
link |
01:10:09.580
The names don't matter.
link |
01:10:10.780
The point is that light landing on the eyes
link |
01:10:13.380
is captured by these melanopsin cells.
link |
01:10:16.700
They absorb that light,
link |
01:10:18.020
translate that light into electrical signals
link |
01:10:20.220
that are handed off to areas of the brain,
link |
01:10:22.000
such as the ventral geniculate.
link |
01:10:24.460
And then the ventral geniculate communicates
link |
01:10:27.640
with this periaqueductal gray area
link |
01:10:30.280
to evoke the release of these endogenous opioids
link |
01:10:33.940
that soothe you and lead to less perception of pain.
link |
01:10:37.980
This is a really important study
link |
01:10:39.380
because it's long been known that in longer days
link |
01:10:43.340
or in bright light environments,
link |
01:10:44.620
we tolerate emotional and physical pain better.
link |
01:10:48.560
Previous studies had shown
link |
01:10:49.980
that it is light landing on our skin
link |
01:10:53.000
that mediates that effect,
link |
01:10:54.340
but only in part.
link |
01:10:55.460
It couldn't explain the entire effect.
link |
01:10:57.400
This very recent study indicates
link |
01:10:59.380
that it's also light arriving at the eyes.
link |
01:11:02.380
And in this case, again, UVB light,
link |
01:11:04.700
ultraviolet blue light of the sort that comes from sunlight
link |
01:11:08.380
that is triggering these anti pain
link |
01:11:10.980
or pain relieving pathways.
link |
01:11:12.700
So once again, we have two parallel pathways.
link |
01:11:15.180
This is a theme you're going to hear
link |
01:11:16.300
over and over and over again,
link |
01:11:18.220
not just in this episode,
link |
01:11:19.380
but in all episodes of the Huberman Lab Podcast,
link |
01:11:21.460
because this is the way that your brain and body are built.
link |
01:11:24.760
Nature rarely relies on one mechanism
link |
01:11:27.940
in order to create an important phenomenon
link |
01:11:30.180
and pain relief is an important phenomenon.
link |
01:11:32.420
So we now have at least two examples
link |
01:11:34.380
of the potent effects of UVB light exposure
link |
01:11:37.960
to the skin and to the eyes.
link |
01:11:39.580
One involving activation of testosterone
link |
01:11:44.260
and estrogen pathways as it relates to mating
link |
01:11:46.340
and another that relates to reducing
link |
01:11:49.540
the total amount of pain that we experience
link |
01:11:51.620
in response to any painful stimuli.
link |
01:11:54.200
So for those of you that are thinking tools and protocols,
link |
01:11:57.140
if you're somebody who's experiencing chronic pain,
link |
01:12:00.120
provided you can do it safely,
link |
01:12:01.760
try to get some UVB exposure, ideally from sunlight.
link |
01:12:06.180
I think the 20 to 30 minute protocol
link |
01:12:07.920
two or three times per week is an excellent one.
link |
01:12:10.520
It seems like a fairly low dose of UVB light exposure.
link |
01:12:14.300
It's hard to imagine getting much damage to the skin.
link |
01:12:17.340
Of course, if you have very sensitive skin,
link |
01:12:19.740
or if you live in an area of the world
link |
01:12:22.040
that is very, very bright and has intense sunlight
link |
01:12:25.420
particular times of year, you'll want to be cautious.
link |
01:12:27.820
Heed the warnings and considerations about sunscreen
link |
01:12:30.460
that I talked about earlier or about wearing a hat.
link |
01:12:32.860
But the point is very clear.
link |
01:12:34.860
Most of us should be getting more UVB exposure
link |
01:12:38.260
from sunlight.
link |
01:12:40.100
I can already hear the screams within the comments
link |
01:12:42.540
or rather the questions within the comments saying,
link |
01:12:44.620
well, what if I live in a part of the world
link |
01:12:46.220
where I don't get much UVB exposure?
link |
01:12:48.760
And I want to emphasize something that I've also emphasized
link |
01:12:51.340
in the many discussions on this podcast
link |
01:12:53.140
related to sleep and circadian rhythms and alertness,
link |
01:12:55.460
which is even on a cloud covered day,
link |
01:12:59.380
you are going to get far more light energy,
link |
01:13:01.940
photons through cloud cover,
link |
01:13:04.960
than you are going to get from an indoor light source,
link |
01:13:08.140
an artificial light source.
link |
01:13:10.140
I can't emphasize this enough.
link |
01:13:12.700
If you look outside in the morning
link |
01:13:14.060
and you see some sunlight,
link |
01:13:16.100
if you see some sunlight throughout the day,
link |
01:13:17.740
you would do yourself a great favor
link |
01:13:20.380
to try and chase some of that sunlight
link |
01:13:22.120
and get into that sunlight,
link |
01:13:24.100
to expose your eyes and your skin to that sunlight
link |
01:13:27.020
as much as you safely can.
link |
01:13:28.140
And when I say as much as you safely can,
link |
01:13:30.580
never ever look at any light, artificial sunlight
link |
01:13:33.020
or otherwise that's so bright that it's painful to look at.
link |
01:13:35.300
It's fine to get that light arriving
link |
01:13:37.080
on your eyes indirectly.
link |
01:13:38.820
It's fine to wear eyeglasses or contact lenses.
link |
01:13:41.340
In fact, if you think about the biology of the eye
link |
01:13:43.540
and the way that those lenses work,
link |
01:13:45.100
that it will just serve to focus that light
link |
01:13:47.480
on to the very cells that you want those light beams
link |
01:13:50.740
to be delivered to.
link |
01:13:51.900
Whereas sunglasses that are highly reflective
link |
01:13:54.180
or trying to get your sunlight exposure
link |
01:13:56.020
through a windshield of a car or through a window
link |
01:13:59.100
simply won't work.
link |
01:14:00.940
I'm sorry to tell you,
link |
01:14:02.060
but most windows are designed to filter out the UVB light.
link |
01:14:06.220
And if you're somebody who's really keen on blue blockers
link |
01:14:09.020
and you're wearing your blue blockers all day,
link |
01:14:11.000
well, don't wear them outside.
link |
01:14:13.020
And in fact, you're probably doing yourself a disservice
link |
01:14:15.900
by wearing them in the morning and in the daytime.
link |
01:14:18.260
There certainly is a place for blue blockers
link |
01:14:20.100
in the evening and nighttime,
link |
01:14:21.300
if you're having issues with falling and staying asleep.
link |
01:14:24.140
But if you think about it, blue blockers,
link |
01:14:26.020
what they're really doing
link |
01:14:26.860
is blocking those short wavelength UVB wavelengths of light
link |
01:14:30.900
that you so desperately need to arrive at your retina
link |
01:14:33.820
and of course also onto your skin
link |
01:14:35.940
in order to get these powerful biological effects
link |
01:14:38.620
on hormones and on pain reduction.
link |
01:14:42.060
And in terms of skin exposure,
link |
01:14:44.340
these data also might make you think a little bit
link |
01:14:46.540
about whether or not you should wear short sleeves
link |
01:14:48.120
or long sleeves, whether or not you want to wear shorts
link |
01:14:50.380
or a skirt or pants.
link |
01:14:51.780
It's all going to depend on the context of your life
link |
01:14:53.920
and the social and other variables that are important.
link |
01:14:57.020
Of course, I don't know each and every one
link |
01:14:59.580
of your circumstances,
link |
01:15:00.540
so I can't tell you to do X or Y or Z, nor would I,
link |
01:15:05.440
but you might take into consideration
link |
01:15:07.180
that it is the total amount of skin exposure
link |
01:15:10.280
that is going to allow you to capture more or fewer photons,
link |
01:15:14.180
depending on, for instance,
link |
01:15:16.180
if you're completely cloaked in clothing
link |
01:15:17.980
and you're just exposed in the hands, neck and face,
link |
01:15:21.420
such as I am now,
link |
01:15:22.620
or whether or not you're outside in shorts and a t-shirt,
link |
01:15:25.100
you're going to get very, very different patterns
link |
01:15:28.340
of biological signaling activation
link |
01:15:30.800
in those two circumstances.
link |
01:15:32.180
Many of you I'm guessing are wondering
link |
01:15:33.900
whether or not you should seek out UVB exposure
link |
01:15:37.140
throughout the entire year or only in the summer months.
link |
01:15:39.620
And that's sort of going to depend on whether or not
link |
01:15:42.300
you experience depression in the winter months,
link |
01:15:46.480
so-called seasonal affective disorder.
link |
01:15:48.900
Some people have mild,
link |
01:15:49.860
some people have severe forms
link |
01:15:51.160
of seasonal affective disorder.
link |
01:15:52.260
Some people love the fall and winter and the shorter days.
link |
01:15:55.140
They love bundling up, they love the leaves,
link |
01:15:56.880
they love the snow, they love the cold,
link |
01:15:58.180
and they don't experience those psychological lows.
link |
01:16:00.140
So it varies tremendously.
link |
01:16:01.920
And there are genetic differences
link |
01:16:03.820
and birthplace origin differences that relate to all this,
link |
01:16:07.780
but really it has to be considered on a case-by-case basis.
link |
01:16:12.620
I personally believe,
link |
01:16:14.060
and this was reinforced by the director
link |
01:16:17.440
of the Chronobiology Unit
link |
01:16:19.020
at the National Institutes of Mental Health, Samir Hattar,
link |
01:16:21.580
that we would all do well to get more UVB exposure
link |
01:16:25.080
from sunlight throughout the entire year,
link |
01:16:27.740
provided we aren't burning our skin
link |
01:16:29.220
or damaging our eyes in some way.
link |
01:16:31.380
In addition to that, during the winter months,
link |
01:16:34.780
if you do experience some drop in energy
link |
01:16:38.020
or increase in depression or psychological lows,
link |
01:16:42.980
it can be very beneficial to access a sad lamp,
link |
01:16:47.460
or if you don't want to buy a sad lamp,
link |
01:16:49.300
because oftentimes they can be very expensive,
link |
01:16:51.220
you might do well to simply get a LED lighting panel.
link |
01:16:55.080
I've described one before,
link |
01:16:56.460
and I want to emphasize that I have no affiliation
link |
01:16:59.340
whatsoever to these commercial sources,
link |
01:17:01.820
but I've described one before and I'll describe it again,
link |
01:17:03.680
and we can provide a link to a couple of examples of these
link |
01:17:06.140
in the show note captions, excuse me.
link |
01:17:09.420
This is a 932,000 lux L-U-X light source
link |
01:17:14.800
that's designed for drawing.
link |
01:17:16.340
It's literally a drawing box.
link |
01:17:17.700
It's a thin panel.
link |
01:17:18.540
It's about the size of a laptop.
link |
01:17:20.460
Very inexpensive compared to the typical sad lamp.
link |
01:17:22.700
I actually have one that I position on my desk all day long.
link |
01:17:25.500
I also happen to have skylights above my desk.
link |
01:17:27.740
I'm fairly sensitive to the effects of light.
link |
01:17:29.860
So in longer days,
link |
01:17:30.700
I feel much better than I do in shorter days.
link |
01:17:32.180
I've never suffered from full-blown
link |
01:17:33.740
seasonal affective disorder,
link |
01:17:35.140
but I keep that light source on throughout the day,
link |
01:17:38.680
throughout the year.
link |
01:17:39.660
But I also make it a point to get outside
link |
01:17:41.500
and get sunlight early in the morning
link |
01:17:42.780
and several times throughout the day.
link |
01:17:44.540
And if it's particularly overcast outside,
link |
01:17:47.220
or there just doesn't seem to be a lot of sunlight
link |
01:17:49.640
coming through those clouds,
link |
01:17:50.920
I will try to look at that light source
link |
01:17:53.500
a little bit more each day
link |
01:17:54.840
in order to trigger these mechanisms.
link |
01:17:57.380
Now, some people may desire to get UVB exposure
link |
01:18:00.140
to their skin,
link |
01:18:01.140
and they want to do that through sources
link |
01:18:02.740
other than sunlight.
