back to indexControlling Sugar Cravings & Metabolism with Science-Based Tools | Huberman Lab Podcast #64
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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 sugar,
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in particular, how our nervous system regulates
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our sugar intake and our seeking of sugar.
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We're also going to discuss how sugar
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regulates our nervous system.
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And as you'll soon learn,
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sugar really impacts our brain and body
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by two main mechanisms.
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One of those mechanisms is based on the sweet taste
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of sugar, which itself is rewarding.
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Even if you're not much of a sweet tooth,
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I confess I'm not,
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most people enjoy sweet tastes more than bitter tastes.
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And the sweet taste of sugar and its various forms
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is strongly reinforcing,
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meaning it triggers the activation of neurons,
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nerve cells in the brain and body
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that make us want to consume more of that sweet substance.
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Incidentally, sweet tastes also make us want
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to eat more of other substances as well.
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You may be familiar with that phenomenon.
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Now, sugar also triggers mechanisms in the brain and body
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based on its nutritive content independent of its sweetness.
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What that means is that the actual caloric content
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and the way that sugar interacts with your nervous system
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at a subconscious level without your awareness
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also impacts your craving and seeking of sugar
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Today, we are going to discuss what happens
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when you ingest sugar in terms of your body's reaction
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and your brain's reaction.
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We're also going to talk about what happens
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when you don't ingest enough sugar.
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Because as it turns out,
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sugar is such a powerful fuel for the brain
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that under conditions where people don't ingest enough sugar
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or where their so-called blood glucose,
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which is basically blood sugar of a particular form
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gets too low, their neurons don't function as well.
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That said, there are conditions of very low blood sugar
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in which neurons can function even better.
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So today we're going to talk about the ins and outs,
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the ups and downs of sugar
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as it relates to your nervous system.
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And by the end of this episode,
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I'm confident that you have a much clearer picture
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as to how much sugar you should be ingesting,
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whether or not you should avoid sugars
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that you're currently eating,
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and you will certainly understand much, much more
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about the energy and fuel sources that your brain relies on,
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which I'm certain will allow you to make
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better informed choices about the foods you eat and avoid
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toward mental health, physical health, and performance.
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I'm pleased to announce that I'm hosting two live events
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The first live event will be hosted in Seattle, Washington
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The second live event will be hosted in Portland, Oregon
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Both are part of a lecture series entitled
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The Brain-Body Contract,
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during which I will discuss science and science-based tools
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for mental health, 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
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is going to be distinct from information covered
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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 that this podcast
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is separate 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 Thesis.
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Thesis makes what are called nootropics,
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which means smart drugs.
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Now, to be honest, I am not a fan of the term nootropics.
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I don't believe in smart drugs in the sense that
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I don't believe that there's any one substance
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or collection of substances that can make us smarter.
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I do believe based on science however,
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that there are particular neural circuits
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and brain functions that allow us to be more focused,
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more alert, access creativity, be more motivated, et cetera.
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That's just the way that the brain works.
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Different neural circuits for different brain states.
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And so the idea of a nootropic
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that's just going to make us smarter all around
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fails to acknowledge that smarter is many things, right?
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If you're an artist, you're a musician, you're doing math,
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you need to be creative.
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These are all different brain processes.
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They only use the highest quality ingredients,
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which of course is essential.
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I've been using thesis for more than six months now,
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My go-to formula is the clarity formula,
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or sometimes I'll use their energy formula before training.
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To get your own personalized nootropic starter kit,
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That's takethesis.com slash Huberman
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Today's episode is also brought to us by Athletic Greens,
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I've been taking Athletic Greens since 2012,
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so I'm delighted that they're sponsoring the podcast.
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The reason I started taking Athletic Greens
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and the reason I still take Athletic Greens
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I've done a couple of episodes now
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Okay, let's talk about sugar.
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Let's talk about how sugar impacts your brain
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and how your brain impacts your pursuit
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or your avoidance of sugar.
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Let's get a few things out of the way first.
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The first thing is that there's nothing inherently bad
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I know the word sugar gets a bad rap nowadays,
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and indeed you're going to hear over and over again
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during this podcast that consuming a lot of refined sugars,
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in particular high fructose corn syrup,
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is known to have a very large number of bad effects
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on the brain and body.
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I don't know that there's anyone
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that really debates that anymore.
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Even if we just agree,
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and I think we should all agree on the so-called
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calories in, calories out principle, right?
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It's a principle of thermodynamics
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that if we ingest more energy than we burn,
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we are going to gain weight.
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If we ingest less energy than we burn,
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we are generally going to lose weight.
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And if the two things are in balance,
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ingestion and burning of energy,
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well then we're going to maintain weight.
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So everyone agrees on that.
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But beyond that, there are a number of ways
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in which particular nutrients,
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in the case of today's episode, sugar,
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impact the way that the brain works,
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such that we tend to seek out more of particular nutrients.
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For instance, if we eat sugar,
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there are two or at least two mechanisms
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by which we will crave more sugar.
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I think most people are aware of that experience,
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but today I'm going to explain exactly how that works.
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But also that when we ingest sugar,
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it has a bunch of different effects
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on the way that our neural circuits work
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that can allow us to be more or less focused,
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more or less agitated, more or less happy,
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more or less depressed in some cases.
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So today, as we explore this thing we're calling sugar,
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we're going to explore that mainly in the context
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of the nervous system,
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but also in the context of how the nervous system regulates
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many, many functions and behaviors
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that are important to all of you.
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Your ability to think, your ability to exercise,
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your ability to gain weight, lose weight,
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whatever your goals might happen to be.
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Sugar plays a critical role in achieving those goals.
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And in some cases, if you're ingesting too much
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at the wrong times or the wrong forms,
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sugar can actually impede those goals.
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In fact, sugar can prevent all the right behaviors
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from allowing you to achieve the goals that you want.
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So today we are going to place sugar
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into its proper context.
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The way I want to start off by doing that
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is to tell you a little bit of what happens when we eat
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and a little bit of what the brain does
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to respond to those events.
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So what happens when we eat?
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Well, I've done an entire episode on metabolism.
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So if you're interested in the full cascade of hormonal
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and neural events that occurs when we eat,
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please check out that episode.
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But for sake of today's discussion,
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let's just take a, what I call top contour view
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of the hormonal response to ingesting food.
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Now, anytime we eat, that is the consequence
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of a number of things that happened before we ate.
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There's a hormone in our brain and body called ghrelin,
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spelled G-H-R-E-L-I-N.
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Ghrelin is a hormone that increases
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depending on how long it's been since we ate last, okay?
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So the longer it's been since we had a meal,
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ghrelin levels are going to be higher and higher and higher.
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And it essentially makes us hungry
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by interacting with particular neurons
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in an area of the brain
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called the arcuate nucleus of the hypothalamus
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and some other areas as well, like the lateral hypothalamus.
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You don't need to know the names of those brain areas,
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but if you'd like to know them, there they are.
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Ghrelin increases, it tends to make us hungry.
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And then when we eat,
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typically what happens is ghrelin levels go down.
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So it's a very logical system.
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Now, when we eat, assuming that we eat carbohydrates,
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but even if we just eat some protein and some fats,
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we will experience a slight,
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or in some cases, a large rise in blood glucose.
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Blood glucose is simply blood sugar.
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And the body and brain,
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we should say particular the nervous system
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doesn't function well if blood sugar is too high or too low.
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So as a consequence, we have another hormone,
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which is released from the pancreas,
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which is called insulin,
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which helps regulate the amount of glucose
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in the bloodstream.
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So even if you were to ingest an entire cup,
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an eight ounce cup of pure table sugar,
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which would send your blood glucose very, very high,
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assuming that you have a normal insulin response,
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that you're not diabetic,
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that insulin response would help clamp
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that blood glucose level
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so that it did not cause damage to your brain and body.
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Because if blood sugar goes too high,
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it's actually toxic to neurons
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and other cells of your body can kill them off.
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And neurons of the central nervous system,
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meaning the brain and spinal cord,
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once they are dead, they do not come back.
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So your biological systems understand this
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at a biological level that is,
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and prevent that death of cells due to high blood sugar
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by keeping insulin around in order to clamp blood glucose.
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Diabetics, we call them type one diabetics
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who don't make insulin have to take insulin when they eat,
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in particular, when they eat foods
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that raise their blood sugar,
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specifically to avoid that neurotoxicity
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and the other deleterious effects of high blood sugar.
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Okay, so ghrelin is a hormone that goes up
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the longer it's been since we've eaten.
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It tends to stimulate hunger.
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When we eat, ghrelin is suppressed.
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Blood glucose typically goes up,
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especially when we eat a carbohydrate containing meal.
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When blood glucose goes up, it's regulated in the body,
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meaning its peaks and its valleys
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are more or less smoothed out,
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and that glucose is sequestered,
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it's taken away where it needs to be taken away,
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and in certain locations, it's delivered to cells
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so that those cells can use the glucose.
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Now, one of the chief organs for glucose utilization
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Neurons are tremendously metabolically active,
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and their preferred mode of metabolism is glucose metabolism.
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In other words, neurons basically run on sugar,
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which is not to say that you should eat a lot of sugar,
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as you'll see today, there are states of mind and body,
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for instance, fasted states,
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in which people report having immense amounts
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of mental clarity,
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and their blood glucose is actually quite low.
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So it is simply not the case
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that the more sugar that you ingest,
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the better that your brain will function,
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but it is the case that for most people,
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meaning people who are not on a ketogenic
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or very low carbohydrate diet,
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they're not adapted to low carbohydrate diets,
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that neurons in their brain and body
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are using glucose in order to function.
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That's what allows those neurons
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to fire electrical potentials,
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that's how we refer to it, firing,
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meaning sending electrical signals down their length
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to communicate with other neurons.
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To illustrate just how important glucose is
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for brain function,
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I'd like to describe a study that just recently came out
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that sits on a long history of similar studies,
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but the one that just came out is particularly interesting.
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Now, I want to point out that unless I say otherwise,
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I'm going to refer to typical diets,
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meaning I have to believe that most people out there
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are ingesting some starch or carbohydrate.
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I do realize there are people
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following very low carbohydrate diets
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or moderately carbohydrate diets,
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I even know that there's some folks out there
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who are on the so-called carnivore diet,
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they only eat meat and organs, maybe a little fruit,
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but I'm going to assume
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that the vast majority of people listening
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ingest proteins and carbohydrates.
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So unless I say ketogenic,
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or I emphasize ketosis itself, which I will,
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I'm referring to a kind of typical diet
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where people are consuming fats, proteins, and carbohydrates.
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I count myself as one such individual.
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At some point, I might try the carnivore diet, who knows,
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I might try a pure vegan diet, who knows,
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but for my entire life up until now, I'm 46 years old,
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I've been a proud omnivore, meaning I've tried
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to eat high quality, as much as I can, unprocessed foods,
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I try and really avoid highly processed foods,
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but I do eat from those three macronutrient groups,
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proteins, carbohydrates, and fats,
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and I'm going to assume that most of you do as well.
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The study I'd like to emphasize recorded from neurons,
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nerve cells in the brain, in particular,
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in the part of the brain that responds to visual images,
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a so-called visual cortex,
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and neurons in the visual cortex are beautifully tuned,
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as we say, to particular features of what we see.
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The primary example of this, the kind of classic example,
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is if you put a little electrode next to a neuron
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in your visual cortex, or if we put you
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into an fMRI scanner machine,
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which can detect neural activity,
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and I were to show you a bunch of just little lines,
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bars of light, they could be dark bars of light,
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they could be light bars of light
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on a screen in front of you, so some would be vertical,
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some will be horizontal, some will be at 45 degrees,
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what we would see is that some neurons respond best,
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meaning they fire a lot of electrical activity
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to vertical lines, other ones respond to horizontal lines,
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and others respond to 45 degree lines.
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And this so-called orientation tuning,
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meaning because of the orientation of the line,
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is a cardinal classic feature of the way
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that your visual system is built.
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And everything that you see, whether it's a face or a dog
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or a cat or a landscape, is built up
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from these very simple neuron responses.
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In other words, when you look at a face,
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there are neurons deep in the brain that respond to faces,
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but the only reason that those neurons can respond
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to those faces is because they receive signals
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from neurons in your visual cortex,
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some of which respond to vertical lines,
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some of which respond to horizontal lines,
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and some of which respond to 45 degree lines,
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and all of those are built up
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in what we call a hierarchical representation,
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which is fancy language for it,
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those are the building blocks by which you see a face
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and you recognize a face.
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And it's really an amazing phenomenon,
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it happens very, very fast,
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you never notice that you're doing this,
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but everything is built up
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from these fundamental orientation tuned neurons.
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Now, orientation tuned neurons are so fundamental
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that they are the building blocks
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by which you make up all other things that you see,
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it's the way you read,
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it's the way that you recognize faces, as I mentioned,
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and everything else.
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Experimentally, it's quite straightforward
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to measure how sharply tuned one of these neurons is.
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In other words, if I were to show you a vertical line
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and find a neuron in your brain
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that responds to vertical lines,
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I could also ask whether or not that neuron fires
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any electrical activity in response
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to a line that's not quite vertical,
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maybe just 10 degrees off vertical,
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or 20 degrees, or 30 degrees.
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And what I eventually would find
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is that that neuron was orientation tuned
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over a particular range of angles,
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it's not only going to respond to vertical lines,
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it's also going to respond to lines
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that are about 10 degrees off vertical in either side,
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but probably not much more, maybe 20,
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but usually it's going to be anywhere from vertical
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to just tilted slightly, okay?
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In the recent experiment
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that was published in the journal Neuron,
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Cell Press Journal, excellent journal,
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the authors asked a really interesting question.
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They asked whether or not the sharpness of tuning,
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the precision of orientation tuning of these neurons
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is dependent on blood glucose level.
