Controlling Sugar Cravings & Metabolism with Science-Based Tools

00:00:00.000 | - Welcome to the Huberman Lab Podcast,

00:00:02.280 | where we discuss science and science-based tools

00:00:04.880 | for everyday life.

00:00:05.900 | I'm Andrew Huberman,

00:00:10.180 | and I'm a professor of neurobiology and ophthalmology

00:00:12.880 | at Stanford School of Medicine.

00:00:14.680 | Today, we are going to discuss sugar,

00:00:16.840 | in particular, how our nervous system regulates

00:00:18.960 | our sugar intake and our seeking of sugar.

00:00:22.100 | We're also going to discuss how sugar

00:00:24.280 | regulates our nervous system.

00:00:25.800 | And as you'll soon learn,

00:00:27.240 | sugar really impacts our brain and body

00:00:29.040 | by two main mechanisms.

00:00:30.920 | One of those mechanisms is based on the sweet taste of sugar,

00:00:34.000 | which itself is rewarding.

00:00:35.940 | Even if you're not much of a sweet tooth,

00:00:37.640 | I confess I'm not,

00:00:39.040 | most people enjoy sweet tastes more than bitter tastes.

00:00:43.080 | And the sweet taste of sugar and its various forms

00:00:46.880 | is strongly reinforcing,

00:00:48.460 | meaning it triggers the activation of neurons,

00:00:50.780 | nerve cells in the brain and body

00:00:52.280 | that make us want to consume more of that sweet substance.

00:00:56.040 | Incidentally, sweet tastes also make us want to eat

00:00:58.860 | more of other substances as well.

00:01:01.140 | You may be familiar with that phenomenon.

00:01:02.940 | Now, sugar also triggers mechanisms in the brain and body

00:01:05.800 | based on its nutritive content,

00:01:07.860 | independent of its sweetness.

00:01:09.680 | What that means is that the actual caloric content

00:01:14.000 | and the way that sugar interacts with your nervous system

00:01:16.780 | at a subconscious level without your awareness

00:01:19.880 | also impacts your craving and seeking of sugar

00:01:22.860 | and other foods.

00:01:24.460 | Today, we are going to discuss what happens

00:01:26.480 | when you ingest sugar in terms of your body's reaction

00:01:30.040 | and your brain's reaction.

00:01:31.620 | We're also going to talk about what happens

00:01:33.020 | when you don't ingest enough sugar.

00:01:35.360 | Because as it turns out,

00:01:36.600 | sugar is such a powerful fuel for the brain

00:01:39.300 | that under conditions where people don't ingest enough sugar

00:01:42.440 | or where their so-called blood glucose,

00:01:44.360 | which is basically blood sugar of a particular form

00:01:46.960 | gets too low, their neurons don't function as well.

00:01:50.660 | That said, there are conditions of very low blood sugar

00:01:53.480 | in which neurons can function even better.

00:01:56.180 | So today we're going to talk about the ins and outs,

00:01:58.560 | the ups and downs of sugar

00:01:59.960 | as it relates to your nervous system.

00:02:01.440 | And by the end of this episode,

00:02:02.900 | I'm confident that you have a much clearer picture

00:02:05.300 | as to how much sugar you should be ingesting,

00:02:08.560 | whether or not you should avoid sugars

00:02:10.400 | that you're currently eating,

00:02:11.680 | and you will certainly understand much, much more

00:02:14.300 | about the energy and fuel sources that your brain relies on,

00:02:17.740 | which I'm certain will allow you to make

00:02:19.720 | better informed choices about the foods you eat and avoid

00:02:22.560 | toward mental health, physical health, and performance.

00:02:25.280 | I'm pleased to announce that I'm hosting two live events

00:02:27.940 | this May.

00:02:28.940 | The first live event will be hosted in Seattle, Washington

00:02:31.680 | on May 17th.

00:02:33.160 | The second live event will be hosted in Portland, Oregon

00:02:35.800 | on May 18th.

00:02:37.160 | Both are part of a lecture series entitled

00:02:39.160 | The Brain-Body Contract,

00:02:40.740 | during which I will discuss science and science-based tools

00:02:43.800 | for mental health, physical health, and performance.

00:02:46.440 | And I should point out that while some of the material

00:02:48.840 | I'll cover will overlap with information covered here

00:02:51.520 | on the Huberman Lab podcast and on various social media

00:02:54.340 | posts, most of the information I will cover

00:02:56.640 | is going to be distinct from information covered

00:02:59.180 | on the podcast or elsewhere.

00:03:01.040 | So once again, it's Seattle on May 17th,

00:03:03.560 | Portland on May 18th.

00:03:04.920 | You can access tickets by going to Hubermanlab.com/tour,

00:03:09.000 | and I hope to see you there.