link |
01:18:03.980
And there, it's a little bit more complicated.
link |
01:18:06.100
There are, of course, canning salons,
link |
01:18:08.280
which basically are beds of UVB light.
link |
01:18:10.660
That's really all they are.
link |
01:18:12.140
I've never been to one.
link |
01:18:13.100
I know people do frequent them
link |
01:18:14.580
in certain parts of the world.
link |
01:18:17.020
There, of course, people are covering their eyes.
link |
01:18:19.260
They are only getting UVB exposure to their skin typically
link |
01:18:21.740
because the UVB exposure,
link |
01:18:23.780
or intensities rather, tends to be very, very high.
link |
01:18:26.500
And so you can actually damage your eyes
link |
01:18:27.880
if you're looking at a very, very bright
link |
01:18:29.900
artificial UVB source up close.
link |
01:18:32.500
So you really have to explore these options for yourself.
link |
01:18:35.140
Sunlight, of course, being the original
link |
01:18:37.120
and still the best way to get UVB exposure.
link |
01:18:40.740
So without knowing your particular circumstances,
link |
01:18:43.320
finances, genetics, or place of origin, et cetera,
link |
01:18:47.340
I can't know whether or not
link |
01:18:48.540
you need to use artificial sources.
link |
01:18:49.860
You're going to have to gauge that.
link |
01:18:51.620
Meanwhile, getting outside,
link |
01:18:54.420
looking at and getting some exposure of UVB onto your skin
link |
01:18:59.300
is going to be beneficial
link |
01:19:00.500
for the vast majority of people out there.
link |
01:19:03.340
And in fact, it's even going to be beneficial
link |
01:19:05.460
for people that are blind.
link |
01:19:08.100
People that are blind provided they still have eyes
link |
01:19:10.720
often maintain these melanopsin cells.
link |
01:19:14.180
So even if you're low vision or no vision,
link |
01:19:16.220
getting UVB exposure to your eyes can be very beneficial
link |
01:19:19.480
for sake of mood, hormone pathways,
link |
01:19:22.220
pain reduction, and so forth.
link |
01:19:24.380
A cautionary note, people who have retinitis pigmentosa,
link |
01:19:28.820
macular degeneration, or glaucoma,
link |
01:19:31.380
as well as people who are especially prone to skin cancers
link |
01:19:34.740
should definitely consult with your ophthalmologist
link |
01:19:37.660
and dermatologist before you start increasing
link |
01:19:40.140
the total amount of UVB exposure that you're getting
link |
01:19:42.640
from any source, sunlight or otherwise.
link |
01:19:44.980
There are additional very interesting
link |
01:19:46.940
and powerful effects of UVB light,
link |
01:19:50.240
in particular on immune function.
link |
01:19:52.500
All the organs of our body are inside our skin.
link |
01:19:57.340
And so information about external conditions,
link |
01:20:00.500
meaning the environment that we're in,
link |
01:20:02.260
need to be communicated to the various organs of our body.
link |
01:20:06.400
Some of them have more direct access
link |
01:20:08.700
to what's going on outside.
link |
01:20:10.620
So for instance, the cells in your brain
link |
01:20:13.820
that reside right over the roof of your mouth,
link |
01:20:15.640
your hypothalamus, they control hormone output
link |
01:20:17.780
and they control the biological functions
link |
01:20:20.600
that we call circadian functions,
link |
01:20:21.980
the ones that change every 24 hours.
link |
01:20:24.440
Well, those are just one or two connections,
link |
01:20:27.060
meaning synapses away from those cells in your eye
link |
01:20:29.780
that perceive UVB light, excuse me.
link |
01:20:33.420
Other organs of your body, such as your spleen,
link |
01:20:35.980
which is involved in the creation of molecules and cells
link |
01:20:39.340
that combat infection.
link |
01:20:41.220
Well, those are a long ways away
link |
01:20:42.940
from those cells in your eye.
link |
01:20:43.900
And in fact, they're a long ways away from your skin.
link |
01:20:47.240
There are beautiful studies showing you that
link |
01:20:49.980
if we get more UVB exposure from sunlight
link |
01:20:53.220
or from appropriate artificial sources,
link |
01:20:57.220
that spleen and immune function are enhanced.
link |
01:21:00.820
And there's a very logical, well-established circuit
link |
01:21:04.260
as to how that happens.
link |
01:21:06.020
Your brain actually connects to your spleen.
link |
01:21:09.320
Now it's not the case that you can simply think,
link |
01:21:12.100
okay, spleen, turn on, release killer cells,
link |
01:21:14.680
go out and combat infection.
link |
01:21:16.380
However, UVB light arriving on the eyes
link |
01:21:20.700
is known to trigger activation of the neurons
link |
01:21:23.500
within the so-called sympathetic nervous system.
link |
01:21:26.020
These neurons are part of the larger thing
link |
01:21:28.360
that we call the autonomic nervous system,
link |
01:21:30.100
meaning it's below or not accessible by conscious control.
link |
01:21:34.180
It's the thing that controls your heartbeat,
link |
01:21:35.540
controls your breathing, and that also activates
link |
01:21:38.020
or flips on the switch of your immune system.
link |
01:21:41.000
When we get a lot of UVB light in our eyes,
link |
01:21:43.540
or I should say sufficient UVB light in our eyes,
link |
01:21:46.860
a particular channel, a particular set of connections
link |
01:21:50.120
within the sympathetic nervous system is activated
link |
01:21:53.220
and our spleen deploys immune cells and molecules
link |
01:21:57.340
that scavenge for and combat infection.
link |
01:22:00.300
So if you've noticed that you get fewer colds and flus
link |
01:22:03.860
and other forms of illness in the summer months,
link |
01:22:06.780
part of that could be because of the increase
link |
01:22:09.860
in temperature in your environment,
link |
01:22:11.120
because typically longer days are associated
link |
01:22:13.280
with more warmth in your environment
link |
01:22:15.620
as opposed to winter days, which are short
link |
01:22:17.460
when it tends to be colder out.
link |
01:22:19.540
Well, that's true, but it's also the case
link |
01:22:23.960
the people around you have fewer colds and flus
link |
01:22:26.440
and that you will get infected with fewer colds and flus
link |
01:22:29.620
and other infections because if those infections,
link |
01:22:34.480
whether or not they're bacterial or viral,
link |
01:22:36.900
arrive in your body, right, if you inhale them
link |
01:22:39.380
or they get into your mouth or on your skin,
link |
01:22:41.980
your spleen meets those infections with a greater output.
link |
01:22:45.500
In other words, the soldiers of your immune system,
link |
01:22:47.540
the chemicals and cell types of your immune system
link |
01:22:50.220
that combat infection are in a more ready deployed stance,
link |
01:22:55.220
if you will.
link |
01:22:56.460
If you want to know more about the immune system
link |
01:22:58.140
and immune function, I did an entire episode
link |
01:23:00.000
about the immune system and the brain in a,
link |
01:23:02.660
you can find that at hubermanlab.com.
link |
01:23:04.820
We talk about cytokines, we talk about killer cells,
link |
01:23:06.820
B cells, T cells, et cetera, a lot of detail there.
link |
01:23:09.500
So we often think about the summer months
link |
01:23:11.720
and the spring months as fewer infections floating around,
link |
01:23:15.300
but in fact, there aren't fewer infections floating around.
link |
01:23:18.840
We are simply better at combating those infections
link |
01:23:21.460
and therefore there's less infection floating around.
link |
01:23:25.060
So we are still confronted with a lot of infections.
link |
01:23:27.620
We're just able to combat them better.
link |
01:23:29.920
What does this mean in terms of a tool?
link |
01:23:31.360
What it means is that during the winter months,
link |
01:23:33.840
we should be especially conscious of accessing UVB light
link |
01:23:38.560
to enhance our spleen function,
link |
01:23:41.320
to make sure that our sympathetic nervous system
link |
01:23:43.700
is activated to a sufficient level
link |
01:23:46.180
to keep our immune system deploying
link |
01:23:48.380
all those killer T cells and B cells and cytokines
link |
01:23:51.100
so that when we encounter the infections,
link |
01:23:52.860
as we inevitably will, right,
link |
01:23:54.740
we're constantly being bombarded with potential infections
link |
01:23:57.740
that we can combat those infections well.
link |
01:24:00.220
And as just a brief aside,
link |
01:24:01.980
but I should mention a brief aside
link |
01:24:03.620
that's related to tens of thousands of quality studies.
link |
01:24:07.240
It is well-known that wound healing is faster
link |
01:24:10.540
when we are getting sufficient UVB exposure.
link |
01:24:13.900
Typically that's associated with the longer days
link |
01:24:16.340
of spring and summer.
link |
01:24:17.700
It is known that turnover of hair cells,
link |
01:24:21.400
the very cells that give rise to hair cells
link |
01:24:23.580
are called stem cells.
link |
01:24:24.420
They live in little so-called niches in our skin
link |
01:24:27.040
with these hair stem cells
link |
01:24:28.540
and your hair grows faster in longer days.
link |
01:24:31.000
That too is triggered by UVB exposure,
link |
01:24:34.460
not just to the skin, but to the eyes.
link |
01:24:37.520
That's right.
link |
01:24:38.460
There was a study published in the Proceedings
link |
01:24:40.700
of the National Academy of Sciences a couple of years ago
link |
01:24:44.100
that showed that the exposure of those melanopsin ganglion
link |
01:24:47.460
cells in your eyes is absolutely critical
link |
01:24:49.940
for triggering the turnover of stem cells
link |
01:24:53.340
in both the skin and hair and also it turns out in nails.
link |
01:24:58.640
So if you've noticed that your skin, your hair
link |
01:25:01.240
and your nails look better and turn over more,
link |
01:25:03.580
meaning grow faster in longer days,
link |
01:25:06.580
that is not a coincidence.
link |
01:25:08.060
That is not just your perception.
link |
01:25:09.780
In fact, hair grows more, skin turns over more,
link |
01:25:13.500
meaning it's going to look more youthful.
link |
01:25:14.880
You're going to essentially remove older skin cells
link |
01:25:18.220
and replace them with new cells.
link |
01:25:20.320
And all the renewing cells and tissues of our body
link |
01:25:23.660
are going to proliferate,
link |
01:25:24.780
are going to recreate themselves more
link |
01:25:27.400
when we're getting sufficient UVB light to our eyes
link |
01:25:30.240
and also to our skin.
link |
01:25:31.980
And so while some of you may think of light therapies
link |
01:25:36.180
such as red light therapies or UVB therapies
link |
01:25:38.560
as kind of new agey or just biohacking,
link |
01:25:41.020
again, a phrase I don't particularly like this notion
link |
01:25:43.380
of biohacking because it implies using one thing
link |
01:25:46.620
for a purpose that it was never intended to have.
link |
01:25:50.660
Well, it turns out that UVB exposure and red light
link |
01:25:54.260
as we'll soon see is a very potent form
link |
01:25:57.500
of increasing things like wound healing and skin health
link |
01:26:00.140
for very logical mechanistically backed reasons.
link |
01:26:04.660
So while I can't account for everything
link |
01:26:07.460
that's being promoted out there in terms of this light source
link |
01:26:09.860
will help your skin look more youthful
link |
01:26:11.280
or will help heal your scars,
link |
01:26:14.340
the mechanistic basis for light having those effects
link |
01:26:17.560
makes total sense.
link |
01:26:19.160
But what you should consider, however,
link |
01:26:21.240
is that if the particular light therapy
link |
01:26:23.700
that you're considering involves very local application
link |
01:26:27.580
rather than illuminating broad swaths of skin,
link |
01:26:32.560
and if it has no involvement with the eyes,
link |
01:26:35.000
meaning there's no delivery of UVB or red light
link |
01:26:38.860
or the other light therapy to the eyes,
link |
01:26:41.420
it's probably not going to be as potent a treatment
link |
01:26:44.940
as would a more systemic activation
link |
01:26:48.140
of larger areas of skin and the eyes.