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So just to cut to the chase, to give you the answer,
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what they found is that when subjects are well-fed,
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neurons that responded to vertical
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responded very strongly to vertical,
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but not very much at all to other angles
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of what we call stimuli,
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to lines that are 10 degrees or 20 degrees off.
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If they looked at neurons that were primarily tuned, right?
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That preferred horizontal lines,
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they found the same thing, okay?
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So it wasn't something unique to vertical lines.
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What they basically found was the sharpness,
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the precision of tuning of neurons in the brain
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was best when subjects were fed.
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And conversely, when subjects were fasted,
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the orientation tuning of these neurons
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became much broader.
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What it meant was that a neuron
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that normally would only respond to vertical
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now responded to other angles of lines as well.
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You might say, well, that's great, right?
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These neurons that at one point could only do one thing
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are now tuned to other things, but it's not so great
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because what that means is that in the fasted state,
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your perception of the outside world is actually distorted.
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It's blurred, it's not as precise as it is when you're fed.
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And when I say fed,
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what I really mean is when glucose is available to neurons.
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Now, for some of you, maybe many of you,
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and including myself, intermittent fasting
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or some variant thereof is actually a state that I like.
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It allows me to focus.
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For instance, as I mentioned before,
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and even earlier in this podcast,
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I tend to eat my first meal sometime around 11 a.m.
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and then I generally eat my last meal
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sometime around 8 p.m.,
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plus or minus an hour on either side.
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I'm not super strict about it.
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On occasion, I'll wake up really hungry
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and I'll eat something before 11 a.m.
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I'm not super strict about this intermittent fasting thing.
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It just seems to be how my appetite works best
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given my schedule, et cetera.
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In the morning, I tend to be most focused
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and I always associate that with the fact that I was fasted.
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I just water and some caffeine
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about 90 minutes after waking up, I drink my caffeine,
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but I hydrate from the time I get up, et cetera, et cetera.
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And I know a lot of other people
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have had the experience of being fasted
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and feeling like they have a lot of mental clarity.
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When you are in a fasted state,
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typically you're going to use fuels
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that are available to the neurons
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based on your intake of food the day before,
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maybe you're using some glycogen,
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maybe you're using some fat,
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maybe you're using some blood sugar
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that's derived from other storage sites in the body.
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You don't actually use fat as a fuel source for neurons
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under typical conditions,
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but there are ways in which proteins and fats
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and glycogen, et cetera are converted
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into fuel that neurons can use.
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What's interesting about this study
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is that the study says that when well fed,
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meaning when blood glucose sugar
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is at a properly elevated level in the bloodstream,
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it can be delivered to the brain
link |
in a way that allows neurons to work best,
link |
which is really all just to underscore
link |
the point that I made earlier,
link |
which is that your nervous system
link |
is extremely metabolically demanding and it loves glucose.
link |
Neurons love glucose.
link |
So the takeaway from this study
link |
is not that you should avoid fasting.
link |
The takeaway from this study
link |
is that there are elements of the fasted state,
link |
in particular the elevations
link |
and things like epinephrine and norepinephrine,
link |
also called adrenaline and noradrenaline,
link |
that can give us this kind of clarity of mind
link |
that many people are pursuing when they fast.
link |
That's kind of one of the reasons a lot of people fast.
link |
They like the way that they feel mentally and physically.
link |
But I think it's only fair to point out
link |
that glucose is the preferred source of fuel
link |
And this study that I mentioned
link |
is one of many studies that have explored
link |
how nutritional status or blood glucose status
link |
in the brain and body influence
link |
neuronal tuning and neuronal function.
link |
And it really points to the fact that ultimately,
link |
your brain as an organ is a glucose consuming machine.
link |
Now, when you eat a food, that food is broken down
link |
and if it contains carbohydrates,
link |
it's going to be converted into glucose.
link |
And that glucose can't get directly
link |
into the brain as a fuel source.
link |
It actually has to be carried
link |
across the so-called blood brain barrier, the BBB.
link |
And the actual metabolism of glucose
link |
and the delivery of the glucose to the neurons
link |
is carried out by a different cell type.
link |
And it's a cell type that you should all know about
link |
because it's the most abundant cell type in your brain
link |
and maybe even in your entire nervous system.
link |
And that's the so-called astrocyte.
link |
Astrocytes are one of several types of glia.
link |
The word glia means glue,
link |
but many people have taken that name glia,
link |
glue, to think that, oh,
link |
the only thing that the astrocytes are doing
link |
is just kind of holding things together.
link |
Actually, the astrocytes are involved
link |
in delivering glucose to the neurons.
link |
They are critically involved
link |
in shaping your neuronal function and brain plasticity,
link |
the brain's ability to change in response to experience.
link |
So these astrocytes are like the little waiters
link |
and waitresses bringing glucose to the neurons
link |
and the neurons are going to do the heavy lifting
link |
that's involved in perception and behavior and action.
link |
So if prior to this episode,
link |
you didn't already realize that glucose,
link |
blood sugar, is vital to the function of your brain
link |
and other neurons of your nervous system, now you know.
link |
And for those of you that have experienced
link |
the increase in mental clarity
link |
that comes after a properly timed,
link |
properly composed,
link |
meaning it has the right macronutrients
link |
and the right ratios and the properly sized meal,
link |
well, then now you have justification
link |
for eating something as a way
link |
to improve the way that your brain works.
link |
It turns out that your brain is going to work best
link |
when it's got glucose available.
link |
Whether you like to fast or not,
link |
that's just the reality of things.
link |
The same thing is also true for the neurons in your body.
link |
The way that you are able to move the limbs of your body,
link |
the way that you are able to perform exercise
link |
or movement of any kind for that matter,
link |
is because neurons called motor neurons
link |
send electrical potentials to the muscle fibers.
link |
They release a neurotransmitter called acetylcholine,
link |
which causes contraction of the muscle fibers
link |
and allows you to move your limbs.
link |
Those neurons are also very metabolically demanding,
link |
especially when you're doing
link |
demanding types of physical work.
link |
And that could be cycling or running or weightlifting
link |
or yoga or whatever it may be.
link |
Those neurons require a ton of glucose.
link |
If you've ever had the experience
link |
of having to think very hard
link |
about how you're generating a movement
link |
or force yourself to continue to endure in a given exercise,
link |
you might've thought, oh, you know, I'm running out of fuel.
link |
That's why I'm getting tired.
link |
That's actually the case sometimes,
link |
but that's not always the case.
link |
One of the reasons that it feels like work
link |
is because your so-called upper motor neurons,
link |
the one that control the lower motor neurons
link |
in your spinal cord, which control your muscles,
link |
they have to be very metabolically active.
link |
It's one thing to engage in a reflexive movement
link |
where you're just walking around
link |
or if you're running continuously,
link |
but when you suddenly have to focus on what you're doing
link |
and you have to generate specific patterns
link |
of motor movement, well, that feels demanding
link |
because one, it increases the release of adrenaline
link |
in your brain and body,
link |
this makes you feel a little bit agitated and more alert,
link |
but also deliberate thought,
link |
deliberately controlling the way that your brain and body
link |
is moving requires more glucose uptake,
link |
more energy in those very neurons.
link |
And this is also why after doing a long bout of exercise,
link |
you might be tired,
link |
but also if you do a bout of skill learning of any kind,
link |
or if you've been reading and thinking
link |
about what you're reading,
link |
or if you had a intense conversation with somebody
link |
where you're really forcing yourself to listen
link |
and hopefully they're listening to you too
link |
and you're really trying to parse what they're saying
link |
and maybe you're doing that right now
link |
and you're trying to really track something,
link |
that's work and that work requires glucose uptake
link |
by neurons both in the brain and in your body.
link |
Now that we've established that glucose
link |
is the preferred source of fuel for the nervous system,
link |
I'd like to concentrate on a few of the other types
link |
of sugars that we ingest on a common basis
link |
and the impact that those have on brain function
link |
and body function.
link |
I'd particularly like to focus on fructose.
link |
Fructose of course is found in fruit.
link |
It's also found in the infamous high fructose corn syrup,
link |
which we will talk about today.
link |
It's worth pointing out that the concentrations
link |
of fructose in fruit is quite low compared
link |
to the concentrations of fructose in high fructose corn syrup.
link |
High fructose corn syrup is approximately 50% fructose,
link |
which turns out to be an enormously high percentage
link |
of anything really, especially when we contrast that
link |
to the concentrations of fructose in fruit.
link |
Fruits have other types of sugars in them as well.
link |
The sucrose content of most fruit and fruit juices is low,
link |
although there are some fruits like melons, peaches,
link |
pineapples, and so forth that contain a little less
link |
than 10% or so of sucrose.
link |
Things like mangoes can have a lot of sucrose,
link |
but typically the amount of fructose,
link |
fructose I think is the proper pronunciation
link |
that people are always correcting me, fructose,
link |
is anywhere from 1% to about 10%, right?
link |
It's really going to vary quite a bit.
link |
And many of you have probably heard
link |
of the so-called glycemic index,
link |
which is basically a measure of how fast blood sugar rises
link |
after eating particular foods, et cetera.
link |
We're going to set aside the glycemic index for now.
link |
We will come back to it.
link |
It has some relationship to the concentrations
link |
of fructose in fruit,
link |
but the point that I'd like to make is that fructose
link |
as a sugar is handled very differently in the body
link |
But I also want to emphasize that because the percentage
link |
of fructose in fruit is rather low,
link |
especially compared to high fructose corn syrup,
link |
many people have demonized fructose saying
link |
that fructose makes you fat or that fruit makes you fat.
link |
If you look at the data, that's not really the case.
link |
The fact of the matter is that the concentrations
link |
of fructose and fruit are so low
link |
that unless someone is consuming a lot of fruit
link |
or they're consuming a lot of fruit
link |
on the backdrop of a highly processed diet
link |
or a diet that has a lot of other stuff
link |
that they might not want to be ingesting,
link |
you can't really say that fructose is fattening.
link |
I don't really think that there's any basis
link |
for saying that fructose itself is bad.
link |
Now, high fructose corn syrup is a different issue
link |
and too much consumption of anything but fructose included,
link |
whether or not it comes from fruit or otherwise,
link |
can be a problem for the ways that it impacts
link |
the neural circuits that process sugar,
link |
not just glucose, but fructose.
link |
And so we'll illustrate those neural circuits in a bit
link |
and it will become very clear to all of you,
link |
regardless of whether or not you have a background
link |
in biology or metabolism, nutrition or otherwise,
link |
why ingesting very high concentrations of fructose
link |
is not going to be a good thing
link |
for the way that your brain functions.
link |
One of the key distinctions between glucose and fructose
link |
is that fructose most likely cannot directly access
link |
the brain, it actually needs to be converted
link |
into glucose in the liver.
link |
And the way that conversion occurs,
link |
feeds back to a set of hormones and neural pathways
link |
that we talked about earlier,
link |
which have a lot to do with appetite.
link |
And to just summarize what is now a lot of very solid data,
link |
fructose and specifically fructose has the ability
link |
to reduce certain hormones and peptides in our body,
link |
whose main job is to suppress ghrelin.
link |
As you recall, ghrelin is a hormone that increases
link |
the longer it's been since we've eaten
link |
and ghrelin makes us hungry
link |
by stimulating particular neurons in our hypothalamus.
link |
It actually makes us really want to eat
link |
and in particular really makes us want to eat
link |
sugary and fatty foods.
link |
Fructose reduces the activity of the hormones
link |
that reduce ghrelin.
link |
And so the net consequence of that
link |
is that fructose increases ghrelin.
link |
So although I, and I think pretty much everyone out there,
link |
say for a few individuals,
link |
agrees that calories in, calories out
link |
is the fundamental principle of weight loss,
link |
weight maintenance or weight gain,
link |
ingesting fructose shifts our hormone system
link |
and as a consequence, our neural pathways within our brain,
link |
the hypothalamus, to be hungrier,
link |
regardless of how many calories we've eaten, okay?
link |
Now, I also want to be absolutely clear.
link |
This does not mean that eating an apple
link |
or eating a melon or eating a couple of apricots
link |
or something is going to make you hyperphagic,
link |
meaning it's going to make you just want to eat
link |
That's simply not the case.
link |
But if you compare fructose and you compare glucose,
link |
not only are they metabolized differently
link |
in the brain and body,
link |
but in addition to that,
link |
fructose has this impact of reducing the hormones
link |
that reduce hunger hormones and neural circuits.
link |
And so fructose does have this kind of twist
link |
in its phenotype, right?
link |
Or it's, I guess if fructose had a dating profile,
link |
this would be a kind of a red flag in that profile.
link |
Because fructose itself,
link |
while it's actually a pretty good fuel source in many ways,
link |
and it's often packaged in things like fruits,
link |
which bring along fiber and vitamins and minerals
link |
that I think for many of us are things
link |
that we should be eating more of and ingesting more of,
link |
it can suppress the pathways that suppress hunger.
link |
And as a consequence, it can increase hunger.
link |
So current recommendations for most people
link |
are to eat more fruits and vegetables.
link |
But for those of you that are trying to control your hunger,
link |
ingesting a lot of fructose
link |
is probably not going to be a good idea.
link |
Certainly ingesting it from high fructose corn syrup
link |
is not going to be a good idea
link |
because of the enormous percentages of fructose
link |
in high fructose corn syrup, 50% or sometimes even more.
link |
But even from fruit,
link |
some people will find that fruit
link |
really quenches their appetite.
link |
Other people will find that fruit stimulates their appetite.
link |
And I suppose if you're trying to stimulate your appetite,
link |
then ingesting more fruit
link |
might actually be advantageous to you.