00:03:10.480 | Before we begin, I'd like to emphasize that this podcast

00:03:13.000 | is separate from my teaching and research roles at Stanford.

00:03:15.600 | It is, however, part of my desire and effort

00:03:17.480 | to bring zero cost to consumer information about science

00:03:20.040 | and science-related tools to the general public.

00:03:22.680 | In keeping with that theme, I'd like to thank the sponsors

00:03:25.240 | of today's podcast.

00:03:26.700 | Our first sponsor is Thesus.

00:03:28.720 | Thesus makes what are called nootropics,

00:03:31.000 | which means smart drugs.

00:03:32.760 | Now, to be honest, I am not a fan of the term nootropics.

00:03:36.080 | I don't believe in smart drugs in the sense that

00:03:38.720 | I don't believe that there's any one substance

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00:03:43.720 | I do believe, based on science, however,

00:03:46.080 | that there are particular neural circuits

00:03:47.620 | and brain functions that allow us to be more focused,

00:03:50.180 | more alert, access creativity, be more motivated, et cetera.

00:03:53.900 | That's just the way that the brain works,

00:03:55.300 | different neural circuits for different brain states.

00:03:57.820 | And so the idea of a nootropic that's just going to make us

00:03:59.860 | smarter all around fails to acknowledge that

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00:07:37.540 | Okay, let's talk about sugar.

00:07:39.260 | Let's talk about how sugar impacts your brain

00:07:41.600 | and how your brain impacts your pursuit

00:07:43.760 | or your avoidance of sugar.

00:07:45.400 | Let's get a few things out of the way first.

00:07:48.400 | The first thing is that there's nothing inherently bad

00:07:51.160 | about sugar.

00:07:52.280 | I know the word sugar gets a bad rap nowadays.

00:07:55.360 | And indeed, you're going to hear over and over again

00:07:57.620 | during this podcast that consuming a lot of refined sugars,

00:08:01.300 | in particular high fructose corn syrup,

00:08:03.620 | is known to have a very large number of bad effects

00:08:07.380 | on the brain and body.

00:08:08.300 | I don't know that there's anyone

00:08:09.460 | that really debates that anymore.

00:08:11.640 | Even if we just agree, and I think we should all agree

00:08:15.420 | on the so-called calories in, calories out principle,

00:08:18.560 | right, it's a principle of thermodynamics

00:08:20.340 | that if we ingest more energy than we burn,

00:08:23.400 | we are going to gain weight.

00:08:24.520 | If we ingest less energy than we burn,

00:08:27.400 | we are generally going to lose weight.

00:08:29.120 | And if the two things are in balance,

00:08:31.360 | ingestion and burning of energy,

00:08:34.340 | well, then we're going to maintain weight.

00:08:36.560 | So everyone agrees on that.

00:08:38.260 | I agree on that.

00:08:39.140 | But beyond that, there are a number of ways

00:08:41.640 | in which particular nutrients,

00:08:43.140 | in the case of today's episode, sugar,

00:08:45.780 | impact the way that the brain works,

00:08:48.420 | such that we tend to seek out more of particular nutrients.

00:08:52.360 | For instance, if we eat sugar,

00:08:54.700 | there are two or at least two mechanisms

00:08:57.380 | by which we will crave more sugar.

00:08:59.480 | I think most people are aware of that experience,

00:09:01.140 | but today I'm going to explain exactly how that works.

00:09:03.660 | But also that when we ingest sugar,

00:09:06.560 | it has a bunch of different effects

00:09:08.220 | on the way that our neural circuits work

00:09:10.920 | that can allow us to be more or less focused,

00:09:13.540 | more or less agitated, more or less happy,

00:09:16.280 | more or less depressed in some cases.

00:09:19.720 | So today, as we explore this thing we're calling sugar,

00:09:22.300 | we're going to explore that mainly

00:09:23.880 | in the context of the nervous system,

00:09:26.020 | but also in the context of how the nervous system

00:09:28.540 | regulates many, many functions and behaviors

00:09:31.260 | that are important to all of you.

00:09:33.300 | Your ability to think, your ability to exercise,

00:09:35.420 | your ability to gain weight, lose weight,

00:09:37.300 | whatever your goals might happen to be,

00:09:39.620 | sugar plays a critical role in achieving those goals.

00:09:42.820 | And in some cases, if you're ingesting too much

00:09:45.420 | at the wrong times or the wrong forms,

00:09:47.160 | sugar can actually impede those goals.

00:09:49.580 | In fact, sugar can prevent all the right behaviors

00:09:52.580 | from allowing you to achieve the goals that you want.

00:09:55.420 | So today we are going to place sugar

00:09:56.940 | into its proper context.