link |
01:26:51.100
Now, again, a cautionary note,
link |
01:26:52.820
I don't want people taking technologies
link |
01:26:54.480
that were designed for local application
link |
01:26:56.500
and beaming those into the eyes.
link |
01:26:58.260
That could be very, very bad and damaging to your retinal
link |
01:27:00.800
and other tissues.
link |
01:27:02.540
Certainly wouldn't want you taking bright light
link |
01:27:05.260
of very high intensity of any kind
link |
01:27:07.440
and getting cavalier about that.
link |
01:27:09.580
Typically the local illumination of say a wound
link |
01:27:12.940
or a particular patch of acne
link |
01:27:14.380
or some other form of skin treatment
link |
01:27:17.020
involves very high intensity light.
link |
01:27:18.820
And if the intensity is too high,
link |
01:27:20.460
you can actually damage that skin.
link |
01:27:22.380
And so as we'll talk about in a few moments,
link |
01:27:24.880
most of those therapies for modifying skin
link |
01:27:27.380
involve actually burning off
link |
01:27:29.460
a small, very thin layer at the top of the epidermis
link |
01:27:33.460
in efforts to trigger the renewal
link |
01:27:35.620
or the activation of stem cells
link |
01:27:37.020
that will replenish that with new cells.
link |
01:27:39.860
So there's a fine line to be had between light therapies
link |
01:27:44.340
that are very localized and intense,
link |
01:27:45.980
which are designed to damage skin
link |
01:27:48.140
and cause reactivation of new stem cells,
link |
01:27:52.500
whether or not it's hair cells or skin cells, et cetera,
link |
01:27:54.740
versus systemic activation
link |
01:27:56.480
across broad swaths of skin in the eyes.
link |
01:27:58.340
You really have to consider this on a case-by-case basis,
link |
01:28:00.880
but at least for now,
link |
01:28:02.720
just consider that increases in hormones,
link |
01:28:05.920
reduction in pain by way of increases in enkephalin
link |
01:28:10.620
and other endogenous opioids,
link |
01:28:12.700
improving immune status by activating the spleen
link |
01:28:15.700
and so on and so on,
link |
01:28:17.380
really are all the downstream consequence
link |
01:28:19.540
of illuminating large swaths of skin
link |
01:28:21.900
and making sure that those neurons within the eye
link |
01:28:23.940
get their adequate UVB exposure
link |
01:28:26.240
or other light wavelength exposure.
link |
01:28:28.220
Not simply beaming a particular wavelength of light
link |
01:28:31.340
at a particular location on the body
link |
01:28:32.900
and hoping that that particular illumination
link |
01:28:35.360
at a particular location on the body
link |
01:28:37.100
is going to somehow change the biology at that location.
link |
01:28:40.460
Our biology just really doesn't work that way.
link |
01:28:43.300
It's possible, but in general,
link |
01:28:45.240
systemic effects through broad scale illumination
link |
01:28:48.420
and illumination to the eye combined with local treatments
link |
01:28:51.580
are very likely to be the ones that have the most success.
link |
01:28:54.340
Now I'd like to shift our attention
link |
01:28:55.680
to the effects of light on mood more specifically.
link |
01:28:57.980
We talked about this
link |
01:28:58.820
in terms of seasonal affective disorder,
link |
01:29:00.680
but many of us don't suffer from seasonal affective disorder.
link |
01:29:03.380
So I'd like to drill a little deeper
link |
01:29:04.820
into how light impacts mood.
link |
01:29:07.640
And here, I want to again paraphrase the statements
link |
01:29:11.760
of Dr. Samra Hattar
link |
01:29:14.460
at the National Institutes of Mental Health.
link |
01:29:16.780
I should mention the director of the Chronobiology Unit
link |
01:29:18.940
at the National Institutes of Mental Health
link |
01:29:20.660
and perhaps one of the top one to two to three world experts
link |
01:29:25.660
in how light can impact mood, appetite,
link |
01:29:28.180
circadian rhythms, and so forth.
link |
01:29:31.660
Samra stated on the podcast,
link |
01:29:33.020
and he said in various other venues as well,
link |
01:29:36.220
that getting as much UVB light in our eyes and on our skin
link |
01:29:40.560
in the early day and throughout the day
link |
01:29:42.380
as is safely possible is going to be beneficial for mood.
link |
01:29:45.500
There's also another time of day,
link |
01:29:48.100
or rather I should say a time of night
link |
01:29:49.780
in which UVB can be leveraged in order to improve mood.
link |
01:29:54.400
But it's actually the inverse
link |
01:29:55.900
of everything we've been talking about up until now.
link |
01:29:59.380
We have a particular neural circuit
link |
01:30:01.740
that originates with those melanopsin cells in our eye
link |
01:30:04.900
that bypass all the areas of the brain
link |
01:30:07.220
associated with circadian clocks.
link |
01:30:09.140
So everything related to sleep and wakefulness
link |
01:30:11.540
that's specifically dedicated to the pathways
link |
01:30:14.760
involving the release of molecules like dopamine,
link |
01:30:16.980
the neuromodulator that's associated with motivation,
link |
01:30:19.900
with feeling good,
link |
01:30:22.120
with feeling like there's possibility in the world
link |
01:30:24.540
and so on and so forth.
link |
01:30:25.760
And other molecules as well,
link |
01:30:26.920
including serotonin and some of those endogenous opioids
link |
01:30:29.700
that we talked about before.
link |
01:30:32.240
That particular pathway involves a brain structure
link |
01:30:34.340
called the perihabenular nucleus.
link |
01:30:36.700
The perihabenular nucleus gets input
link |
01:30:39.700
from the cells in the eye that respond to UVB light
link |
01:30:43.420
and frankly to bright light of other wavelengths as well.
link |
01:30:46.740
Because as you recall, if a light is bright enough,
link |
01:30:49.440
even if it's not UV or blue light,
link |
01:30:51.340
it can activate those cells in the eye.
link |
01:30:53.820
Those cells in the eye communicate
link |
01:30:55.340
to the perihabenular nucleus.
link |
01:30:57.380
And as it turns out, if this pathway is activated
link |
01:31:01.060
at the wrong time of each 24 hour cycle,
link |
01:31:04.740
mood gets worse.
link |
01:31:07.060
Dopamine output gets worse.
link |
01:31:09.740
Molecules that are there specifically to make us feel good
link |
01:31:13.180
actually are reduced in their output.
link |
01:31:16.980
So while UVB exposure in the morning
link |
01:31:19.460
and throughout the day is going to be very important
link |
01:31:22.820
for elevating and maintaining elevated mood,
link |
01:31:26.500
avoiding UVB light at night is actually a way
link |
01:31:30.820
in which we can prevent activation
link |
01:31:33.660
of this eye to perihabenular pathway
link |
01:31:36.900
that can actually turn on depression.
link |
01:31:38.900
To be very direct and succinct about this,
link |
01:31:41.640
avoid exposure to UVB light from artificial sources
link |
01:31:45.820
between the hours of 10 PM and 4 AM.
link |
01:31:48.460
And if you're somebody who suffers from low mood
link |
01:31:51.780
and overall has a kind of mild depression
link |
01:31:54.660
or even severe depression, of course,
link |
01:31:56.460
please see a psychiatrist, see a trained psychologist,
link |
01:31:59.340
get that treated.
link |
01:32:00.940
But you would do especially well to avoid UVB exposure
link |
01:32:06.460
from artificial sources, not just from 10 PM to 4 AM,
link |
01:32:09.560
but really be careful about getting too much exposure
link |
01:32:12.020
to UVB even in the late evening.
link |
01:32:14.380
So 8 PM perhaps to 4 AM.
link |
01:32:17.180
I can't emphasize this enough that if you view UVB light,
link |
01:32:21.740
you activate those neurons in your eye very potently.
link |
01:32:24.540
And if those cells communicate
link |
01:32:26.780
to the perihabenular nucleus, which they do,
link |
01:32:28.660
you will truncate or reduce the amount of dopamine
link |
01:32:31.620
that you release.
link |
01:32:33.360
So if you want to keep your mood elevated,
link |
01:32:36.120
get a lot of light, UVB light throughout the day,
link |
01:32:38.880
and at night, really be cautious about getting UVB exposure
link |
01:32:42.840
from artificial sources.
link |
01:32:44.120
Now let's say you're somebody who has no issues with mood.
link |
01:32:46.920
You're just the happiest person all year long,
link |
01:32:49.500
or maybe you just have subtle variations in your mood.
link |
01:32:52.520
You feel great about that.
link |
01:32:54.980
Turns out that you still want to be very careful
link |
01:32:57.900
about light exposure between the hours of 10 PM or so
link |
01:33:02.040
and 4 AM, in fact, even during sleep.
link |
01:33:04.980
There's a recent study that just came out
link |
01:33:06.780
in the proceedings of the National Academy of Sciences,
link |
01:33:09.720
and it's entitled light exposure during sleep
link |
01:33:12.700
in pairs cardiometabolic function.
link |
01:33:14.980
This is a very interesting study
link |
01:33:17.660
where they took human subjects, young adults,
link |
01:33:20.180
and having them sleep in rooms
link |
01:33:22.620
that had different lighting conditions,
link |
01:33:24.000
either dim light or slightly bright light.
link |
01:33:27.880
Now, many people can't fall asleep in brightly lit rooms.
link |
01:33:30.420
So they acknowledged this.
link |
01:33:32.220
These were not very brightly lit rooms.
link |
01:33:33.940
These were rooms that had just a little bit
link |
01:33:36.220
of overhead room lighting, a hundred lux,
link |
01:33:39.220
which is not very bright at all.
link |
01:33:41.260
Or they had them sleep in a room that had very dim light,
link |
01:33:43.880
which is less than three lux.
link |
01:33:45.780
If you want to get a sense of how bright three lux is
link |
01:33:49.140
versus a hundred lux,
link |
01:33:50.740
I would encourage you to download the free app Light Meter.
link |
01:33:53.860
I have no relationship to the app.
link |
01:33:55.380
It's a pretty cool app.
link |
01:33:56.220
However, I've used it for a long time
link |
01:33:57.540
where you can basically point your phone
link |
01:34:00.040
at a particular light source, sun or otherwise,
link |
01:34:02.320
and you just press the button
link |
01:34:03.220
and it'll give you an approximate readout of lux,
link |
01:34:05.580
which is the light intensity that the phone happens
link |
01:34:08.760
to be staring out at at that location.
link |
01:34:10.900
It's not exact, but it's a pretty good
link |
01:34:14.060
back of the envelope measure of light intensity.
link |
01:34:17.420
So these subjects were either sleeping in a very dim room,
link |
01:34:20.380
three lux is very, very dim,
link |
01:34:22.140
or a somewhat dim room, a hundred lux.
link |
01:34:25.900
In this study, they measured things like melatonin levels.
link |
01:34:29.180
They looked at heart rate.
link |
01:34:30.920
They looked at measures of insulin and glucose management.
link |
01:34:35.900
Now, in previous episodes,
link |
01:34:38.020
I've talked about how glucose blood sugar is regulated
link |
01:34:41.340
by insulin because you don't want your glucose levels
link |
01:34:43.920
to be too high, hyperglycemia or too low.
link |
01:34:46.580
Hypoglycemia and the hormone insulin is involved
link |
01:34:49.140
in sequestering and shuttling glucose in the bloodstream.
link |
01:34:52.480
Basically how well you manage glucose in the bloodstream
link |
01:34:55.380
can be indirectly measured by your insulin levels.
link |
01:34:58.460
And it's well-known that sleep deprivation
link |
01:35:01.460
can disrupt glucose regulation by insulin.
link |
01:35:06.460
However, in this study,
link |
01:35:08.260
subjects were sleeping the whole night through.
link |
01:35:10.120
It just so happens that some of the subjects
link |
01:35:11.720
were sleeping in this very dimly lit room, three lux,
link |
01:35:14.120
and other subjects were sleeping
link |
01:35:15.360
in a somewhat dimly lit room, a hundred lux.
link |
01:35:19.720
What's incredible about this study is that both rooms
link |
01:35:23.220
were sufficiently dim that melatonin levels
link |
01:35:25.280
were not altered in either case.
