back to indexUsing 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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and probiotics that ensure a healthy gut microbiome.
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If you'd like to try Athletic Greens,
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you can go to athleticgreens.com slash Huberman
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to claim a special offer.
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They'll give you five free travel packs
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that make it very easy to mix up Athletic Greens
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while you're on the road, so in the car and on the plane.
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I should mention that Athletic Greens is delicious.
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I love the way it tastes.
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I mix mine with some water
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and a little bit of lemon or lime juice.
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The special offer is the five free travel packs
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plus a year supply of vitamin D3K2.
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Vitamin D3 has been shown to be important
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for a tremendous number of biological functions.
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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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for calcium regulation.
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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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or for us to be very creative
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or for us to be able to switch tasks easily.
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Thesis understands this.
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I should also mention
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and the things you don't want.
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So if you want to try
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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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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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that's lmnt.com slash Huberman
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to claim a free Element sample pack.
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You only cover the cost of shipping.
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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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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
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because there is still energy at those wavelengths.
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I'll give a few examples of this.
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Humans are not a species that can see
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into the infrared realm of the spectrum.
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A pit viper, meaning a snake that has infrared sensors,
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however, can sense in the infrared.
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So if you were to walk through a jungle
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and there's a pit viper there,
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it sees you as a cloud of heat emission
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because your body is emitting infrared energy all the time.
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You're casting off infrared energy.
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The snake can see it, you can't.
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If you were to put on a particular set of goggles
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that were infrared goggles,
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well, then you would be able to see the heat emissions
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of any organism, human or otherwise,
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that could emit infrared energy.
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Let's take the opposite end of the spectrum.
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We are familiar with seeing things that are blue or green
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or very pale blue, but as we say below that,
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meaning even shorter wavelength light is out there.
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Ultraviolet light is a really good example
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of light energy that's coming from the sun
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and is in our environment
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and is being reflected off surfaces all the time.
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We don't see it and yet if it's very bright outside,
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that ultraviolet light can burn our skin.
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As you'll learn in today's episode,
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ultraviolet light can also positively impact us.
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In fact, I will describe a particular set of new results
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that show that ultraviolet light
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viewed for just a few minutes each day
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or landing on the skin for just a few minutes each day
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can actually offset a lot of pain.
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It actually has the ability to reduce the amount of pain
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sensed by your body and we now understand
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the specific circuits in the brain and body
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that allow that to happen.
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I'll talk about that
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and the related protocols a little bit later.
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So the important thing to understand
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about the physics of light is that there's energy
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at all these different wavelengths.
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We only see some of those wavelengths,
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which basically is to say that light impacts us
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at many different levels and the so-called levels
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that I'm referring to are the different wavelengths of light
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and you're welcome to think of the different wavelengths
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of light as different colors,
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but do understand that there are truly colors of light
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that you and I can't see and yet that have powerful impact
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on your brain and body.
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Now, the third bullet point to understand
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about the physics of light
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is that different wavelengths of light
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because of the way that their wave travels
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can penetrate tissues to different depths.
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This is very, very important.
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Today, we're going to talk a lot about red light therapies
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and near infrared light therapies.
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Those are so-called longer wavelengths.
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Longer wavelength, just think of a bigger, longer wave,
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a bigger curve, as opposed to short wavelength light,
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which is going to be shorter.
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A short wavelength light would be something like blue
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or green light or ultraviolet light.
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Blue, green and ultraviolet light,
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because it's short wavelength light,
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doesn't tend to penetrate tissues very easily.
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It has to do with the way that the physics of light
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interacts with the physical properties of your skin
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and other tissues of your body.
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But basically, if you were to shine UV light
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onto your arm, for instance,
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it could impact the skin on the surface of the arm
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and maybe some of the cells
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just beneath the top layer of skin,
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but it wouldn't penetrate much deeper.
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Long wavelength light like red light and near infrared light
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has this amazing ability to penetrate through tissues,
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including your skin.
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And so if we were to shine red light
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or near infrared light onto your arm,
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it would pass through that top layer of skin.
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It might impact it a little bit,
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but it could penetrate deeper into your skin,
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not just to the skin layers,
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but maybe even down to the bone,
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maybe even down to the bone marrow.
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And for many people, this will be hard to conceptualize.
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You think, well, wait, I've got a skin there.
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Doesn't the light just bounce off?
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And the answer is no,
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because of the way that long wavelength light
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interacts with the absorbance properties of your skin.
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Absorbance properties is just the way
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that the skin takes light energy
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and converts it into a different form of energy.
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And your skin is not able to take long wavelength light
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like red light and near infrared light and absorb it,
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but the tissues deeper in your body can.
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So if you shine red light or near infrared light
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onto the surface of your skin,
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you'll see a red glow there as a reflectance
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on the surface of your skin.
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But a lot of the photon energy,
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the light energy in those longer wavelengths
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is indeed passing through those top layers of skin
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into the deeper layers of skin
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and can even make it into the deep layers of your arm.
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And as we start to transition from the physics of light
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to the biological impacts of light,
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just understanding that the different wavelengths of light
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impact our tissues at different levels,
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literally at different depths,
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will help you better understand
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how light of different colors, of different intensities,
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and how long you are exposed to those colors
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and intensities of light can change the way
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that the cells and the organs of your body work.
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And if it didn't sound weird enough
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that you can pass light through particular tissues
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and have them land and be absorbed
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at tissues deeper in your body,
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well, it turns out that different wavelengths of light
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are also best absorbed by particular
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so-called organelles within your cells.
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What are organelles?
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Organelles are the different compartments
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and different functions within a given cell.
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So for instance, your mitochondria,
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which are responsible for generating ATP
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and energy in your cells,
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those exist at a particular depth,
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at a particular location within a cell.
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They're not all at the cell surface.
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They sit somewhat deeper in the cell.
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The nucleus of your individual cells contains DNA,
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and that sits at a particular depth
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or location within your cell.
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Different wavelengths of light
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not only can penetrate down into different tissues
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and into different cells of your body,
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but they can also penetrate and access particular organelles,
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meaning mitochondria or the nucleus
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or the different aspects of your cells
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that are responsible for different functions.
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This is exquisitely important,
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and it's exquisitely powerful
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because as you'll learn today,
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particular wavelengths of light
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can be used to stimulate the function
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of particular organelles within particular cells
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within particular organs of your body.
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I can think of no other form of energy,
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not sound, not chemical energy, so not drugs,
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not food, not touch,
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no form of energy that can target the particular locations
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in our cells, in our organelles, in our organs,
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and in our body to the extent that light can.
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if you had to imagine a real world surgical tool
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by which to modulate our biology,
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light would be the sharpest
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and the most precise of those tools.
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Now let's talk about how light is converted
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into biological signals.
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There are several ways in which that is accomplished,
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but the fundamental thing to understand
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is this notion of absorption of light energy.
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Certain pigments or colors
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in the thing that is receiving the light energy,
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meaning the thing that the light energy lands on
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are going to absorb particular wavelengths of light.
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Now, I promise you that you already intuitively know
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For instance, if you were to sit outside
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on a very bright sunny day
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and you had a table in front of you that was metal,
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you might find it hard to look down at that metal table
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because it's reflecting a lot of light
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of particular wavelengths.
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If that table were pitch black, however,
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it wouldn't reflect quite as much
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and you would be able to comfortably look at it.
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If that table were red, it might be somewhere in between.
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If that table were green,
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it would be also somewhere in between,
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but let's say it were very light blue,
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well, then it might reflect almost as much
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as a table that were just metal or a white table surface.
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So the absorbance properties of a given surface
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will determine whether or not light energy goes
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and stays at that location
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and has an impact on that location
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or whether or not it bounces off.
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Every biological function of light
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has to do with the absorbance or the reflectance of light
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or light passing through that particular thing,
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meaning that particular cell or compartment within a cell.
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I'd like to make it clear how this works
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by using the three primary examples
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of how you take light in your environment
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and convert it into biological events.
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We have photoreceptors in the back of our eyes.
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These photoreceptors come in two major types,
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the so-called rods and the cones.
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The rods are very elongated, they look like rods,
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and the cones look like little triangles.
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Rods and cones have within them photo pigment.
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They have dark stuff that's stacked up in little layers.
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Rods absorb light of essentially any wavelength.
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There's some variation to that,
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but let's just say rods don't care
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about the different colors of light.
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They will absorb light energy, photon energy.
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If it's red, if it's green, if it's blue, if it's yellow,
link |
doesn't matter as long as that light is bright enough.
link |
And it turns out that rods are very, very sensitive.
link |
They can detect very, very small numbers of photons.
link |
And rods are essentially what you use
link |
to see in very low light conditions.
link |
We'll return more to vision later.
link |
The cones come in three major varieties.
link |
At least for most people who aren't colorblind,
link |
you have so-called red cones, green cones, and blue cones,
link |
but they're not really red, green, and blue
link |
in the back of your eye.
link |
They are cones that either absorb long wavelength light,
link |
red, that absorb medium wavelength light,
link |
green, or short wavelength light, blue.
link |
The reason that they can absorb different wavelengths
link |
of light is they have different photo pigments.
link |
So much as the example I gave before,
link |
where you have different tables outside
link |
in the sunny environment,
link |
and some are reflecting light more than others,
link |
others are absorbing light more than others.
link |
Well, so too the photoreceptors,
link |
meaning the cones are absorbing light of different
link |
wavelengths to different extents.
link |
And in a absolutely incredible way,
link |
your brain is actually able to take that information
link |
and create this perception that we have of color.
link |
But that's another story altogether that we'll just touch
link |
on a little bit more later,
link |
but that if you want to learn all about,
link |
you can go to our episode on vision.
link |
So that's photoreceptors in the back of your eye,
link |
absorbing light of different wavelengths, rods and cones.
link |
The other place of course,
link |
where light can impact our body is on our surface,
link |
on our skin and skin has pigment too.
link |
We call that pigment melanin.
link |
We have within our skin multiple cell types,
link |
but in the top layer of skin,
link |
which is called the epidermis,
link |
we have keratinocytes and we have melanocytes.
link |
And the melanocytes are the cells that create pigmentation
link |
And of course there is wide variation in the degree to which
link |
there's pigmentation of the skin,
link |
which has to do with genetics,
link |
also has to do with where you were born and raised,
link |
how much light exposure you have throughout the year, right?
link |
So people toward the equator tend to have more melanocyte
link |
activity than people who are located at the North pole.
link |
And of course people live at different locations
link |
throughout the earth,
link |
regardless of their genetic background
link |
or where they were born.
link |
And so, as you all know, with light exposure,
link |
those melanocytes will turn on genetic programs
link |
and other biological programs that lead to enhanced
link |
pigmentation on the skin, which we call tanning.
link |
The way they do that is by absorbing UV light specifically.
link |
So with melanocytes,
link |
we have a very specific example of how a pigment absorbs
link |
light of a particular length, in this case,
link |
ultraviolet short wavelength light,
link |
which in turn creates a set of biological signals within
link |
those cells that in turn creates changes in our skin
link |
So we have photoreceptors,
link |
we have melanocytes and the third example I'd like to
link |
provide is that of every cell of your body.
link |
And what I mean by that is that every cell of your body,
link |
meaning a cell that is part of your bone tissue or your bone
link |
marrow or heart tissue or liver or spleen,
link |
if light can access those cells,
link |
it will change the way that those cells function for better
link |
For many organs within our body that reside deep to our
link |
skin, light never arrives at those cells.
link |
A really good example of this that we'll touch on later is
link |
Unless you have massive damage to your body surface,
link |
unless you literally have a hole in your body,
link |
light will never land directly on your spleen,
link |
but the spleen still responds to light information through
link |
indirect pathways.
link |
And those indirect pathways arise through light arriving on
link |
the skin and light arriving on the eyes.
link |
So a key principle that I'm going to return to again and
link |
again today is that the ways in which light can impact the
link |
biology of your organelles, your cells,
link |
your organs and the tissues,
link |
and indeed your whole body can either be direct.
link |
light onto your skin impacting skin or light onto your
link |
photoreceptors impacting the photoreceptors of your eye,
link |
or it can be indirect.
link |
It can be light arriving on your photoreceptors,
link |
the photoreceptors then informing another cell type,
link |
which informs another cell type,
link |
which then relays a signal and kind of a bucket brigade
link |
manner off to the spleen and says to the spleen,
link |
Hey, there's a lot of UV light out here.
link |
We're actually under stress.
link |
there's so much UV light that you need to activate an immune
link |
program to protect the skin.
link |
And in response to that,
link |
the spleen can deploy certain signals and certain cell types
link |
to go out and start repairing skin that's being damaged by
link |
So we have direct signals and we have indirect signals,
link |
but in every case,
link |
it starts with light,
link |
a particular wavelengths being absorbed by particular
link |
pigments or properties of the surfaces that those light
link |
And as you recall from our discussion about the physics of
link |
it's not just about light impinging on the surface of your
link |
Light can actually penetrate deep to the skin and access at
link |
least certain tissues and cells of your body.
link |
Even though you can't see those wavelengths of light,
link |
they are getting into you all the time.
link |
So perhaps the best way to wrap this discussion about the
link |
physics and the biology of light with a bit of a bow is to
link |
think about light as a transducer,
link |
meaning a communicator of what's going on in the environment
link |
And that some of those signals are arriving at the surface
link |
and impacting the surface of your body.
link |
But many of those signals are being taken by cells at the
link |
surface of your body,
link |
meaning your melanocytes in your skin and the
link |
photoreceptors of your eyes,
link |
and then being passed off as a set of instructions to the
link |
other organs and tissues of your body.
link |
Light can impact our biology in very fast,
link |
moderately fast and slow ways.
link |
But even the slow ways in which light can impact our biology
link |
can be very powerful and very long lasting.
link |
Just as a quick example of the rapid effects of light on our
link |
biology, if you were to go from a room that is dimly lit,
link |
or dark into a very brightly lit room,
link |
you would immediately feel very alert.
link |
You might say, no, that's not true.
link |
Sometimes I wake up and it's dark and I kind of stumble out
link |
and it's lighter out in the next room.
link |
And it takes me a while to wake up.
link |
But if we were to move you from a room that was very dark to
link |
a signal conveyed from your eyes to an area of your brain
link |
stem called the locus coeruleus would cause the release of
link |
adrenaline similar to the release of adrenaline.
link |
If you were to be dropped into very,
link |
very cold water, all of a sudden,
link |
you just an immediate wake up signal to your brain and body.
link |
So that's an example of a rapid effect of light on your
link |
biology, not a very typical one,
link |
but nonetheless one that has a hardwired biological
link |
mechanism at the other end of the spectrum or what we call
link |
slow integrating effects of light on our biology.
link |
So what I mean by that are ways in which your body is taking
link |
information about light in the environment,
link |
not in the sort of snapshot acute sense,
link |
but averaging the amount of light in your environment.
link |
And that average light information is changing the way that
link |
your biology works.
link |
But even though this is a slow process,
link |
as I mentioned before, it's a very powerful one.
link |
The primary example of this are so-called
link |
circannual rhythms, circannual rhythms are literally a
link |
calendar that exists within your body that uses not numbers,
link |
but amounts of hormone that are released into your brain and
link |
body each day and each night as a way of knowing where you
link |
are in the 365 day calendar year.
link |
Now that might seem kind of crazy, but it's not crazy.