00:09:59.020 | The way I want to start off by doing that

00:10:01.100 | is to tell you a little bit of what happens when we eat

00:10:04.220 | and a little bit of what the brain does

00:10:06.800 | to respond to those events.

00:10:09.440 | So what happens when we eat?

00:10:10.860 | Well, I've done an entire episode on metabolism.

00:10:14.460 | So if you're interested in the full cascade

00:10:17.660 | of hormonal and neural events that occurs when we eat,

00:10:20.820 | please check out that episode.

00:10:22.360 | But for sake of today's discussion,

00:10:24.020 | let's just take a, what I call top contour view

00:10:26.900 | of the hormonal response to ingesting food.

00:10:30.100 | Now, anytime we eat, that is the consequence

00:10:32.740 | of a number of things that happened before we ate.

00:10:35.960 | There's a hormone in our brain and body called ghrelin,

00:10:38.500 | spelled G-H-R-E-L-I-N.

00:10:40.960 | Ghrelin is a hormone that increases depending

00:10:44.460 | on how long it's been since we ate last, okay?

00:10:47.140 | So the longer it's been since we had a meal,

00:10:49.720 | ghrelin levels are going to be higher and higher and higher.

00:10:52.620 | And it essentially makes us hungry by interacting

00:10:55.540 | with particular neurons in an area of the brain

00:10:57.940 | called the arcuate nucleus of the hypothalamus

00:11:00.380 | and some other areas as well, like the lateral hypothalamus.

00:11:03.740 | You don't need to know the names of those brain areas,

00:11:05.380 | but if you'd like to know them, there they are.

00:11:08.340 | Ghrelin increases, it tends to make us hungry.

00:11:11.700 | And then when we eat,

00:11:13.460 | typically what happens is ghrelin levels go down.

00:11:16.460 | So it's a very logical system.

00:11:18.220 | Now, when we eat, assuming that we eat carbohydrates,

00:11:22.180 | but even if we just eat some protein and some fats,

00:11:24.960 | we will experience a slight, or in some cases,

00:11:28.460 | a large rise in blood glucose.

00:11:31.020 | Blood glucose is simply blood sugar.

00:11:33.660 | And the body and brain, we should say particular,

00:11:37.660 | the nervous system doesn't function well

00:11:40.020 | if blood sugar is too high or too low.

00:11:42.260 | So as a consequence, we have another hormone,

00:11:44.320 | which is released from the pancreas,

00:11:45.660 | which is called insulin,

00:11:46.820 | which helps regulate the amount of glucose

00:11:49.620 | in the bloodstream.

00:11:50.580 | So even if you were to ingest an entire cup,

00:11:53.860 | an eight ounce cup of pure table sugar,

00:11:56.040 | which would send your blood glucose very, very high,

00:11:58.660 | assuming that you have a normal insulin response,

00:12:00.500 | that you're not diabetic,

00:12:02.320 | that insulin response would help clamp

00:12:04.460 | that blood glucose level so that it did not cause damage

00:12:08.300 | to your brain and body.

00:12:09.720 | Because if blood sugar goes too high,

00:12:11.280 | it's actually toxic to neurons

00:12:13.120 | and other cells of your body can kill them off.

00:12:15.120 | And neurons of the central nervous system,

00:12:17.280 | meaning the brain and spinal cord,

00:12:18.400 | once they are dead, they do not come back.

00:12:20.300 | So your biological systems understand this

00:12:23.540 | at a biological level, that is,

00:12:25.260 | and prevent that death of cells due to high blood sugar

00:12:28.580 | by keeping insulin around in order to clamp blood glucose.

00:12:33.500 | Diabetics, we call them type one diabetics

00:12:35.680 | who don't make insulin,

00:12:36.820 | have to take insulin when they eat,

00:12:38.460 | in particular, when they eat foods

00:12:39.620 | that raise their blood sugar,

00:12:40.940 | specifically to avoid that neurotoxicity

00:12:42.940 | and the other deleterious effects of high blood sugar.

00:12:45.420 | Okay, so ghrelin is a hormone that goes up

00:12:47.340 | the longer it's been since we've eaten.

00:12:49.060 | It tends to stimulate hunger.

00:12:51.220 | When we eat, ghrelin is suppressed.

00:12:53.640 | Blood glucose typically goes up,

00:12:55.500 | especially when we eat a carbohydrate-containing meal.

00:12:59.260 | When blood glucose goes up, it's regulated in the body,

00:13:02.420 | meaning its peaks and its valleys

00:13:04.740 | are more or less smoothed out

00:13:06.620 | and that glucose is sequestered.

00:13:08.400 | It's taken away where it needs to be taken away.

00:13:10.980 | And in certain locations, it's delivered to cells

00:13:13.360 | so that those cells can use the glucose.

00:13:15.940 | Now, one of the chief organs for glucose utilization

00:13:19.200 | is the brain.