link |
01:35:27.460
This is really key.
link |
01:35:28.300
It's not as if one group experienced a lot of bright light
link |
01:35:31.460
through their eyelids and others did not.
link |
01:35:33.600
Melatonin levels were not disrupted.
link |
01:35:35.520
And given how potently light can inhibit melatonin,
link |
01:35:38.240
this speaks to the fact that this very dim condition
link |
01:35:41.440
of three lux and the somewhat dim condition of a hundred lux
link |
01:35:44.840
was not actually perceived by the subjects,
link |
01:35:48.040
nor was it disrupting these hormone pathways.
link |
01:35:50.720
They also looked at glucose responses.
link |
01:35:53.240
They had people essentially take a fasting glucose test
link |
01:35:56.440
in different conditions.
link |
01:35:57.340
I won't go into all the details,
link |
01:35:58.920
but here's what they found.
link |
01:36:00.380
In healthy adults,
link |
01:36:01.920
even just one night of sleeping in a moderately lit
link |
01:36:06.400
environment, this hundred lux environment caused changes,
link |
01:36:10.880
increases in nighttime heart rate,
link |
01:36:12.600
which means that the sympathetic nervous system
link |
01:36:14.400
was overly active as compared to people that slept
link |
01:36:17.080
in a completely dark or in a very, very dimly lit room.
link |
01:36:20.860
Decreases in heart rate variability.
link |
01:36:23.460
And here I should point out that heart rate variability
link |
01:36:25.720
or HRV is a good thing.
link |
01:36:27.420
We want heart rate variability.
link |
01:36:28.660
So they saw increases in heart rate,
link |
01:36:30.360
decreases in heart rate variability and increases
link |
01:36:33.680
in next morning insulin resistance,
link |
01:36:36.320
which is an indication that glucose management is suffering.
link |
01:36:40.740
So this is powerful.
link |
01:36:43.280
The results of this study essentially indicate that even
link |
01:36:46.400
just one night of sleeping the whole night through
link |
01:36:49.120
in a dimly lit environment is disrupting the way
link |
01:36:52.460
that our autonomic nervous system is functioning,
link |
01:36:54.920
altering so-called autonomic tone,
link |
01:36:57.520
making us less relaxed is probably the best way
link |
01:37:00.260
to describe it.
link |
01:37:01.480
Even though we are asleep,
link |
01:37:03.080
disrupting the way that our cardiometabolic function
link |
01:37:06.820
operates such that we have lower heart rate variability
link |
01:37:09.820
and increased insulin resistance.
link |
01:37:12.880
This is not a good thing for any of us to experience.
link |
01:37:15.640
So while we've mainly been talking about the positive
link |
01:37:18.240
effects of UVB light and other forms of light.
link |
01:37:21.180
Now we have two examples,
link |
01:37:22.920
one from the work of Hatar and colleagues showing
link |
01:37:25.600
that UVB exposure via the perihabenula can diminish
link |
01:37:29.480
the output of dopamine and other molecules that make
link |
01:37:32.480
us feel good if that UVB exposure is in the middle
link |
01:37:34.840
of the night or late evening.
link |
01:37:36.760
And now we have yet another study performed in this case
link |
01:37:39.800
in humans indicating that even if we fall asleep
link |
01:37:43.160
and sleep the whole night through,
link |
01:37:44.560
if the room that we're sleeping in has too many locks,
link |
01:37:47.520
too much light energy,
link |
01:37:48.820
that light energy is no doubt going through the eyelids,
link |
01:37:51.820
which it can activating the particular cells in the eye
link |
01:37:55.600
that trigger an increase in sympathetic nervous system
link |
01:37:59.160
activation and disrupting our metabolism.
link |
01:38:02.340
And this study rests on a number of other recent studies
link |
01:38:05.640
published in Cell,
link |
01:38:06.680
which is a superb journal and other journals showing that
link |
01:38:09.400
during the course of a healthy deep night's sleep,
link |
01:38:13.040
our body actually transitions through various forms
link |
01:38:15.400
of metabolic function.
link |
01:38:16.760
We actually experience ketosis like states.
link |
01:38:20.400
We experience gluconeogenesis.
link |
01:38:22.840
We experience different forms of metabolism associated
link |
01:38:25.640
with different stages of sleep.
link |
01:38:27.200
Not something that we're going into in depth in this podcast,
link |
01:38:29.760
we will in a future podcast.
link |
01:38:31.760
What this study shows is that light exposure even in sleep
link |
01:38:35.920
is disrupting our autonomic, in this case,
link |
01:38:38.480
the sympathetic arm of the autonomic nervous system
link |
01:38:40.920
in ways that are disrupting metabolism probably in sleep,
link |
01:38:44.240
but certainly outside of sleep.
link |
01:38:46.240
So that we wake up and have our first meal of the day,
link |
01:38:48.400
or even if you're intermittent fasting,
link |
01:38:49.680
you eat that first meal of the day.
link |
01:38:51.280
If your sleep is taking place in an environment
link |
01:38:54.280
that's overly illuminated,
link |
01:38:56.560
well, that's disrupting your cardiac function
link |
01:38:59.260
and your metabolism.
link |
01:39:00.680
I've been talking a lot about UVB light,
link |
01:39:02.440
which is short wavelength light.
link |
01:39:03.940
So UV light, blue light, maybe even some blue green light,
link |
01:39:07.140
that's going to be short wavelength light.
link |
01:39:08.640
Now I'd like to shift our attention to the other end
link |
01:39:10.440
of the spectrum, meaning the light spectrum,
link |
01:39:12.320
to talk about red light and infrared light,
link |
01:39:14.320
which is long wavelength light.
link |
01:39:16.220
Many so-called low level light therapies,
link |
01:39:19.920
the acronym is LLLT, low level light therapies
link |
01:39:23.960
involve the use of red light and infrared light.
link |
01:39:27.560
Sometimes low level light therapies involve the use of UVB,
link |
01:39:31.080
but more often than not these days,
link |
01:39:32.720
when we hear LLLT, low level light therapy,
link |
01:39:35.720
it's referring to red light
link |
01:39:37.480
and near infrared light therapies.
link |
01:39:41.920
Low level light therapies have been shown to be effective
link |
01:39:44.560
for a huge number of biological phenomenon
link |
01:39:47.600
and medical treatments.
link |
01:39:49.380
I can't summarize all of those now.
link |
01:39:50.900
It would take me many, many hours.
link |
01:39:52.720
It would be an effective episode for curing insomnia,
link |
01:39:55.360
but it wouldn't inform you properly
link |
01:39:57.320
about the use of light for your health.
link |
01:39:59.760
Rather, I'd like to just emphasize
link |
01:40:01.340
some of the top contour of those studies
link |
01:40:03.520
and point out that for instance,
link |
01:40:05.980
low level light therapy with infrared light
link |
01:40:08.120
has been shown to be effective for the treatment of acne
link |
01:40:10.920
and other sorts of skin lesions.
link |
01:40:13.000
Been some really nice studies actually,
link |
01:40:15.160
where they use subjects as their own internal control.
link |
01:40:17.960
So people who believe it or not
link |
01:40:19.120
agreed to have half of their face illuminated
link |
01:40:21.620
with red light or near infrared light
link |
01:40:23.880
and the other half of their face serve as a control
link |
01:40:26.000
and to do that for several weeks at a time.
link |
01:40:28.300
And you can see pretty impressive reductions
link |
01:40:31.060
in skin lesions, reductions in scars from acne
link |
01:40:35.200
and reduction in acne lesions themselves,
link |
01:40:38.180
meaning the accumulation of new acne cysts
link |
01:40:40.980
with low level light therapy
link |
01:40:42.540
using red light and infrared light.
link |
01:40:44.560
Sometimes however, there is a resistance of that acne
link |
01:40:49.240
to the low level light therapy
link |
01:40:50.580
such that people will get an initial improvement
link |
01:40:52.760
and then it will go away despite continuing the treatment.
link |
01:40:55.660
So you're probably asking, or at least you should be asking,
link |
01:40:58.200
how is it that shining red light on our skin
link |
01:41:00.740
can impact things like acne and wound healing, et cetera?
link |
01:41:04.600
Well, to understand that we have to think back
link |
01:41:06.720
to the beginning of the episode
link |
01:41:08.340
where I described how long wavelength lights
link |
01:41:10.720
such as red light and near infrared light,
link |
01:41:13.080
which is even longer than red light,
link |
01:41:15.120
can pass through certain surfaces, including our skin.
link |
01:41:19.140
So our skin has an epidermis, which is on the outside
link |
01:41:21.780
and the dermis, which is in the deeper layers.
link |
01:41:24.400
Red light and infrared light
link |
01:41:25.960
can pass down into the deeper layers of our skin
link |
01:41:29.020
where it can change the metabolic function
link |
01:41:31.740
of particular cells.
link |
01:41:32.860
So let's just take acne as an example.
link |
01:41:35.600
Within the dermis, the deep layers of our skin,
link |
01:41:37.900
we have what are called sebaceous glands
link |
01:41:39.700
that actually make the oil that is present in our skin.
link |
01:41:43.700
Those sebaceous glands are often nearby hair follicles.
link |
01:41:46.700
So if you've ever had an infected hair follicle,
link |
01:41:50.100
that's not a coincidence
link |
01:41:51.480
that hair follicles tend to get infected.
link |
01:41:53.100
Part of it is because there's actually a portal down
link |
01:41:56.220
and around the hair follicle,
link |
01:41:57.380
but the sebaceous gland is where the oil is created
link |
01:42:00.500
that is going to give rise to, for instance, acne lesions.
link |
01:42:03.740
Also in the dermis and the deep layers of the skin
link |
01:42:06.900
are the melanocytes.
link |
01:42:07.900
They're not just in the epidermis,
link |
01:42:08.900
they're also in the deeper layers of the skin.
link |
01:42:11.780
And you have the stem cells that give rise
link |
01:42:14.740
to additional skin cells.
link |
01:42:16.800
If the top layers of the epidermis are damaged,
link |
01:42:19.180
those stem cells can become activated.
link |
01:42:21.260
And you also have the stem cells
link |
01:42:23.520
that give rise to hair follicles.
link |
01:42:25.340
So by shining red light or near infrared light
link |
01:42:29.620
on a localized patch of skin,
link |
01:42:31.580
provided that red light is not of such high intensity
link |
01:42:34.940
that it burns the skin,
link |
01:42:36.500
but is of sufficient intensity
link |
01:42:38.520
that provides just a little bit of damage
link |
01:42:41.080
to the upper layers of the skin, the epidermis,
link |
01:42:43.820
and that it triggers certain biological pathways
link |
01:42:47.180
within the cells of the sebaceous gland
link |
01:42:49.500
and the stem cells within the hair cell niche
link |
01:42:52.460
and the stem cells in skin.
link |
01:42:54.020
What happens is the top layers of the skin
link |
01:42:56.660
are basically burned off by a very low level of burn
link |
01:43:00.460
and or the cells in the deeper layer
link |
01:43:02.420
start to churn out new cells
link |
01:43:03.900
which go and rescue the lesion,
link |
01:43:07.380
essentially clear out the lesion
link |
01:43:09.620
and replace that lesion with healthy skin cells.
link |
01:43:12.020
This does work in the context of wound healing,
link |
01:43:17.420
getting scars to disappear.
link |
01:43:19.020
It also works to remove certain patches of pigmentation.
link |
01:43:22.980
There are sometimes cases where people will get
link |
01:43:24.840
a red blotchiness due to certain skin conditions
link |
01:43:28.580
or some darker pigmentation that they want removed
link |
01:43:31.340
or that they need removed
link |
01:43:32.560
because it's a potential skin cancer threat.
link |
01:43:36.020
Now, how is red light actually doing it
link |
01:43:37.860
within the cells of the sebaceous gland,
link |
01:43:39.520
the stem cells, et cetera?
link |
01:43:41.000
Well, long wavelength light
link |
01:43:43.180
can actually get deep into the skin.