link |
So fructose provides a bridge for us
link |
between a particular kind of sugar, hormone function,
link |
in this case, ghrelin and the hypothalamus,
link |
which leads us to the next question,
link |
which is what is it about sugar
link |
that makes it such an attractive thing for us?
link |
Why do we like it so much?
link |
And the obvious answer that most people arrive at is,
link |
well, it just tastes really, really good,
link |
but that's actually not the way it works.
link |
The rewarding properties, as we say, of sugar,
link |
whether or not they come in the form of sucrose or fructose
link |
or foods that increase glucose to a very high level,
link |
actually is not just related to the taste of the foods
link |
that produce that elevation in glucose, sucrose, or fructose.
link |
It is in part, but that's only part of the story.
link |
And the rest of the story, once you understand it,
link |
can actually place you in a position
link |
to much better control your sugar intake of all kinds,
link |
but also your food intake in ways
link |
that can allow you to make much better choices
link |
about the foods you ingest.
link |
And actually, at this point,
link |
I should probably give a confession.
link |
I've said today, and I'll say it again,
link |
and I've said it on previous podcasts,
link |
I don't have much of a sweet tooth, and indeed, that's true.
link |
And I can kind of pass on chocolate or ice cream
link |
or things like that.
link |
It seems like with each successive year,
link |
sweet things are less and less appealing to me.
link |
Of course, savory foods,
link |
anything that is really fatty, salty, savory,
link |
those don't last long in my presence.
link |
But I always say I don't really like sweet things so much,
link |
and I like sweet people,
link |
but I don't tend to like sweet foods,
link |
which is true, but there's probably one exception,
link |
and that's mangoes.
link |
And it turns out that mangoes have the highest percentage
link |
of sugar in them, in particular fructose,
link |
as well as other forms of sugars.
link |
So what I do, because I love mangoes so much,
link |
is I will have mangoes probably twice a week,
link |
but I'll have them after some sort of resistance training
link |
or hard run or something like that,
link |
because it is the case that after you exercise hard,
link |
in particular exercise that is of the high intensity variety
link |
that your body is more efficient
link |
at using circulating blood sugar.
link |
It's able to store that or use that for fuel.
link |
And so what I'll typically do is just take the mango,
link |
actually eat the peels too.
link |
I know there are probably some people are going to cringe
link |
when they hear that.
link |
I find them delicious,
link |
so I just bite into those things like apples.
link |
I don't eat the pits, however.
link |
So now I want to take us on a journey
link |
into the nervous system to explain the pathways
link |
in the brain and body that regulate our appetite for sugar.
link |
Now, keep in mind what I already told you before,
link |
which is that when we ingest foods,
link |
they're broken down into various components
link |
and glucose is going to be shuttled to the brain
link |
and of course, to other neurons in our spinal cord
link |
and elsewhere and to our muscles, et cetera,
link |
in order for all of those cells and organs and tissues
link |
to be able to function.
link |
The fact that so many cells and organs and tissues
link |
require glucose in order to function
link |
has led to a situation where you have dedicated
link |
neural machinery, pieces of your brain
link |
that are almost entirely, if not entirely devoted
link |
to seeking out of sugar or foods that contain sugars
link |
and to make sure that you not only seek those out,
link |
but you know where those foods are
link |
and that you ingest more and more and more of them.
link |
And there are two main ways that these neural circuits work.
link |
In fact, we can say that there are two neural circuits
link |
entirely that work in parallel.
link |
And this is a common theme throughout the nervous system
link |
and that's parallel pathways.
link |
Parallel pathways are the ways
link |
that you can distinguish light from dark.
link |
Parallel pathways are the ways that you can distinguish
link |
high-pitched sounds from low-pitched sounds.
link |
Parallel pathways are the ways that you can flex your muscles
link |
versus extend your muscles.
link |
For instance, if you move your wrist
link |
closer to your shoulder, you're flexing your bicep
link |
and you're actually inhibiting,
link |
you're actually preventing the action of your tricep.
link |
If you move your wrist away from your shoulder,
link |
you are essentially using your extensor, your tricep,
link |
and you're inhibiting the activity of your bicep.
link |
So for every function in your body
link |
that you might think is controlled by one brain area
link |
or one neural circuit, almost always,
link |
there are two or more so-called parallel pathways
link |
that ensure that that particular behavior happens.
link |
Now, in the case of sugar consumption,
link |
the two parallel pathways involve one pathway
link |
related to the actual taste and the perception
link |
of sweet tastes that lead not just you,
link |
but every animal that we're aware of
link |
to seek more sweet-containing foods.
link |
The other parallel pathway is related
link |
to the nutritive component of sweet foods,
link |
meaning the degree to which a given food
link |
will raise blood glucose.
link |
I want to repeat that.
link |
One pathway in your brain and body
link |
is devoted to getting you to seek out sweet-tasting things
link |
that you perceive as sweet,
link |
and another parallel pathway is devoted
link |
to getting you to seek out foods
link |
that lead to increases in blood glucose.
link |
It just so happens that the foods
link |
that lead to big increases in blood glucose
link |
typically are associated with that sweet taste.
link |
Now, this is distinctly different
link |
than the neural pathways that control seeking
link |
of savory foods or salty foods or spicy foods,
link |
for that matter, or bitter foods.
link |
The sweet pathway is what we would call hardwired.
link |
It exists, as far as we know,
link |
in every mammal that even exists in fruit flies,
link |
Basically, getting sweet stuff into the body
link |
might seem like it has a lot to do with the taste,
link |
but it has just as much to do
link |
with the nutritive components that sweet-tasting foods carry
link |
and the fact that your nervous system
link |
and so many cells in your brain and body run on glucose.
link |
If you recall earlier, I said,
link |
even if you ingest fructose,
link |
fructose can be converted into glucose in the liver.
link |
And I mentioned, of course,
link |
that fructose may actually work directly on the brain.
link |
That's still unclear for humans.
link |
The jury's still out on that.
link |
But the fundamental thing to understand here
link |
is that when you think you want a piece of chocolate
link |
or you think you want a piece of cake
link |
or you're craving something sweet,
link |
you are both craving the taste
link |
and your neurons are literally craving
link |
the nutritive components that arrive with that taste.
link |
And simply by understanding that can allow you
link |
to circumvent some of the sugar cravings
link |
that you might otherwise be a complete hopeless victim to.
link |
Also in this episode, I will talk about ways
link |
that you can sort of undermine or short-circuit
link |
these circuits, if you will,
link |
in order to reduce sugar cravings on a regular basis,
link |
if that's your goal.
link |
Two parallel pathways.
link |
One of the parallel pathways has to do
link |
with conscious perception.
link |
So animals of all kinds, mice, rats, and humans
link |
will prefer sugary taste to non-sugary taste.
link |
When we eat something that tastes sweet,
link |
we register that sweet taste by way of sweet receptors,
link |
literally little ports or portals of neurons
link |
on our tongue and on our palate.
link |
A lot of people don't realize this,
link |
but there are a lot of taste receptors on the soft palate
link |
and around the mouth, so on the sides of the mouth.
link |
So you're actually tasting things,
link |
not just with your tongue,
link |
but with your entire mouth and your palate.
link |
So when you ingest something sweet,
link |
very quickly there are signals sent
link |
from those neurons in your mouth
link |
to brain areas that cause you to seek out
link |
or at least pay attention to the source
link |
and the abundance of those sweet things.
link |
They literally change your perception.
link |
In fact, there are beautiful neuroimaging studies
link |
that show that when people ingest a sugary drink,
link |
their perception of images of foods change very much
link |
to make those foods appear more appetizing
link |
and not just foods that contain sugar.
link |
Results of those studies do show that there's an increase,
link |
for instance, in the perception of detail
link |
and images of ice cream after you ingest a sweet drink
link |
or even put like a hard candy into your mouth,
link |
it will make you seek out sugary things more,
link |
it will make sugary things look more appetizing,
link |
but also other foods more appetizing.
link |
So I think it's important that people recognize that fact
link |
that when you have a sweet taste in your mouth
link |
or when you've tasted something sweet within your mouth,
link |
I should say, your perception of food
link |
has immediately shifted.
link |
These are fast neural pathways,
link |
then we'll get into some of the brain structures
link |
in a moment, but these are fast neural pathways
link |
that shift your entire self
link |
toward seeking more sugary stuff and more food generally.
link |
Now, does that mean that you should
link |
never ingest anything sweet?
link |
No, certainly I'm not saying that.
link |
Everyone has to decide for themselves
link |
what the appropriate amount of sugar intake is,
link |
but I find it remarkable when people say,
link |
oh, you know, I need to get my sugar fix
link |
or I need to have my chocolate
link |
or I need to have a little bit of something
link |
to just kind of take care of that sugar appetite
link |
because in taking care of that sugar appetite,
link |
maybe for the very disciplined of you,
link |
you can just have that one piece of chocolate
link |
and it's great and you can relish in it,
link |
but it does shift the way
link |
that you perceive other foods as well.
link |
And the way it does that is through our,
link |
probably if you're a listener to this podcast now,
link |
old friend, but incredible neuromodulator dopamine.
link |
Dopamine is a molecule that is released
link |
from several places in the brain.
link |
There's a so-called mesolimbic reward pathway,
link |
which is a whole set of places in the brain or circuits
link |
designed to get us motivated
link |
and craving and in pursuit of things.
link |
And then of course,
link |
there are areas of the brain that are involved in movement
link |
that are linked up with those areas involved in motivation.
link |
That makes perfect sense.
link |
Why would you have a brain area involved in motivation
link |
if you couldn't actually do something with that motivation?
link |
So the way that your brain is designed
link |
is when there's an increase in dopamine
link |
in the mesolimbic reward pathway,
link |
there are signals sent to an area of the brain
link |
called the striatum.
link |
We're going to spend a little bit of time today
link |
It's got a dorsal part, meaning an upper part,
link |
and a ventral part, which means a lower part.
link |
And the dopamine sent to those areas places us, excuse me,
link |
into modes of action to pursue particular things.
link |
Sugar or sweet tastes, I should say to be more specific,
link |
have an incredibly potent ability
link |
to activate dopamine release
link |
within the mesolimbic reward pathway.
link |
This has been shown over and over and over again
link |
in animal models and in humans.
link |
This is especially true, I should mention,
link |
through the ingestion of sweet liquids.
link |
Now, this becomes a very important point to us
link |
a little later on when we talk about the proliferation
link |
of sodas and sweet drinks,
link |
and dare I even say non-sugar or diet sodas.
link |
We're going to get into that a little bit later,
link |
perhaps one of the most third rail topics in nutrition.
link |
But when we ingest something sweet,
link |
the perception of that sweet taste increases dopamine
link |
in the mesolimbic reward pathways,
link |
which then are conveyed to pathways for motor behavior,
link |
and in general, place us into modes of focused action
link |
toward getting more of whatever was sweet.
link |
Again, for those of you that are very disciplined,
link |
you can probably eat that one piece of chocolate
link |
But if you understand the way that dopamine works,
link |
what you'll realize is that when this dopamine pathway
link |
is triggered, it tends to create not the sensation
link |
or the perception of satiety,
link |
of feeling like something is enough,
link |
but rather to produce the sensation of wanting more.
link |
As described in the episode that I hosted
link |
with my phenomenal colleague
link |
from Stanford School of Medicine, Dr. Anna Lemke,
link |
she's an expert on addiction and dopamine pathways.
link |
The dopamine circuits of the brain
link |
have what we call a pleasure pain balance.
link |
And there I'm paraphrasing what Dr. Anna Lemke has said
link |
and has written about in her beautiful book,
link |
''Dopamine Nation.''
link |
If you haven't read that book, I highly recommend it.
link |
Whether or not you have issues with addiction
link |
or you know people that do, or you don't,
link |
it's an incredibly important read,
link |
especially if you're interested
link |
in understanding motivated behaviors
link |
and ways to channel your behaviors in life
link |
toward healthy motivated behaviors
link |
and make sure that you avoid some of the common pitfalls
link |
that people fall into, not just addiction,
link |
but things like overuse of social media
link |
or wasting time in general, it's a phenomenal book.
link |
In that book and of course, within research articles,
link |
you will find evidence of this so-called
link |
pleasure pain balance that exists
link |
within our dopamine circuits.
link |
Nobody has dopamine circuits that allow them
link |
to escape this pleasure pain balance.
link |
And the way this works is that any time
link |
that we engage in a behavior or we ingest something
link |
that increases our levels of dopamine,
link |
there is a subsequent increase in the neural circuits
link |
that control our sense of frustration, pain, and lack.
link |
And you can actually notice this phenomenon.
link |
If for instance, you're somebody who really likes chocolate
link |
or you really like something else,
link |
pay attention to the way that you experience
link |
indulging in that thing.
link |
If you eat that piece of chocolate
link |
and you really focus on savoring its amazing taste,
link |
you'll notice that it provides some quenching
link |
of your desire for let's say sweet stuff
link |
or chocolate or both.
link |
But right as you stop experiencing that,
link |
right as that chocolate intake tapers off,
link |
as you swallow it down your throat
link |
or you just pause for a second afterwards,
link |
what you'll notice is that your brain and body
link |
actually orient toward wanting more.
link |
And that wanting of more is really the action
link |
of the neural circuits that underlie pain
link |
and are pushing your dopamine levels back down.
link |
And when these circuits go awry,
link |
or I should say when people fail to control themselves
link |
within the context of that pleasure pain balance,
link |
the typical behavior is to reach for yet another chocolate
link |
or to then look for something that will quench that desire
link |
and get dopamine levels back up.
link |
Now, the way these pleasure pain circuits work
link |
is very diabolical because it turns out
link |
that were you to take another piece of chocolate,
link |
yes, your dopamine levels would go back up,
link |
but not to the same extent that they did
link |
the first bite of chocolate that you had.