00:13:20.580 | Neurons are tremendously metabolically active

00:13:23.760 | and their preferred mode of metabolism

00:13:27.420 | is glucose metabolism.

00:13:28.820 | In other words, neurons basically run on sugar,

00:13:32.020 | which is not to say that you should eat a lot of sugar.

00:13:34.640 | As you'll see today, there are states of mind and body,

00:13:37.820 | for instance, fasted states,

00:13:39.500 | in which people report having immense amounts

00:13:42.540 | of mental clarity

00:13:43.860 | and their blood glucose is actually quite low.

00:13:46.340 | So it is simply not the case

00:13:48.180 | that the more sugar that you ingest,

00:13:49.980 | the better that your brain will function.

00:13:51.700 | But it is the case that for most people,

00:13:53.920 | meaning people who are not on a ketogenic

00:13:55.820 | or very low carbohydrate diet,

00:13:57.320 | they're not adapted to low carbohydrate diets,

00:13:59.460 | that neurons in their brain and body

00:14:02.060 | are using glucose in order to function.

00:14:04.060 | That's what allows those neurons

00:14:05.300 | to fire electrical potentials.

00:14:06.900 | That's how we refer to it, firing,

00:14:08.520 | meaning sending electrical signals down their length

00:14:11.060 | to communicate with other neurons.

00:14:13.220 | To illustrate just how important glucose is

00:14:15.440 | for brain function,

00:14:16.900 | I'd like to describe a study that just recently came out

00:14:20.320 | that sits on a long history of similar studies,

00:14:23.100 | but the one that just came out is particularly interesting.

00:14:25.540 | Now, I want to point out that unless I say otherwise,

00:14:29.980 | I'm going to refer to typical diets,

00:14:32.780 | meaning I have to believe that most people out there

00:14:35.640 | are ingesting some starch or carbohydrate.

00:14:37.940 | I do realize there are people

00:14:39.100 | following very low carbohydrate diets

00:14:41.140 | or moderately carbohydrate diets.

00:14:42.660 | I even know that there's some folks out there

00:14:43.940 | who are on the so-called carnivore diet.

00:14:45.560 | They only eat meat and organs, maybe a little fruit,

00:14:48.540 | but I'm going to assume that the vast majority

00:14:50.660 | of people listening ingest proteins and carbohydrates.

00:14:55.080 | So unless I say ketogenic,

00:14:56.780 | or I emphasize ketosis itself, which I will,

00:14:59.860 | I'm referring to a kind of typical diet

00:15:01.420 | where people are consuming fats, proteins, and carbohydrates.

00:15:04.520 | I count myself as one such individual.

00:15:07.660 | At some point, I might try the carnivore diet, who knows?

00:15:10.000 | I might try a pure vegan diet, who knows?

00:15:12.700 | But for my entire life up until now, I'm 46 years old,

00:15:15.720 | I've been a proud omnivore, meaning I've tried

00:15:18.320 | to eat high quality, as much as I can, unprocessed foods.

00:15:22.020 | I try and really avoid highly processed foods,

00:15:23.920 | but I do eat from those three macronutrient groups,

00:15:26.200 | proteins, carbohydrates, and fats.

00:15:28.160 | And I'm going to assume that most of you do as well.

00:15:30.820 | The study I'd like to emphasize,

00:15:32.420 | recorded from neurons, nerve cells in the brain,

00:15:37.840 | in particular in the part of the brain

00:15:39.280 | that responds to visual images,

00:15:41.680 | so-called visual cortex.

00:15:43.180 | And neurons in the visual cortex are beautifully tuned,

00:15:47.300 | as we say, to particular features of what we see.

00:15:50.940 | The primary example of this, the kind of classic example,

00:15:55.020 | is if you put a little electrode next to a neuron

00:15:57.580 | in your visual cortex, or if we put you

00:15:59.780 | into an fMRI scanner machine,

00:16:03.040 | which can detect neural activity,

00:16:04.560 | and I were to show you a bunch of just little lines,

00:16:08.900 | bars of light, they could be dark bars of light,

00:16:10.760 | they could be light bars of light

00:16:12.540 | on a screen in front of you.

00:16:14.660 | So some would be vertical, some will be horizontal,

00:16:16.620 | some will be at 45 degrees.

00:16:18.360 | What we would see is that some neurons respond best,

00:16:23.140 | meaning they fire a lot of electrical activity

00:16:25.760 | to vertical lines.

00:16:26.700 | Other ones respond to horizontal lines,

00:16:28.760 | and others respond to 45 degree lines.

00:16:31.620 | And this so-called orientation tuning,

00:16:34.220 | meaning because of the orientation of the line,

00:16:36.060 | is a cardinal classic feature of the way

00:16:39.280 | that your visual system is built.