link |
01:43:45.160
I mentioned that before,
link |
01:43:46.000
but can also get into individual cells
link |
01:43:49.780
and can access the so-called organelles,
link |
01:43:51.700
which I described at the beginning of the episode.
link |
01:43:53.340
In particular, they can access the mitochondria
link |
01:43:55.800
which are responsible for producing ATP.
link |
01:43:58.500
Now, the simple way to think about this
link |
01:44:00.540
for sake of this discussion is that as cells age
link |
01:44:06.140
and in particular in very metabolically active cells,
link |
01:44:09.100
they accumulate what are called ROSs,
link |
01:44:12.780
reactive oxygen species.
link |
01:44:14.960
And as reactive oxygen species go up,
link |
01:44:18.760
ATP energy production in those cells tends to go down.
link |
01:44:22.360
It's a general statement,
link |
01:44:23.400
but it's a general statement that in most cases is true.
link |
01:44:27.160
There are some minor exceptions that don't concern us
link |
01:44:29.880
that have to do with cell types different
link |
01:44:31.720
than the ones that I'm talking about now.
link |
01:44:33.520
So the way to think about this is that red light passes
link |
01:44:35.880
into the deeper layers of the skin,
link |
01:44:37.980
activates mitochondria, which increases ATP
link |
01:44:40.940
and directly or indirectly
link |
01:44:42.720
reduces these reactive oxygen species.
link |
01:44:45.040
These reactive oxygen species are not good.
link |
01:44:48.200
We don't want them.
link |
01:44:49.360
They cause cellular damage, cellular death,
link |
01:44:52.360
and for the most part,
link |
01:44:53.840
just inhibit the way that our cells work.
link |
01:44:56.660
So if you've heard of red light
link |
01:44:58.560
or near infrared light therapies designed to heal skin
link |
01:45:02.540
or improve skin quality or remove lesions
link |
01:45:05.040
or get rid of scars or unwanted pigmentation,
link |
01:45:07.860
that is not pseudoscience, that is not woo science,
link |
01:45:12.360
that is grounded in the very biology of how light interacts
link |
01:45:15.640
with mitochondria and reactive oxygen species.
link |
01:45:18.360
Some of you may also find it interesting to note
link |
01:45:20.540
that some of the cream-based treatments for acne,
link |
01:45:23.640
for instance, like retinoic acid,
link |
01:45:25.400
Retin-A is actually a derivative of vitamin A
link |
01:45:30.040
and the pathway involving retinoic acid and vitamin A,
link |
01:45:33.720
believe it or not,
link |
01:45:34.560
is very similar to the natural biological pathway
link |
01:45:38.560
by which photopigments in the eye convert light information
link |
01:45:42.000
into biological changes within those cells.
link |
01:45:44.680
So the key point here is that light is activating
link |
01:45:48.420
particular pathways in cells
link |
01:45:50.280
that can either drive death of cells
link |
01:45:52.840
or can make those cells essentially younger
link |
01:45:55.720
by increasing ATP by way of improving mitochondrial function
link |
01:46:00.560
and in recent years,
link |
01:46:01.840
there've been some just beautiful examples
link |
01:46:04.360
that exist not only in the realm of skin biology,
link |
01:46:07.720
but in the realm of neurobiology,
link |
01:46:10.200
whereby red light and near infrared light
link |
01:46:12.800
can actually be used to enhance the function of the cells
link |
01:46:15.640
that for instance, allow us to see better
link |
01:46:17.760
and indeed cells that allow us to think better.
link |
01:46:20.600
So now I'd like to review those data
link |
01:46:22.320
because not only are they interesting in their own right,
link |
01:46:25.660
but they also point to some very interesting
link |
01:46:28.500
and powerful application of low cost or zero cost tools
link |
01:46:31.920
that we can use to improve our vision.
link |
01:46:34.460
If you are somebody who's interested
link |
01:46:35.840
in the use of red light or near infrared light,
link |
01:46:38.880
so-called LLLT, low level light therapies
link |
01:46:41.720
for treatment of dermatologic issues,
link |
01:46:44.160
so anything related to skin,
link |
01:46:45.920
I will include a link to a excellent set of reviews.
link |
01:46:49.160
The first one is light emitting diodes in dermatology,
link |
01:46:52.240
a systematic review of randomized controlled trials.
link |
01:46:55.220
That one includes review of a very large number of studies
link |
01:46:58.480
came out just a few years ago in 2018
link |
01:47:00.840
and I think is very clearly and cleanly laid out
link |
01:47:03.880
for anyone to access.
link |
01:47:05.240
You can see the degree of effects of red light,
link |
01:47:07.120
for instance, on treatment of acne or scarring, et cetera.
link |
01:47:09.360
And I'll also provide a link to another review,
link |
01:47:12.040
which is low level light therapy in skin,
link |
01:47:14.320
stimulating healing and restoring.
link |
01:47:16.080
So for those of you that are interested,
link |
01:47:17.760
again, in dermatologic issues
link |
01:47:19.420
and the kind of restoring youthfulness
link |
01:47:21.920
and the kind of general themes of anti-aging and longevity
link |
01:47:25.840
and how red light therapies can be used for that,
link |
01:47:28.740
I will encourage you to take a look at those reviews.
link |
01:47:31.360
What you're going to find is that rarely, if ever,
link |
01:47:35.240
is there a study looking at whole body red light illumination
link |
01:47:38.840
for sake of treating and improving skin.
link |
01:47:41.880
And I mention this because I get a lot of questions
link |
01:47:44.320
about infrared sauna
link |
01:47:46.320
and global illumination with red lights.
link |
01:47:49.400
We'll talk more about cases where global illumination
link |
01:47:52.520
of your whole body or your whole face
link |
01:47:54.600
with red lights might be useful,
link |
01:47:56.560
but in terms of infrared sauna,
link |
01:47:58.400
I've mentioned on this podcast before,
link |
01:47:59.880
and I will certainly go deeper on this
link |
01:48:01.400
in an upcoming episode,
link |
01:48:02.400
all about the use of heat and temperature
link |
01:48:04.840
for augmenting our biology.
link |
01:48:06.960
But in general,
link |
01:48:08.900
infrared saunas don't get hot enough temperature wise
link |
01:48:13.040
in order to trigger some of the important effects
link |
01:48:16.000
on growth hormone and heat shock proteins
link |
01:48:17.880
and some of the other things
link |
01:48:18.760
that sauna has been shown to be excellent for.
link |
01:48:21.960
That's a general statement.
link |
01:48:22.900
I realize there are some infrared saunas
link |
01:48:24.520
that do get hot enough.
link |
01:48:26.400
There are very few data on the use of whole body illumination
link |
01:48:30.760
with infrared saunas.
link |
01:48:32.560
They really point to any specific
link |
01:48:35.240
mechanistically supported effects.
link |
01:48:37.400
Almost all the positive effects that you're going to see
link |
01:48:39.560
of red light and low level light therapies,
link |
01:48:41.880
certainly the ones discussed in the reviews
link |
01:48:43.320
that I just mentioned,
link |
01:48:44.200
are going to be the consequence
link |
01:48:46.800
of very directed illumination
link |
01:48:49.320
of particular patches of skin that are seeking repair
link |
01:48:52.080
or that people are seeking the repair of.
link |
01:48:54.240
So again, I don't want to disparage infrared saunas,
link |
01:48:58.000
but in general, they don't get hot enough
link |
01:48:59.360
to trigger most of the positive effects
link |
01:49:01.080
that sauna have been demonstrated to have.
link |
01:49:03.880
And it's unclear at all as to whether or not
link |
01:49:07.000
they can enhance skin quality, youthfulness,
link |
01:49:09.320
restore top layers of skin that are damaged,
link |
01:49:14.160
repair acne, et cetera.
link |
01:49:15.720
So more on heat saunas and infrared saunas
link |
01:49:18.080
in their comparison in an upcoming episode.
link |
01:49:20.680
So let's talk about a clear set of examples
link |
01:49:23.560
where red light and near infrared light
link |
01:49:26.760
have been shown to have positive effects on our health.
link |
01:49:30.360
And these are the data that I referred to
link |
01:49:32.400
at the beginning of the episode
link |
01:49:33.760
from Dr. Glenn Jeffrey at University College London,
link |
01:49:37.000
who again is a longstanding member
link |
01:49:40.600
of the neuroscience community
link |
01:49:41.680
working on visual neuroscience
link |
01:49:43.240
and who over the last decade or so
link |
01:49:45.400
has really emphasized the exploration of red light
link |
01:49:48.520
and near infrared light
link |
01:49:49.960
for restoration of neuronal function as we age.
link |
01:49:53.960
This is absolutely critical.
link |
01:49:55.200
We know that we don't accumulate many new brain cells
link |
01:49:59.400
as we get older.
link |
01:50:00.240
And in some areas of our nervous system,
link |
01:50:02.220
such as our neural retina,
link |
01:50:04.000
which is the part of our eye that's responsible
link |
01:50:06.040
for translating light information to electrical signals
link |
01:50:08.480
so that we can see,
link |
01:50:10.160
we don't get any new cells
link |
01:50:12.140
after the time in which we were born.
link |
01:50:14.000
So the ability to keep our neurons healthy
link |
01:50:16.560
is extremely important for our visual system,
link |
01:50:19.400
extremely important for our hippocampus,
link |
01:50:22.160
an area of the brain involved in memory.
link |
01:50:24.260
And I should just mention
link |
01:50:25.980
that even if people don't get Alzheimer's,
link |
01:50:28.040
there's always going to be some degree
link |
01:50:29.960
of age-related dementia.
link |
01:50:31.860
Sadly, nobody is as cognitively sharp
link |
01:50:35.660
in the years before they die
link |
01:50:36.960
as they are 20 years before that.
link |
01:50:39.200
It's just never the case.
link |
01:50:40.320
We're all getting worse at thinking, feeling,
link |
01:50:43.080
perceiving, et cetera.
link |
01:50:44.480
The question is how quickly we are getting worse.
link |
01:50:46.680
So any mechanism by which we can preserve
link |
01:50:49.560
or reverse neuronal function
link |
01:50:51.600
turns out to be immensely beneficial.
link |
01:50:55.360
The Jeffrey Lab has published two studies in recent years
link |
01:50:58.960
on humans that looked directly, no pun intended,
link |
01:51:03.520
at how red light and near infrared light
link |
01:51:05.800
can improve visual function.
link |
01:51:08.300
I'm going to describe the parameters of those studies
link |
01:51:10.320
and then I'm going to describe what they found exactly.
link |
01:51:13.220
The mechanistic motivation for these studies,
link |
01:51:17.600
again, traces back to this effect of light on mitochondria.
link |
01:51:22.480
So to go a little bit deeper into that mechanism
link |
01:51:24.240
just briefly so that you can frame
link |
01:51:26.840
any potential protocol that you would develop.
link |
01:51:30.600
When light arrives on cells, including neurons,
link |
01:51:36.000
that light can penetrate into the cells
link |
01:51:37.620
if it's of the appropriate wavelength,
link |
01:51:38.980
red light can do that, it can get into cells,
link |
01:51:40.960
it can access the mitochondria,
link |
01:51:42.240
it can increase ATP.
link |
01:51:44.880
In general, anytime ATP is doing its thing
link |
01:51:47.840
to increase energy in cells,
link |
01:51:50.080
it's involving this thing called cytochrome C,
link |
01:51:54.440
which is an oxidase.
link |
01:51:55.620
Anytime you hear ACE, A-S-E in biology,
link |
01:51:58.720
it's going to be an enzyme.
link |
01:51:59.800
It's involved in some process of degrading a molecule
link |
01:52:02.920
and creating another molecule typically.
link |
01:52:05.200
So ATP in cytochrome C is going to give you ATP.
link |
01:52:08.440
Now that's a great thing,
link |
01:52:10.560
but it creates a by-product.
link |
01:52:13.280
It breaks things down such that you get these ROSs,
link |
01:52:16.080
these reactive oxygen species.