link |
The earth travels around the sun once every 365 days.
link |
And depending on where you are on the earth, where you live,
link |
you are going to get more or less light each day on average,
link |
depending on the time of year.
link |
So if you're in the Northern hemisphere in the winter months,
link |
days are shorter, nights are longer.
link |
In the summer months, days are longer, nights are shorter.
link |
And of course things change whether or not you're in the
link |
Northern hemisphere or the Southern hemisphere.
link |
But nonetheless, in short days,
link |
you have more darkness that's obvious.
link |
And if you understand that light arriving on the eyes is
link |
absorbed by a particular cell type called the intrinsically
link |
photosensitive ganglion cell, it's just a name.
link |
You don't need to know the name,
link |
but if you want it's the so-called intrinsically
link |
photosensitive ganglion cell also called the
link |
melanopsin cell, because it contains an opsin,
link |
a photo pigment that absorbs short wavelength light that
link |
arrives through sunlight,
link |
those cells communicate to particular stations in the brain
link |
that in turn connect to your so-called pineal gland,
link |
which is this little pea-sized gland in the middle of your
link |
brain that releases a hormone called melatonin.
link |
And the only thing you need to know is that light activates
link |
these particular cells,
link |
the intrinsically photosensitive melanopsin cells,
link |
which in turn shuts down the production of melatonin from
link |
If you think about this in terms of the travel of the earth
link |
around the sun across the year,
link |
what it means is that in short days,
link |
because there's very little light on average landing on
link |
the duration of melatonin release will be much longer
link |
because as I mentioned before light inhibits,
link |
it shuts down melatonin.
link |
Whereas in the summer months,
link |
much more light on average will land on your eyes, right?
link |
Because days are longer.
link |
Even if you're spending more time indoors on average,
link |
you're going to get more light to activate these cells.
link |
And because light shuts down melatonin production,
link |
what you'll find is that the duration of melatonin release
link |
for the pineal is much shorter.
link |
So melatonin is a transducer.
link |
It's a communicator of how much light on average is in your
link |
physical environment.
link |
What this means is for people living in the Northern
link |
you're getting more melatonin release in the winter months
link |
than you are in the summer months.
link |
So you have a calendar system that is based in a hormone.
link |
And that hormone is using light in order to determine where
link |
you are in that journey around the sun.
link |
Now this is beautiful.
link |
At least to me, it's beautiful because what it means is that
link |
the environment around us is converted into a signal that
link |
changes the environment within us.
link |
That signal is melatonin and melatonin is well-known for its
link |
role in making us sleepy each night and allowing us to fall
link |
Many of you have probably heard before,
link |
I am not a big fan of melatonin supplementation for a number
link |
of reasons, but just as a quick aside,
link |
the levels of melatonin that are in most supplements are far
link |
too high to really be considered physiological.
link |
They are indeed super physiological in most cases.
link |
And melatonin can have a number of different effects,
link |
not just related to sleep, but that's supplemented melatonin.
link |
Here I'm talking about our natural production and release of
link |
according to where we are in the 365 day calendar year.
link |
Indogenous melatonin,
link |
meaning the melatonin that we make within our bodies
link |
naturally, not melatonin that's supplemented,
link |
has two general categories of effects.
link |
The first set of effects are so-called regulatory effects,
link |
and the others are protective effects.
link |
The regulatory effects are for instance,
link |
that melatonin can positively impact bone mass.
link |
So melatonin can, for instance,
link |
turn on the production of osteoblasts,
link |
which are essentially stem cells that make more bone for us
link |
that make our bones stronger,
link |
and that can replace damaged aspects of our bone.
link |
Melatonin is also involved in maturation of the gonads
link |
during puberty, the ovaries and the testes.
link |
Although there, the effects of melatonin tend to be
link |
suppressive on maturation of the ovaries and testes,
link |
meaning high levels of melatonin tend to reduce testicle
link |
volume and reduce certain functions within the testes,
link |
including sperm production and testosterone production.
link |
And within the ovaries,
link |
melatonin can suppress the maturation of eggs, et cetera.
link |
Now, I don't want anyone to get scared
link |
if you've been taking melatonin,
link |
mostly effects of melatonin on those functions
link |
but I should point out that one of the reasons
link |
why children don't go into puberty until a particular age
link |
is that young children tend to have
link |
chronically high endogenous melatonin,
link |
and that is healthy to keep them out of puberty
link |
until it's the right time for puberty to happen.
link |
So melatonin can increase bone mass,
link |
but reduces gonad mass, so to speak.
link |
It's going to have varying effects
link |
depending on the ratios and levels of other hormones
link |
and other biological events in the body.
link |
But as you can see, melatonin has these powerful
link |
regulatory effects on other tissues.
link |
I should also mention that melatonin
link |
is a powerful modulator of placental development.
link |
So for anyone that's pregnant,
link |
if you're considering melatonin supplementation,
link |
please, please, please talk to your OBGYN,
link |
talk to your other doctor as well.
link |
You want to be very, very cautious
link |
because of the powerful effects that melatonin can have
link |
on the developing fetus and placenta.
link |
For people that are not pregnant, in fact, all people,
link |
melatonin has a powerful effect on the central nervous
link |
system as a whole.
link |
Your brain and spinal cord are the major components
link |
of your central nervous system.
link |
And melatonin, because it's associated with darkness,
link |
which is just another way of saying that
link |
light suppresses melatonin, melatonin is thereby associated
link |
with the dark phase of each 24 hour cycle,
link |
it can have a number of different effects
link |
in terms of waking up or making our body feel more sleepy.
link |
And it does that by way of impacting cells
link |
within our nervous system,
link |
literally turning on certain brain areas,
link |
turning off other brain areas.
link |
And it does that through a whole cascade
link |
of biological mechanisms,
link |
a bit too detailed to get into today.
link |
So melatonin is regulating how awake or asleep we are.
link |
It tends to make us more asleep, incidentally.
link |
It's regulating our timing of puberty
link |
and it's regulating how our gonads,
link |
the testes and ovaries function,
link |
even in adulthood to some extent,
link |
and it's regulating bone mass.
link |
As I mentioned before, melatonin also has protective effects.
link |
It can activate our immune system.
link |
It is among the most potent antioxidants.
link |
So it is known to have certain anti-cancer properties
link |
and things of that sort,
link |
which is not to say that you simply want more melatonin.
link |
I think a lot of people get misled
link |
when they hear something like melatonin
link |
has anti-cancer properties.
link |
That doesn't mean that just cranking up
link |
the levels of melatonin by supplementing it
link |
or by spending time in darkness and not getting any light,
link |
which would of course inhibit melatonin
link |
is going to be beneficial for combating cancer.
link |
That's not the way it works.
link |
It is actually the rise and fall of melatonin
link |
every 24 hour cycle and the changes in the duration
link |
of that melatonin signal throughout the seasons
link |
that has these anti-cancer and antioxidant effects.
link |
So when we think about light impacting our biology,
link |
the reason I bring up melatonin
link |
as the primary example of that is A,
link |
because melatonin impacts so many important functions
link |
within our brain and body,
link |
but also because hormones in general, not always,
link |
but in general are responsible
link |
for the slow modulatory effects on our biology.
link |
And so I'm using this as an example
link |
of how light throughout the year is changing the way
link |
that the different cells and tissues
link |
and organs of your body are working
link |
and that melatonin is the transducer of that signal.
link |
So at this point we can say
link |
light powerfully modulates melatonin,
link |
meaning it shuts down melatonin.
link |
Melatonin is both beneficial for certain tissues
link |
and suppressive for other tissues and functions.
link |
What should we do with this information?
link |
Well, it's very well established now
link |
that one of the best things that we can all do
link |
is to get the proper amount of sunlight each day.
link |
And by proper, I mean appropriate for that time of year.
link |
So in the summer months where the days are longer
link |
and nights are shorter,
link |
we would all do well to get more sunlight in our eyes.
link |
And again, it's going to be to our eyes
link |
because as you recall, the pineal sits deep in the brain
link |
and light can't access the pineal directly,
link |
at least not in humans.
link |
So in order to get light information to the pineal
link |
and thereby get the proper levels of melatonin,
link |
according to the time of year,
link |
we should all try and get outside as much as possible
link |
during the long days of summer and spring.
link |
And in the winter months,
link |
it makes sense to spend more time indoors.
link |
For those of you that suffer
link |
from seasonal affective disorder,
link |
which is a seasonal depression
link |
or feel low during the fall and winter months,
link |
there are ways to offset this.
link |
We did an entire episode on mood and circadian rhythms
link |
where we describe this.
link |
So it does make sense for some people
link |
to get more bright light in their eyes early in the morning
link |
and throughout the day during the winter months as well.
link |
But nonetheless, changes in melatonin,
link |
meaning changes in the duration of melatonin release
link |
across the year are normal and healthy.
link |
So provided that you're not suffering from depression,
link |
it's going to be healthy to somewhat modulate your amount
link |
of indoor and outdoor time across the year.
link |
The other thing to understand
link |
is this very firmly established fact,
link |
which is light powerfully inhibits melatonin.
link |
If you wake up in the middle of the night
link |
and you go into the bathroom and you flip on the lights,
link |
and those are very bright overhead fluorescent lights,
link |
your melatonin levels,
link |
which would ordinarily be quite high
link |
in the middle of the night,
link |
because you've been eyes closed in the dark presumably,
link |
will immediately plummet to near zero or zero.
link |
We would all do well, regardless of time of year,
link |
to not destroy our melatonin
link |
in the middle of the night in this way.
link |
So if you need to get up in the middle of the night
link |
and use the restroom,
link |
which is a perfectly normal behavior for many people,
link |
use the minimum amount of light required
link |
in order to safely move through the environment
link |
that you need to move through.
link |
Melatonin needs to come on early in the night.
link |
It actually starts rising in the evening and towards sleep.
link |
But then as you close your eyes and you go to sleep,
link |
melatonin levels are going to continue to rise,
link |
at least for several hours into the night.
link |
Again, if you get up in the middle of the night,
link |
really try hard not to flip on a lot of bright lights.
link |
If you do that every once in a while,
link |
it's not going to be a problem.
link |
But if you're doing that night after night,
link |
you are really disrupting this fundamental signal
link |
that occurs every night,
link |
regardless of winter, spring, summer, et cetera,
link |
and that is communicating information
link |
about where your brain and body should be in time.
link |
And I know that's a little bit of a tricky concept,
link |
but really our body is not meant to function
link |
in the same way during the winter months
link |
as the summer months.
link |
There are functions that are specifically optimal
link |
for the shorter days of winter.
link |
And there are functions that are specifically optimal
link |
for the longer days of summer.
link |
So again, try to avoid bright light exposure to your eyes
link |
in the middle of the night.
link |
And for those of you that are doing shift work,
link |
what I can say is try and avoid getting bright light
link |
in your eyes in the middle of your sleep cycle.
link |
So even if you're sleeping in the middle of the day,
link |
because you have to work at night,
link |
if you wake up during that bout of sleep,
link |
really try hard to limit the amount of light,
link |
which is going to be harder for shift workers, right?
link |
Because there are generally a lot more lights on
link |
and bright lights outside too.
link |
You would want to close the blinds
link |
and limit artificial light inside.
link |
One way to bypass some of the inhibitory effects
link |
of light on melatonin
link |
is to change your physical environment
link |
by for instance, dimming the lights.
link |
That's one simple way, very low cost way.
link |
In fact, you'll save money by dimming the lights
link |
or turning them off.
link |
The other is if you are going to use light
link |
using long wavelength light,
link |
because as you recall these intrinsically
link |
photosensitive melanopsin cells within your retina
link |
that convey the signal about bright light
link |
in your environment to impact melatonin,
link |
to shut down melatonin,
link |
respond to short wavelengths of light.
link |
So red light is long wavelength light.
link |
You now understand that from our discussion
link |
about the physics of light.
link |
And if you were to use amber colored light or red light,
link |
and even better dim amber or dim red light
link |
in the middle of the night,
link |
well then you would probably not reduce melatonin at all,
link |
unless those red lights and amber lights
link |
are very, very bright.
link |
Any light provided it's bright enough
link |
will shut down melatonin production.
link |
One final point about melatonin,
link |
and this relates to melatonin supplementation as well,
link |
is that now that you understand how potently melatonin
link |
can impact things like cardiovascular function,
link |
immune function, anticancer properties,
link |
bone mass, gonad function, et cetera,
link |
you can understand why it would make sense to be cautious
link |
about melatonin supplementation,
link |
because supplementation tends to be pretty static.
link |
It's X number of milligrams per night.
link |
Whereas normally endogenously,
link |
the amount of melatonin that you're releasing each night
link |
is changing according to time of year,
link |
or if you happen to live in an area
link |
where there isn't much change in day length across the year.
link |
So for instance, if you live near the equator,
link |
well, then your body is accustomed
link |
to having regular amounts of melatonin each night.
link |
When you start supplementing melatonin,
link |
you start changing the total amount of melatonin obviously,
link |
but you're also changing the normal rhythms
link |
in how much melatonin is being released
link |
into your brain and body across the 365 day calendar year.
link |
So while I'm somebody who readily embraces supplementation
link |
in various forms for things like sleep and focus, et cetera,
link |
when it comes to melatonin, I'm extremely cautious.
link |
And I think it's also one of the few examples
link |
where a hormone is available without prescription
link |
You can just go into a pharmacy or drug store,
link |
order online this hormone,
link |
which is known to have all these powerful effects.
link |
So I get very, very concerned
link |
when I hear about people taking melatonin,
link |
especially at the levels that are present
link |
in most supplements.
link |
It's been recognized for a very long time.
link |
And in fact, there are now data to support the fact
link |
that animals of all kinds, including humans,
link |
will seek out mates and engage in mating behavior
link |
more frequently during the long days of spring and summer.
link |
That's right, in seasonally breeding animals,
link |
of course, this is the case, but in humans as well,
link |
there is more seeking out of mates and mating behavior
link |
in longer day times of year.
link |
Now you could imagine at least two mechanisms
link |
by which this occurs.
link |
The first mechanism we could easily map to melatonin
link |
and the fact that melatonin is suppressive
link |
to various aspects of the so-called gonadal axis,
link |
which is basically a fancy way of saying
link |
that melatonin inhibits testosterone and estrogen output
link |
from the testes and from the ovaries.
link |
I just want to remind people that both males and females
link |
make testosterone and estrogen,
link |
although in different ratios typically in males versus
link |
females, and that both testosterone and estrogen
link |
are critical for the desire to mate
link |
and for mating behavior.
link |
There's a broad misconception that testosterone
link |
is involved in mating behavior and estrogen is involved
link |
in other behaviors, but having enough estrogen is critical
link |
for both males and females in order to maintain the desire
link |
to mate and indeed the ability to mate.
link |
I discussed this on the episode on optimizing testosterone
link |
and estrogen, so if you'd like more details on that,
link |
please see that episode of the Huberman Lab Podcast.
link |
Okay, so if melatonin is suppressive
link |
to the so-called gonadal axis and reduces overall levels
link |
of testosterone and estrogen in males and females,
link |
and the light inhibits melatonin,
link |
then when there's more light, then there's less melatonin
link |
and a more hormone output from the gonads.
link |
And indeed that's how the system works,
link |
but that's not the entire story.