link |
In fact, we can say that the longer it's been
link |
since you've indulged in something that you really enjoy
link |
or would like, the greater the dopamine you will experience
link |
when you finally engage in that behavior
link |
or indulge that thing, ingest that thing,
link |
and the greater the dopamine increase,
link |
the greater the subsequent action of those pain circuits.
link |
So this puts you on a very complicated seesaw.
link |
It's a very wobbly precarious state to be in,
link |
which is not to say you shouldn't have a piece of chocolate.
link |
It's just to say that the sweet taste of sweet things,
link |
in particular things that we crave very much
link |
and we wait and wait and wait,
link |
and then we allow ourselves to indulge,
link |
those trigger changes in our neurochemistry
link |
and our neural circuits that place us
link |
in a very vulnerable place
link |
to either want more and more of that thing
link |
or to seek out other ways to fill that kind of emptiness
link |
that we feel or that gap like, oh, I would love more,
link |
but I'm not going to allow myself more.
link |
Now, again, I'm not saying
link |
that you shouldn't pursue pleasurable things.
link |
I mean, this molecule dopamine exists for a reason.
link |
It's the, frankly,
link |
because of its involvement in sex and reproduction,
link |
it's the reason we're all here in the first place,
link |
because last time I checked,
link |
the only way any of us got here was one way or another,
link |
sperm met egg and there was conception.
link |
I still believe there are no exceptions to that
link |
that I'm aware of anyways.
link |
That is a process where I should say
link |
the events leading up to that process
link |
typically involve dopamine in one way or another.
link |
There are exceptions to that too, but you get the idea.
link |
These dopamine pathways are not evil, they're not bad,
link |
but once you understand the way they work,
link |
you can leverage them to your advantage
link |
as opposed to them leveraging you to their advantage.
link |
Okay, so when you ingest something sweet,
link |
you perceive that sweet taste and a cascade ensues
link |
within your brain that makes you want more
link |
of the sweet thing.
link |
That's the conscious pathway for sugar perception,
link |
for sweet perception.
link |
Now there's the second pathway.
link |
The second pathway is what's called
link |
the post-ingestive reinforcing properties of sugar,
link |
which is really just a fancy nerd speak way of saying,
link |
there are events that happen within your stomach
link |
and below your conscious detection
link |
that are also driving you to seek out sweet tasting things
link |
independent of their taste
link |
and foods that increase blood glucose
link |
independent of their taste.
link |
In order to illustrate the immense power
link |
of these subconscious circuits for sugar seeking,
link |
I'd like to describe an experiment.
link |
And this is just one experiment of many,
link |
of dozens or more experiments done in animal models
link |
and humans, which essentially illustrate the same thing.
link |
And as I described this experiment,
link |
I think you will come to understand
link |
the power of these circuits.
link |
I'll provide a link to this study in the caption.
link |
The first author is Freeman.
link |
The paper was published in Frontiers in Bioscience,
link |
but there have been others, papers in Nature Neuroscience,
link |
papers in Neuron, Cell Press Journals, et cetera,
link |
many, many journals, many, many papers.
link |
If subjects are given the choice of drinking plain water
link |
or a sweet tasting fluid,
link |
their preference for the sweet tasting fluid
link |
is much, much higher, right?
link |
Sweet things taste better than plain water,
link |
at least for most people and certainly for animals.
link |
Now, if for instance, you take an animal
link |
which completely lacks sweet receptors,
link |
and you can do this through some molecular genetic tools
link |
and gymnastics in the laboratory,
link |
we call these knockout mice
link |
where you can knock out a particular receptor
link |
You can confirm that there's no perception of sweet things
link |
or at least no preference for sweet things
link |
In humans, you can numb the mouth.
link |
There are other pharmacologic ways
link |
that you can eliminate sweet receptors in the mouth.
link |
And by doing that, people will tell you,
link |
no, I can't taste anything sweet.
link |
It's just, you could give them an ice cream,
link |
you could give them pure sucrose,
link |
you give them table sugar,
link |
and they wouldn't be able to perceive it as sweet.
link |
If you eliminate the perception of sweet taste in the mouth
link |
and you offer people or laboratory animals water
link |
versus some sugar containing solution,
link |
you eliminate the preference for the sugary solution,
link |
which tells us that the perception of sweet
link |
is important for the preference for sweet tasting drink.
link |
This is also true for sweet tasting foods,
link |
However, in both animal models and in humans,
link |
after about 15 minutes,
link |
subjects start preferring the sugary water,
link |
even though they can't taste that it is sweeter.
link |
So to repeat that,
link |
if you eliminate the ability to sense sweet,
link |
to perceive sweetness in foods,
link |
then you eliminate the preference for sweet beverages
link |
So that's not surprising.
link |
But if you wait about 15 minutes,
link |
the preference for the sweet beverage
link |
or the sweet food comes back.
link |
Now that doesn't mean that they can perceive the sweetness.
link |
In fact, the way these experiments are done is very clever.
link |
You offer people various cups of different things
link |
or different food items,
link |
and then you just look at what they eat more of
link |
or what they prefer to eat more of.
link |
So this experiment is so crucial because what it says
link |
is that the preference for sugar containing foods
link |
is in part due to the sweetness of those foods,
link |
but in part due to something else.
link |
And this something else is what we call
link |
the post-ingestive effect.
link |
And as I mentioned before, it took about 15 minutes.
link |
And you've actually experienced this,
link |
whether you realize it or not,
link |
this phenomenon of post-ingestive rewarding properties
link |
meaning what happens in your body when you ingest something
link |
that increases your blood glucose very much
link |
has no doubt controlled you from the inside
link |
below your awareness.
link |
This was happening to you and you didn't realize it.
link |
And here's how it works.
link |
We all have neurons within our gut.
link |
These neurons have a name.
link |
They are called neuropod cells.
link |
Neuropod cells were famously discovered
link |
by professor Dr. Diego Bajorquez at Duke University.
link |
And these cells respond to, among other things,
link |
to the presence of sugar within the gut.
link |
So when we ingest a sugary food or drink,
link |
or we ingest a food or drink that simply contains
link |
fructose, sucrose, glucose, or some other form of sugar
link |
that later through metabolism
link |
will be converted into glucose,
link |
the neuropod cells are able to register the presence
link |
of those sweet or glucose stimulating foods.
link |
And in response to that, send electrical signals,
link |
because electrical signals are the way neurons communicate,
link |
up to the brain via the so-called vagus nerve.
link |
The vagus nerve, of course, being a nerve pathway,
link |
famous for its role in relaxation.
link |
That's kind of the assumption out there
link |
that it's always involved in relaxation.
link |
That's not the case.
link |
It's involved in a lot of things besides relaxation,
link |
but nonetheless, these neuropod cells send
link |
electrical signals through a particular highway
link |
within the vagus to the so-called nodose ganglion.
link |
This is a cluster.
link |
A ganglion is just a cluster of neurons.
link |
And then the nodose ganglion sends on information
link |
to the nucleus of the solitary tract.
link |
The nucleus of the solitary tract is an area of the brain
link |
that we're going to talk about extensively today.
link |
It's very important for understanding sugar preference.
link |
These neuropod cells also trigger activation
link |
of dopamine pathways within the mesolimbic reward pathway.
link |
In other words, there are signals conveyed from the gut,
link |
meaning stomach and intestines, to the brain
link |
anytime we ingest sweet foods,
link |
but it has nothing to do with our perception
link |
of them being sweet.
link |
It has everything to do with the fact
link |
that sweetness of food is almost always correlated
link |
with an ability to increase blood glucose.
link |
And the net effect of this is a parallel pathway
link |
by which dopamine is increased further.
link |
Now, the experiment that I described before
link |
of animals or humans ingesting something
link |
that contains sugar,
link |
but not being able to perceive its sweetness,
link |
and yet after a period of time,
link |
still preferring that food or drink
link |
to non-sugar containing food or drinks,
link |
even though they can't distinguish their tastes,
link |
is dependent on these neuropod cells and related pathways.
link |
What this means for you
link |
is that anytime you eat something sweet,
link |
that substance is actually causing your gut,
link |
your stomach and your intestine,
link |
or to be more precise, I should say,
link |
that food substance is causing the neuropod cells
link |
in your stomach and intestines
link |
to send a parallel set of signals up to your brain saying,
link |
eat more of that, or simply eat more,
link |
eat more, eat more, and preferably eat more sweet foods.
link |
So we've all heard of hidden sugars,
link |
meaning the sugars that manufacturers have put into foods
link |
and disguise them with other flavors.
link |
I talked about this in the episode on salt,
link |
using salt to mask the taste of sweetness
link |
so that people ingest more sugar.
link |
That is not an accident that hidden sugars
link |
are often hidden with salt or with other flavors.
link |
It's done so that people will, meaning you or me,
link |
will want to ingest more of a particular food
link |
independent of how sweet that food tastes.
link |
And in fact, some crackers, for instance,
link |
chips, for instance, you might think,
link |
oh, well, you know, chips, they're not sweet,
link |
they're salty and savory.
link |
Again, I'll mention I love salty savory foods,
link |
including certain foods.
link |
I love kettle chips, for instance,
link |
that I try not to walk by them in the grocery store.
link |
I usually have to eat one bag while I'm in the store
link |
and then another later.
link |
The savory foods are often laden with these hidden sugars
link |
that we can't register as sweetness,
link |
but trigger the neuropod cells,
link |
which then further trigger dopamine,
link |
which make us want more of them.
link |
Now, we may be able to resist eating more of them,
link |
but it makes us crave more food in general.
link |
Now, we will talk about ways to regulate this pathway,
link |
to sort of intervene in this subconscious pathway.
link |
But for now, I'm hoping that just the understanding
link |
that we all have this pathway,
link |
this is hardwired into our body,
link |
could potentially allow people to better understand
link |
why is it that their cravings are so intense,
link |
that it's not necessarily just about the taste of that food.
link |
And when you consider this in concert with the fact
link |
that we have this dopamine pain pleasure balance,
link |
excuse me, that I referred to earlier,
link |
you start to realize that there are multiple mechanisms
link |
hardwired into us that make it especially hard
link |
to not eat the sweet thing
link |
or to not eat the food that we're craving.
link |
And indeed, that's the case.
link |
We have two major accelerators.
link |
It's like a car with two accelerators,
link |
and we will talk about the brakes,
link |
but two ways that really get us into forward motion
link |
toward pursuing the consumption of sweet foods.
link |
Now, if it doesn't already seem diabolical enough
link |
that sweet things that we perceive as sweet
link |
make us want to eat more of those because of dopamine
link |
and then send us down this pain pleasure pathway
link |
that I mentioned earlier,
link |
and the fact that we have this subconscious circuit
link |
coming from the neuropod cells in our gut
link |
that are registering the presence of sugar
link |
or glucose increasing foods in our gut
link |
and sending those signals to the brain
link |
for yet more dopamine pain pleasure challenges,
link |
there's a third layer to this whole thing.
link |
And that has to do with how sugar is metabolized
link |
in the brain, or I should say how glucose is used.
link |
Without getting into too much detail,
link |
some of the more beautiful studies of neuroimaging
link |
and evaluating which brain areas are active
link |
when we eat certain foods were done
link |
by Dr. Dana Small's lab at Yale University
link |
and in some of her previous work when she was elsewhere,
link |
and of course, by other laboratories too.
link |
And they used an approach called
link |
positron emission tomography,
link |
and they and others have used PET scanning,
link |
as it's called, positron emission tomography,
link |
along with a tool called 2-Deoxyglucose.
link |
2-Deoxyglucose is actually involved
link |
in the procedure of seeing which brain areas are active
link |
when people eat foods or engage in other types of behaviors.
link |
But the way that 2-Deoxyglucose sometimes shorten 2-DG,
link |
the way that it works is to block glucose uptake
link |
from neurons and instead bring along with it
link |
a marker that one can see through imaging.
link |
So in other words, a tool for looking at what parts
link |
of the brain are active when eating particular foods
link |
actually prevents foods such as sugar
link |
from allowing glucose to get into particular neurons.
link |
Now, that might seem like a bad situation.
link |
You'd say, well, wait, you're trying to understand
link |
how sugar works in the brain,
link |
and then you block the ability for sugar glucose
link |
to bind to or be used by these neurons
link |
because of the thing that you're using for the experiment.
link |
Exactly, it's a huge problem,
link |
but it turns out to be a huge problem
link |
that led to a great insight.
link |
And the great insight is this.
link |
The preference for sweet tasting foods and liquids
link |
is actually blocked by 2-Deoxyglucose.
link |
What that means experimentally,
link |
but also in terms of what it means for you and me
link |
in the real world is that there's yet
link |
a third parallel pathway that's related
link |
to the use of blood sugar, the use of glucose by neurons
link |
that further reinforces our desire to eat more sweet things.
link |
And the preference for sweet foods
link |
can actually be eliminated through 2-Deoxyglucose.
link |
Now, I definitely don't want people going out
link |
and consuming 2-Deoxyglucose.
link |
This is a laboratory tool.
link |
It is not something that you should be ingesting.
link |
So don't go look it up and try and get some.
link |
There might be other uses for it, but that's not the point.
link |
The point is that it is the sweet taste of sugary foods.
link |
It is the signals coming from your gut,
link |
from your digestive tract to your brain.
link |
And it's the use of the metabolic consequences
link |
of sugary foods that are acting as a three-pronged push
link |
on your desire to consume more sugary foods.
link |
So this car analogy that I used before
link |
where it's some weird car that has two accelerators,
link |
it actually has three accelerators.
link |
And so with three accelerators,
link |
all pushing the system hard, we can say,
link |
wow, there must be something really special
link |
about this pathway.
link |
And indeed there is.
link |
This pathway is the quickest source of fuel for the brain
link |
and the rest of the nervous system.