00:16:41.140 | And everything that you see,

00:16:43.560 | whether it's a face or a dog or a cat or a landscape,

00:16:46.980 | is built up from these very simple neuron responses.

00:16:51.140 | In other words, when you look at a face,

00:16:53.580 | there are neurons deep in the brain that respond to faces,

00:16:56.140 | but the only reason that those neurons

00:16:57.920 | can respond to those faces is because they receive signals

00:17:00.660 | from neurons in your visual cortex,

00:17:02.800 | some of which respond to vertical lines,

00:17:04.460 | some of which respond to horizontal lines,

00:17:06.100 | and some of which respond to 45 degree lines,

00:17:08.220 | and all of those are built up

00:17:10.000 | in what we call a hierarchical representation,

00:17:12.000 | which is fancy language for it.

00:17:13.160 | Those are the building blocks by which you see a face

00:17:15.680 | and you recognize a face.

00:17:16.660 | And it's really an amazing phenomenon.

00:17:18.120 | It happens very, very fast.

00:17:19.740 | You never notice that you're doing this,

00:17:21.420 | but everything is built up

00:17:22.320 | from these fundamental orientation-tuned neurons.

00:17:26.060 | Now, orientation-tuned neurons are so fundamental

00:17:30.080 | that they are the building blocks

00:17:31.820 | by which you make up all other things that you see.

00:17:34.900 | It's the way you read,

00:17:35.740 | it's the way that you recognize faces, as I mentioned,

00:17:38.040 | and everything else.

00:17:39.000 | Experimentally, it's quite straightforward

00:17:43.180 | to measure how sharply tuned one of these neurons is.

00:17:47.200 | In other words, if I were to show you a vertical line

00:17:50.280 | and find a neuron in your brain

00:17:51.700 | that responds to vertical lines,

00:17:53.600 | I could also ask whether or not

00:17:55.940 | that neuron fires any electrical activity

00:17:58.500 | in response to a line that's not quite vertical,

00:18:02.120 | maybe just 10 degrees off vertical,

00:18:04.140 | or 20 degrees, or 30 degrees.

00:18:06.060 | And what I eventually would find

00:18:07.680 | is that that neuron was orientation-tuned

00:18:10.980 | over a particular range of angles.

00:18:13.060 | It's not only going to respond to vertical lines,

00:18:15.240 | it's also going to respond to lines

00:18:16.580 | that are about 10 degrees off vertical in either side,

00:18:19.300 | but probably not much more, maybe 20,

00:18:22.220 | but usually it's going to be anywhere from vertical

00:18:25.020 | to just tilted slightly, okay?

00:18:27.140 | In the recent experiment

00:18:30.340 | that was published in the journal Neuron,

00:18:31.800 | Cell Press Journal, excellent journal,

00:18:33.880 | the authors asked a really interesting question.

00:18:36.180 | They asked whether or not the sharpness of tuning,

00:18:38.920 | the precision of orientation tuning of these neurons

00:18:41.940 | is dependent on blood glucose level.

00:18:44.780 | So just to cut to the chase, to give you the answer,

00:18:47.080 | what they found is that when subjects are well-fed,

00:18:51.200 | neurons that responded to vertical

00:18:53.180 | responded very strongly to vertical,

00:18:55.020 | but not very much at all to other angles

00:18:57.840 | of what we call stimuli,

00:18:59.760 | to lines that are 10 degrees or 20 degrees off.

00:19:02.120 | If they looked at neurons that were primarily tuned,

00:19:06.100 | right, that preferred horizontal lines,

00:19:08.280 | they found the same thing, okay?

00:19:09.760 | So it wasn't something unique to vertical lines.

00:19:11.380 | What they basically found was the sharpness,

00:19:13.660 | the precision of tuning of neurons in the brain

00:19:16.500 | was best when subjects were fed.

00:19:19.840 | And conversely, when subjects were fasted,

00:19:22.880 | the orientation tuning of these neurons

00:19:25.580 | became much broader.

00:19:27.620 | What it meant was that a neuron

00:19:29.020 | that normally would only respond to vertical

00:19:30.980 | now responded to other angles of lines as well.

00:19:33.740 | You might say, well, that's great, right?

00:19:35.260 | These neurons that at one point could only do one thing

00:19:37.060 | are now tuned to other things, but it's not so great

00:19:39.900 | because what that means is that in the fasted state,

00:19:43.580 | your perception of the outside world is actually distorted.

00:19:47.480 | It's blurred.

00:19:48.320 | It's not as precise as it is when you're fed.

00:19:51.240 | And when I say fed, what I really mean

00:19:53.000 | is when glucose is available to neurons.

00:19:55.500 | Now, for some of you, maybe many of you,

00:19:58.380 | and including myself, intermittent fasting

00:20:01.340 | or some variant thereof is actually a state that I like.