link |
It turns out that there is a second so-called parallel
link |
pathway, meaning a different biological pathway that operates
link |
in parallel to the light suppression of melatonin pathway
link |
that provides a basis for longer days,
link |
inspiring more desire to mate and more mating behavior.
link |
So if we think of the first pathway involving melatonin
link |
as sort of a break on these reproductive hormones,
link |
the second mechanism is more like an accelerator
link |
on those hormones, and yet it still involves light.
link |
As I'm about to tell you, in animals such as mice,
link |
but also in humans, exposure to light,
link |
in particular UV blue light, so short wavelengths of light,
link |
can trigger increases in testosterone and estrogen
link |
and the desire to mate.
link |
Now what's especially important about this accelerator
link |
on the desire to mate and mating behavior and hormones
link |
is that it is driven by exposure to light,
link |
but it is not the exposure of light to the eyes.
link |
It turns out that it is the exposure of your skin
link |
to particular wavelengths of light that is triggering
link |
increases in the hormones, testosterone and estrogen,
link |
leading to increased desire to mate.
link |
As it turns out, your skin, which most of us just think of
link |
as a way to protect the organs of our body
link |
or something to hang clothes on or ornaments on,
link |
if you're somebody who has earrings and so forth,
link |
your skin is actually an endocrine organ,
link |
meaning it is a hormone producing
link |
and hormone influencing organ.
link |
I promise what I'm about to tell you next
link |
will forever change the way that you think about your skin
link |
and light and the desire to mate
link |
and indeed even mating behavior.
link |
I think the results are best understood
link |
by simply going through the primary data,
link |
meaning the actual research on this topic.
link |
And to do so, I'm going to review a recent paper
link |
that was published in the journal Cell Reports,
link |
Cell Press Journal, excellent journal.
link |
This is a paper that came out in 2021,
link |
entitled Skin Exposure to UVB Light
link |
Induces a Skin Brain Gonad Axis and Sexual Behavior.
link |
And I want to emphasize that this was a paper
link |
that focused on mice in order to address specific mechanisms
link |
because in mice, you can so-called knock out
link |
particular genes, you can remove particular genes
link |
to understand mechanism.
link |
You just can't do that in humans
link |
in any kind of controlled way,
link |
at least not at this point in time.
link |
And this study also explores humans
link |
and looked at human subjects, both men and women.
link |
The basic finding of this study was that
link |
when mice or humans were exposed to UVB,
link |
meaning ultraviolet blue light,
link |
so short wavelength light of the sort
link |
that comes through in sunshine,
link |
but is also available through various artificial sources.
link |
If they received enough exposure of that light
link |
to their skin, there were increases in testosterone
link |
that were observed within a very brief period of time,
link |
also increases in the hormone estrogen.
link |
And I should point out that the proper ratios
link |
of estrogen and testosterone were maintained
link |
in both males and females,
link |
at least as far as these data indicate.
link |
And mice tended to seek out mating more and mate more.
link |
There were also increases in gonadal weight,
link |
literally increases in testes size and in ovarian size
link |
when mice were exposed to this UVB light
link |
past a certain threshold.
link |
Now, as I mentioned before, the study also looked at humans.
link |
They did not look at testes size or ovarian size
link |
in the human subjects.
link |
However, because they are humans,
link |
they did address the psychology of these human beings
link |
and address whether or not they had increases in,
link |
for instance, aggressiveness or in passionate feelings
link |
and how their perception of other people changed
link |
when they were getting a lot of UVB light exposure
link |
So before I get into some of the more important details
link |
of the study and how it was done
link |
and how you can leverage this information for yourself,
link |
if you desire, I just want to highlight
link |
some of the basic findings overall.
link |
UVB exposure increased these so-called sex steroid levels
link |
in mice and humans.
link |
The sex steroid hormones, when we say steroids,
link |
we don't mean anabolic steroids taken exogenously.
link |
I think when people hear the word steroids,
link |
they always think steroid abuse or use.
link |
Rather steroid hormones such as testosterone and estrogen
link |
went up when mice or humans had a lot of UVB exposure
link |
Second of all, UVB light exposure to the skin,
link |
enhanced female attractiveness,
link |
so the perceived attractiveness of females by males
link |
and increase the receptiveness or the desire to mate
link |
UVB light exposure also changed various aspects
link |
of female biology related to fertility,
link |
in particular, follicle growth.
link |
Follicle and egg maturation are well-known indices
link |
of fertility and of course correlate
link |
with the menstrual cycle in adult humans
link |
and is related overall to the propensity to become pregnant.
link |
UVB light exposure enhanced maturation of the follicle
link |
which just meant that more healthy eggs were being produced.
link |
These are impressive effects.
link |
First of all, they looked at a large number of variables
link |
in the study and the fact that they looked at mice
link |
and humans is terrific.
link |
I think that oftentimes we find it hard to translate data
link |
from mice to humans.
link |
So the fact that they looked at both in parallel
link |
In the mice and in the humans,
link |
they established a protocol that essentially involved
link |
exposing the skin to UV light that was equivalent
link |
to about 20 to 30 minutes of midday sun exposure.
link |
Now, of course, where you live in the world
link |
will dictate whether or not that midday sun
link |
is very, very bright and intense,
link |
or is less bright, maybe there's cloud cover, et cetera.
link |
But since I'm imagining that most people are interested
link |
in the ways to increase testosterone
link |
and or estrogen in humans and are not so much interested
link |
in increasing testosterone in mice,
link |
I'm going to just review what they did
link |
in the human population or the human subjects.
link |
What they did is they had people,
link |
first of all, establish a baseline.
link |
And the way they establish a baseline
link |
was a little bit unusual,
link |
but it will make perfect sense to you.
link |
They had people wear long sleeves and essentially cover up
link |
and avoid sunlight for a few days
link |
so they could measure their baseline hormones
link |
in the absence of getting a lot of UVB light exposure
link |
from the sun or from other sources.
link |
Now, of course, these people had access
link |
to artificial lights,
link |
but as I've pointed out on this podcast before,
link |
it's pretty unusual that you'll get enough UVB exposure
link |
from artificial lights throughout the day.
link |
And in the morning, you need a lot of UVB exposure,
link |
or we should be getting a lot of UVB exposure to our eyes
link |
and to our face and to our skin throughout the day,
link |
provided we're not getting sunburned.
link |
This is actually a healthy thing for mood
link |
and for energy throughout the day.
link |
It's only at night, basically between the hours
link |
of about 10 p.m. and 4 a.m.
link |
that even a tiny bit of UVB exposure from artificial sources
link |
can mess us up in terms of our sleep
link |
and our energy levels and so on.
link |
And that's because of the potent effect of UVB
link |
on suppressing melatonin.
link |
So the point here is that they establish a baseline
link |
whereby people were getting some artificial light exposure
link |
throughout the day, but they weren't getting outside a lot.
link |
They weren't getting a lot of sunlight.
link |
And then they had people receive a dose
link |
of UVB light exposure that was about 20 to 30 minutes
link |
They had people wear short sleeves, no hat, no sunglasses.
link |
Some people wore sleeveless shirts.
link |
They encouraged people to wear shorts.
link |
So they were indeed wearing clothing.
link |
They were not naked and they were wearing clothing
link |
that was culturally and situationally appropriate,
link |
at least for the part of the world where this study was done
link |
and they had people do that two or three times a week.
link |
So in terms of a protocol that you might export
link |
from this study, basically getting outside
link |
for about 30 minutes, two or three times a week
link |
in a minimum of clothing and yet still
link |
wearing enough clothing that is culturally appropriate.
link |
They were outside, they weren't sunbathing,
link |
flipping over on their back and front.
link |
They were just moving about doing things they could read.
link |
They could talk, they could go about other activities,
link |
but they weren't wearing a broad brim hat
link |
or a hat of any kind.
link |
They're just getting a lot of sun exposure to their skin.
link |
They did this for a total of 10 to 12 UVB treatments.
link |
So this took several weeks, right?
link |
It took about a month if you think about it,
link |
two or three times per week for a total
link |
of 10 to 12 UVB treatments.
link |
These treatments, of course,
link |
are just being outside in the sun.
link |
And then they measured hormones
link |
and they measured the psychology of these male
link |
and female adult subjects.
link |
Let's first look at the psychological changes
link |
that these human subjects experienced
link |
after getting 10 to 12 of these UVB light exposure,
link |
outdoor and sunlight type treatments.
link |
They did this by collecting blood samples
link |
throughout the study.
link |
And they saw significant increases
link |
in the hormones beta estradiol,
link |
which is one of the major forms of estrogen,
link |
progesterone, another important steroid hormone,
link |
and testosterone in both men and women.
link |
Now, an important point is that the testosterone increases
link |
were significantly higher in men that happened
link |
to originate from countries that had low UV exposure
link |
compared to individuals from countries
link |
with high UV exposure.
link |
Now, this ought to make sense if we understand
link |
a little bit about how the skin functions
link |
as an endocrine organ.
link |
Many of you have probably heard of vitamin D3,
link |
which is a vitamin that we all make.
link |
Many people supplement it as well
link |
if they need additional vitamin D3.
link |
We all require sunlight in order to allow vitamin D3
link |
to be synthesized and perform its roles in the body.
link |
And it turns out that people who have darker skin
link |
actually need more vitamin D3 and or more sunlight exposure
link |
in order to activate that D3 pathway
link |
than do people with paler skin.
link |
And this should make sense to all of you,
link |
given what you now understand about melanocytes,
link |
that cell type that we discussed earlier,
link |
because melanocytes have pigment within them.
link |
And if you have darker skin,
link |
it means that you have more melanocytes
link |
or that you have melanocytes
link |
that are more efficient at creating pigment.
link |
And as a consequence, the light that lands on your skin
link |
will be absorbed by those melanocytes
link |
and less of it is able to impact the D3 pathway.
link |
Whereas if you have pale skin,
link |
more of the light that lands on your skin
link |
can trigger the synthesis
link |
and assist the actions of vitamin D3.
link |
Similarly, in this study,
link |
they found that people who had paler skin
link |
and or who originated from countries
link |
where they had less UVB light exposure across the year
link |
had greater, meaning more significant increases
link |
in testosterone overall than did people
link |
who already were getting a lot of UVB exposure.
link |
This led them to explore so-called seasonal changes
link |
in testosterone that occurred normally
link |
in the absence of any light exposure treatment.
link |
So up until now, I've been talking about
link |
the aspects of this study involving people getting outside
link |
for about 20 to 30 minutes per day in sunlight
link |
in a minimum of clothing.
link |
There was an increase in testosterone observed
link |
in both men and women.
link |
The increases in testosterone were greater for people
link |
that had paler skin than darker skin.
link |
So the data I'm about to describe
link |
also come from this same paper,
link |
but do not involve 20 to 30 minute
link |
daily sun exposure protocols.
link |
It's simply addressing whether or not
link |
testosterone levels change as a function of time of year.
link |
They measure testosterone across the 12 month calendar.
link |
This study was done on subjects living
link |
in the Northern hemisphere for the entire year.
link |
And so in the months of January, February, and March,
link |
of course, the length of days is shortest
link |
and the length of nights is longest.
link |
And of course, in the spring and summer months,
link |
June, July, August, September, and so on,
link |
the days are much longer and the nights are shorter.
link |
And what they observed was very obvious.
link |
They observed that testosterone levels were lowest
link |
in the winter months and were highest
link |
in the months of June, July, August, and September.
link |
Now, these are very important data.
link |
At least to my knowledge,
link |
these are the first data systematically exploring
link |
the levels of sex steroid hormones in humans
link |
as a function of time of year and thereby as a function
link |
of how much sunlight exposure they're getting.
link |
And what's remarkable about these data
link |
is that they map very well to the data in mice
link |
and the other data in this paper on humans,
link |
which illustrate that if you're getting more UVB exposure,
link |
your testosterone levels are higher.
link |
This study went a step further
link |
and explored whether or not the amount of sunlight exposure
link |
that one is getting to their skin influences
link |
their psychology in terms of whether
link |
or not they have increased desire to mate and so on.
link |
It's well known that sunlight exposure
link |
to the eyes can increase mood.
link |
And I talked about this in the podcast episode
link |
with my guest, Dr. Samir Hatar,
link |
who's the director of the Chronobiology Unit
link |
at the National Institutes of Mental Health.
link |
And Samir's recommendation is that people get
link |
as much bright light exposure as they safely can
link |
in the morning and throughout the day
link |
for sake of both sleep and energy,
link |
but also for enhancing mood and regulating appetite.
link |
In this study, it was found that both males and females
link |
had higher levels of romantic passion
link |
after getting the UV treatment.
link |
In fact, some of them reported increases in romantic passion
link |
from just one or two of these UV treatments.
link |
So they didn't have to go through all 10 or 12
link |
in order to get a statistically significant increase
link |
Now, when we talk about passion,
link |
as the authors of this paper acknowledge,
link |
there's really two forms.
link |
There is emotional and sexual,
link |
and they parse this pretty finely.
link |
I don't want to go into all the details
link |
and we can provide a reference and link to this study
link |
if you'd like to look at those details.
link |
But what they found was that women receiving
link |
this UVB light exposure focused more on increases
link |
in physical arousal and sexual passion.
link |
Whereas the men actually scored higher
link |
on the cognitive dimensions of passion,
link |
such as obsessive thoughts about their partner and so on.
link |
Regardless, both males and females experienced
link |
and reported a increase in sexual passion
link |
and desire to mate.
link |
And we now know there were increases
link |
in testosterone and estrogen,
link |
which of course could be driving the psychological changes.
link |
Although I'm sure that those interact in both directions,
link |
meaning the hormones no doubt affect psychology
link |
and no doubt the psychology,
link |
these changes in passionate feelings,
link |
no doubt also increased or changed
link |
the hormone levels as well.
link |
And I want to reemphasize that there was a component
link |
of the study that had no deliberate daylight,
link |
sunlight exposure for 20 or 30 minutes,
link |
but rather just looked at hormone levels
link |
throughout the year and found that the increase
link |
in day length correlated with increases
link |
in testosterone and sexual passion.
link |
Now, my opinion, this is a very noteworthy study
link |
because it really illustrates that sunlight
link |
and day length can impact the melatonin pathway
link |
and thereby take the foot off the brake, so to speak,
link |
on testosterone, estrogen, and the desire to mate.
link |
It also emphasizes that sunlight, UVB light,
link |
can directly trigger hormone pathways
link |
and desire to mate and mating behavior.
link |
Now, the study went a step further
link |
in defining the precise mechanism
link |
by which light can impact all these hormones
link |
and this desire to mate.
link |
And here, understanding the mechanism is key
link |
if you want to export a particular protocol
link |
or tool that you might apply.
link |
We talked earlier about how UVB light exposure
link |
to the eyes triggers activation
link |
of these particular neurons within the eye
link |
and then with centers deeper in the brain
link |
and eventually the pineal gland
link |
to suppress the output of melatonin
link |
and thereby to allow testosterone and estrogen
link |
to exist at higher levels
link |
because melatonin can inhibit testosterone and estrogen.
link |
In this study, they were able to very clearly establish
link |
that it is sunlight exposure to our skin
link |
that is causing these hormone increases
link |
that they observed in mice and humans.
link |
And the way they did that
link |
was to use the so-called knockout technology,
link |
the ability to remove specific genes
link |
within specific tissues of the body.