link |
It's the preferred source of fuel
link |
for the brain and nervous system.
link |
And I realized, as I say that,
link |
all the ketonistas are probably going,
link |
no, actually ketones are the preferred source.
link |
Okay, I acknowledge that.
link |
There are conditions under which
link |
you can bring your blood glucose very low,
link |
and there are reasons to do that.
link |
Actually ketosis has been a terrifically successful
link |
treatment for a lot of forms of epilepsy,
link |
in particular, pediatric epilepsy.
link |
Many people do derive benefit from ketogenic diets,
link |
so I'm not knocking ketogenic diets,
link |
but if you were to look at what neurons normally prefer,
link |
meaning in a typical diet regimen, it would be glucose.
link |
And the fact that fructose
link |
is eventually converted to glucose,
link |
the fact that when we ingest sucrose,
link |
it's eventually converted into a fuel that neurons can use,
link |
that's very much in the glucose pathway.
link |
What you basically arrive at is the fact
link |
that your nervous system is a glucose consuming machine,
link |
and you've got at least three pathways
link |
of which I've described that are pushing on your brain,
link |
consciously and subconsciously,
link |
to get you to seek and consume more sugar.
link |
Now that all sounds like a pretty depressing picture,
link |
at least for those of you that are trying
link |
to reduce your sugar intake.
link |
And of course, we can all reduce sugar intake
link |
by way of sheer will.
link |
We can not have those foods at home.
link |
We can restrict ourselves from those.
link |
But there are some things that we all can
link |
and perhaps should do in order to regulate these pathways,
link |
such that we don't feel so controlled by them,
link |
but rather that we control their output.
link |
And of course they are us and we are them.
link |
So this gets into all sorts of issues of consciousness
link |
and free will that I certainly don't want to cover
link |
But nonetheless, I think once you understand
link |
that these circuits exist,
link |
and you understand that there are simple substitutions
link |
and modifications that one can make to their food intake
link |
that can work within these pathways
link |
and even bypass some of these pathways,
link |
you start to realize that you have a lot more control
link |
over sugar intake and sugar appetite
link |
than you previously thought.
link |
Now, many of you have heard of the so-called glycemic index.
link |
The glycemic index is a measure
link |
of how quickly blood sugar rises
link |
after ingesting particular foods
link |
and very broadly speaking,
link |
we can say that there are low glycemic index foods
link |
of less than 55 typically is the measurement
link |
or medium glycemic index foods,
link |
which go from about 55 to 69
link |
and then so-called high glycemic foods, which are above 70.
link |
And of course there's additional nuance
link |
related to glycemic load
link |
and many more features of the glycemic index.
link |
A couple of things to understand
link |
about how the glycemic index is measured.
link |
And then I'd like to just briefly talk about
link |
how the glycemic index can be leveraged
link |
to short circuit some of the neural circuits
link |
that would otherwise lead us to crave
link |
and perhaps even ingest sugary foods.
link |
First of all, measurements of glycemic indices of food
link |
are typically made by having people
link |
ingest those foods in isolation.
link |
And in general, we can say that anytime we ingest fiber
link |
and or fat lipids along with a particular food,
link |
it will reduce the glycemic index of that particular food,
link |
either the absolute level of blood glucose
link |
that a particular food causes
link |
or the rate at which that elevation in blood glucose occurs.
link |
And this is why there are some
link |
seemingly paradoxical aspects to sweet stuff
link |
in terms of the glycemic index.
link |
For instance, ice cream has a lower glycemic index
link |
provided it's ice cream that includes fat,
link |
which I hope it would
link |
because that's the good tasting ice cream in my opinion.
link |
Compared to something like mangoes or table sugar, right?
link |
So the glycemic index is not something
link |
to hold wholly in most cases
link |
because most people are not ingesting foods in isolation.
link |
And there's actually a lot of argument
link |
as to whether or not the glycemic index
link |
is really as vital as some people claim.
link |
There's also the context in which you
link |
ingest particular foods.
link |
As I mentioned earlier,
link |
after I do hard training of any kind,
link |
meaning training that ought to deplete glycogen,
link |
so hard resistance training,
link |
I actually make it a point to ingest
link |
some very sweet high glycemic foods like a mango.
link |
I'll also ingest some starches
link |
because I'm trying to replenish glycogen.
link |
I'm also trying to spike my blood sugar a little bit
link |
because that can be advantageous
link |
in terms of certain strength
link |
and hypertrophy protocols, et cetera.
link |
But most of the time I'm avoiding these high glycemic foods
link |
and high sugar foods.
link |
I should point that out.
link |
Now, why am I telling you about the glycemic index?
link |
Well, if we zoom out and take our perspective
link |
on all of this discussion about the glycemic index
link |
through the lens of the nervous system,
link |
and we remind ourselves that neurons prefer glucose
link |
for energy and that all sweet things
link |
or things that we perceive as sweet,
link |
but also sweet things that are ingested
link |
and registered by those neuro pod cells in our gut
link |
trigger the release of dopamine
link |
and trigger these neural circuits
link |
to make us want to eat more of these foods.
link |
What we start to realize is that
link |
a sharp rise in blood glucose
link |
or a very high degree of elevation in blood glucose
link |
is going to be a much more potent signal
link |
than will a more moderate rise in blood glucose
link |
or a slower rise in blood glucose.
link |
So if we think about the analogy of three accelerators,
link |
meaning three parallel neural circuits,
link |
all essentially there to get us to seek out
link |
and consume more sweet tasting and sugary foods,
link |
well then the glycemic index is sort of our measurement
link |
of how hard we are pushing down
link |
or how fast we are pushing down on those three accelerators.
link |
And so those of you that are trying to reduce sugar intake,
link |
and you want to do that through an understanding
link |
of how these neural circuits work,
link |
and you want to short circuit some of the dopamine release
link |
that's caused by ingesting sugary foods,
link |
it can be advantageous to ingest sweet foods
link |
either alone or in combination with foods
link |
that reduce glycemic index or reduce glycemic load.
link |
So that might mean making different food choices.
link |
So paying attention to sweet tasting foods
link |
that can satisfy sugar cravings,
link |
but do not have as steep,
link |
or I should say do not cause
link |
a steeper rise in blood sugar,
link |
or it could mean consuming other foods
link |
along with sweet foods in order to reduce
link |
the glycemic index and thereby slow
link |
or blunt the release of dopamine.
link |
You might think, well, why would I want to do that?
link |
I want the maximum dopamine output
link |
in response to a given sweet food.
link |
I don't just want the level 10,
link |
I want the level 100 output of dopamine,
link |
but you really don't because of the pleasure pain balance
link |
that dopamine causes.
link |
And in fact, if we consider some of the non-food substances
link |
that really push hard on these dopamine pathways,
link |
we can come up with a somewhat sinister,
link |
but nonetheless appropriate analogy.
link |
The drug cocaine causes very robust potent increases
link |
in dopamine within the brain,
link |
and typically causes people to want to ingest more cocaine
link |
because of those sharp increases in dopamine.
link |
But within the category of the drug cocaine,
link |
there are various modes of ingestion.
link |
Some people inhale it,
link |
some people will inject it intravenously,
link |
some people will smoke it.
link |
And those different forms of taking cocaine
link |
actually impact the dopamine circuits differently.
link |
And it turns out that crack cocaine,
link |
the smokable form of cocaine rock,
link |
increases dopamine to a very high degree,
link |
but also very, very quickly.
link |
And it is the sharp rise in dopamine over time,
link |
not so much the absolute level of dopamine
link |
that makes crack cocaine so absolutely addictive.
link |
So sometimes you'll hear, you know, sugar is like crack.
link |
Well, that's getting a little extreme
link |
because even though I don't think the measurements
link |
have been done in the same experiment,
link |
I think it's reasonable to think
link |
that the absolute level of dopamine
link |
caused by ingesting sugar, at least for most people,
link |
is not going to be as high as the absolute level
link |
of dopamine caused by smoking crack.
link |
Of course, it goes without saying,
link |
please don't do cocaine in any form, by the way.
link |
It is appropriate to say
link |
that the rate of dopamine increase over time
link |
has a profound effect on how people will
link |
and if people will go on to want to pursue more
link |
of what caused that increase in dopamine.
link |
So what I'm basically saying is
link |
if you're going to ingest sweet foods
link |
in order to satisfy a sweet craving,
link |
ingesting sweet foods for which the glycemic index is lower
link |
or in which you've adjusted those glycemic index foods
link |
through the co-ingestion of fiber or maybe fat
link |
might be beneficial.
link |
So is this justification for putting peanut butter
link |
on that piece of chocolate or for having a bowl of ice cream
link |
along with the mango that you're craving?
link |
In some sense, yes.
link |
However, there's also the issue of how sweet
link |
and how delicious something tastes.
link |
Highly palatable foods, absolutely delicious foods,
link |
trigger that one neural circuit, that one accelerator
link |
that we're talking about in terms of our analogy
link |
of three accelerators.
link |
And the more delicious something tastes within our mouth,
link |
the further increase in dopamine.
link |
So if you really wanted to adjust your sugar cravings
link |
and you really still want to ingest some sugary foods,
link |
you probably would be better off combining fiber
link |
with that sugary or sweet food.
link |
Now, I do realize that it's somewhat unusual
link |
and you probably get some strange stares
link |
if you decided to consume broccoli, for instance,
link |
along with your chocolate or with another dessert
link |
that would otherwise cause a steep increase in blood sugar
link |
and has a high glycemic index.
link |
But nonetheless, if your goal is to blunt
link |
your sugar cravings, what you really need to do
link |
is blunt that dopamine increase.
link |
So what we're really talking about here
link |
is trying to reduce the dopamine signal
link |
that is the consequence of ingesting sweet foods.
link |
And we're talking about doing that
link |
through these different parallel pathways,
link |
not just by preventing sweet taste,
link |
but also by preventing the post-ingestive effects
link |
And of course, the backdrop to all of this
link |
is that most of us, again, most of us, not all of us,
link |
should probably be ingesting fewer refined sugars.
link |
Certainly there are exceptions to that,
link |
but I think the bulk of data point to the fact
link |
that ingesting these highly palatable,
link |
certainly highly palatable, highly processed foods
link |
or foods that contain a lot of high fructose corn syrup
link |
can be really deleterious to our health,
link |
especially in kids.
link |
And I'm not going to cite off a bunch of statistics.
link |
You've all heard them before that for hundreds of years,
link |
we ingested the equivalent of a few cups
link |
or pounds of sugar per year.
link |
And now people are ingesting hundreds of pounds
link |
of sugar per year.
link |
The major culprit always seems to be sugary drinks,
link |
meaning soft drinks.
link |
And I think indeed that's the case.
link |
I do want to point out the incredible work
link |
of Dr. Robert Lustig, who's a pediatric endocrinologist
link |
at University of California, San Francisco,
link |
who was really early in the game of voicing the dangers
link |
of so-called hidden sugars and highly processed foods.
link |
There are other people, of course, now talking about this.
link |
His laboratory has done important work showing,
link |
for instance, that if high fructose corn syrup
link |
or even just fructose is replaced with glucose,
link |
even if the same number of calories is ingested,
link |
that there are important,
link |
meaning significant reductions in type two diabetes,
link |
some of the metabolic syndromes associated
link |
with high fructose corn syrup and on and on and on.
link |
And of course there are other culprits in type two diabetes.
link |
There are other factors that are going to lead to obesity,
link |
but I think the work from Lustig and others
link |
has really illustrated that we should all be trying
link |
to reduce our intake of highly refined sugars
link |
and high fructose corn syrup,
link |
and certainly trying to reduce our intake
link |
of very sugary drinks, not just soft drinks,
link |
but also fruit juices that contain a lot of sugar.
link |
Now, even for people that are of healthy weight
link |
and who don't have metabolic syndromes,
link |
there may be an additional reason
link |
to not want to ingest very sweet foods
link |
and highly refined sugars.
link |
And this has to do with a new and emerging area
link |
of nutrition neuroscience.
link |
And I want to point out that these are new data, right?
link |
So it's not a lock.
link |
The double-blind placebo-controlled studies
link |
in large populations have not been finished.
link |
So I want to make sure that that's clear,
link |
but I also want to make clear
link |
what some of the really exciting data
link |
coming from Dana Small's lab at Yale
link |
and from other laboratories are showing.
link |
And this has to do with what's called
link |
conditioned taste preference.
link |
Using a kind of Pavlovian paradigm,
link |
what they do is they have people,
link |
and these studies were done in people,
link |
ingest maltodextrin, which increases blood glucose.
link |
Doesn't have much flavor,
link |
but even if it does have a little bit of subtle flavor,
link |
the maltodextrin is cloaked by some other flavor.
link |
And by cloaking it with that other flavor
link |
or pairing it with that other flavor,
link |
what they find is that over time,
link |
because the maltodextrin increases blood glucose
link |
and they're ingesting a particular flavor
link |
along with that maltodextrin,
link |
they can then remove the maltodextrin
link |
and the flavor will induce an increase in insulin.
link |
The increase in insulin, of course,
link |
is the consequence of the fact
link |
that anytime there's a rise in blood glucose,
link |
provided the person isn't diabetic,
link |
there's a parallel increase in insulin.
link |
Now, this is very interesting because what it says is,
link |
well, at a first pass, it says that we are very Pavlovian
link |
in terms of our physiological responses to foods
link |
and particular flavors come to be associated
link |
with particular patterns of blood glucose increase
link |
and hence patterns of insulin increase
link |
because of course insulin manages glucose in the bloodstream,
link |
as I mentioned earlier, this also has implications
link |
for understanding things like artificial sweeteners.
link |
And here, I want to highlight that this is still
link |
very controversial work and needs more data,
link |
but nonetheless, I'd like to share it
link |
with you for consideration.