00:20:04.180 | It allows me to focus.

00:20:05.220 | For instance, as I mentioned before,

00:20:06.920 | and even earlier in this podcast,

00:20:08.140 | I tend to eat my first meal sometime around 11 a.m.

00:20:11.660 | And then I generally eat my last meal sometime

00:20:14.180 | around 8 p.m., plus or minus an hour on either side.

00:20:16.580 | I'm not super strict about it.

00:20:17.620 | And occasionally I'll wake up really hungry

00:20:18.980 | and I'll eat something before 11 a.m.

00:20:20.500 | I'm not super strict about this intermittent fasting thing.

00:20:23.900 | It just seems to be how my appetite works best

00:20:26.260 | given my schedule, et cetera.

00:20:27.700 | In the morning, I tend to be most focused.

00:20:31.900 | And I always associate that with the fact that I was fasted.

00:20:35.220 | I ingest water and some caffeine

00:20:37.140 | about 90 minutes after waking up.

00:20:38.580 | I drink my caffeine,

00:20:39.420 | but I hydrate from the time I get up, et cetera, et cetera.

00:20:41.780 | And I know a lot of other people

00:20:43.740 | have had the experience of being fasted

00:20:45.820 | and feeling like they have a lot of mental clarity.

00:20:48.460 | When you are in a fasted state,

00:20:50.300 | typically you're going to use fuels

00:20:52.980 | that are available to the neurons

00:20:54.820 | based on your intake of food the day before.

00:20:57.900 | Maybe you're using some glycogen.

00:20:59.700 | Maybe you're using some fat.

00:21:01.280 | Maybe you're using some blood sugar

00:21:03.220 | that's derived from other storage sites in the body.

00:21:06.100 | You don't actually use fat

00:21:08.580 | as a fuel source for neurons under typical conditions,

00:21:11.500 | but there are ways in which proteins and fats

00:21:13.800 | and glycogen, et cetera,

00:21:15.220 | are converted into fuel that neurons can use.

00:21:18.140 | What's interesting about this study

00:21:19.660 | is that the study says that when well-fed,

00:21:23.240 | meaning when blood glucose, sugar,

00:21:25.820 | is at a properly elevated level in the bloodstream,

00:21:30.460 | it can be delivered to the brain

00:21:32.160 | in a way that allows neurons to work best,

00:21:34.100 | which is really all just to underscore

00:21:35.880 | the point that I made earlier,

00:21:36.920 | which is that your nervous system

00:21:38.300 | is extremely metabolically demanding,

00:21:40.220 | and it loves glucose.

00:21:41.880 | Neurons love glucose.

00:21:44.100 | So the takeaway from this study

00:21:46.000 | is not that you should avoid fasting.

00:21:47.980 | The takeaway from this study

00:21:48.920 | is that there are elements of the fasted state,

00:21:51.320 | in particular the elevations

00:21:52.540 | in things like epinephrine and norepinephrine,

00:21:54.420 | also called adrenaline and noradrenaline,

00:21:56.640 | that can give us this kind of clarity of mind

00:21:59.180 | that many people are pursuing when they fast.

00:22:01.520 | That's kind of one of the reasons a lot of people fast.

00:22:03.380 | They like the way that they feel mentally and physically.

00:22:06.500 | But I think it's only fair to point out

00:22:09.480 | that glucose is the preferred source of fuel for the brain.

00:22:12.380 | And this study that I mentioned

00:22:14.180 | is one of many studies that have explored

00:22:16.220 | how nutritional status or blood glucose status

00:22:18.820 | in the brain and body influence neuronal tuning

00:22:21.640 | and neuronal function.

00:22:23.260 | And it really points to the fact that ultimately,

00:22:26.900 | your brain as an organ is a glucose-consuming machine.

00:22:31.020 | Now, when you eat a food, that food is broken down,

00:22:36.020 | and if it contains carbohydrates,

00:22:37.660 | it's going to be converted into glucose.

00:22:39.420 | And that glucose can't get directly into the brain

00:22:41.620 | as a fuel source.

00:22:42.460 | It actually has to be carried across

00:22:43.780 | the so-called blood-brain barrier, the BBB.

00:22:46.660 | And the actual metabolism of glucose

00:22:50.060 | and the delivery of the glucose to the neurons

00:22:52.380 | is carried out by a different cell type.

00:22:54.340 | And it's a cell type that you should all know about

00:22:56.100 | because it's the most abundant cell type in your brain

00:22:59.340 | and maybe even in your entire nervous system.

00:23:01.140 | And that's the so-called astrocyte.

00:23:03.180 | Astrocytes are one of several types of glia.