link |
And what they found is that UVB light,
link |
meaning sunlight exposed skin upregulated,
link |
meaning increased the activity of something called P53,
link |
which is involved in the maturation of cells
link |
and various aspects of cellular function.
link |
And the cells they were focused on were the keratinocytes,
link |
which you are now familiar with from our earlier discussion
link |
about the fact that the epidermis of your skin
link |
contains mainly keratinocytes and melanocytes.
link |
Sunlight exposure increased P53 activity in the skin
link |
and P53 activity was required
link |
for the downstream increases in ovarian size,
link |
in testicular size, in testosterone increases,
link |
in the estrogen increases
link |
and the various other changes that they observed
link |
at the physiological level
link |
when animals or humans were exposed to sunlight.
link |
So these data are important
link |
because what they mean is that not only is it important
link |
that we get sunlight exposure early in the day
link |
and throughout the day to our eyes,
link |
at least as much as is safely possible,
link |
but that we also need to get UVB sunlight exposure
link |
onto our skin if we want to activate this P53 pathway
link |
in keratinocytes and the testosterone and estrogen increases
link |
that are downstream of that P53 pathway.
link |
So even though the gene knockout studies were done on mice,
link |
they clearly show that if you remove P53 from the skin,
link |
that these effects simply do not occur.
link |
So in terms of thinking about a protocol
link |
to increase testosterone and estrogen,
link |
mood and feelings of passion,
link |
the idea is that you would want to get
link |
this two to three exposures per week minimum
link |
of 20 to 30 minutes of sunlight exposure
link |
onto as much of your body
link |
as you can reasonably expose it to.
link |
And when I say reasonably, I mean,
link |
of course you have to obey cultural constraints,
link |
decency constraints,
link |
and of course you have to also obey the fact
link |
that sunlight can burn your skin.
link |
So many people are probably going to ask
link |
what happens if you wear sunscreen?
link |
In theory, because sunscreen has UV protection,
link |
it would block some of these effects.
link |
Now I'm not suggesting that people
link |
do away with sunscreen entirely.
link |
I do hope to do an episode all about sunscreen
link |
in the future because sunscreen
link |
is a bit of a controversial topic.
link |
Skin cancers are a real thing
link |
and many people are especially prone to skin cancer.
link |
So you need to take that seriously.
link |
Some people are not very prone to skin cancers
link |
and can tolerate much more sun exposure.
link |
You're probably familiar with the simple fact
link |
that if you've gone outside on the beach with friends,
link |
some people get burned very easily, others don't.
link |
So you really should prioritize the health
link |
and the avoidance of sunburn on your skin.
link |
However, these data and other data point to the fact
link |
that we should all probably be striving
link |
to get more sunlight exposure onto our skin
link |
during the winter months
link |
and still getting sunlight exposure onto our skin
link |
in the summer months,
link |
provided we can do that without damaging our skin.
link |
Another set of very impressive effects of UVB light,
link |
whether or not it comes from sunlight
link |
or from an artificial source is the effect of UVB light
link |
on our tolerance for pain.
link |
It turns out that our tolerance for pain
link |
varies across the year and that our pain tolerance
link |
is increased in longer day conditions.
link |
And as we saw with the effects of UVB on hormones
link |
and mating, again, this is occurring via UVB exposure
link |
to the skin and UVB exposure to the eyes.
link |
I want to just describe two studies
link |
that really capture the essence of these results.
link |
I'm going to discuss these in kind of a top contour fashion.
link |
I won't go into it as quite as much depth
link |
as I did the last study,
link |
but I will provide links to these studies as well.
link |
The first study is entitled skin exposure to ultraviolet B
link |
rapidly activate systemic neuroendocrine
link |
and immunosuppressive responses.
link |
And you might hear that and think,
link |
oh, immunosuppressive, that's bad.
link |
But basically what they observed is that
link |
even one exposure to UVB light
link |
changed the output of particular hormones
link |
and neurochemicals in the body,
link |
such as corticotropin hormone and beta endorphins,
link |
which are these endogenous opioids.
link |
We've all heard of the opioid crisis,
link |
which is people getting addicted to opioids
link |
that they are taking in drug form, pharmaceuticals.
link |
But here I'm referring to endorphins
link |
that our body naturally manufactures and releases
link |
in order to counter pain
link |
and act as a somewhat of a psychological soother also,
link |
because of course, physical pain and emotional pain
link |
are intimately linked in the brain and body.
link |
What they found was that exposure to UVB light
link |
increased the release of these beta endorphins.
link |
It caused essentially the release
link |
of an endogenous pain killer.
link |
Now, a second study that came out very recently,
link |
just this last week, in fact,
link |
published in the journal Neuron,
link |
cell press journal, excellent journal,
link |
is entitled a visual circuit related
link |
to the periaqueductal gray area
link |
for the anti-nociceptive effects of bright light treatment.
link |
I'll translate a little bit of that for you.
link |
The periaqueductal gray is a region of the midbrain
link |
that contains a lot of neurons
link |
that can release endogenous opioids,
link |
things like beta enkephalin,
link |
things like enkephalin, things like mu opioid.
link |
These are all names of chemicals
link |
that your body can manufacture
link |
that act as endogenous painkillers
link |
and increase your tolerance for pain.
link |
They actually make you feel less pain overall
link |
by shutting down some of the neurons that perceive pain
link |
or by reducing their activity, not to a dangerous level.
link |
They're not going to block the pain response
link |
so that you burn yourself unnecessarily
link |
or harm yourself unnecessarily,
link |
but they act as a bit of a painkiller from the inside.
link |
If you heard the word anti-nociceptive,
link |
nociception is basically the perception
link |
or the way in which neurons respond to painful stimuli.
link |
So you can think of nociceptive events
link |
in your nervous system as painful events.
link |
And there I'm using a broad brush.
link |
I realized that the experts in pain will say,
link |
oh, it's not a really a pain circuit, et cetera, et cetera.
link |
But for sake of today's discussion,
link |
it's fair to say that nociception is the perception of pain.
link |
So if this title is a visual circuit
link |
related to the periaqueductal gray,
link |
which is this area that releases these endogenous opioids
link |
for the anti-nociceptive,
link |
the anti-pain effects of bright light treatment.
link |
The key finding of this study
link |
is that it is light landing on the eyes
link |
and captured by the specific cells
link |
I was talking about earlier,
link |
those intrinsically photosensitive melanopsin ganglion cells
link |
is the long name for them,
link |
but these particular neurons in your eye
link |
and in my eye incidentally,
link |
that communicate with particular brain areas.
link |
These brain areas have names.
link |
If you want to know them for you aficionados
link |
or for you ultra curious folks,
link |
they have names like the ventrolateral geniculate nucleus
link |
and the inter geniculate leaflet.
link |
The names don't matter.
link |
The point is that light landing on the eyes
link |
is captured by these melanopsin cells.
link |
They absorb that light,
link |
translate that light into electrical signals
link |
that are handed off to areas of the brain,
link |
such as the ventral geniculate.
link |
And then the ventral geniculate communicates
link |
with this periaqueductal gray area
link |
to evoke the release of these endogenous opioids
link |
that soothe you and lead to less perception of pain.
link |
This is a really important study
link |
because it's long been known that in longer days
link |
or in bright light environments,
link |
we tolerate emotional and physical pain better.
link |
Previous studies had shown
link |
that it is light landing on our skin
link |
that mediates that effect,
link |
It couldn't explain the entire effect.
link |
This very recent study indicates
link |
that it's also light arriving at the eyes.
link |
And in this case, again, UVB light,
link |
ultraviolet blue light of the sort that comes from sunlight
link |
that is triggering these anti pain
link |
or pain relieving pathways.
link |
So once again, we have two parallel pathways.
link |
This is a theme you're going to hear
link |
over and over and over again,
link |
not just in this episode,
link |
but in all episodes of the Huberman Lab Podcast,
link |
because this is the way that your brain and body are built.
link |
Nature rarely relies on one mechanism
link |
in order to create an important phenomenon
link |
and pain relief is an important phenomenon.
link |
So we now have at least two examples
link |
of the potent effects of UVB light exposure
link |
to the skin and to the eyes.
link |
One involving activation of testosterone
link |
and estrogen pathways as it relates to mating
link |
and another that relates to reducing
link |
the total amount of pain that we experience
link |
in response to any painful stimuli.
link |
So for those of you that are thinking tools and protocols,
link |
if you're somebody who's experiencing chronic pain,
link |
provided you can do it safely,
link |
try to get some UVB exposure, ideally from sunlight.
link |
I think the 20 to 30 minute protocol
link |
two or three times per week is an excellent one.
link |
It seems like a fairly low dose of UVB light exposure.
link |
It's hard to imagine getting much damage to the skin.
link |
Of course, if you have very sensitive skin,
link |
or if you live in an area of the world
link |
that is very, very bright and has intense sunlight
link |
particular times of year, you'll want to be cautious.
link |
Heed the warnings and considerations about sunscreen
link |
that I talked about earlier or about wearing a hat.
link |
But the point is very clear.
link |
Most of us should be getting more UVB exposure
link |
I can already hear the screams within the comments
link |
or rather the questions within the comments saying,
link |
well, what if I live in a part of the world
link |
where I don't get much UVB exposure?
link |
And I want to emphasize something that I've also emphasized
link |
in the many discussions on this podcast
link |
related to sleep and circadian rhythms and alertness,
link |
which is even on a cloud covered day,
link |
you are going to get far more light energy,
link |
photons through cloud cover,
link |
than you are going to get from an indoor light source,
link |
an artificial light source.
link |
I can't emphasize this enough.
link |
If you look outside in the morning
link |
and you see some sunlight,
link |
if you see some sunlight throughout the day,
link |
you would do yourself a great favor
link |
to try and chase some of that sunlight
link |
and get into that sunlight,
link |
to expose your eyes and your skin to that sunlight
link |
as much as you safely can.
link |
And when I say as much as you safely can,
link |
never ever look at any light, artificial sunlight
link |
or otherwise that's so bright that it's painful to look at.
link |
It's fine to get that light arriving
link |
on your eyes indirectly.
link |
It's fine to wear eyeglasses or contact lenses.
link |
In fact, if you think about the biology of the eye
link |
and the way that those lenses work,
link |
that it will just serve to focus that light
link |
on to the very cells that you want those light beams
link |
to be delivered to.
link |
Whereas sunglasses that are highly reflective
link |
or trying to get your sunlight exposure
link |
through a windshield of a car or through a window
link |
simply won't work.
link |
I'm sorry to tell you,
link |
but most windows are designed to filter out the UVB light.
link |
And if you're somebody who's really keen on blue blockers
link |
and you're wearing your blue blockers all day,
link |
well, don't wear them outside.
link |
And in fact, you're probably doing yourself a disservice
link |
by wearing them in the morning and in the daytime.
link |
There certainly is a place for blue blockers
link |
in the evening and nighttime,
link |
if you're having issues with falling and staying asleep.
link |
But if you think about it, blue blockers,
link |
what they're really doing
link |
is blocking those short wavelength UVB wavelengths of light
link |
that you so desperately need to arrive at your retina
link |
and of course also onto your skin
link |
in order to get these powerful biological effects
link |
on hormones and on pain reduction.
link |
And in terms of skin exposure,
link |
these data also might make you think a little bit
link |
about whether or not you should wear short sleeves
link |
or long sleeves, whether or not you want to wear shorts
link |
or a skirt or pants.
link |
It's all going to depend on the context of your life
link |
and the social and other variables that are important.
link |
Of course, I don't know each and every one
link |
of your circumstances,
link |
so I can't tell you to do X or Y or Z, nor would I,
link |
but you might take into consideration
link |
that it is the total amount of skin exposure
link |
that is going to allow you to capture more or fewer photons,
link |
depending on, for instance,
link |
if you're completely cloaked in clothing
link |
and you're just exposed in the hands, neck and face,
link |
or whether or not you're outside in shorts and a t-shirt,
link |
you're going to get very, very different patterns
link |
of biological signaling activation
link |
in those two circumstances.
link |
Many of you I'm guessing are wondering
link |
whether or not you should seek out UVB exposure
link |
throughout the entire year or only in the summer months.
link |
And that's sort of going to depend on whether or not
link |
you experience depression in the winter months,
link |
so-called seasonal affective disorder.
link |
Some people have mild,
link |
some people have severe forms
link |
of seasonal affective disorder.
link |
Some people love the fall and winter and the shorter days.
link |
They love bundling up, they love the leaves,
link |
they love the snow, they love the cold,
link |
and they don't experience those psychological lows.
link |
So it varies tremendously.
link |
And there are genetic differences
link |
and birthplace origin differences that relate to all this,
link |
but really it has to be considered on a case-by-case basis.
link |
I personally believe,
link |
and this was reinforced by the director
link |
of the Chronobiology Unit
link |
at the National Institutes of Mental Health, Samir Hattar,
link |
that we would all do well to get more UVB exposure
link |
from sunlight throughout the entire year,
link |
provided we aren't burning our skin
link |
or damaging our eyes in some way.
link |
In addition to that, during the winter months,
link |
if you do experience some drop in energy
link |
or increase in depression or psychological lows,
link |
it can be very beneficial to access a sad lamp,
link |
or if you don't want to buy a sad lamp,
link |
because oftentimes they can be very expensive,
link |
you might do well to simply get a LED lighting panel.
link |
I've described one before,
link |
and I want to emphasize that I have no affiliation
link |
whatsoever to these commercial sources,
link |
but I've described one before and I'll describe it again,
link |
and we can provide a link to a couple of examples of these
link |
in the show note captions, excuse me.
link |
This is a 932,000 lux L-U-X light source
link |
that's designed for drawing.
link |
It's literally a drawing box.
link |
It's a thin panel.
link |
It's about the size of a laptop.
link |
Very inexpensive compared to the typical sad lamp.
link |
I actually have one that I position on my desk all day long.
link |
I also happen to have skylights above my desk.
link |
I'm fairly sensitive to the effects of light.
link |
So in longer days,
link |
I feel much better than I do in shorter days.
link |
I've never suffered from full-blown
link |
seasonal affective disorder,
link |
but I keep that light source on throughout the day,
link |
throughout the year.
link |
But I also make it a point to get outside
link |
and get sunlight early in the morning
link |
and several times throughout the day.
link |
And if it's particularly overcast outside,
link |
or there just doesn't seem to be a lot of sunlight
link |
coming through those clouds,
link |
I will try to look at that light source
link |
a little bit more each day
link |
in order to trigger these mechanisms.
link |
Now, some people may desire to get UVB exposure
link |
and they want to do that through sources
link |
other than sunlight.
link |
And there, it's a little bit more complicated.
link |
There are, of course, canning salons,
link |
which basically are beds of UVB light.
link |
That's really all they are.
link |
I've never been to one.
link |
I know people do frequent them
link |
in certain parts of the world.
link |
There, of course, people are covering their eyes.
link |
They are only getting UVB exposure to their skin typically
link |
because the UVB exposure,
link |
or intensities rather, tends to be very, very high.
link |
And so you can actually damage your eyes
link |
if you're looking at a very, very bright
link |
artificial UVB source up close.
link |
So you really have to explore these options for yourself.
link |
Sunlight, of course, being the original
link |
and still the best way to get UVB exposure.