link |
The small laboratory has done studies in humans,
link |
both in adults and in children,
link |
showing that if the flavor of artificial sweeteners
link |
is paired with maltodextrin,
link |
and then the maltodextrin is removed,
link |
that the artificial sweetener taste itself
link |
can subsequently increase insulin in the bloodstream.
link |
In other words, taking something that increases blood sugar,
link |
attaching a flavor experience to that,
link |
having children or adults ingest that thing,
link |
allows the nervous system to associate that flavor
link |
with that increase in blood glucose,
link |
but then you can remove the glucose increasing substance
link |
and the flavor alone will increase insulin
link |
because insulin typically follows blood glucose.
link |
So this is a conditioning effect.
link |
Now, the reason these data are controversial
link |
First of all, the landscape around the discussion
link |
around artificial sweeteners is definitely
link |
what I would call a barbed wire topic.
link |
And I want to preface what I'm about to say next
link |
by saying I actually ingest artificial sweeteners.
link |
I will have the occasional diet soda, not every day,
link |
maybe, I don't know, once or twice a month.
link |
I don't particularly like the taste,
link |
but I'll do it just because it's around
link |
and I want some caffeine and I like the carbonation
link |
if I'm on a plane or something.
link |
I do ingest plant-based non-caloric sweeteners.
link |
To my knowledge, there have not been high quality studies
link |
of plant-based non-caloric sweeteners
link |
in the context that I'm referring to here, okay?
link |
Nonetheless, these studies show that particular flavors
link |
can be conditioned to cause an insulin increase
link |
and the flavor associated with certain artificial sweeteners
link |
is included in that category of flavors
link |
that can induce insulin even in the absence
link |
of something that can increase blood glucose.
link |
Now, the simple takeaway from these studies
link |
would be the following.
link |
And this is actually the one interpretation
link |
that Dana Small has offered to her data,
link |
but she offers other interpretations as well.
link |
One interpretation is that if people are going to ingest
link |
artificial sweeteners and they do that along with foods
link |
that very sharply increase blood glucose,
link |
then there is the potential, highlight the potential
link |
for those same artificial sweeteners to increase insulin
link |
even in the absence of food.
link |
In other words, let's just draw the scenario out
link |
in the real world.
link |
You're having a diet soda
link |
along with a cheeseburger and fries.
link |
You do that every day for lunch, okay?
link |
This somewhat extreme example, but natural world example.
link |
You do that every day for lunch
link |
and then you just have a diet soda alone.
link |
The extreme interpretation of the data
link |
that they've collected says, well,
link |
that diet soda alone will increase insulin
link |
even though there's no increase in blood glucose
link |
because you haven't ingested food with it
link |
because you conditioned that taste of artificial sweetener
link |
to the experience of a rise in glucose and hence insulin.
link |
Now, the counter argument to this would be,
link |
well, that's a very unusual situation.
link |
Maltodextrin causes big increases in blood glucose,
link |
so that's not really a fair experiment
link |
or it's not a natural world experiment.
link |
And I think that's a decent assessment,
link |
although I will point out that one of the reasons
link |
why this study is so controversial
link |
or why these data are so controversial
link |
is that the experiment actually had to be stopped
link |
and particularly the experiment in children
link |
had to be stopped because the changes in insulin
link |
that were observed early in the study were so detrimental
link |
that the institutional review board quite appropriately
link |
said, we can't do this to these kids.
link |
They're experiencing these odd shifts in insulin
link |
that are not healthy for them
link |
when they're just ingesting artificial sweeteners
link |
in the absence of these glucose increasing foods.
link |
So once again, I do ingest artificial sweeteners.
link |
I'm not saying that they are dangerous.
link |
I'm not saying that they are not dangerous.
link |
I'm saying that you have to decide for yourself.
link |
In previous episodes, I've highlighted
link |
that artificial sweeteners have been shown
link |
in studies of animals that when given in very high doses,
link |
sucralose in particular,
link |
there can be fairly robust disruption to the gut microbiome,
link |
which is vital for immune health and brain health,
link |
et cetera, et cetera.
link |
But thus far our knowledge of how artificial sweeteners
link |
negatively impacts or positively impacts, I should say,
link |
the microbiome and other deleterious effects on the body
link |
has mainly been explored in animal studies.
link |
Again, the work by Dana Small has been done in humans.
link |
There's some parallel work by others in animal models.
link |
I bring it up today to illustrate the following point.
link |
Normally we have a pathway
link |
that we don't have to condition at all.
link |
It's there from birth,
link |
whereby ingestion of sweet foods
link |
causes increases in dopamine.
link |
And there are parallel pathways
link |
by which neurons in our gut and elsewhere in our body
link |
trigger further increases in dopamine.
link |
So there's no need for a conditioned response
link |
or to become Pavlovian about this, right?
link |
You're hardwired to want to eat sweet things
link |
by at least two and probably three parallel pathways.
link |
Now, the work from Dana Small's lab and others
link |
that have illustrated this condition flavor preference,
link |
I think beautifully show that any flavor
link |
that's associated with a glucose spike
link |
or a long sustained increase in glucose
link |
can also be conditioned.
link |
In other words, the circuits for dopamine
link |
that reinforce the desire to eat particular things
link |
is not unique to the sugar pathway.
link |
And this is one of the reasons, I believe,
link |
why ingestion of sweet foods
link |
doesn't just lead us to want to eat more sweet foods.
link |
I think that is absolutely clear
link |
based on animal data and on human data.
link |
I think that's robust.
link |
It's actually the stuff of textbooks now, but in addition,
link |
ingesting sweet foods and or foods that raise blood glucose,
link |
but that we don't perceive as sweet.
link |
So for instance, foods with hidden sugars,
link |
sugars that have been masked by salty or spicy tastes
link |
increases our desire for glucose elevating foods
link |
and food generally.
link |
I think that's the only logical interpretation of the data
link |
that I can arrive at.
link |
So for people that struggle with regulating their appetite
link |
or with regulating their sugar appetite,
link |
I think the understanding of conditioned flavor preference
link |
while a little bit complicated ought to be useful
link |
in trying to navigate reducing sugar cravings
link |
As a segue into tools to control sugar intake
link |
as a means to both regulate sugar intake itself,
link |
as well as food intake overall
link |
and steer us towards healthier choices.
link |
I'd like to talk about some of the special populations
link |
out there that might want to be especially wary
link |
of having a dysregulated sugar appetite system.
link |
And the group I'm referring to specifically
link |
are those with attention deficit hyperactivity disorder,
link |
or I should say, and or people who have issues
link |
with focus and attention generally.
link |
And I think more and more nowadays,
link |
I'm hearing that people are having a hard time focusing.
link |
This probably has something to do with our interactions
link |
with electronic devices.
link |
As I always say, if a picture is worth a thousand words,
link |
a movie is worth a million pictures,
link |
and the fact that we can access so many movies
link |
in just by scrolling with our thumb
link |
is something that the nervous system
link |
has just never contended with before in human history.
link |
I'm confident in that.
link |
And it's not that it can't deal with it.
link |
The question is, what's the trade-off?
link |
You know, what are the consequences of that?
link |
So attention and ability to focus
link |
is obviously key to success in school,
link |
success in relationships,
link |
success in the workplace and success in life.
link |
We could probably even go so far as to say
link |
one's ability to succeed in anything
link |
is proportional to one's ability to focus
link |
and then deliberately defocus
link |
when the time comes to defocus, right?
link |
Because we all need rest and we need to disengage
link |
and then re-engage.
link |
If you look at the sum total of the meta-analyses
link |
and the clinical data on ADHD and nutrition,
link |
you arrive at a pretty clear answer,
link |
which is that sugar consumption,
link |
in particular highly refined sugars,
link |
is just not good for people with ADHD
link |
or with attentional issues.
link |
Now, as I say that, I also want you to recall
link |
the earlier study that I referred to
link |
whereby the tuning of neurons in the brain
link |
is highly dependent on glucose.
link |
So this doesn't mean consuming no glucose
link |
is going to be a good idea.
link |
It doesn't mean that the ketogenic diet
link |
is necessarily the best diet for ADHD,
link |
although there are some people pursuing that
link |
and exploring that.
link |
And we'll do yet another episode on ADHD at some point
link |
that goes a little bit deeper into that
link |
because there's some new data.
link |
I did do a very long and fairly extensive episode on ADHD.
link |
You're welcome to look that up if you like
link |
in our archive, excuse me, in our archive
link |
at hubermanlab.com.
link |
It's all timestamped.
link |
So, you know, because a number of people said,
link |
oh, you know, it's an episode on ADHD
link |
and you made it two and a half hours long.
link |
Yes, we did because we wanted it to be as comprehensive
link |
as we could at the time, but it is timestamped.
link |
So you can just jump to the particular topics of interest
link |
in their short little cassettes there.
link |
Now, if you'd like to know upon what I'm basing
link |
the statement that sugar consumption
link |
and highly refined sugar consumption
link |
is potentially bad for ADHD,
link |
basing this mainly on the conclusions
link |
of a really nice paper,
link |
the title of the paper is sugar consumption,
link |
sugar sweetened beverages
link |
and attention deficit hyperactivity disorder,
link |
a systematic review and meta analysis.
link |
And this is a paper, we'll put a link to this
link |
This was publishing complimentary therapies in medicine,
link |
which is a bit of an atypical journal in some sense,
link |
but I really like this meta analysis.
link |
The sum total of this meta analysis is really that
link |
when especially kids get beyond four sugary drinks per week,
link |
so four sodas of, you know, typical 12 ounce soda,
link |
when they get past four 12 ounce sugary sodas,
link |
they didn't, as far as I know,
link |
look at artificial sweetened sodas.
link |
That's when you start to see
link |
a shift towards more negative outcomes,
link |
more symptoms of existing ADHD.
link |
Now where the controversy comes in
link |
is whether or not sugar consumption
link |
can actually trigger or cause ADHD.
link |
And I don't think we can conclude that at all at this time.
link |
And this review, if you decide to check it out,
link |
review slash meta analysis, I should say,
link |
if you decide to check it out,
link |
goes into some of the nuance around that.
link |
What's also interesting in terms of ADHD and sugar intake,
link |
and probably has relevance to all of us,
link |
is that they also cover some of the interesting data
link |
showing that supplementation with omega-3 fatty acids
link |
can actually be beneficial for people
link |
and particular kids with ADHD.
link |
I've talked before about the utility of omega-3s
link |
that's been shown in various studies
link |
that have compared omega-3 fatty acid intake
link |
to say prescription antidepressants, like SSRIs,
link |
like Prozac, Zoloft, and similar, fluoxetine.
link |
And the results of those studies are pretty clear,
link |
at least to me, that provided that one gets
link |
at least one gram of EPA essential fatty acids,
link |
so it's not just getting one gram per day,
link |
but one or more grams per day
link |
of the EPA form of essential fatty acid
link |
can rival some prescription antidepressants
link |
and or decrease the amount of antidepressants
link |
that's required to take,
link |
which for a lot of people can be a very useful thing
link |
because of the side effect profile
link |
of many of those antidepressants.
link |
Of course, talk to your psychiatrist, talk to your doctor,
link |
but the omega-3s are no doubt powerful.
link |
And then of course, there's a whole story
link |
about omega-3s and heart health.
link |
And of course, like anything else,
link |
there's some controversy around omega-3s,
link |
but I think the data are clear enough to me
link |
around mood and cardiovascular health
link |
that certainly I personally ingest them,
link |
but as always, I always say,
link |
anytime you're going to add or remove anything
link |
from your nutrition, supplementation, exercise,
link |
or otherwise your lifestyle,
link |
definitely consult with a board certified physician.
link |
I don't just say that to protect me.
link |
I say that to protect you.
link |
You are responsible for your health ultimately.
link |
So omega-3 supplementation has been shown
link |
to be beneficial for ADHD.
link |
Why am I talking about this in the context of an episode
link |
on sugar and the nervous system?
link |
Well, if you remember those neuropod cells,
link |
those cells in your gut that respond to sugar
link |
and send signals up to the brain
link |
to cause the release of dopamine,
link |
well, it turns out that neuropod cells
link |
also respond to amino acids and to fatty acids,
link |
in particular, essential fatty acids.
link |
So the cells that we call neuropod cells have three jobs.
link |
One is to detect levels of sugar in the gut.
link |
The other is to detect levels of amino acids
link |
and to detect levels of particular essential fatty acids
link |
and communicate that information to the brain.
link |
And I should point out,
link |
when I say communicate that information,
link |
they're not actually saying, hey, there's amino acids here,
link |
or hey, there's sugar here,
link |
or hey, there's essential fatty acids,
link |
because the language of these cells is somewhat generic.
link |
It's just the firing of electrical potentials.
link |
But that's the key point.
link |
It's generic and all three, or any of those three,
link |
sugar essential fatty acids or amino acids
link |
will trigger these neurons to signal to the brain
link |
to increase dopamine.
link |
And it is not coincidental
link |
that omega-3 fatty acid supplementation
link |
can help ameliorate some of the symptoms of ADHD
link |
by way of presumably increasing dopamine
link |
in this neuropod to dopamine pathway
link |
that we talked about earlier.
link |
The whole thing has a very nice logical structure to it
link |
and points to, yet again,
link |
the immense value of bringing the proper amounts,
link |
maybe even supplementing the proper amounts
link |
of omega-3 fatty acids
link |
and the proper amounts of amino acids into the gut
link |
as a way to supplant some of the stimulation
link |
of these pathways that would otherwise be caused by sugar.
link |
There's actually a version of this where one could say,
link |
if you want to reduce sugar cravings,
link |
you might consider increasing certain forms
link |
of amino acid intake or certain forms of fatty acid intake.
link |
So what are some ways
link |
that we can reduce our sugar cravings?