link |
01:52:18.080
And those reactive oxygen species,
link |
01:52:19.860
for those of you that want to know,
link |
01:52:21.160
are involved in things like redox signaling
link |
01:52:23.860
and reactive oxygen species actually change
link |
01:52:27.280
which genes are made in a cell.
link |
01:52:29.560
So the goal of any treatment to keep neurons
link |
01:52:32.400
or other cells youthful and functioning well,
link |
01:52:35.840
and to prevent or reverse aging
link |
01:52:38.880
is going to be to increase ATP
link |
01:52:41.320
and to reduce reactive oxygen species.
link |
01:52:44.160
And in doing so, to disrupt some of the normal pathways
link |
01:52:48.480
associated with aging.
link |
01:52:51.860
The Jeffrey Lab approached these studies
link |
01:52:53.600
with that understanding of how mitochondria
link |
01:52:55.800
and reactive oxygen species and ATP work.
link |
01:52:58.700
And what they did was exquisitely simple
link |
01:53:01.560
to the point of being elegant.
link |
01:53:02.880
And what they found was really, really exciting.
link |
01:53:05.240
What they did is they had people, subjects
link |
01:53:09.200
that were either younger, so in their 20s,
link |
01:53:11.420
or 40 years old or older,
link |
01:53:15.000
view red light of about 670 nanometers.
link |
01:53:18.000
670 nanometers would appear red to you and me.
link |
01:53:21.500
They had them do that, excuse me,
link |
01:53:23.640
at a distance that was safe for their eyes.
link |
01:53:25.600
So at about a foot away.
link |
01:53:27.720
Now, a foot away from a very intense red light
link |
01:53:31.700
could actually be damaging to the eye.
link |
01:53:32.960
So they had them do this at about a foot away
link |
01:53:35.200
from a red light that was of low enough intensity
link |
01:53:37.960
that did not damage the eyes.
link |
01:53:39.960
And they had them do that anywhere
link |
01:53:41.280
from two to three minutes per day.
link |
01:53:44.120
And in one study, they had them do that
link |
01:53:45.840
for a long period of time of about 12 weeks.
link |
01:53:48.360
And in the other study, they had them do that
link |
01:53:49.760
just for a couple of weeks.
link |
01:53:51.680
What's remarkable is that when you collapse the results
link |
01:53:54.560
across these two studies,
link |
01:53:56.080
what they found is that when looking at these subjects
link |
01:53:58.660
ranging from 28 years old to about 72 years old,
link |
01:54:02.880
the major findings were that in individuals 40 years old
link |
01:54:08.180
or older, so in the 40 to 72 year old bracket,
link |
01:54:12.920
but not in the subjects younger than 40 years old,
link |
01:54:16.600
they saw an improvement in visual function.
link |
01:54:20.120
That improvement in visual function
link |
01:54:21.480
was an improvement in visual acuity,
link |
01:54:23.760
meaning the ability to resolve fine detail
link |
01:54:26.880
and using a particular measure of visual function,
link |
01:54:30.500
which is called the Tritan exam, T-R-I-T-A-N, Tritan exam,
link |
01:54:36.900
which specifically addresses the function
link |
01:54:40.320
of the so-called short wavelength cones,
link |
01:54:42.360
the ones that respond to green and blue light,
link |
01:54:45.000
they saw a 22% improvement in visual acuity,
link |
01:54:48.840
which in the landscape of visual testing
link |
01:54:52.240
is an extremely exciting result, okay?
link |
01:54:55.540
So I think in most studies of improvements of vision,
link |
01:54:59.220
you'd be very excited to see an improvement of 5% or 10%.
link |
01:55:03.320
So a 22% improvement in visual acuity,
link |
01:55:06.520
even though it's in this very specific form
link |
01:55:08.980
of visual testing, this Tritan exam or this Tritan score,
link |
01:55:13.720
well, that turns out to be very significant
link |
01:55:16.000
and translates to the real world in an important way.
link |
01:55:20.200
In particular, as we age,
link |
01:55:23.080
we tend to lose certain neurons within our retina,
link |
01:55:26.120
but we don't tend to lose cones.
link |
01:55:28.520
We tend to lose rods.
link |
01:55:30.180
We tend to lose other cells within the retina,
link |
01:55:32.280
including the cells that connect the eye to the brain,
link |
01:55:34.240
the so-called ganglion cells.
link |
01:55:35.800
Cones, for whatever reason,
link |
01:55:37.600
are pretty resilient to age-related loss.
link |
01:55:40.200
However, because rods and cones both
link |
01:55:44.480
are not just among the most metabolically active cells
link |
01:55:47.720
in your entire body,
link |
01:55:49.120
but the most metabolically active cells in your entire body.
link |
01:55:52.960
That's right, your rods and cones are the cells that demand
link |
01:55:56.200
and that use the most energy of all the cells in your body.
link |
01:56:00.940
Not your skin cells, not your spleen cells,
link |
01:56:02.520
not your stomach cells.
link |
01:56:03.720
Even if you talk a lot,
link |
01:56:04.920
not the cells that are responsible for moving your mouth,
link |
01:56:07.140
it is the rods and cones of your neural retina
link |
01:56:09.680
that are responsible for using the most amount
link |
01:56:12.680
of ATP and energy in your entire body.
link |
01:56:15.640
And because of that,
link |
01:56:16.960
those cells tend to accumulate
link |
01:56:19.080
a lot of reactive oxygen species as we age.
link |
01:56:23.140
Red light of the sort used in these studies
link |
01:56:25.360
was able to reduce the amount of reactive oxygen species
link |
01:56:29.920
in the rods and cones,
link |
01:56:31.360
and to rescue the function of this particular cone type,
link |
01:56:35.200
the short wavelength and medium wavelength cones,
link |
01:56:37.020
which if you think about the study
link |
01:56:38.480
is a little bit surprising
link |
01:56:39.720
because it was red light and near infrared light,
link |
01:56:42.360
not short wavelength light that was used
link |
01:56:44.880
in order to create this improvement in cellular function.
link |
01:56:48.520
But if you step back a little bit further,
link |
01:56:50.960
it makes perfect sense
link |
01:56:52.360
because there's nothing specific about the red light
link |
01:56:55.800
in the sense that it's not that it gets delivered
link |
01:56:57.920
only to red cones.
link |
01:56:59.560
That red light and near infrared light
link |
01:57:01.480
is being absorbed by all the photoreceptors within the eye,
link |
01:57:04.660
the rods and the blue cones and the green cones
link |
01:57:07.600
and the red cones.
link |
01:57:08.440
It's just that the red cones absorb that light best.
link |
01:57:11.760
So the important takeaway here
link |
01:57:14.560
is that viewing red light and near infrared light
link |
01:57:17.840
at a distance at which it is safe
link |
01:57:19.760
for just a couple of minutes each day
link |
01:57:22.420
allowed a reversal of the aging process of these neurons,
link |
01:57:25.920
which some people have heard me say before
link |
01:57:28.640
and I'll just say it again,
link |
01:57:30.320
the retina, including your photoreceptors
link |
01:57:32.200
are not just connected to your brain,
link |
01:57:34.160
they're not just near your brain,
link |
01:57:35.280
they are actual central nervous system tissue.
link |
01:57:37.400
They are the only two pieces of your brain,
link |
01:57:39.540
meaning your neural retinas
link |
01:57:40.680
are the only two pieces of your brain
link |
01:57:41.920
that reside outside your skull
link |
01:57:43.300
or at least outside the cranial vault.
link |
01:57:45.000
So here we're seeing a reversal of the aging process
link |
01:57:48.280
in neurons by shining red light on those neurons.
link |
01:57:51.560
Now, of course, the Jeffrey lab
link |
01:57:54.060
is primarily interested in vision
link |
01:57:55.720
and humans are most dependent on vision
link |
01:57:58.040
as a sense to navigate the world and survive.
link |
01:57:59.860
So this is really wonderful.
link |
01:58:01.240
Here we're looking at a therapy
link |
01:58:03.040
that can reverse age-related vision loss,
link |
01:58:06.560
at least in some individuals.
link |
01:58:08.680
But as you can imagine,
link |
01:58:09.580
the study was also done on these cells
link |
01:58:10.960
because they reside outside the skull
link |
01:58:13.080
and you can shine light directly on them, right?
link |
01:58:15.320
I'm sure that there are many people out there
link |
01:58:16.980
who are interested in how they can improve the function,
link |
01:58:19.480
say, of the neurons in their brain responsible for memory.
link |
01:58:22.640
And in a few minutes,
link |
01:58:23.460
I'll describe the non-invasive applications of light
link |
01:58:27.040
to try and restore the function of those cells as well.
link |
01:58:31.100
So a little bit more about the studies from the Jeffrey lab.
link |
01:58:35.920
One of the things that they observed
link |
01:58:37.580
was a reduction in so-called drusen, D-R-U-S-E-N.
link |
01:58:41.760
Drusen are little fatty deposits,
link |
01:58:45.760
little cholesterol deposits
link |
01:58:47.440
that accumulate in the eye as we age.
link |
01:58:49.880
We've all heard about cholesterol
link |
01:58:51.540
within our veins and arteries
link |
01:58:53.080
and how that can clog our veins and arteries
link |
01:58:55.660
and how, of course,
link |
01:58:57.280
clogging of veins and arteries is not a good thing.
link |
01:58:59.760
Well, our neural retina being so metabolically active
link |
01:59:02.540
requires a lot of blood flow.
link |
01:59:04.140
It's heavily vascularized.
link |
01:59:06.140
And drusen are a special form of cholesterol
link |
01:59:09.080
that accumulate in the eye.
link |
01:59:11.240
As it turns out,
link |
01:59:12.080
these red light and near infrared light therapies
link |
01:59:15.040
explored by the Jeffrey lab
link |
01:59:16.480
were able to actually reduce or reverse
link |
01:59:19.560
some of the accumulation of drusen.
link |
01:59:21.600
And so in addition to reducing reactive oxygen species,
link |
01:59:25.640
the idea in mind now is that red light
link |
01:59:27.980
may actually reduce cholesterol deposits
link |
01:59:31.520
and reactive oxygen species
link |
01:59:34.080
in order to improve neuronal function.
link |
01:59:36.520
So what should you and I do with these results?
link |
01:59:38.720
Or should we do anything with these results?
link |
01:59:40.240
Well, first of all, I want to emphasize
link |
01:59:42.220
that even though these studies are very exciting,
link |
01:59:44.680
they are fairly recent.
link |
01:59:45.920
And so more data as always are needed.
link |
01:59:48.960
There's some additional features of these studies
link |
01:59:50.640
that I think are also important to consider.
link |
01:59:52.600
First of all,
link |
01:59:54.000
the exposure to red light needed to happen early in the day,
link |
01:59:58.360
at least within the first three hours of waking.
link |
02:00:02.000
How would one do that?
link |
02:00:03.120
Well, nowadays,
link |
02:00:04.040
there are a number of different red light panels
link |
02:00:06.600
and different red light sources
link |
02:00:08.880
that certainly fall within the range of red light
link |
02:00:11.740
and near infrared light that one could use.
link |
02:00:14.260
I don't have any affiliation to any companies or products
link |
02:00:17.680
that promote or make those red light therapies.
link |
02:00:21.640
I do own a red light panel.
link |
02:00:23.380
So I confess I have started using this protocol.
link |
02:00:25.920
I am older than 40 years old.
link |
02:00:27.800
I also have been experimenting with these red light panels
link |
02:00:30.880
as a way of addressing other changes in biological tissues
link |
02:00:35.500
for which I'm doing blood work, et cetera.
link |
02:00:37.140
And I'm going to talk about that in a future episode.
link |
02:00:39.480
But that of course is what I call anacodata.
link |
02:00:41.560
It only relates to my experience.
link |
02:00:43.180
So today,
link |
02:00:44.800
and certainly on all episodes of the Human Lab Podcast,
link |
02:00:47.720
we emphasize peer reviewed studies almost exclusively
link |
02:00:50.720
talking about anacodata only when highlighting it
link |
02:00:53.440
as anacodata.
link |
02:00:54.840
So if you're somebody who wants to explore red light therapy
link |
02:00:58.560
here's what you need to do.