link |
So without knowing your particular circumstances,
link |
finances, genetics, or place of origin, et cetera,
link |
I can't know whether or not
link |
you need to use artificial sources.
link |
You're going to have to gauge that.
link |
Meanwhile, getting outside,
link |
looking at and getting some exposure of UVB onto your skin
link |
is going to be beneficial
link |
for the vast majority of people out there.
link |
And in fact, it's even going to be beneficial
link |
for people that are blind.
link |
People that are blind provided they still have eyes
link |
often maintain these melanopsin cells.
link |
So even if you're low vision or no vision,
link |
getting UVB exposure to your eyes can be very beneficial
link |
for sake of mood, hormone pathways,
link |
pain reduction, and so forth.
link |
A cautionary note, people who have retinitis pigmentosa,
link |
macular degeneration, or glaucoma,
link |
as well as people who are especially prone to skin cancers
link |
should definitely consult with your ophthalmologist
link |
and dermatologist before you start increasing
link |
the total amount of UVB exposure that you're getting
link |
from any source, sunlight or otherwise.
link |
There are additional very interesting
link |
and powerful effects of UVB light,
link |
in particular on immune function.
link |
All the organs of our body are inside our skin.
link |
And so information about external conditions,
link |
meaning the environment that we're in,
link |
need to be communicated to the various organs of our body.
link |
Some of them have more direct access
link |
to what's going on outside.
link |
So for instance, the cells in your brain
link |
that reside right over the roof of your mouth,
link |
your hypothalamus, they control hormone output
link |
and they control the biological functions
link |
that we call circadian functions,
link |
the ones that change every 24 hours.
link |
Well, those are just one or two connections,
link |
meaning synapses away from those cells in your eye
link |
that perceive UVB light, excuse me.
link |
Other organs of your body, such as your spleen,
link |
which is involved in the creation of molecules and cells
link |
that combat infection.
link |
Well, those are a long ways away
link |
from those cells in your eye.
link |
And in fact, they're a long ways away from your skin.
link |
There are beautiful studies showing you that
link |
if we get more UVB exposure from sunlight
link |
or from appropriate artificial sources,
link |
that spleen and immune function are enhanced.
link |
And there's a very logical, well-established circuit
link |
as to how that happens.
link |
Your brain actually connects to your spleen.
link |
Now it's not the case that you can simply think,
link |
okay, spleen, turn on, release killer cells,
link |
go out and combat infection.
link |
However, UVB light arriving on the eyes
link |
is known to trigger activation of the neurons
link |
within the so-called sympathetic nervous system.
link |
These neurons are part of the larger thing
link |
that we call the autonomic nervous system,
link |
meaning it's below or not accessible by conscious control.
link |
It's the thing that controls your heartbeat,
link |
controls your breathing, and that also activates
link |
or flips on the switch of your immune system.
link |
When we get a lot of UVB light in our eyes,
link |
or I should say sufficient UVB light in our eyes,
link |
a particular channel, a particular set of connections
link |
within the sympathetic nervous system is activated
link |
and our spleen deploys immune cells and molecules
link |
that scavenge for and combat infection.
link |
So if you've noticed that you get fewer colds and flus
link |
and other forms of illness in the summer months,
link |
part of that could be because of the increase
link |
in temperature in your environment,
link |
because typically longer days are associated
link |
with more warmth in your environment
link |
as opposed to winter days, which are short
link |
when it tends to be colder out.
link |
Well, that's true, but it's also the case
link |
the people around you have fewer colds and flus
link |
and that you will get infected with fewer colds and flus
link |
and other infections because if those infections,
link |
whether or not they're bacterial or viral,
link |
arrive in your body, right, if you inhale them
link |
or they get into your mouth or on your skin,
link |
your spleen meets those infections with a greater output.
link |
In other words, the soldiers of your immune system,
link |
the chemicals and cell types of your immune system
link |
that combat infection are in a more ready deployed stance,
link |
If you want to know more about the immune system
link |
and immune function, I did an entire episode
link |
about the immune system and the brain in a,
link |
you can find that at hubermanlab.com.
link |
We talk about cytokines, we talk about killer cells,
link |
B cells, T cells, et cetera, a lot of detail there.
link |
So we often think about the summer months
link |
and the spring months as fewer infections floating around,
link |
but in fact, there aren't fewer infections floating around.
link |
We are simply better at combating those infections
link |
and therefore there's less infection floating around.
link |
So we are still confronted with a lot of infections.
link |
We're just able to combat them better.
link |
What does this mean in terms of a tool?
link |
What it means is that during the winter months,
link |
we should be especially conscious of accessing UVB light
link |
to enhance our spleen function,
link |
to make sure that our sympathetic nervous system
link |
is activated to a sufficient level
link |
to keep our immune system deploying
link |
all those killer T cells and B cells and cytokines
link |
so that when we encounter the infections,
link |
as we inevitably will, right,
link |
we're constantly being bombarded with potential infections
link |
that we can combat those infections well.
link |
And as just a brief aside,
link |
but I should mention a brief aside
link |
that's related to tens of thousands of quality studies.
link |
It is well-known that wound healing is faster
link |
when we are getting sufficient UVB exposure.
link |
Typically that's associated with the longer days
link |
of spring and summer.
link |
It is known that turnover of hair cells,
link |
the very cells that give rise to hair cells
link |
are called stem cells.
link |
They live in little so-called niches in our skin
link |
with these hair stem cells
link |
and your hair grows faster in longer days.
link |
That too is triggered by UVB exposure,
link |
not just to the skin, but to the eyes.
link |
There was a study published in the Proceedings
link |
of the National Academy of Sciences a couple of years ago
link |
that showed that the exposure of those melanopsin ganglion
link |
cells in your eyes is absolutely critical
link |
for triggering the turnover of stem cells
link |
in both the skin and hair and also it turns out in nails.
link |
So if you've noticed that your skin, your hair
link |
and your nails look better and turn over more,
link |
meaning grow faster in longer days,
link |
that is not a coincidence.
link |
That is not just your perception.
link |
In fact, hair grows more, skin turns over more,
link |
meaning it's going to look more youthful.
link |
You're going to essentially remove older skin cells
link |
and replace them with new cells.
link |
And all the renewing cells and tissues of our body
link |
are going to proliferate,
link |
are going to recreate themselves more
link |
when we're getting sufficient UVB light to our eyes
link |
and also to our skin.
link |
And so while some of you may think of light therapies
link |
such as red light therapies or UVB therapies
link |
as kind of new agey or just biohacking,
link |
again, a phrase I don't particularly like this notion
link |
of biohacking because it implies using one thing
link |
for a purpose that it was never intended to have.
link |
Well, it turns out that UVB exposure and red light
link |
as we'll soon see is a very potent form
link |
of increasing things like wound healing and skin health
link |
for very logical mechanistically backed reasons.
link |
So while I can't account for everything
link |
that's being promoted out there in terms of this light source
link |
will help your skin look more youthful
link |
or will help heal your scars,
link |
the mechanistic basis for light having those effects
link |
makes total sense.
link |
But what you should consider, however,
link |
is that if the particular light therapy
link |
that you're considering involves very local application
link |
rather than illuminating broad swaths of skin,
link |
and if it has no involvement with the eyes,
link |
meaning there's no delivery of UVB or red light
link |
or the other light therapy to the eyes,
link |
it's probably not going to be as potent a treatment
link |
as would a more systemic activation
link |
of larger areas of skin and the eyes.
link |
Now, again, a cautionary note,
link |
I don't want people taking technologies
link |
that were designed for local application
link |
and beaming those into the eyes.
link |
That could be very, very bad and damaging to your retinal
link |
and other tissues.
link |
Certainly wouldn't want you taking bright light
link |
of very high intensity of any kind
link |
and getting cavalier about that.
link |
Typically the local illumination of say a wound
link |
or a particular patch of acne
link |
or some other form of skin treatment
link |
involves very high intensity light.
link |
And if the intensity is too high,
link |
you can actually damage that skin.
link |
And so as we'll talk about in a few moments,
link |
most of those therapies for modifying skin
link |
involve actually burning off
link |
a small, very thin layer at the top of the epidermis
link |
in efforts to trigger the renewal
link |
or the activation of stem cells
link |
that will replenish that with new cells.
link |
So there's a fine line to be had between light therapies
link |
that are very localized and intense,
link |
which are designed to damage skin
link |
and cause reactivation of new stem cells,
link |
whether or not it's hair cells or skin cells, et cetera,
link |
versus systemic activation
link |
across broad swaths of skin in the eyes.
link |
You really have to consider this on a case-by-case basis,
link |
but at least for now,
link |
just consider that increases in hormones,
link |
reduction in pain by way of increases in enkephalin
link |
and other endogenous opioids,
link |
improving immune status by activating the spleen
link |
and so on and so on,
link |
really are all the downstream consequence
link |
of illuminating large swaths of skin
link |
and making sure that those neurons within the eye
link |
get their adequate UVB exposure
link |
or other light wavelength exposure.
link |
Not simply beaming a particular wavelength of light
link |
at a particular location on the body
link |
and hoping that that particular illumination
link |
at a particular location on the body
link |
is going to somehow change the biology at that location.
link |
Our biology just really doesn't work that way.
link |
It's possible, but in general,
link |
systemic effects through broad scale illumination
link |
and illumination to the eye combined with local treatments
link |
are very likely to be the ones that have the most success.
link |
Now I'd like to shift our attention
link |
to the effects of light on mood more specifically.
link |
We talked about this
link |
in terms of seasonal affective disorder,
link |
but many of us don't suffer from seasonal affective disorder.
link |
So I'd like to drill a little deeper
link |
into how light impacts mood.
link |
And here, I want to again paraphrase the statements
link |
of Dr. Samra Hattar
link |
at the National Institutes of Mental Health.
link |
I should mention the director of the Chronobiology Unit
link |
at the National Institutes of Mental Health
link |
and perhaps one of the top one to two to three world experts
link |
in how light can impact mood, appetite,
link |
circadian rhythms, and so forth.
link |
Samra stated on the podcast,
link |
and he said in various other venues as well,
link |
that getting as much UVB light in our eyes and on our skin
link |
in the early day and throughout the day
link |
as is safely possible is going to be beneficial for mood.
link |
There's also another time of day,
link |
or rather I should say a time of night
link |
in which UVB can be leveraged in order to improve mood.
link |
But it's actually the inverse
link |
of everything we've been talking about up until now.
link |
We have a particular neural circuit
link |
that originates with those melanopsin cells in our eye
link |
that bypass all the areas of the brain
link |
associated with circadian clocks.
link |
So everything related to sleep and wakefulness
link |
that's specifically dedicated to the pathways
link |
involving the release of molecules like dopamine,
link |
the neuromodulator that's associated with motivation,
link |
with feeling good,
link |
with feeling like there's possibility in the world
link |
and so on and so forth.
link |
And other molecules as well,
link |
including serotonin and some of those endogenous opioids
link |
that we talked about before.
link |
That particular pathway involves a brain structure
link |
called the perihabenular nucleus.
link |
The perihabenular nucleus gets input
link |
from the cells in the eye that respond to UVB light
link |
and frankly to bright light of other wavelengths as well.
link |
Because as you recall, if a light is bright enough,
link |
even if it's not UV or blue light,
link |
it can activate those cells in the eye.
link |
Those cells in the eye communicate
link |
to the perihabenular nucleus.
link |
And as it turns out, if this pathway is activated
link |
at the wrong time of each 24 hour cycle,
link |
Dopamine output gets worse.
link |
Molecules that are there specifically to make us feel good
link |
actually are reduced in their output.
link |
So while UVB exposure in the morning
link |
and throughout the day is going to be very important
link |
for elevating and maintaining elevated mood,
link |
avoiding UVB light at night is actually a way
link |
in which we can prevent activation
link |
of this eye to perihabenular pathway
link |
that can actually turn on depression.
link |
To be very direct and succinct about this,
link |
avoid exposure to UVB light from artificial sources
link |
between the hours of 10 PM and 4 AM.
link |
And if you're somebody who suffers from low mood
link |
and overall has a kind of mild depression
link |
or even severe depression, of course,
link |
please see a psychiatrist, see a trained psychologist,
link |
But you would do especially well to avoid UVB exposure
link |
from artificial sources, not just from 10 PM to 4 AM,
link |
but really be careful about getting too much exposure
link |
to UVB even in the late evening.
link |
So 8 PM perhaps to 4 AM.
link |
I can't emphasize this enough that if you view UVB light,
link |
you activate those neurons in your eye very potently.
link |
And if those cells communicate
link |
to the perihabenular nucleus, which they do,
link |
you will truncate or reduce the amount of dopamine
link |
So if you want to keep your mood elevated,
link |
get a lot of light, UVB light throughout the day,
link |
and at night, really be cautious about getting UVB exposure
link |
from artificial sources.
link |
Now let's say you're somebody who has no issues with mood.
link |
You're just the happiest person all year long,
link |
or maybe you just have subtle variations in your mood.
link |
You feel great about that.
link |
Turns out that you still want to be very careful
link |
about light exposure between the hours of 10 PM or so
link |
and 4 AM, in fact, even during sleep.
link |
There's a recent study that just came out
link |
in the proceedings of the National Academy of Sciences,
link |
and it's entitled light exposure during sleep
link |
in pairs cardiometabolic function.
link |
This is a very interesting study
link |
where they took human subjects, young adults,
link |
and having them sleep in rooms
link |
that had different lighting conditions,
link |
either dim light or slightly bright light.
link |
Now, many people can't fall asleep in brightly lit rooms.
link |
So they acknowledged this.
link |
These were not very brightly lit rooms.
link |
These were rooms that had just a little bit
link |
of overhead room lighting, a hundred lux,
link |
which is not very bright at all.
link |
Or they had them sleep in a room that had very dim light,
link |
which is less than three lux.
link |
If you want to get a sense of how bright three lux is
link |
versus a hundred lux,
link |
I would encourage you to download the free app Light Meter.
link |
I have no relationship to the app.
link |
It's a pretty cool app.
link |
However, I've used it for a long time
link |
where you can basically point your phone
link |
at a particular light source, sun or otherwise,
link |
and you just press the button
link |
and it'll give you an approximate readout of lux,
link |
which is the light intensity that the phone happens
link |
to be staring out at at that location.
link |
It's not exact, but it's a pretty good
link |
back of the envelope measure of light intensity.
link |
So these subjects were either sleeping in a very dim room,
link |
three lux is very, very dim,
link |
or a somewhat dim room, a hundred lux.
link |
In this study, they measured things like melatonin levels.
link |
They looked at heart rate.
link |
They looked at measures of insulin and glucose management.
link |
Now, in previous episodes,
link |
I've talked about how glucose blood sugar is regulated
link |
by insulin because you don't want your glucose levels
link |
to be too high, hyperglycemia or too low.
link |
Hypoglycemia and the hormone insulin is involved
link |
in sequestering and shuttling glucose in the bloodstream.
link |
Basically how well you manage glucose in the bloodstream
link |
can be indirectly measured by your insulin levels.
link |
And it's well-known that sleep deprivation
link |
can disrupt glucose regulation by insulin.
link |
However, in this study,
link |
subjects were sleeping the whole night through.
link |
It just so happens that some of the subjects
link |
were sleeping in this very dimly lit room, three lux,
link |
and other subjects were sleeping
link |
in a somewhat dimly lit room, a hundred lux.