link |
And ideally, ways that we can do that
link |
that also benefit us in other ways,
link |
both nutritionally and from the neuroscience standpoint?
link |
Well, these neuropod cells that respond to
link |
and signal the brain when we ingest sugar,
link |
as I mentioned, also respond to amino acids
link |
and essential fatty acids.
link |
We already talked about the essential fatty acids.
link |
I make it a particular point to ingest anywhere
link |
from one to three grams, that's grams,
link |
of EPA essential fatty acid per day.
link |
I make it a point to do that
link |
with the ingestion of high quality omega-3s.
link |
For me, the simplest way to do that,
link |
and I think for most people,
link |
the lowest cost way to do that
link |
is to use some liquid form of fish oil
link |
or some capsule form of fish oil.
link |
You really do have to see how much essential fatty acid
link |
in the form of EPA is in those.
link |
If you try and do that only through capsules,
link |
it can get kind of expensive,
link |
depending on which particular brands you use.
link |
Some have more EPA, some less.
link |
You can, of course, also do this through foods.
link |
You can do this with non-fish sources,
link |
through things like algae, and there's some other forms.
link |
You can look it up online now,
link |
plant-based sources of EPAs.
link |
You can do this with high quality fish oil.
link |
In any case, that does seem,
link |
at least based on a modest amount,
link |
but nonetheless solid literature,
link |
to reduce sugar craving somewhat,
link |
but that could easily be by mere replacement of calories.
link |
So we don't know yet, based on human studies,
link |
whether or not the ingestion of those EPAs
link |
is specifically activating the neuropod cells,
link |
which specifically activates dopamine release
link |
and bypasses the need for, or the craving for sugar.
link |
We don't know that yet,
link |
but logically it holds up to assume that.
link |
The fact that these neuropod cells,
link |
and I should say other neurons within the gut,
link |
respond very robustly to the presence
link |
of particular amino acids is also a potential lever
link |
by which one could reduce sugar cravings.
link |
And there's an interesting literature
link |
around the amino acid glutamine,
link |
in particular supplementing with the amino acid glutamine,
link |
as it relates to sugar cravings,
link |
and certainly as it relates to other aspects of the gut,
link |
in particular leaky gut.
link |
The use of supplemental glutamine
link |
to try and treat leaky gut is not a new phenomenon.
link |
There are other approaches too, of course,
link |
but there are many people who are experimenting
link |
with supplementing with glutamine several grams per day,
link |
often even five grams distributed
link |
through three or four different servings throughout the day
link |
as a way to blunt their sugar cravings.
link |
Now, there has not yet been a large-scale clinical trial
link |
using glutamine to reduce sugar cravings,
link |
but the results of the few studies that I looked at,
link |
as well as my understanding of the logic
link |
of these neural circuits, including the neuropod cells,
link |
brings us to a conclusion that it makes sense
link |
why if there's a population of neurons within our gut
link |
that responds very robustly to the presence of sugar,
link |
fatty acids, or amino acids,
link |
that the intake of particular amino acids
link |
would allow the dopamine pathways
link |
that might otherwise be triggered by sugar
link |
to be triggered by something like glutamine,
link |
which has very few or no calories.
link |
And in fact, having talked about this previously,
link |
a number of people that I know went out and tried this.
link |
Now, this is, of course, is what I call anecdata, right?
link |
This is not a quality peer-reviewed study.
link |
Many of them have reported back that they actually feel
link |
as if their sugar cravings are reduced.
link |
I know some people who actually take glutamine
link |
and mix it with full fat cream
link |
and take it kind of like a shot of full fat cream,
link |
which sounds absolutely delicious, by the way.
link |
Glutamine is a little bit chalky,
link |
so it's not that great tasting to ingest with sugar.
link |
I should mention, if you do try and take this approach
link |
of ingesting glutamine to reduce sugar cravings,
link |
you want to increase the amount of glutamine
link |
that you take somewhat gradually.
link |
It can create some gastric distress.
link |
If you just, you know,
link |
I certainly wouldn't take a big tablespoon of it,
link |
throw it in water and chug it down three times a day.
link |
Some of you with very hearty stomachs
link |
can probably tolerate that.
link |
You know, if you're like my, you know, my bulldog,
link |
which unfortunately passed away, but Costello,
link |
I always imagined that if ever we did an autopsy on him,
link |
he'd have like a license plate
link |
and like a human being in his gut,
link |
because it seemed like he could ingest anything
link |
But of course, many people have kind of sensitive guts.
link |
So if you're going to try taking glutamine
link |
as a means to reduce sugar cravings,
link |
just know that the studies are still ongoing.
link |
Some people have achieved benefit.
link |
Please also realize that there's an entire literature
link |
devoted to the potential hazards of increasing glutamine
link |
if you have a preexisting cancer.
link |
So if you have cancer or you're cancer prone,
link |
I would really discourage you from this approach.
link |
And in any case, as always, talk to your doctor.
link |
The logic nonetheless is there,
link |
why increasing amino acid intake or fatty acid intake
link |
might decrease sugar craving.
link |
Now, there are other ways to reduce sugar craving,
link |
and there are certainly ways to reduce the sharp rise
link |
in blood glucose that can occur
link |
when we ingest sugary sweet foods,
link |
or even just an abundance of carbohydrate foods.
link |
And there are a huge number of these things.
link |
I'm going to sort of layer up through the ones
link |
that you might find in your cupboard or at the grocery store
link |
and then get into some of the more extravagant,
link |
or I should say esoteric ones.
link |
Many of which, however, can be quite potent.
link |
The first of which is simple lemon juice, right?
link |
There was an old lore and actually some papers
link |
pointing to the idea that the ingestion of vinegar,
link |
either white vinegar or wine vinegar
link |
could somehow blunt blood glucose
link |
after the ingestion of sugary foods
link |
or the ingestion of a lot of carbohydrate foods
link |
or even just a big meal.
link |
Actually, Tim Ferriss, I should say the great Tim Ferriss,
link |
because I do have great respect for the fact
link |
that he seems to be about 10 years ahead of everything,
link |
both in terms of nutrition and skill learning
link |
and things of that sort.
link |
Some of the things that he predicted in his books,
link |
the four hour body and the four hour chef
link |
actually turned out to be true based on scientific data,
link |
some of which only exists in the animal models,
link |
but now also some predictions that played out to be true
link |
in both the animal models and the human model.
link |
So I think that Tim certainly deserves a hat tip
link |
for the fact that he experimented with these methods
link |
and reported his experiences with those methods
link |
and that now some of them,
link |
many of them have been validated
link |
by what I perceive to be quality science.
link |
He talked about the fact that,
link |
at least in his experiments on himself,
link |
the ingestion of vinegar did not seem to blunt blood glucose
link |
and he was using continuous glucose monitors.
link |
These incidentally, another example
link |
of where Ferriss was early to the game
link |
and the rest of us are kind of just in his wake,
link |
he talked about the use of blood glucose monitors.
link |
Those I think at the time were implanted below the skin.
link |
Nowadays, they're less invasive blood glucose monitors,
link |
things like levels and so forth,
link |
and these are actually becoming pretty popular.
link |
I've worn one of these before,
link |
they're actually pretty informative.
link |
I learned, for instance, that when I go in the sauna,
link |
that I experienced a sharp rise in blood glucose
link |
and that makes sense because of the dehydration
link |
associated with being in the sauna,
link |
a lot of sweating, the concentration of sugar
link |
in the bloodstream goes up.
link |
So there's some other things that certain foods
link |
affect my blood glucose one way or another.
link |
It's kind of an interesting and fun experiment
link |
that some of you might be interested in doing as well.
link |
Regardless, there are now data pointing to the fact
link |
that lemon juice and lime juice,
link |
a couple of tablespoons or so,
link |
if ingested before or even during
link |
or even after consumption of sugary foods,
link |
or I should say foods that sharply increase blood glucose
link |
or large carbohydrate meals
link |
can actually blunt the blood glucose response.
link |
And I did see that when I did my own experiments on myself
link |
with continuous glucose monitor, it was kind of fun
link |
to do those experiments.
link |
I preferred to do those experiments
link |
by eating somewhat larger meals of things
link |
that didn't contain a lot of sugar.
link |
I saw some big increases in blood glucose
link |
in certain instances.
link |
And then I would ingest some lemon juice or lime juice,
link |
typically mixed in with water.
link |
And sure enough, you could see a blunting
link |
of the blood glucose response.
link |
And of course, this was real time blood continuous,
link |
hence continuous blood glucose monitoring.
link |
So for those of you that are interested
link |
in blunting your blood sugar response, certain foods,
link |
that's a simple low cost way to do that
link |
if you want to explore it.
link |
I will say if you are fasting
link |
and you already have low blood glucose
link |
and you ingest lemon juice,
link |
or I should say it's some lemon juice and water
link |
or lime juice and water,
link |
be careful because you can actually become hypoglycemic,
link |
for the very same reasons that lemon juice and lime juice
link |
can blunt blood glucose
link |
when your blood glucose levels are moderate to high.
link |
You can also reduce blood glucose levels even further
link |
when blood glucose levels are low.
link |
Now that's lemon juice and lime juice there,
link |
but we can't say that has to do with acidic things generally
link |
and just as a side point,
link |
many of you have probably seen in the store,
link |
so-called adjusted pH waters or foods and drinks
link |
that are supposed to adjust your pH.
link |
Hate to break it to you,
link |
but your pH is very tightly regulated
link |
throughout your brain and body.
link |
You do not want this to change.
link |
It is entirely impossible,
link |
at least in any safe way,
link |
that you would become quote unquote more alkaline
link |
by ingesting an alkaline water or something like that.
link |
It is true that your pH, your alkalinity and acidity
link |
varies in different compartments in your body.
link |
Unless you are hemorrhaging or vomiting
link |
or there's something badly wrong with you health-wise
link |
and you're in a really dire circumstance,
link |
you don't want big shifts in your body pH
link |
and your body has all sorts of ways
link |
of buffering against changes in pH.
link |
So I encourage you not to fall on the,
link |
or hop on the bandwagon of adjusting pH
link |
and becoming less acidic and that kind of thing.
link |
When you ingest lemon juice or lime juice,
link |
the mechanism by which it blunts blood glucose
link |
is probably twofold.
link |
One is probably through the post-ingestive effects
link |
of glucose in the gut,
link |
meaning the way in which sugars are interacting
link |
with neurons and other components of your gut circuitry
link |
to impact things like gastric emptying time,
link |
to impact things like the firing of those neuropod cells
link |
and their signaling to the brain.
link |
But almost certainly it has something to do
link |
also with the perception of sour taste on the tongue.
link |
We didn't go into this too much today,
link |
but you of course don't just have sweet taste receptors
link |
in your mouth, you also have bitter taste receptors,
link |
you have salty taste receptors,
link |
you have sour taste receptors in your mouth
link |
and on your, and of course,
link |
that means your tongue and palate,
link |
and those are interacting.
link |
If you ingest a substance that's just sweet
link |
or mostly sweet, that causes a certain set of effects
link |
on your blood glucose, but also your brain,
link |
dopamine and the other neural circuits of your brain.
link |
If you also ingest something that's sour,
link |
like lemon juice or lime juice,
link |
it adjusts the output of those neural circuits
link |
So again, we have a situation,
link |
we have two parallel pathways.
link |
One that's post-ingestive coming from phenomenon
link |
within our gut, neurons,
link |
but also things like gastric emptying time,
link |
the clearance and the transfer of food
link |
and the conversion of food into particular nutrients
link |
and the circulation of glucose in your bloodstream
link |
and how it gets into the brain,
link |
but also simply by ingesting something sour,
link |
you are changing the way that sweet things
link |
impact your brain.
link |
And so I think it stands to reason that the lemon juice,
link |
lime juice effect is not going to be magic.
link |
It's going to have everything to do with the way
link |
that ingesting sour foods can adjust the taste,
link |
excuse me, can adjust the neural response
link |
to taste of sweet foods.
link |
And in fact, we know based on the beautiful work
link |
of Charles Zucker at Columbia Medical School,
link |
that that's exactly what happens.
link |
They've measured the activity of neurons
link |
at various locations in the so-called taste pathways
link |
And they found that when particular tastes
link |
like just sweet or just bitter or just sour
link |
evoke certain ensembles of neurons to fire
link |
in particular sequences,
link |
when sweet and sour are co-ingested,
link |
when bitter and sour are co-ingested,
link |
you get distinct ensembles,
link |
meaning distinct patterns of activity of those neurons
link |
and of course, distinct patterns of downstream activity
link |
within the brain and body.
link |
So while it is still somewhat mysterious
link |
as to how exactly things like lemon juice and lime juice
link |
can reduce our blood glucose spikes
link |
when we ingest those with sweet foods
link |
or carbohydrate-laden foods or with big meals,
link |
you can use this as a tool with the understanding
link |
that there's a grounding in the biology
link |
of the way these circuits work.
link |
Now, some of you have probably heard that cinnamon
link |
can be a useful tool for controlling blood sugar.
link |
And indeed that's the case.
link |
It's very clear that cinnamon can adjust the rate
link |
of glucose entry into the bloodstream,
link |
possibly by changing the rate of gastric emptying.
link |
It might slow the rate of gastric emptying
link |
and thereby also reduce the glycemic index
link |
of particular foods.
link |
So I suppose if I were going to eat a mango
link |
and I hadn't just done a bunch of hard training,
link |
I might sprinkle some cinnamon on it here.
link |
I always enjoy kind of coming up with new ideas
link |
of ways that I can eat foods during these podcasts.
link |
In any event, there's some debate out there.
link |
If you look online as to whether or not
link |
Saigon cinnamon, Cassia cinnamon,
link |
excuse me, or Ceylon cinnamon is best
link |
for purposes of blunting blood glucose spikes.