00:23:06.360 | The word glia means glue,

00:23:08.080 | but many people have taken that name, glia, glue,

00:23:11.580 | to think that, oh, the only thing

00:23:13.140 | that the astrocytes are doing

00:23:14.020 | is just kind of holding things together.

00:23:15.460 | Actually, the astrocytes are involved

00:23:17.100 | in delivering glucose to the neurons.

00:23:19.660 | They are critically involved in shaping

00:23:21.700 | your neuronal function and brain plasticity,

00:23:23.940 | the brain's ability to change in response to experience.

00:23:26.140 | So these astrocytes are like the little waiters

00:23:28.060 | and waitresses bringing glucose to the neurons.

00:23:30.940 | And the neurons are going to do the heavy lifting

00:23:32.540 | that's involved in perception and behavior and action.

00:23:35.420 | So if prior to this episode,

00:23:37.580 | you didn't already realize that glucose, blood sugar,

00:23:40.780 | is vital to the function of your brain

00:23:43.500 | and other neurons of your nervous system, now you know.

00:23:46.900 | And for those of you that have experienced

00:23:49.620 | the increase in mental clarity

00:23:52.140 | that comes after a properly timed, properly composed,

00:23:57.140 | meaning it has the right macronutrients

00:23:58.820 | and the right ratios and the properly sized meal,

00:24:01.700 | well, then now you have justification for eating something

00:24:04.420 | as a way to improve the way that your brain works.

00:24:07.220 | It turns out that your brain is going to work best

00:24:09.020 | when it's got glucose available.

00:24:10.820 | Whether you like to fast or not,

00:24:12.300 | that's just the reality of things.

00:24:13.820 | The same thing is also true for the neurons in your body.

00:24:17.360 | The way that you are able to move the limbs of your body,

00:24:19.740 | the way that you are able to perform exercise

00:24:22.620 | or movement of any kind for that matter,

00:24:24.760 | is because neurons called motor neurons

00:24:27.380 | send electrical potentials to the muscle fibers.

00:24:30.180 | They release a neurotransmitter called acetylcholine,

00:24:32.540 | which causes contraction of the muscle fibers

00:24:34.460 | and allows you to move your limbs.

00:24:36.700 | Those neurons are also very metabolically demanding,

00:24:39.540 | especially when you're doing

00:24:41.140 | demanding types of physical work.

00:24:42.820 | And that could be cycling or running or weightlifting

00:24:44.540 | or yoga or whatever it may be.

00:24:46.900 | Those neurons require a ton of glucose.

00:24:50.400 | If you've ever had the experience

00:24:51.700 | of having to think very hard

00:24:53.620 | about how you're generating a movement

00:24:55.340 | or force yourself to continue to endure in a given exercise,

00:24:59.420 | you might've thought, oh, you know, I'm running out of fuel.

00:25:01.900 | That's why I'm getting tired.

00:25:02.980 | It's hard to do.

00:25:04.280 | That's actually the case sometimes,

00:25:06.420 | but that's not always the case.

00:25:09.060 | One of the reasons that it feels like work

00:25:11.280 | is because your so-called upper motor neurons,

00:25:13.320 | the one that control the lower motor neurons

00:25:15.060 | in your spinal cord, which control your muscles,

00:25:17.160 | they have to be very metabolically active.

00:25:19.080 | It's one thing to engage in a reflexive movement

00:25:21.140 | where you're just walking around

00:25:22.180 | or if you're running continuously,

00:25:23.780 | but when you suddenly have to focus on what you're doing

00:25:25.940 | and you have to generate specific patterns of motor movement,

00:25:28.860 | well, that feels demanding because one,

00:25:32.380 | it increases the release of adrenaline

00:25:34.100 | in your brain and body,

00:25:34.940 | which makes you feel a little bit agitated and more alert,

00:25:37.140 | but also deliberate thought,

00:25:40.140 | deliberately controlling the way

00:25:41.720 | that your brain and body is moving

00:25:43.900 | requires more glucose uptake,

00:25:45.780 | more energy in those very neurons.

00:25:47.960 | And this is also why after doing a long bout of exercise,

00:25:50.660 | you might be tired,

00:25:51.500 | but also if you do a bout of skill learning of any kind,

00:25:55.720 | or if you've been reading and thinking

00:25:57.260 | about what you're reading,

00:25:58.580 | or if you had a intense conversation with somebody

00:26:01.420 | where you're really forcing yourself to listen,

00:26:03.940 | and hopefully they're listening to you too,

00:26:05.420 | and you're really trying to parse what they're saying,

00:26:07.060 | and maybe you're doing that right now

00:26:08.300 | and you're trying to really track something, that's work.

00:26:11.180 | And that work requires glucose uptake by neurons,

00:26:13.620 | both in the brain and in your body.