link |
What's incredible about this study is that both rooms
link |
were sufficiently dim that melatonin levels
link |
were not altered in either case.
link |
This is really key.
link |
It's not as if one group experienced a lot of bright light
link |
through their eyelids and others did not.
link |
Melatonin levels were not disrupted.
link |
And given how potently light can inhibit melatonin,
link |
this speaks to the fact that this very dim condition
link |
of three lux and the somewhat dim condition of a hundred lux
link |
was not actually perceived by the subjects,
link |
nor was it disrupting these hormone pathways.
link |
They also looked at glucose responses.
link |
They had people essentially take a fasting glucose test
link |
in different conditions.
link |
I won't go into all the details,
link |
but here's what they found.
link |
In healthy adults,
link |
even just one night of sleeping in a moderately lit
link |
environment, this hundred lux environment caused changes,
link |
increases in nighttime heart rate,
link |
which means that the sympathetic nervous system
link |
was overly active as compared to people that slept
link |
in a completely dark or in a very, very dimly lit room.
link |
Decreases in heart rate variability.
link |
And here I should point out that heart rate variability
link |
or HRV is a good thing.
link |
We want heart rate variability.
link |
So they saw increases in heart rate,
link |
decreases in heart rate variability and increases
link |
in next morning insulin resistance,
link |
which is an indication that glucose management is suffering.
link |
So this is powerful.
link |
The results of this study essentially indicate that even
link |
just one night of sleeping the whole night through
link |
in a dimly lit environment is disrupting the way
link |
that our autonomic nervous system is functioning,
link |
altering so-called autonomic tone,
link |
making us less relaxed is probably the best way
link |
Even though we are asleep,
link |
disrupting the way that our cardiometabolic function
link |
operates such that we have lower heart rate variability
link |
and increased insulin resistance.
link |
This is not a good thing for any of us to experience.
link |
So while we've mainly been talking about the positive
link |
effects of UVB light and other forms of light.
link |
Now we have two examples,
link |
one from the work of Hatar and colleagues showing
link |
that UVB exposure via the perihabenula can diminish
link |
the output of dopamine and other molecules that make
link |
us feel good if that UVB exposure is in the middle
link |
of the night or late evening.
link |
And now we have yet another study performed in this case
link |
in humans indicating that even if we fall asleep
link |
and sleep the whole night through,
link |
if the room that we're sleeping in has too many locks,
link |
too much light energy,
link |
that light energy is no doubt going through the eyelids,
link |
which it can activating the particular cells in the eye
link |
that trigger an increase in sympathetic nervous system
link |
activation and disrupting our metabolism.
link |
And this study rests on a number of other recent studies
link |
published in Cell,
link |
which is a superb journal and other journals showing that
link |
during the course of a healthy deep night's sleep,
link |
our body actually transitions through various forms
link |
of metabolic function.
link |
We actually experience ketosis like states.
link |
We experience gluconeogenesis.
link |
We experience different forms of metabolism associated
link |
with different stages of sleep.
link |
Not something that we're going into in depth in this podcast,
link |
we will in a future podcast.
link |
What this study shows is that light exposure even in sleep
link |
is disrupting our autonomic, in this case,
link |
the sympathetic arm of the autonomic nervous system
link |
in ways that are disrupting metabolism probably in sleep,
link |
but certainly outside of sleep.
link |
So that we wake up and have our first meal of the day,
link |
or even if you're intermittent fasting,
link |
you eat that first meal of the day.
link |
If your sleep is taking place in an environment
link |
that's overly illuminated,
link |
well, that's disrupting your cardiac function
link |
and your metabolism.
link |
I've been talking a lot about UVB light,
link |
which is short wavelength light.
link |
So UV light, blue light, maybe even some blue green light,
link |
that's going to be short wavelength light.
link |
Now I'd like to shift our attention to the other end
link |
of the spectrum, meaning the light spectrum,
link |
to talk about red light and infrared light,
link |
which is long wavelength light.
link |
Many so-called low level light therapies,
link |
the acronym is LLLT, low level light therapies
link |
involve the use of red light and infrared light.
link |
Sometimes low level light therapies involve the use of UVB,
link |
but more often than not these days,
link |
when we hear LLLT, low level light therapy,
link |
it's referring to red light
link |
and near infrared light therapies.
link |
Low level light therapies have been shown to be effective
link |
for a huge number of biological phenomenon
link |
and medical treatments.
link |
I can't summarize all of those now.
link |
It would take me many, many hours.
link |
It would be an effective episode for curing insomnia,
link |
but it wouldn't inform you properly
link |
about the use of light for your health.
link |
Rather, I'd like to just emphasize
link |
some of the top contour of those studies
link |
and point out that for instance,
link |
low level light therapy with infrared light
link |
has been shown to be effective for the treatment of acne
link |
and other sorts of skin lesions.
link |
Been some really nice studies actually,
link |
where they use subjects as their own internal control.
link |
So people who believe it or not
link |
agreed to have half of their face illuminated
link |
with red light or near infrared light
link |
and the other half of their face serve as a control
link |
and to do that for several weeks at a time.
link |
And you can see pretty impressive reductions
link |
in skin lesions, reductions in scars from acne
link |
and reduction in acne lesions themselves,
link |
meaning the accumulation of new acne cysts
link |
with low level light therapy
link |
using red light and infrared light.
link |
Sometimes however, there is a resistance of that acne
link |
to the low level light therapy
link |
such that people will get an initial improvement
link |
and then it will go away despite continuing the treatment.
link |
So you're probably asking, or at least you should be asking,
link |
how is it that shining red light on our skin
link |
can impact things like acne and wound healing, et cetera?
link |
Well, to understand that we have to think back
link |
to the beginning of the episode
link |
where I described how long wavelength lights
link |
such as red light and near infrared light,
link |
which is even longer than red light,
link |
can pass through certain surfaces, including our skin.
link |
So our skin has an epidermis, which is on the outside
link |
and the dermis, which is in the deeper layers.
link |
Red light and infrared light
link |
can pass down into the deeper layers of our skin
link |
where it can change the metabolic function
link |
of particular cells.
link |
So let's just take acne as an example.
link |
Within the dermis, the deep layers of our skin,
link |
we have what are called sebaceous glands
link |
that actually make the oil that is present in our skin.
link |
Those sebaceous glands are often nearby hair follicles.
link |
So if you've ever had an infected hair follicle,
link |
that's not a coincidence
link |
that hair follicles tend to get infected.
link |
Part of it is because there's actually a portal down
link |
and around the hair follicle,
link |
but the sebaceous gland is where the oil is created
link |
that is going to give rise to, for instance, acne lesions.
link |
Also in the dermis and the deep layers of the skin
link |
are the melanocytes.
link |
They're not just in the epidermis,
link |
they're also in the deeper layers of the skin.
link |
And you have the stem cells that give rise
link |
to additional skin cells.
link |
If the top layers of the epidermis are damaged,
link |
those stem cells can become activated.
link |
And you also have the stem cells
link |
that give rise to hair follicles.
link |
So by shining red light or near infrared light
link |
on a localized patch of skin,
link |
provided that red light is not of such high intensity
link |
that it burns the skin,
link |
but is of sufficient intensity
link |
that provides just a little bit of damage
link |
to the upper layers of the skin, the epidermis,
link |
and that it triggers certain biological pathways
link |
within the cells of the sebaceous gland
link |
and the stem cells within the hair cell niche
link |
and the stem cells in skin.
link |
What happens is the top layers of the skin
link |
are basically burned off by a very low level of burn
link |
and or the cells in the deeper layer
link |
start to churn out new cells
link |
which go and rescue the lesion,
link |
essentially clear out the lesion
link |
and replace that lesion with healthy skin cells.
link |
This does work in the context of wound healing,
link |
getting scars to disappear.
link |
It also works to remove certain patches of pigmentation.
link |
There are sometimes cases where people will get
link |
a red blotchiness due to certain skin conditions
link |
or some darker pigmentation that they want removed
link |
or that they need removed
link |
because it's a potential skin cancer threat.
link |
Now, how is red light actually doing it
link |
within the cells of the sebaceous gland,
link |
the stem cells, et cetera?
link |
Well, long wavelength light
link |
can actually get deep into the skin.
link |
I mentioned that before,
link |
but can also get into individual cells
link |
and can access the so-called organelles,
link |
which I described at the beginning of the episode.
link |
In particular, they can access the mitochondria
link |
which are responsible for producing ATP.
link |
Now, the simple way to think about this
link |
for sake of this discussion is that as cells age
link |
and in particular in very metabolically active cells,
link |
they accumulate what are called ROSs,
link |
reactive oxygen species.
link |
And as reactive oxygen species go up,
link |
ATP energy production in those cells tends to go down.
link |
It's a general statement,
link |
but it's a general statement that in most cases is true.
link |
There are some minor exceptions that don't concern us
link |
that have to do with cell types different
link |
than the ones that I'm talking about now.
link |
So the way to think about this is that red light passes
link |
into the deeper layers of the skin,
link |
activates mitochondria, which increases ATP
link |
and directly or indirectly
link |
reduces these reactive oxygen species.
link |
These reactive oxygen species are not good.
link |
We don't want them.
link |
They cause cellular damage, cellular death,
link |
and for the most part,
link |
just inhibit the way that our cells work.
link |
So if you've heard of red light
link |
or near infrared light therapies designed to heal skin
link |
or improve skin quality or remove lesions
link |
or get rid of scars or unwanted pigmentation,
link |
that is not pseudoscience, that is not woo science,
link |
that is grounded in the very biology of how light interacts
link |
with mitochondria and reactive oxygen species.
link |
Some of you may also find it interesting to note
link |
that some of the cream-based treatments for acne,
link |
for instance, like retinoic acid,
link |
Retin-A is actually a derivative of vitamin A
link |
and the pathway involving retinoic acid and vitamin A,
link |
believe it or not,
link |
is very similar to the natural biological pathway
link |
by which photopigments in the eye convert light information
link |
into biological changes within those cells.
link |
So the key point here is that light is activating
link |
particular pathways in cells
link |
that can either drive death of cells
link |
or can make those cells essentially younger
link |
by increasing ATP by way of improving mitochondrial function
link |
and in recent years,
link |
there've been some just beautiful examples
link |
that exist not only in the realm of skin biology,
link |
but in the realm of neurobiology,
link |
whereby red light and near infrared light
link |
can actually be used to enhance the function of the cells
link |
that for instance, allow us to see better
link |
and indeed cells that allow us to think better.
link |
So now I'd like to review those data
link |
because not only are they interesting in their own right,
link |
but they also point to some very interesting
link |
and powerful application of low cost or zero cost tools
link |
that we can use to improve our vision.
link |
If you are somebody who's interested
link |
in the use of red light or near infrared light,
link |
so-called LLLT, low level light therapies
link |
for treatment of dermatologic issues,
link |
so anything related to skin,
link |
I will include a link to a excellent set of reviews.
link |
The first one is light emitting diodes in dermatology,
link |
a systematic review of randomized controlled trials.
link |
That one includes review of a very large number of studies
link |
came out just a few years ago in 2018
link |
and I think is very clearly and cleanly laid out
link |
for anyone to access.
link |
You can see the degree of effects of red light,
link |
for instance, on treatment of acne or scarring, et cetera.
link |
And I'll also provide a link to another review,
link |
which is low level light therapy in skin,
link |
stimulating healing and restoring.
link |
So for those of you that are interested,
link |
again, in dermatologic issues
link |
and the kind of restoring youthfulness
link |
and the kind of general themes of anti-aging and longevity
link |
and how red light therapies can be used for that,
link |
I will encourage you to take a look at those reviews.
link |
What you're going to find is that rarely, if ever,
link |
is there a study looking at whole body red light illumination
link |
for sake of treating and improving skin.
link |
And I mention this because I get a lot of questions
link |
about infrared sauna
link |
and global illumination with red lights.
link |
We'll talk more about cases where global illumination
link |
of your whole body or your whole face
link |
with red lights might be useful,
link |
but in terms of infrared sauna,
link |
I've mentioned on this podcast before,
link |
and I will certainly go deeper on this
link |
in an upcoming episode,
link |
all about the use of heat and temperature
link |
for augmenting our biology.
link |
infrared saunas don't get hot enough temperature wise
link |
in order to trigger some of the important effects
link |
on growth hormone and heat shock proteins
link |
and some of the other things
link |
that sauna has been shown to be excellent for.
link |
That's a general statement.
link |
I realize there are some infrared saunas
link |
that do get hot enough.
link |
There are very few data on the use of whole body illumination
link |
with infrared saunas.
link |
They really point to any specific
link |
mechanistically supported effects.
link |
Almost all the positive effects that you're going to see
link |
of red light and low level light therapies,
link |
certainly the ones discussed in the reviews
link |
that I just mentioned,
link |
are going to be the consequence
link |
of very directed illumination
link |
of particular patches of skin that are seeking repair
link |
or that people are seeking the repair of.
link |
So again, I don't want to disparage infrared saunas,
link |
but in general, they don't get hot enough
link |
to trigger most of the positive effects
link |
that sauna have been demonstrated to have.
link |
And it's unclear at all as to whether or not
link |
they can enhance skin quality, youthfulness,
link |
restore top layers of skin that are damaged,
link |
repair acne, et cetera.
link |
So more on heat saunas and infrared saunas
link |
in their comparison in an upcoming episode.
link |
So let's talk about a clear set of examples
link |
where red light and near infrared light
link |
have been shown to have positive effects on our health.
link |
And these are the data that I referred to
link |
at the beginning of the episode
link |
from Dr. Glenn Jeffrey at University College London,
link |
who again is a longstanding member
link |
of the neuroscience community
link |
working on visual neuroscience
link |
and who over the last decade or so
link |
has really emphasized the exploration of red light
link |
and near infrared light
link |
for restoration of neuronal function as we age.
link |
This is absolutely critical.
link |
We know that we don't accumulate many new brain cells
link |
And in some areas of our nervous system,
link |
such as our neural retina,
link |
which is the part of our eye that's responsible
link |
for translating light information to electrical signals
link |
so that we can see,
link |
we don't get any new cells
link |
after the time in which we were born.
link |
So the ability to keep our neurons healthy
link |
is extremely important for our visual system,
link |
extremely important for our hippocampus,
link |
an area of the brain involved in memory.
link |
And I should just mention
link |
that even if people don't get Alzheimer's,
link |
there's always going to be some degree
link |
of age-related dementia.
link |
Sadly, nobody is as cognitively sharp
link |
in the years before they die
link |
as they are 20 years before that.
link |
It's just never the case.
link |
We're all getting worse at thinking, feeling,
link |
perceiving, et cetera.
link |
The question is how quickly we are getting worse.
link |
So any mechanism by which we can preserve
link |
or reverse neuronal function
link |
turns out to be immensely beneficial.
link |
The Jeffrey Lab has published two studies in recent years
link |
on humans that looked directly, no pun intended,
link |
at how red light and near infrared light
link |
can improve visual function.
link |
I'm going to describe the parameters of those studies
link |
and then I'm going to describe what they found exactly.
link |
The mechanistic motivation for these studies,
link |
again, traces back to this effect of light on mitochondria.
link |
So to go a little bit deeper into that mechanism
link |
just briefly so that you can frame
link |
any potential protocol that you would develop.