link |
02:00:59.600
You need to make sure that that red light source,
link |
02:01:02.120
whatever source you happen to use,
link |
02:01:04.160
whether or not you purchase it or make one.
link |
02:01:05.520
And in fact, these red light sources
link |
02:01:07.280
are very, very easy to make.
link |
02:01:08.860
You could essentially take a bright flashlight
link |
02:01:11.600
and cover it with a film or a filter
link |
02:01:14.120
that would only allow particular long wavelengths
link |
02:01:17.420
to pass through.
link |
02:01:18.260
This would be very easy to look up online
link |
02:01:19.880
and figure out how to do this.
link |
02:01:20.720
You could probably do this for just a few dollars
link |
02:01:23.560
or you could purchase a red light unit
link |
02:01:25.520
if that was within your budget
link |
02:01:27.480
and something that you're interested in.
link |
02:01:29.000
You want to make sure that it's not so bright
link |
02:01:30.840
that you're damaging your eye.
link |
02:01:32.600
A good rule of thumb
link |
02:01:33.600
is that something isn't painful to look at.
link |
02:01:35.920
And in fact, I should just emphasize
link |
02:01:37.400
that anytime you look at any light source,
link |
02:01:39.560
sunlight or otherwise,
link |
02:01:40.800
that it's painful and makes you want to squint
link |
02:01:42.400
or close your eyes.
link |
02:01:43.240
That means it's too bright to look at
link |
02:01:44.900
without closing your eyes.
link |
02:01:46.000
Okay, that's sort of a duh,
link |
02:01:47.420
but I would loathe to think that anyone
link |
02:01:49.520
would harm themselves with bright light in any way.
link |
02:01:51.760
I don't just say that to protect us.
link |
02:01:52.980
I say that to protect you, of course,
link |
02:01:54.880
because you are responsible for your health.
link |
02:01:56.720
And again, retinal neurons do not regenerate.
link |
02:01:59.320
Once they are gone and dead, they do not come back.
link |
02:02:02.160
There's no technology to replace them
link |
02:02:03.780
at this current state in time.
link |
02:02:06.280
So please don't damage your retinas.
link |
02:02:08.400
So is a red light source safe to look at
link |
02:02:10.840
if it is not painful to look at?
link |
02:02:13.480
Chances are it is.
link |
02:02:14.560
And yet I would still encourage you
link |
02:02:16.040
to talk to your optometrist or ophthalmologist
link |
02:02:19.220
before getting into any extensive protocols.
link |
02:02:21.940
But if you were still determined to pursue
link |
02:02:24.100
the sorts of protocols that are in the Jeffrey studies,
link |
02:02:26.320
certainly we'll provide a link to those studies.
link |
02:02:28.440
Again, it involves looking at these red light panels,
link |
02:02:31.160
blinking aloud for two minutes to three minutes,
link |
02:02:36.160
every morning for a period of two weeks or more.
link |
02:02:41.600
And if you're older than 40,
link |
02:02:44.820
that could very well have an effect.
link |
02:02:46.200
If you're younger than 40, excuse me,
link |
02:02:48.520
that's unlikely to have an effect.
link |
02:02:50.680
At least that was what was observed
link |
02:02:52.460
in these particular studies.
link |
02:02:54.080
The lights were not flashing.
link |
02:02:55.520
It was continuous illumination.
link |
02:02:57.220
Again, you're allowed to blink.
link |
02:02:58.800
It does not have to even be direct illumination.
link |
02:03:00.800
It can be somewhat indirect illumination,
link |
02:03:02.460
much as we described for the use of UVB light before.
link |
02:03:06.220
The wavelength of light is important.
link |
02:03:08.200
It is red light and near-infrared light
link |
02:03:10.180
that is going to be effective in this scenario.
link |
02:03:14.000
The authors of this study emphasized
link |
02:03:15.640
that it was red light of 670 nanometers in wavelength
link |
02:03:20.240
and near-infrared light of 790 nanometers in wavelength
link |
02:03:25.760
that were effective,
link |
02:03:26.840
and that those wavelengths could be complimentary.
link |
02:03:29.720
That's probably why, or maybe it's just coincidental,
link |
02:03:33.200
but it's a fortunate coincidence
link |
02:03:35.240
that a lot of the commercially available red light panels
link |
02:03:37.680
that you'll find out there
link |
02:03:38.520
combine both red light and near-infrared light.
link |
02:03:41.480
However, I want to emphasize that most of the panels
link |
02:03:44.280
that are commercially available
link |
02:03:46.080
are going to be too bright to safely look at very close up.
link |
02:03:50.480
And in fact, that's why most of those red light panels
link |
02:03:53.000
are designed for illumination of the skin
link |
02:03:54.960
and oftentimes arrive in their packaging
link |
02:03:57.480
with eye protectors that are actually designed
link |
02:04:00.040
to shield out all the red light.
link |
02:04:01.760
So take the potential dangers of excessive illumination
link |
02:04:06.220
of the eyes with any wavelength of light seriously,
link |
02:04:09.240
but if you're going to explore 670 and 790 nanometer light
link |
02:04:12.800
for sake of enhancing neuronal function,
link |
02:04:16.340
set it at a distance that's comfortable to look at
link |
02:04:18.640
and that doesn't force you to squint
link |
02:04:20.340
or doesn't make you feel uncomfortable physically
link |
02:04:22.960
as if you need to turn away
link |
02:04:24.320
during the period of that two to three minute illumination
link |
02:04:27.800
each day.
link |
02:04:30.220
In terms of turning away from light,
link |
02:04:32.400
I'll just briefly mention that that is not an accident
link |
02:04:36.000
or a coincidence that you have that response
link |
02:04:37.760
to very bright light.
link |
02:04:38.980
There is a so-called photic avoidance pathway
link |
02:04:41.960
that involves cells within your retina,
link |
02:04:43.640
these ganglion cells that communicate
link |
02:04:45.260
with yet another brain station,
link |
02:04:48.120
a certain area of your thalamus
link |
02:04:49.880
that communicate to areas of your brain
link |
02:04:52.400
that are associated with pain.
link |
02:04:53.560
So literally that can trigger headache
link |
02:04:55.320
and that can trigger the squint reflex.
link |
02:04:58.380
Biology is just beautiful in this way.
link |
02:05:00.420
Too much light is bad for us in that it can damage our eyes
link |
02:05:03.480
and other aspects of our body.
link |
02:05:05.160
So if we look at a light that's too bright,
link |
02:05:07.380
our eyes send a signal to the brain
link |
02:05:08.980
that gives us a sort of a headache
link |
02:05:10.360
and a desire to squint and turn away.
link |
02:05:12.100
So that can be a useful guide
link |
02:05:14.040
in terms of gauging how bright a light should be
link |
02:05:16.680
or at least how far away you should be from a bright source
link |
02:05:19.960
in order to safely engage with that light source.
link |
02:05:23.080
So the studies I just described, once again,
link |
02:05:25.880
involve the use of red light early in the day
link |
02:05:27.980
within three hours of waking
link |
02:05:29.400
and are for the sake of improving neuronal function.
link |
02:05:31.760
Red light has also been shown to be beneficial
link |
02:05:35.760
late in the day and even in the middle of the night.
link |
02:05:38.160
And when I say middle of the night,
link |
02:05:40.280
I'm referring to studies that explore the use of red light
link |
02:05:43.080
for shift workers.
link |
02:05:44.600
I know that most people are not working
link |
02:05:46.380
in the middle of the night, at least I hope they're not,
link |
02:05:48.040
but some of you may do that from time to time.
link |
02:05:50.440
All-nighters for studying, I confess,
link |
02:05:51.920
I still pull all-nighters every once in a while
link |
02:05:53.580
to prepare things like podcasts and other deadlines,
link |
02:05:57.160
really try not to, happens less and less as I get older
link |
02:05:59.760
because I think I get more disciplined
link |
02:06:01.640
and or less good at pulling all-nighters.
link |
02:06:04.960
But I realized that many people are doing shift work
link |
02:06:07.360
or they have to work certainly past 10 PM
link |
02:06:09.760
or maybe they're taking care of young children
link |
02:06:11.600
in the middle of the night and they have to be up.
link |
02:06:14.040
In that case, red light can actually be very beneficial.
link |
02:06:16.400
And nowadays there are a lot of sources
link |
02:06:17.920
of red light available just as red light bulbs.
link |
02:06:20.840
You don't need a panel.
link |
02:06:21.940
So what I'm basically saying is that it can be beneficial
link |
02:06:25.220
to use red lights at night.
link |
02:06:28.080
The study I'd like to emphasize in this context
link |
02:06:30.160
is entitled Red Light,
link |
02:06:31.880
a novel non-pharmacological intervention
link |
02:06:34.160
to promote alertness in shift workers.
link |
02:06:36.800
So beautiful study.
link |
02:06:38.000
They explored the use of different wavelengths of light.
link |
02:06:41.360
So blue light of 460 nanometers or red light
link |
02:06:45.260
or dim white light of different brightnesses, et cetera,
link |
02:06:49.480
and looked at things like melatonin.
link |
02:06:52.720
How much does light of a given color
link |
02:06:55.160
and intensity suppress melatonin?
link |
02:06:56.800
They looked at cortisol, a stress hormone.
link |
02:06:58.600
They looked at wakefulness.
link |
02:07:00.320
How much or to what degree could a given color of light
link |
02:07:03.600
increase wakefulness at different hours of the day?
link |
02:07:06.220
The takeaway from this study is very clear.
link |
02:07:08.320
If you need to be awake late at night
link |
02:07:10.540
for sake of shift work or studying
link |
02:07:12.320
or taking care of children, et cetera,
link |
02:07:14.760
red light is going to be your best choice
link |
02:07:17.520
because if the red light is sufficiently dim,
link |
02:07:22.120
it's not going to inhibit melatonin production
link |
02:07:25.000
and it's not going to increase cortisol at night.
link |
02:07:28.080
Cortisol should be high early in the day
link |
02:07:30.800
or at least should be elevated
link |
02:07:31.960
relative to other times of day if you are healthy.
link |
02:07:34.500
A late shifted increase in cortisol,
link |
02:07:36.420
however, 9 p.m. cortisol, 10 p.m. cortisol
link |
02:07:39.040
is well known to be associated with depression
link |
02:07:42.100
and other aspects of mental health,
link |
02:07:44.480
or I should say mental illness.
link |
02:07:46.360
So if you do need to be awake at night or even all night,
link |
02:07:50.100
red light is going to be the preferred light source.
link |
02:07:53.620
And in terms of how bright to make it,
link |
02:07:55.360
well, as dim as you can while still being able
link |
02:07:59.000
to perform the activities that you need to perform,
link |
02:08:00.840
that's going to be your best guide.
link |
02:08:03.040
I'll provide a link to this study as well.
link |
02:08:05.420
Again, it's a really important study
link |
02:08:08.120
because it emphasized that there are forms of light,
link |
02:08:10.320
red light, provided it's dim,
link |
02:08:12.240
that can allow you to stimulate the alertness
link |
02:08:15.400
that light landing on the eyes can provide.
link |
02:08:19.080
So it allows you to stay awake
link |
02:08:20.200
and to do whatever work that you need to do.
link |
02:08:22.520
It does not seem to alter melatonin production.
link |
02:08:26.040
So that's good.
link |
02:08:26.860
It does not seem to alter levels
link |
02:08:28.880
or timing of cortisol production.
link |
02:08:31.000
So yet another case where red light used correctly
link |
02:08:34.680
can be beneficial.
link |
02:08:35.800
Up until now, we've been talking about the effects
link |
02:08:37.760
of shining different wavelengths of light
link |
02:08:40.160
on the skin or on our eyes
link |
02:08:43.120
and the downstream health consequences
link |
02:08:45.640
of that illumination.
link |
02:08:47.560
However, one of the most important goals
link |
02:08:49.560
of science and medicine is to figure out
link |
02:08:52.000
how to change the health of our brain.