link |
But I think the, at least by my read of the data
link |
and from what I found, it doesn't really matter
link |
provided it's real cinnamon.
link |
And you have to actually look and make sure
link |
that it's real cinnamon because a lot of cinnamon
link |
that you buy is not real.
link |
I do want to provide a cautionary note
link |
about cinnamon however.
link |
Cinnamon contains something called Coumadin,
link |
which can be toxic at high levels.
link |
So you don't want to ingest more than about a teaspoon,
link |
maybe a teaspoon and a half of cinnamon per day
link |
because you'll start to exceed the threshold
link |
at which cinnamon could start to be problematic.
link |
But certainly if you're going to have a big meal
link |
or a meal that has a lot of sugar in it
link |
or a lot of carbohydrate laden foods
link |
and you don't want an increase in blood glucose,
link |
you could put cinnamon in a beverage,
link |
you could put cinnamon on food
link |
in order to blunt that blood glucose increase,
link |
reduce the glycemic index
link |
by way of reducing gastric emptying time.
link |
Again, just making sure that you don't get out past
link |
that one and a half teaspoons per day
link |
because you really don't want to start dealing
link |
with any of the toxicity related to Coumadin.
link |
So we've talked about lemon juice and lime juice
link |
and cinnamon, these are kind of commonplace
link |
Then of course we can venture into the more esoteric
link |
or I would say the more advanced tools
link |
for adjusting sugar intake.
link |
And the one that comes to mind is of course berberine.
link |
Berberine is a derivative of tree bark
link |
and is a very, very potent substance
link |
for reducing blood glucose.
link |
So much so that is on par with metformin or glibenclamide
link |
which are prescription drugs specifically used
link |
to reduce blood glucose.
link |
So using berberine is a serious step,
link |
you should absolutely talk to your doctor about it.
link |
I know of a number of people that use it
link |
to lower blood glucose when they eat really large meals.
link |
I know the number of people that are using it
link |
to get to some of the other effects of metformin
link |
that people have discussed, things like activating
link |
or tapping into the so-called AMPK pathway, reducing mTOR.
link |
These are people that are aiming their activities
link |
at increasing longevity,
link |
a somewhat controversial approach still
link |
but I know many people are doing it.
link |
It is true that if you ingest berberine
link |
your blood glucose will plummet.
link |
And I point that out because I've actually tried it before,
link |
it gave me brutal headaches and I felt really dizzy
link |
and I felt like I couldn't see straight
link |
and actually I couldn't see straight.
link |
Why did it do that?
link |
Well, it made me hypoglycemic,
link |
it actually drove my blood glucose down too far.
link |
And the reason it did that is that I took berberine
link |
on an empty stomach, I know some people can tolerate it.
link |
I would say be very cautious about ingesting berberine
link |
on an empty stomach or if you are in a low carbohydrate diet
link |
unless you really know what you're doing
link |
and you have a medical professional
link |
to kind of guide you through that.
link |
If I took berberine along with a very large meal
link |
that include a lot of carbohydrates,
link |
I can recall the days in which Costello and I
link |
would eat a couple of pizzas
link |
and then we might get ice cream, that kind of thing.
link |
Then I felt perfectly fine on even up to 750 milligrams
link |
or a gram of berberine.
link |
It has a kind of unique property
link |
of making you feel not overwhelmed
link |
by the amount of blood glucose increase
link |
that you're experiencing from eating a big meal.
link |
I don't quite know how else to describe it.
link |
It's almost as if you can keep eating
link |
and eating and eating.
link |
And of course you have to protect
link |
your gastric volume, right?
link |
I mean, you only have so much space
link |
in your stomach to ingest food.
link |
I wasn't using it to gorge on food.
link |
I just heard about it.
link |
I was interested in experimenting with it.
link |
I don't have any chronic blood sugar issues,
link |
but again, when I took it on an empty stomach,
link |
it made me hypoglycemic on a low carbohydrate intake,
link |
hypoglycemic, not a good experience.
link |
And again, an experience I think to avoid,
link |
but provided there's a lot of glucose in your bloodstream.
link |
And certainly if you are of the experimental type
link |
or you're trying to regulate blood glucose,
link |
berberine might be a good option.
link |
But again, talk to your doctor.
link |
It does have some other interesting effects
link |
in terms of lowering total cholesterol
link |
that are research supported
link |
of reducing insulin a little bit.
link |
Well, that's not surprising.
link |
If you reduce blood glucose,
link |
you're going to reduce insulin
link |
because of course insulin manages blood glucose
link |
in the bloodstream.
link |
So I would place berberine
link |
and of course metformin and glibenclamide
link |
in the kind of the heavy hitting potent tools
link |
for regulating blood glucose.
link |
Now, this is an episode not about sugar per se,
link |
but sugar viewed through the lens of the nervous system.
link |
And what's interesting about berberine,
link |
metformin, glibenclamide and related substances
link |
is that some of the effects are of course
link |
on gastric emptying or buffering blood glucose
link |
within the bloodstream, et cetera.
link |
But there appear to also be some neural effects
link |
of having chronically low glucose
link |
or blunting blood glucose through things like berberine.
link |
And some of those neural effects
link |
include longstanding changes in the hormonal cascades
link |
that are the consequence of having low blood sugar
link |
and thereby changes in the neural circuits
link |
that manage blood glucose overall.
link |
The simple way of saying this
link |
is that by maintaining low to moderate blood glucose,
link |
either by not ingesting heavily carbohydrate-laden foods,
link |
so here I'm speaking to the low carb
link |
and to the ketogenic types,
link |
or by blunting blood glucose
link |
through things like metformin or berberine,
link |
even if ingesting carbohydrates, maybe even some sugars.
link |
Over time, it seems that there's a adjustment,
link |
what we call a homeostatic regulation of the neural circuits
link |
that control things like sugar craving.
link |
And indeed, some people report
link |
feeling fewer sugar cravings over time.
link |
Now, I didn't use berberine for a very long period of time.
link |
I've never used metformin.
link |
I have experienced a somewhat odd but welcome phenomenon
link |
of with each progressive year of my life,
link |
I have fewer and fewer sugar cravings.
link |
Why that is, I don't know.
link |
I suspect it might have something to do with my sleep,
link |
and I'll talk about that in a few minutes.
link |
But if you're going to explore berberine
link |
or metformin or otherwise,
link |
in addition to working with a doctor,
link |
I think you should understand why you're doing it, right?
link |
I think that many of the effects can be quite potent.
link |
They can happen in both the immediate term,
link |
in terms of regulating blood glucose.
link |
They can send you hypoglycemic if you aren't careful.
link |
They can also cause longstanding changes
link |
to the neural circuitry that regulates blood sugar over time,
link |
some of which might be welcome changes, right?
link |
Reduce sugar cravings, for instance.
link |
And if you're really, really serious
link |
about modulating blood glucose through things like berberine,
link |
the typical dose range, again,
link |
is anywhere from half a gram to 1.5 grams daily.
link |
That's the typical dosages that have been explored.
link |
And there are some other substances like sodium cuprate,
link |
which are known to augment the effects of berberine
link |
via the AMPK pathways.
link |
They basically can increase the ability for berberine
link |
to have its glucose-lowering actions.
link |
But that, of course, is getting into the really potent,
link |
what I would call sharp blade tools
link |
for controlling blood glucose.
link |
And listen, anytime you're dealing with blood glucose,
link |
you are dealing with the brain's preferred source of fuel.
link |
And anytime you're dealing
link |
with the brain's preferred source of fuel,
link |
you have to be especially cautious
link |
about depriving the brain of what it needs.
link |
So whether or not you're low carb, high carb,
link |
keto, vegan, carnivore,
link |
these substances like berberine are very, very potent,
link |
and you need to take them seriously.
link |
There is yet another tool for controlling sugar cravings
link |
and the neural circuits that regulate sugar craving
link |
and its downstream consequences.
link |
And this tool is what I would call a high-performance tool,
link |
but it's one that you probably didn't suspect,
link |
I've done extensive episodes about sleep,
link |
and we actually have an episode called Master Your Sleep.
link |
You can find that episode easily at HubermanLab.com.
link |
It's available in all the various formats,
link |
YouTube, Apple, Spotify, et cetera,
link |
and provides a lot of tools.
link |
And on social media, I provide a lot of tools.
link |
Often we have a newsletter that provides tools
link |
on how to maximize sleep.
link |
What is the role of sleep in sugar metabolism,
link |
sugar hunger, and the way that the brain
link |
regulates those things?
link |
Well, there's a really exciting study that came out
link |
This study was published in the journal Cell Report,
link |
Cell Press Journal, excellent journal.
link |
And the reason I love this study so much
link |
is it involved having people,
link |
so yes, this was done in humans,
link |
sleep in the laboratory.
link |
That's not unusual.
link |
There's a sleep lab at Stanford.
link |
There's sleep labs elsewhere.
link |
But what they did was they actually measured
link |
from the breath of these people
link |
and they extracted from their breath
link |
the metabolites that would allow them to understand
link |
what sorts of metabolism was occurring
link |
in these people's bodies at different phases of sleep.
link |
And this is a really remarkable study.
link |
They actually did this every 10 seconds
link |
throughout the entire night.
link |
So in little tiny 10 sec bins,
link |
meaning at very high resolution,
link |
they could evaluate what is the metabolism in the brain
link |
and body that people experience as they go from REM sleep,
link |
rapid eye movement sleep, to slow wave sleep, and so on.
link |
And I'll go deeper into the study again in the future
link |
because it's so interesting and I think so important.
link |
But what they discovered was that each stage of sleep
link |
was associated with a very particular signature pattern
link |
of metabolism and particular phases of sleep
link |
are associated with sugar metabolism
link |
or more with fat metabolism
link |
or more with other aspects of metabolism.
link |
And the reason why I think this study is important
link |
to discuss in the context of today's discussion
link |
about sugar in the brain is that many people
link |
have experienced the effects of disrupted sleep
link |
on their appetite.
link |
And in particular, it's been reported
link |
that when people are sleep deprived
link |
or the quality of their sleep is disrupted,
link |
that their appetite for sugary foods increases.
link |
Now that was always assumed to be
link |
due to some metabolic need
link |
that was triggered by the sleep deprivation
link |
or by the poor sleep.
link |
But in reading over this study,
link |
some of the more important points made by the authors
link |
relate to the fact that, well,
link |
sleep is known to have incredibly important effects
link |
on brain and body for a variety of systems,
link |
immune system, neural functioning, et cetera.
link |
This very organized sequence
link |
of particular forms of metabolism
link |
being active during particular phases of sleep,
link |
which are very, very well orchestrated as we know,
link |
slow wave sleep and REM sleep being orchestrated
link |
in 90 minutes, so-called ultradian cycles
link |
and so on and so forth,
link |
is thought to perhaps set up the brain and body
link |
to be able to regulate itself in the waking hours.
link |
And therefore, when people are sleep deprived
link |
or deprived of certain forms or states within sleep,
link |
such as rapid eye movement sleep,
link |
that it creates a disruption
link |
in a particular set of metabolic pathways.
link |
Now, we don't want to leap too far from this study
link |
to sugar metabolism and the neural circuits
link |
controlling sugar metabolism.
link |
But I will say this,
link |
if you look at the sum total of the data on obesity
link |
or on type two diabetes
link |
or on metabolic syndromes of any kind,
link |
you almost always see disruptions in sleep.
link |
Now, some of those could be due to sleep apnea
link |
caused by even just the size of somebody's neck
link |
or the weight of their body.
link |
In other words, we don't know the direction of the effect.
link |
Metabolic syndromes could disrupt sleep,
link |
which disrupt metabolic syndromes.
link |
And indeed, the authors point out quite appropriately
link |
that they don't understand the direction of the effects
link |
that they observe either.
link |
But there is now a plethora of data pointing to the fact
link |
that getting quality sleep each night
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helps regulate not only appetite,
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but also the specific forms of metabolism
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that drive specific appetites.
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So the takeaway is,
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while there are extravagant and potent
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and interesting ways to regulate blood glucose,
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everything from cinnamon to lemon juice to berberine
link |
to sodium caprate to behavioral tools
link |
to the mere understanding of how the direct
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and indirect pathways go from the gut to dopamine, et cetera.
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If you're not establishing the firm foundation
link |
of proper metabolism,
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all of those things are going to be
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sort of rearranging deck chairs on the Titanic
link |
as sometimes described.
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So we can't overstate the importance of getting regular,
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sufficient amount of high quality sleep
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at least 80% of the time,
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not just for sake of immune system function,
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for clear thinking, et cetera,
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but also for properly regulating our metabolism,
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including our sugar metabolism.
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Thank you for joining me for this discussion
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about sugar and the nervous system
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and how they are regulating each other
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in both the brain and body.
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If you're enjoying and or learning from this podcast,
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That's the best way to support us.
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In addition, we have a Patreon.
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There I cover science and science-based tools
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but often is distinct from the content of the podcast.
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During today's episode and on many previous episodes
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of the Huberman Lab podcast, I discussed supplements.
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While supplements aren't necessary for everybody,
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many people derive tremendous benefit from them.
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One issue with supplements is that
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if you're going to take them,
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you want to make sure that they have
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the absolute highest quality.
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For that reason, we partnered with Thorne, that's T-H-O-R-N-E
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because Thorne is partnered, for instance,
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with all the major sports teams and the Mayo Clinic.
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There's tremendous trust in the fact
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that Thorne supplements contain the specific amounts
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of supplements that are listed on the bottle
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and that the quality of the ingredients they include
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are of the very highest standards.
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If you want to see the 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 you can get 20% off any of the supplements listed there.
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Also, if you navigate further 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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Also, if you haven't yet signed up
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And last, but certainly not least,
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