link |
When light arrives on cells, including neurons,
link |
that light can penetrate into the cells
link |
if it's of the appropriate wavelength,
link |
red light can do that, it can get into cells,
link |
it can access the mitochondria,
link |
it can increase ATP.
link |
In general, anytime ATP is doing its thing
link |
to increase energy in cells,
link |
it's involving this thing called cytochrome C,
link |
which is an oxidase.
link |
Anytime you hear ACE, A-S-E in biology,
link |
it's going to be an enzyme.
link |
It's involved in some process of degrading a molecule
link |
and creating another molecule typically.
link |
So ATP in cytochrome C is going to give you ATP.
link |
Now that's a great thing,
link |
but it creates a by-product.
link |
It breaks things down such that you get these ROSs,
link |
these reactive oxygen species.
link |
And those reactive oxygen species,
link |
for those of you that want to know,
link |
are involved in things like redox signaling
link |
and reactive oxygen species actually change
link |
which genes are made in a cell.
link |
So the goal of any treatment to keep neurons
link |
or other cells youthful and functioning well,
link |
and to prevent or reverse aging
link |
is going to be to increase ATP
link |
and to reduce reactive oxygen species.
link |
And in doing so, to disrupt some of the normal pathways
link |
associated with aging.
link |
The Jeffrey Lab approached these studies
link |
with that understanding of how mitochondria
link |
and reactive oxygen species and ATP work.
link |
And what they did was exquisitely simple
link |
to the point of being elegant.
link |
And what they found was really, really exciting.
link |
What they did is they had people, subjects
link |
that were either younger, so in their 20s,
link |
or 40 years old or older,
link |
view red light of about 670 nanometers.
link |
670 nanometers would appear red to you and me.
link |
They had them do that, excuse me,
link |
at a distance that was safe for their eyes.
link |
So at about a foot away.
link |
Now, a foot away from a very intense red light
link |
could actually be damaging to the eye.
link |
So they had them do this at about a foot away
link |
from a red light that was of low enough intensity
link |
that did not damage the eyes.
link |
And they had them do that anywhere
link |
from two to three minutes per day.
link |
And in one study, they had them do that
link |
for a long period of time of about 12 weeks.
link |
And in the other study, they had them do that
link |
just for a couple of weeks.
link |
What's remarkable is that when you collapse the results
link |
across these two studies,
link |
what they found is that when looking at these subjects
link |
ranging from 28 years old to about 72 years old,
link |
the major findings were that in individuals 40 years old
link |
or older, so in the 40 to 72 year old bracket,
link |
but not in the subjects younger than 40 years old,
link |
they saw an improvement in visual function.
link |
That improvement in visual function
link |
was an improvement in visual acuity,
link |
meaning the ability to resolve fine detail
link |
and using a particular measure of visual function,
link |
which is called the Tritan exam, T-R-I-T-A-N, Tritan exam,
link |
which specifically addresses the function
link |
of the so-called short wavelength cones,
link |
the ones that respond to green and blue light,
link |
they saw a 22% improvement in visual acuity,
link |
which in the landscape of visual testing
link |
is an extremely exciting result, okay?
link |
So I think in most studies of improvements of vision,
link |
you'd be very excited to see an improvement of 5% or 10%.
link |
So a 22% improvement in visual acuity,
link |
even though it's in this very specific form
link |
of visual testing, this Tritan exam or this Tritan score,
link |
well, that turns out to be very significant
link |
and translates to the real world in an important way.
link |
In particular, as we age,
link |
we tend to lose certain neurons within our retina,
link |
but we don't tend to lose cones.
link |
We tend to lose rods.
link |
We tend to lose other cells within the retina,
link |
including the cells that connect the eye to the brain,
link |
the so-called ganglion cells.
link |
Cones, for whatever reason,
link |
are pretty resilient to age-related loss.
link |
However, because rods and cones both
link |
are not just among the most metabolically active cells
link |
in your entire body,
link |
but the most metabolically active cells in your entire body.
link |
That's right, your rods and cones are the cells that demand
link |
and that use the most energy of all the cells in your body.
link |
Not your skin cells, not your spleen cells,
link |
not your stomach cells.
link |
Even if you talk a lot,
link |
not the cells that are responsible for moving your mouth,
link |
it is the rods and cones of your neural retina
link |
that are responsible for using the most amount
link |
of ATP and energy in your entire body.
link |
And because of that,
link |
those cells tend to accumulate
link |
a lot of reactive oxygen species as we age.
link |
Red light of the sort used in these studies
link |
was able to reduce the amount of reactive oxygen species
link |
in the rods and cones,
link |
and to rescue the function of this particular cone type,
link |
the short wavelength and medium wavelength cones,
link |
which if you think about the study
link |
is a little bit surprising
link |
because it was red light and near infrared light,
link |
not short wavelength light that was used
link |
in order to create this improvement in cellular function.
link |
But if you step back a little bit further,
link |
it makes perfect sense
link |
because there's nothing specific about the red light
link |
in the sense that it's not that it gets delivered
link |
only to red cones.
link |
That red light and near infrared light
link |
is being absorbed by all the photoreceptors within the eye,
link |
the rods and the blue cones and the green cones
link |
and the red cones.
link |
It's just that the red cones absorb that light best.
link |
So the important takeaway here
link |
is that viewing red light and near infrared light
link |
at a distance at which it is safe
link |
for just a couple of minutes each day
link |
allowed a reversal of the aging process of these neurons,
link |
which some people have heard me say before
link |
and I'll just say it again,
link |
the retina, including your photoreceptors
link |
are not just connected to your brain,
link |
they're not just near your brain,
link |
they are actual central nervous system tissue.
link |
They are the only two pieces of your brain,
link |
meaning your neural retinas
link |
are the only two pieces of your brain
link |
that reside outside your skull
link |
or at least outside the cranial vault.
link |
So here we're seeing a reversal of the aging process
link |
in neurons by shining red light on those neurons.
link |
Now, of course, the Jeffrey lab
link |
is primarily interested in vision
link |
and humans are most dependent on vision
link |
as a sense to navigate the world and survive.
link |
So this is really wonderful.
link |
Here we're looking at a therapy
link |
that can reverse age-related vision loss,
link |
at least in some individuals.
link |
But as you can imagine,
link |
the study was also done on these cells
link |
because they reside outside the skull
link |
and you can shine light directly on them, right?
link |
I'm sure that there are many people out there
link |
who are interested in how they can improve the function,
link |
say, of the neurons in their brain responsible for memory.
link |
And in a few minutes,
link |
I'll describe the non-invasive applications of light
link |
to try and restore the function of those cells as well.
link |
So a little bit more about the studies from the Jeffrey lab.
link |
One of the things that they observed
link |
was a reduction in so-called drusen, D-R-U-S-E-N.
link |
Drusen are little fatty deposits,
link |
little cholesterol deposits
link |
that accumulate in the eye as we age.
link |
We've all heard about cholesterol
link |
within our veins and arteries
link |
and how that can clog our veins and arteries
link |
and how, of course,
link |
clogging of veins and arteries is not a good thing.
link |
Well, our neural retina being so metabolically active
link |
requires a lot of blood flow.
link |
It's heavily vascularized.
link |
And drusen are a special form of cholesterol
link |
that accumulate in the eye.
link |
these red light and near infrared light therapies
link |
explored by the Jeffrey lab
link |
were able to actually reduce or reverse
link |
some of the accumulation of drusen.
link |
And so in addition to reducing reactive oxygen species,
link |
the idea in mind now is that red light
link |
may actually reduce cholesterol deposits
link |
and reactive oxygen species
link |
in order to improve neuronal function.
link |
So what should you and I do with these results?
link |
Or should we do anything with these results?
link |
Well, first of all, I want to emphasize
link |
that even though these studies are very exciting,
link |
they are fairly recent.
link |
And so more data as always are needed.
link |
There's some additional features of these studies
link |
that I think are also important to consider.
link |
the exposure to red light needed to happen early in the day,
link |
at least within the first three hours of waking.
link |
How would one do that?
link |
there are a number of different red light panels
link |
and different red light sources
link |
that certainly fall within the range of red light
link |
and near infrared light that one could use.
link |
I don't have any affiliation to any companies or products
link |
that promote or make those red light therapies.
link |
I do own a red light panel.
link |
So I confess I have started using this protocol.
link |
I am older than 40 years old.
link |
I also have been experimenting with these red light panels
link |
as a way of addressing other changes in biological tissues
link |
for which I'm doing blood work, et cetera.
link |
And I'm going to talk about that in a future episode.
link |
But that of course is what I call anacodata.
link |
It only relates to my experience.
link |
and certainly on all episodes of the Human Lab Podcast,
link |
we emphasize peer reviewed studies almost exclusively
link |
talking about anacodata only when highlighting it
link |
So if you're somebody who wants to explore red light therapy
link |
here's what you need to do.
link |
You need to make sure that that red light source,
link |
whatever source you happen to use,
link |
whether or not you purchase it or make one.
link |
And in fact, these red light sources
link |
are very, very easy to make.
link |
You could essentially take a bright flashlight
link |
and cover it with a film or a filter
link |
that would only allow particular long wavelengths
link |
This would be very easy to look up online
link |
and figure out how to do this.
link |
You could probably do this for just a few dollars
link |
or you could purchase a red light unit
link |
if that was within your budget
link |
and something that you're interested in.
link |
You want to make sure that it's not so bright
link |
that you're damaging your eye.
link |
A good rule of thumb
link |
is that something isn't painful to look at.
link |
And in fact, I should just emphasize
link |
that anytime you look at any light source,
link |
sunlight or otherwise,
link |
that it's painful and makes you want to squint
link |
or close your eyes.
link |
That means it's too bright to look at
link |
without closing your eyes.
link |
Okay, that's sort of a duh,
link |
but I would loathe to think that anyone
link |
would harm themselves with bright light in any way.
link |
I don't just say that to protect us.
link |
I say that to protect you, of course,
link |
because you are responsible for your health.
link |
And again, retinal neurons do not regenerate.
link |
Once they are gone and dead, they do not come back.
link |
There's no technology to replace them
link |
at this current state in time.
link |
So please don't damage your retinas.
link |
So is a red light source safe to look at
link |
if it is not painful to look at?
link |
Chances are it is.
link |
And yet I would still encourage you
link |
to talk to your optometrist or ophthalmologist
link |
before getting into any extensive protocols.
link |
But if you were still determined to pursue
link |
the sorts of protocols that are in the Jeffrey studies,
link |
certainly we'll provide a link to those studies.
link |
Again, it involves looking at these red light panels,
link |
blinking aloud for two minutes to three minutes,
link |
every morning for a period of two weeks or more.
link |
And if you're older than 40,
link |
that could very well have an effect.
link |
If you're younger than 40, excuse me,
link |
that's unlikely to have an effect.
link |
At least that was what was observed
link |
in these particular studies.
link |
The lights were not flashing.
link |
It was continuous illumination.
link |
Again, you're allowed to blink.
link |
It does not have to even be direct illumination.
link |
It can be somewhat indirect illumination,
link |
much as we described for the use of UVB light before.
link |
The wavelength of light is important.
link |
It is red light and near-infrared light
link |
that is going to be effective in this scenario.
link |
The authors of this study emphasized
link |
that it was red light of 670 nanometers in wavelength
link |
and near-infrared light of 790 nanometers in wavelength
link |
that were effective,
link |
and that those wavelengths could be complimentary.
link |
That's probably why, or maybe it's just coincidental,
link |
but it's a fortunate coincidence
link |
that a lot of the commercially available red light panels
link |
that you'll find out there
link |
combine both red light and near-infrared light.
link |
However, I want to emphasize that most of the panels
link |
that are commercially available
link |
are going to be too bright to safely look at very close up.
link |
And in fact, that's why most of those red light panels
link |
are designed for illumination of the skin
link |
and oftentimes arrive in their packaging
link |
with eye protectors that are actually designed
link |
to shield out all the red light.
link |
So take the potential dangers of excessive illumination
link |
of the eyes with any wavelength of light seriously,
link |
but if you're going to explore 670 and 790 nanometer light
link |
for sake of enhancing neuronal function,
link |
set it at a distance that's comfortable to look at
link |
and that doesn't force you to squint
link |
or doesn't make you feel uncomfortable physically
link |
as if you need to turn away
link |
during the period of that two to three minute illumination
link |
In terms of turning away from light,
link |
I'll just briefly mention that that is not an accident
link |
or a coincidence that you have that response
link |
to very bright light.
link |
There is a so-called photic avoidance pathway
link |
that involves cells within your retina,
link |
these ganglion cells that communicate
link |
with yet another brain station,
link |
a certain area of your thalamus
link |
that communicate to areas of your brain
link |
that are associated with pain.
link |
So literally that can trigger headache
link |
and that can trigger the squint reflex.
link |
Biology is just beautiful in this way.
link |
Too much light is bad for us in that it can damage our eyes
link |
and other aspects of our body.
link |
So if we look at a light that's too bright,
link |
our eyes send a signal to the brain
link |
that gives us a sort of a headache
link |
and a desire to squint and turn away.
link |
So that can be a useful guide
link |
in terms of gauging how bright a light should be
link |
or at least how far away you should be from a bright source
link |
in order to safely engage with that light source.
link |
So the studies I just described, once again,
link |
involve the use of red light early in the day
link |
within three hours of waking
link |
and are for the sake of improving neuronal function.
link |
Red light has also been shown to be beneficial
link |
late in the day and even in the middle of the night.
link |
And when I say middle of the night,
link |
I'm referring to studies that explore the use of red light
link |
for shift workers.
link |
I know that most people are not working
link |
in the middle of the night, at least I hope they're not,
link |
but some of you may do that from time to time.
link |
All-nighters for studying, I confess,
link |
I still pull all-nighters every once in a while
link |
to prepare things like podcasts and other deadlines,
link |
really try not to, happens less and less as I get older
link |
because I think I get more disciplined
link |
and or less good at pulling all-nighters.
link |
But I realized that many people are doing shift work
link |
or they have to work certainly past 10 PM
link |
or maybe they're taking care of young children
link |
in the middle of the night and they have to be up.
link |
In that case, red light can actually be very beneficial.
link |
And nowadays there are a lot of sources
link |
of red light available just as red light bulbs.
link |
You don't need a panel.
link |
So what I'm basically saying is that it can be beneficial
link |
to use red lights at night.
link |
The study I'd like to emphasize in this context
link |
is entitled Red Light,
link |
a novel non-pharmacological intervention
link |
to promote alertness in shift workers.
link |
So beautiful study.
link |
They explored the use of different wavelengths of light.
link |
So blue light of 460 nanometers or red light
link |
or dim white light of different brightnesses, et cetera,
link |
and looked at things like melatonin.
link |
How much does light of a given color
link |
and intensity suppress melatonin?
link |
They looked at cortisol, a stress hormone.
link |
They looked at wakefulness.
link |
How much or to what degree could a given color of light
link |
increase wakefulness at different hours of the day?
link |
The takeaway from this study is very clear.
link |
If you need to be awake late at night
link |
for sake of shift work or studying
link |
or taking care of children, et cetera,
link |
red light is going to be your best choice
link |
because if the red light is sufficiently dim,
link |
it's not going to inhibit melatonin production
link |
and it's not going to increase cortisol at night.