link |
02:08:54.600
And of course, our brain is contained within our skull
link |
02:08:58.240
and therefore we can't just shine light
link |
02:09:01.160
onto the outside of our head
link |
02:09:03.440
and expect it to change the activity
link |
02:09:05.360
of neurons deep within the brain
link |
02:09:07.000
unless those neurons are linked up
link |
02:09:10.100
with our eyes or with our skin.
link |
02:09:12.580
And as it turns out,
link |
02:09:13.520
even though there are a lot of brain areas
link |
02:09:15.480
that are connected through neural circuits
link |
02:09:17.680
and hormone circuits through our eye
link |
02:09:19.580
and believe it or not, also to our skin,
link |
02:09:22.240
many brain areas are not.
link |
02:09:25.840
Brain areas such as the hippocampus,
link |
02:09:27.800
which is involved in learning and memory,
link |
02:09:30.220
brain areas such as our neocortex.
link |
02:09:33.180
Well, some areas of our neocortex,
link |
02:09:34.840
such as our visual cortex,
link |
02:09:36.460
are indirectly linked to our eyes.
link |
02:09:38.400
So if we shine light on our eyes,
link |
02:09:39.600
we can change the activity of neurons in our neocortex.
link |
02:09:42.420
But there are other brain areas that are not directly
link |
02:09:46.520
or even indirectly connected to our visual system,
link |
02:09:50.060
not at least in any immediate way.
link |
02:09:53.080
So that raises the question of how do you change
link |
02:09:55.040
the activity of neurons in the brain?
link |
02:09:56.400
Well, there's pharmacology.
link |
02:09:58.080
You can take pills, you can inject drugs
link |
02:10:01.060
that will change the pharmacology of neurons
link |
02:10:02.860
and the way they operate in fire.
link |
02:10:04.800
Of course, antidepressants are one such instance.
link |
02:10:07.760
Opioid drugs are another.
link |
02:10:09.720
There's a huge array of psychoactive compounds,
link |
02:10:12.720
meaning compounds that will change the levels
link |
02:10:14.720
of chemicals in your brain.
link |
02:10:16.760
Some of those work, many of them also carry side effects.
link |
02:10:20.700
It's all rather indirect,
link |
02:10:22.540
meaning you have lots of different cells
link |
02:10:24.320
in different areas of your brain
link |
02:10:25.300
that utilize the same chemicals.
link |
02:10:26.640
So a drug, for instance, to increase serotonin
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02:10:29.060
for sake of improving depression
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02:10:31.520
will also often have the effect of reducing
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02:10:34.760
certain neurons output of serotonin in the hippocampus
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02:10:38.980
and cause changes in appetite or changes in libido
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02:10:41.280
and so on and so forth.
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02:10:43.440
You could imagine using electrical stimulation,
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02:10:45.260
putting wires into the brain
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02:10:46.420
and stimulating specific brain areas
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02:10:48.520
in order to activate the neurons in those brain areas.
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02:10:51.320
And certainly that works and has been done experimentally
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02:10:53.960
and is done during neurosurgery exams, et cetera,
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02:10:56.860
but involves removing a piece of skull.
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02:10:59.600
So that's not very practical.
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02:11:01.320
In principle, light would be a wonderful way
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02:11:04.360
to modulate the activity of neurons deep within the brain.
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02:11:08.480
But again, the skull is in the way.
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02:11:11.520
Recent studies, however, have figured out ways
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02:11:14.400
that light can be delivered to the eyes
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02:11:16.720
to change global patterns of firing in the brain
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02:11:20.200
in ways that can be beneficial to the brain.
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02:11:22.640
And the work that I'm referring to now
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02:11:25.480
is mainly the work of Liwei Tsai at MIT,
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02:11:28.560
Massachusetts Institute of Technology and her colleagues.
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02:11:32.160
And what they've discovered is that
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02:11:33.720
there's a particular pattern of brain activity
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02:11:36.840
called gamma activity.
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02:11:38.940
Gamma activity is one so-called wavelength
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02:11:42.080
of electrical activity in the brain.
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02:11:44.200
So not wavelengths of light,
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02:11:45.220
but wavelengths of electrical activity in the brain
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02:11:47.980
that can be restorative for certain aspects
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02:11:50.520
of learning and memory
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02:11:51.560
and can actually help create molecular changes in neurons
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02:11:55.160
that lead to clearance of debris
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02:11:57.600
and even reductions in age-related cognitive decline.
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02:12:01.760
So the way to think about brain waves
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02:12:04.760
and brain oscillations is that neurons
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02:12:08.040
are electrically active, that involves chemicals, et cetera.
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02:12:11.120
And they can be active in very slow, big wave forms.
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02:12:15.200
So you can think of delta waves,
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02:12:17.840
meaning so you can imagine a wave of electrical activity
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02:12:20.400
that comes along very infrequently.
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02:12:22.200
So a given neuron fires
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02:12:24.160
and then some period of time later fires
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02:12:26.920
and then some period of time even later fires.
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02:12:29.680
Or you can imagine that that same cell is very active,
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02:12:32.520
fires, fires, fires, fires, fires.
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02:12:34.340
You can imagine if it's firing very often,
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02:12:36.000
it's going to be short wavelength, right?
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02:12:38.400
Shorter gaps between firing,
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02:12:40.340
or if it's firing very seldom,
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02:12:43.560
you're going to think about that
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02:12:45.480
as longer wavelength firing.
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02:12:47.280
Turns out that gamma waves are one pattern of firing
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02:12:51.020
that lead to downstream metabolic functions
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02:12:54.760
and biological functions that end up clearing away debris
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02:12:57.340
that's associated with aging in cells.
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02:13:00.220
And that also lead to molecular changes
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02:13:03.280
that enhance the kind of youthfulness of neurons,
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02:13:06.400
so to speak.
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02:13:09.200
How do we induce gamma oscillations within the brain?
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02:13:12.400
Well, what Liwei, Tsai and colleagues
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02:13:15.680
have beautifully shown is that
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02:13:18.320
by delivering certain patterns of light flicker,
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02:13:22.040
so lights going on and off at a particular frequency,
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02:13:25.320
the brain as a whole starts to entrain,
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02:13:28.480
meaning it matches to those particular patterns
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02:13:30.860
of light flicker,
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02:13:31.700
even though many of the brain areas that do this
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02:13:34.400
are not directly within the visual system or visual pathway.
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02:13:38.720
So the studies that I'm referred to are several,
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02:13:42.080
but the one that I'd like to highlight is entitled
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02:13:43.960
Gamma Entrainment Binds Higher Order Brain Regions
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02:13:46.820
and Offers Neuroprotection.
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02:13:49.160
What they essentially did was to expose subjects
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02:13:52.560
to 40 Hertz, which is a particular frequency
link |
02:13:56.640
of illumination to the eyes.
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02:13:59.160
So it's light goes on, light goes off,
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02:14:01.360
light goes on, light goes off at a frequency of 40 Hertz.
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02:14:06.200
And when they did that,
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02:14:07.480
and they recorded the activity of neurons within the brain,
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02:14:10.360
not just within the visual areas of the brain,
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02:14:12.920
but within other areas as well,
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02:14:14.840
they observed increased gamma oscillations,
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02:14:18.820
meaning that the electrical activity of the brain at large
link |
02:14:23.040
started to match to the patterns of light
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02:14:26.080
that were delivered to the eyes.
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02:14:27.980
This is really exciting and very unique
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02:14:29.720
from the different types of phototherapies
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02:14:31.620
that we've been talking about up until now.
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02:14:33.200
All the patterns of phototherapy
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02:14:35.080
that we've been talking about up until now
link |
02:14:36.680
involved constant illumination with a given wavelength.
link |
02:14:39.320
Here, it is wavelength generating patterns of illumination,
link |
02:14:44.880
light on, light off, light on, light off
link |
02:14:46.600
at a particular frequency.
link |
02:14:48.480
So what they found, for instance,
link |
02:14:49.740
using this pattern of stimulation,
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02:14:51.200
and by the way, the stimulation was called GENUS,
link |
02:14:53.640
Gamma Entrainment Using Sensory Stimulation,
link |
02:14:56.160
so G-E-N-U-S, Gamma Entrainment Using Sensory Stimulation,
link |
02:15:00.000
had a number of really interesting effects.
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02:15:01.560
First of all, it reduced so-called amyloid plaques
link |
02:15:04.920
and phosphorylated tau.
link |
02:15:06.680
Amyloid plaques and phosphorylated tau
link |
02:15:08.360
are associated with Alzheimer's
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02:15:09.760
and normal age-related cognitive decline.
link |
02:15:12.840
So this is incredible, right?
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02:15:15.920
A pattern of flashing light delivered to the eyes
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02:15:19.240
creates a pattern of neuronal firing,
link |
02:15:21.360
not just in the visual areas of the brain,
link |
02:15:23.120
but in other areas of the brain as well,
link |
02:15:25.600
that in turn trigger molecular pathways
link |
02:15:28.720
that reduce some of the markers
link |
02:15:32.000
and the cause of age-related cognitive decline
link |
02:15:34.460
in Alzheimer's, and in parallel to that,
link |
02:15:37.200
they observed an upregulation
link |
02:15:39.120
of some of the biological pathways
link |
02:15:41.300
that lead to enhancement of neuronal function,
link |
02:15:43.500
maintenance of synapses,
link |
02:15:44.620
which are the connections between neurons,
link |
02:15:46.480
and so on and so on.
link |
02:15:48.320
They have discovered and list out a huge number
link |
02:15:50.820
of these biological effects,
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02:15:52.400
both the reduction in bad things, so to speak,
link |
02:15:55.280
and the improvement in good biological pathways.
link |
02:15:59.080
And I find these studies so exciting because,
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02:16:02.880
first of all, they're noninvasive, right?
link |
02:16:05.560
There's no drilling through the skull.
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02:16:07.520
They are very tractable and in the experimental sense,
link |
02:16:11.760
meaning that you could imagine
link |
02:16:14.020
that if 40 hertz stimulation turns out
link |
02:16:15.920
to be the very best stimulation protocol
link |
02:16:17.820
to induce these gamma oscillations, well, great,
link |
02:16:20.360
but because it's noninvasive,
link |
02:16:22.280
it's fairly easy to explore 50 hertz stimulation,
link |
02:16:25.080
100 hertz stimulation, 20 hertz stimulation,
link |
02:16:27.480
and to do that with different wavelengths of light.
link |
02:16:30.540
And so that's what's happening now.
link |
02:16:31.780
The PSI lab and other labs are really starting
link |
02:16:33.600
to explore the full range of variables
link |
02:16:36.680
that can impact oscillations within the brain
link |
02:16:39.680
and their downstream consequences.
link |
02:16:41.440
So again, this is phototherapy,
link |
02:16:43.600
but phototherapy of a very different sort
link |
02:16:45.400
that we've been talking about up until now.
link |
02:16:47.840
It's phototherapy designed to trigger activation
link |
02:16:50.920
of biological pathways far away
link |
02:16:53.360
from the very tissue that's being illuminated.
link |
02:16:55.240
And it calls to mind the same sorts of mechanisms
link |
02:16:57.320
that we were talking about earlier,
link |
02:16:58.320
where illumination of the skin with UVB light
link |
02:17:00.840
is setting off an enormous number of different cascades
link |
02:17:03.120
in different organs and tissues, including the spleen,
link |
02:17:05.680
the testes, the ovaries, and so on.
link |
02:17:08.140
So again, light has these powerful effects,
link |
02:17:11.760
both locally on the cells that light is delivered to,
link |
02:17:15.060
but also systemically in terms of the cells
link |
02:17:18.440
that are changing their electrical and chemical outputs
link |
02:17:21.680
are modifying lots and lots of biological programs.
link |
02:17:24.720
Is there an actionable tool related to these studies yet?
link |
02:17:27.920
Well, that sort of depends on how adventurous you are.
link |
02:17:30.260
Right now, these studies are being explored
link |
02:17:32.860
in the context of clinical trials
link |
02:17:34.500
in people with Alzheimer's dementia
link |
02:17:36.300