link |
Cortisol should be high early in the day
link |
or at least should be elevated
link |
relative to other times of day if you are healthy.
link |
A late shifted increase in cortisol,
link |
however, 9 p.m. cortisol, 10 p.m. cortisol
link |
is well known to be associated with depression
link |
and other aspects of mental health,
link |
or I should say mental illness.
link |
So if you do need to be awake at night or even all night,
link |
red light is going to be the preferred light source.
link |
And in terms of how bright to make it,
link |
well, as dim as you can while still being able
link |
to perform the activities that you need to perform,
link |
that's going to be your best guide.
link |
I'll provide a link to this study as well.
link |
Again, it's a really important study
link |
because it emphasized that there are forms of light,
link |
red light, provided it's dim,
link |
that can allow you to stimulate the alertness
link |
that light landing on the eyes can provide.
link |
So it allows you to stay awake
link |
and to do whatever work that you need to do.
link |
It does not seem to alter melatonin production.
link |
It does not seem to alter levels
link |
or timing of cortisol production.
link |
So yet another case where red light used correctly
link |
can be beneficial.
link |
Up until now, we've been talking about the effects
link |
of shining different wavelengths of light
link |
on the skin or on our eyes
link |
and the downstream health consequences
link |
of that illumination.
link |
However, one of the most important goals
link |
of science and medicine is to figure out
link |
how to change the health of our brain.
link |
And of course, our brain is contained within our skull
link |
and therefore we can't just shine light
link |
onto the outside of our head
link |
and expect it to change the activity
link |
of neurons deep within the brain
link |
unless those neurons are linked up
link |
with our eyes or with our skin.
link |
And as it turns out,
link |
even though there are a lot of brain areas
link |
that are connected through neural circuits
link |
and hormone circuits through our eye
link |
and believe it or not, also to our skin,
link |
many brain areas are not.
link |
Brain areas such as the hippocampus,
link |
which is involved in learning and memory,
link |
brain areas such as our neocortex.
link |
Well, some areas of our neocortex,
link |
such as our visual cortex,
link |
are indirectly linked to our eyes.
link |
So if we shine light on our eyes,
link |
we can change the activity of neurons in our neocortex.
link |
But there are other brain areas that are not directly
link |
or even indirectly connected to our visual system,
link |
not at least in any immediate way.
link |
So that raises the question of how do you change
link |
the activity of neurons in the brain?
link |
Well, there's pharmacology.
link |
You can take pills, you can inject drugs
link |
that will change the pharmacology of neurons
link |
and the way they operate in fire.
link |
Of course, antidepressants are one such instance.
link |
Opioid drugs are another.
link |
There's a huge array of psychoactive compounds,
link |
meaning compounds that will change the levels
link |
of chemicals in your brain.
link |
Some of those work, many of them also carry side effects.
link |
It's all rather indirect,
link |
meaning you have lots of different cells
link |
in different areas of your brain
link |
that utilize the same chemicals.
link |
So a drug, for instance, to increase serotonin
link |
for sake of improving depression
link |
will also often have the effect of reducing
link |
certain neurons output of serotonin in the hippocampus
link |
and cause changes in appetite or changes in libido
link |
and so on and so forth.
link |
You could imagine using electrical stimulation,
link |
putting wires into the brain
link |
and stimulating specific brain areas
link |
in order to activate the neurons in those brain areas.
link |
And certainly that works and has been done experimentally
link |
and is done during neurosurgery exams, et cetera,
link |
but involves removing a piece of skull.
link |
So that's not very practical.
link |
In principle, light would be a wonderful way
link |
to modulate the activity of neurons deep within the brain.
link |
But again, the skull is in the way.
link |
Recent studies, however, have figured out ways
link |
that light can be delivered to the eyes
link |
to change global patterns of firing in the brain
link |
in ways that can be beneficial to the brain.
link |
And the work that I'm referring to now
link |
is mainly the work of Liwei Tsai at MIT,
link |
Massachusetts Institute of Technology and her colleagues.
link |
And what they've discovered is that
link |
there's a particular pattern of brain activity
link |
called gamma activity.
link |
Gamma activity is one so-called wavelength
link |
of electrical activity in the brain.
link |
So not wavelengths of light,
link |
but wavelengths of electrical activity in the brain
link |
that can be restorative for certain aspects
link |
of learning and memory
link |
and can actually help create molecular changes in neurons
link |
that lead to clearance of debris
link |
and even reductions in age-related cognitive decline.
link |
So the way to think about brain waves
link |
and brain oscillations is that neurons
link |
are electrically active, that involves chemicals, et cetera.
link |
And they can be active in very slow, big wave forms.
link |
So you can think of delta waves,
link |
meaning so you can imagine a wave of electrical activity
link |
that comes along very infrequently.
link |
So a given neuron fires
link |
and then some period of time later fires
link |
and then some period of time even later fires.
link |
Or you can imagine that that same cell is very active,
link |
fires, fires, fires, fires, fires.
link |
You can imagine if it's firing very often,
link |
it's going to be short wavelength, right?
link |
Shorter gaps between firing,
link |
or if it's firing very seldom,
link |
you're going to think about that
link |
as longer wavelength firing.
link |
Turns out that gamma waves are one pattern of firing
link |
that lead to downstream metabolic functions
link |
and biological functions that end up clearing away debris
link |
that's associated with aging in cells.
link |
And that also lead to molecular changes
link |
that enhance the kind of youthfulness of neurons,
link |
How do we induce gamma oscillations within the brain?
link |
Well, what Liwei, Tsai and colleagues
link |
have beautifully shown is that
link |
by delivering certain patterns of light flicker,
link |
so lights going on and off at a particular frequency,
link |
the brain as a whole starts to entrain,
link |
meaning it matches to those particular patterns
link |
even though many of the brain areas that do this
link |
are not directly within the visual system or visual pathway.
link |
So the studies that I'm referred to are several,
link |
but the one that I'd like to highlight is entitled
link |
Gamma Entrainment Binds Higher Order Brain Regions
link |
and Offers Neuroprotection.
link |
What they essentially did was to expose subjects
link |
to 40 Hertz, which is a particular frequency
link |
of illumination to the eyes.
link |
So it's light goes on, light goes off,
link |
light goes on, light goes off at a frequency of 40 Hertz.
link |
And when they did that,
link |
and they recorded the activity of neurons within the brain,
link |
not just within the visual areas of the brain,
link |
but within other areas as well,
link |
they observed increased gamma oscillations,
link |
meaning that the electrical activity of the brain at large
link |
started to match to the patterns of light
link |
that were delivered to the eyes.
link |
This is really exciting and very unique
link |
from the different types of phototherapies
link |
that we've been talking about up until now.
link |
All the patterns of phototherapy
link |
that we've been talking about up until now
link |
involved constant illumination with a given wavelength.
link |
Here, it is wavelength generating patterns of illumination,
link |
light on, light off, light on, light off
link |
at a particular frequency.
link |
So what they found, for instance,
link |
using this pattern of stimulation,
link |
and by the way, the stimulation was called GENUS,
link |
Gamma Entrainment Using Sensory Stimulation,
link |
so G-E-N-U-S, Gamma Entrainment Using Sensory Stimulation,
link |
had a number of really interesting effects.
link |
First of all, it reduced so-called amyloid plaques
link |
and phosphorylated tau.
link |
Amyloid plaques and phosphorylated tau
link |
are associated with Alzheimer's
link |
and normal age-related cognitive decline.
link |
So this is incredible, right?
link |
A pattern of flashing light delivered to the eyes
link |
creates a pattern of neuronal firing,
link |
not just in the visual areas of the brain,
link |
but in other areas of the brain as well,
link |
that in turn trigger molecular pathways
link |
that reduce some of the markers
link |
and the cause of age-related cognitive decline
link |
in Alzheimer's, and in parallel to that,
link |
they observed an upregulation
link |
of some of the biological pathways
link |
that lead to enhancement of neuronal function,
link |
maintenance of synapses,
link |
which are the connections between neurons,
link |
and so on and so on.
link |
They have discovered and list out a huge number
link |
of these biological effects,
link |
both the reduction in bad things, so to speak,
link |
and the improvement in good biological pathways.
link |
And I find these studies so exciting because,
link |
first of all, they're noninvasive, right?
link |
There's no drilling through the skull.
link |
They are very tractable and in the experimental sense,
link |
meaning that you could imagine
link |
that if 40 hertz stimulation turns out
link |
to be the very best stimulation protocol
link |
to induce these gamma oscillations, well, great,
link |
but because it's noninvasive,
link |
it's fairly easy to explore 50 hertz stimulation,
link |
100 hertz stimulation, 20 hertz stimulation,
link |
and to do that with different wavelengths of light.
link |
And so that's what's happening now.
link |
The PSI lab and other labs are really starting
link |
to explore the full range of variables
link |
that can impact oscillations within the brain
link |
and their downstream consequences.
link |
So again, this is phototherapy,
link |
but phototherapy of a very different sort
link |
that we've been talking about up until now.
link |
It's phototherapy designed to trigger activation
link |
of biological pathways far away
link |
from the very tissue that's being illuminated.
link |
And it calls to mind the same sorts of mechanisms
link |
that we were talking about earlier,
link |
where illumination of the skin with UVB light
link |
is setting off an enormous number of different cascades
link |
in different organs and tissues, including the spleen,
link |
the testes, the ovaries, and so on.
link |
So again, light has these powerful effects,
link |
both locally on the cells that light is delivered to,
link |
but also systemically in terms of the cells
link |
that are changing their electrical and chemical outputs
link |
are modifying lots and lots of biological programs.
link |
Is there an actionable tool related to these studies yet?
link |
Well, that sort of depends on how adventurous you are.
link |
Right now, these studies are being explored
link |
in the context of clinical trials
link |
in people with Alzheimer's dementia
link |
and other forms of neuronal degeneration.
link |
Is it dangerous to look at a 40 Hertz flickering light?
link |
Well, in general, the answer is going to be no.
link |
However, if you're prone to epilepsy, for instance,
link |
staring at a flickering light of a given continuous
link |
frequency can induce seizure, right?
link |
That might surprise some of you, but it shouldn't,
link |
because as this study illustrates,
link |
and as anyone who's ever been out at night to a club
link |
or something illustrates,
link |
when you look at a strobe light, for instance,
link |
your whole world of visual perception changes,
link |
but actually the rhythm at which you perceive music,
link |
at which you perceive conversation,
link |
at which you perceive the movement of your body
link |
actually changes according to the patterns of visual flicker
link |
in most cases strobe,
link |
if we're using the sort of club dancing example,
link |
your brain is in training to its outside environment.
link |
So given the power of flickering lights
link |
to entrain brain rhythms, I think at this stage,
link |
it's probably too preliminary to really suggest
link |
a specific protocol, but I would definitely keep an eye out
link |
for these sorts of studies.
link |
They are coming out all the time.
link |
And I think in a very short period,
link |
we're going to see specific protocols
link |
that one could potentially use even at home.
link |
And of course, these are non-invasive protocols
link |
in order to place the brain into a particular state,
link |
not just for sake of offsetting neurodegeneration,
link |
but also for enhancing focus,
link |
for enhancing the transition into sleep
link |
and other brain states as well.
link |
Today, I covered what I would say is a lot of information.
link |
My goal was to give you an understanding
link |
of how light can be used to change the activities of cells
link |
organelles within those cells, entire organs,
link |
and how that can happen locally and systemically.
link |
We talked about the power of light to impact our biology
link |
at the endocrine level, neuronal level, immune level,
link |
mood, et cetera, through both illumination of the eyes
link |
and the skin and other tissues as well.
link |
I realized that even though this was a lot of information,
link |
there are many aspects of phototherapy that I did not cover.
link |
I know there's a lot of interest nowadays, for instance,
link |
in the use of red light and other wavelength light therapies
link |
for ovarian health and testicular health.
link |
In fact, I get a lot of questions such as,
link |
can red light be used to improve testosterone output?
link |
And if so, is that best accomplished by shining red light
link |
on the skin or directly on the gonads, on the testicles?
link |
I'm going to cover those data at a future time.
link |
Right now, the studies that have been done in rodents,
link |
I don't think are easily enough translated to humans.
link |
And the studies that are happening in humans now
link |
are exciting in the sense that they hold a lot of potential,
link |
but the data aren't clear yet.
link |
However, the data using UVB on the skin of men and women
link |
in order to increase hormone, in particular,
link |
testosterone and estrogen output,
link |
those data I think are very exciting and very actionable.
link |
We talked about those earlier.
link |
So if you want more information
link |
on how phototherapy can be used,
link |
certainly we will do another episode on phototherapy
link |
in these other contexts.
link |
If you're learning from and are enjoying this podcast,
link |
please subscribe to our YouTube channel.
link |
That's a terrific zero cost way to support us.
link |
In addition, please subscribe to the podcast
link |
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link |
And on Apple, you have the opportunity
link |
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If you have questions or feedback or comments
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or suggestions about topics that you'd like us to cover
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link |
or guests that you would like me to interview
link |
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link |
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link |
in the comment section on YouTube.
link |
We do read all the comments.
link |
In addition, please check out the sponsors
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link |
That's the best way to support this podcast.
link |
In addition, we have a Patreon.
link |
It's patreon.com slash Andrew Huberman,
link |
and there you can support the podcast
link |
at any level that you like.
link |
During today's podcast,
link |
we didn't really talk about supplements,
link |
but we do talk about supplements and their various uses
link |
in many other episodes of the Huberman Lab Podcast.
link |
While supplements aren't necessary for everybody,
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many people derive tremendous benefit from them.
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For that reason, we've partnered with Thorne, T-H-O-R-N-E,
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because Thorne supplements are of the very highest quality
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If you'd like to see the Thorne supplements that I take,
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you can go to thorne.com slash the letter U slash Huberman,
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and there you can get 20% off any of the supplements
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And if you happen to navigate deeper into the Thorne site
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through that portal, thorne.com slash U slash Huberman,
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you can also get 20% off any of the other supplements
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that Thorne makes.
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If you're not already following us on Instagram and Twitter,
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It's Huberman Lab on Instagram.
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It's also Huberman Lab on Twitter.
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And at both places, I provide science
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and science-based tools,
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some of which overlap with the content of this podcast,
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much of which is unique from the content of this podcast.
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If you're not already subscribing to our newsletter,
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you might consider doing so.
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It's the so-called neural network newsletter.
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You can find it at HubermanLab.com.
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Just go into the menu, look up neural network newsletter.
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You provide us your email.
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We provide summaries of podcasts,
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summaries of actionable protocols and so forth.
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We do not share your email with anybody else.
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And we have a very clear privacy policy there
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at that website if you choose to explore it.
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I'm also pleased to announce
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that we have some live events coming up.
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So I will be giving a lecture called the Brain Body Contract
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where I'll talk about science and science-based tools,
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some of which overlap with the content
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of the Huberman Lab podcast.
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Much of which is unique
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and has never been presented publicly before.
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The first one is going to be May 17th, 2022
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in Seattle, Washington.
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The second one is going to be May 18th in Portland, Oregon.
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To access tickets, you can go to the link
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at HubermanLab.com slash tour.
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So thank you once again for joining me today
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for this deep dive discussion into phototherapies,
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meaning the power of light
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to modulate our biology and health.
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And as always, thank you for your interest in science.