00:26:15.580 | Now that we've established that glucose

00:26:17.060 | is the preferred source of fuel for the nervous system,

00:26:20.500 | I'd like to concentrate on a few of the other types of sugars

00:26:24.100 | that we ingest on a common basis,

00:26:27.220 | and the impact that those have on brain function

00:26:30.860 | and body function.

00:26:32.000 | I'd particularly like to focus on fructose.

00:26:35.740 | Fructose, of course, is found in fruit.

00:26:37.340 | It's also found in the infamous high fructose corn syrup,

00:26:40.420 | which we will talk about today.

00:26:42.580 | It's worth pointing out that the concentrations of fructose

00:26:44.980 | in fruit is quite low compared to the concentrations

00:26:48.260 | of fructose in high fructose corn syrup.

00:26:50.320 | High fructose corn syrup is approximately 50% fructose,

00:26:55.080 | which turns out to be an enormously high percentage

00:26:58.820 | of anything really, especially when we contrast that

00:27:03.040 | to the concentrations of fructose in fruit.

00:27:05.560 | Fruits have other types of sugars in them as well.

00:27:09.380 | The sucrose content of most fruit and fruit juices is low,

00:27:13.060 | although there are some fruits like melons, peaches,

00:27:15.900 | pineapples, and so forth, that contain a little less

00:27:19.540 | than 10% or so of sucrose.

00:27:22.060 | Things like mangoes can have a lot of sucrose,

00:27:24.500 | but typically the amount of fructose, fructose,

00:27:27.340 | I think is the proper pronunciation

00:27:28.980 | that people are always correcting me, fructose,

00:27:31.920 | is anywhere from 1% to about 10%, right?

00:27:38.620 | It's really going to vary quite a bit.

00:27:40.420 | And many of you have probably heard

00:27:41.740 | of the so-called glycemic index,

00:27:43.280 | which is basically a measure of how fast blood sugar rises

00:27:46.100 | after eating particular foods, et cetera.

00:27:48.400 | We're going to set aside the glycemic index for now.

00:27:50.560 | We will come back to it.

00:27:51.920 | It has some relationship to the concentrations

00:27:54.260 | of fructose in fruit.

00:27:55.780 | But the point that I'd like to make is that fructose

00:27:58.020 | as a sugar is handled very differently in the body

00:28:01.100 | than is glucose.

00:28:02.980 | But I also want to emphasize that because the percentage

00:28:07.540 | of fructose in fruit is rather low,

00:28:09.960 | especially compared to high fructose corn syrup.

00:28:13.180 | Many people have demonized fructose saying

00:28:16.040 | that fructose makes you fat or that fruit makes you fat.

00:28:20.700 | If you look at the data, that's not really the case.

00:28:23.560 | The fact of the matter is that the concentrations

00:28:25.300 | of fructose and fruit are so low

00:28:27.140 | that unless someone is consuming a lot of fruit

00:28:29.420 | or they're consuming a lot of fruit on the backdrop

00:28:32.460 | of a highly processed diet or a diet that has a lot

00:28:35.900 | of other stuff that they might not want to be ingesting,

00:28:38.220 | you can't really say that fructose is fattening.

00:28:40.260 | I don't really think that there's any basis

00:28:42.340 | for saying that fructose itself is bad.

00:28:44.380 | Now, high fructose corn syrup is a different issue

00:28:47.460 | and too much consumption of anything but fructose included,

00:28:50.820 | whether or not it comes from fruit or otherwise,

00:28:52.540 | can be a problem for the ways that it impacts

00:28:55.340 | the neural circuits that process sugar,

00:28:58.500 | not just glucose, but fructose.

00:29:00.280 | And so we'll illustrate those neural circuits in a bit

00:29:02.300 | and it will become very clear to all of you,

00:29:04.760 | regardless of whether or not you have a background

00:29:06.300 | in biology or metabolism, nutrition or otherwise,

00:29:09.300 | why ingesting very high concentrations of fructose

00:29:12.320 | is not going to be a good thing

00:29:13.860 | for the way that your brain functions.

00:29:16.660 | One of the key distinctions between glucose and fructose

00:29:19.580 | is that fructose most likely cannot directly access

00:29:23.360 | the brain, it actually needs to be converted

00:29:25.420 | into glucose in the liver.

00:29:27.540 | And the way that conversion occurs feeds back

00:29:31.360 | to a set of hormones and neural pathways

00:29:33.360 | that we talked about earlier,

00:29:34.800 | which have a lot to do with appetite.

00:29:36.500 | And to just summarize what is now a lot of very solid data,

00:29:40.640 | fructose and specifically fructose has the ability

00:29:45.780 | to reduce certain hormones and peptides in our body

00:29:49.620 | whose main job is to suppress ghrelin.

00:29:52.860 | As you recall, ghrelin is a hormone that increases

00:29:56.180 | the longer it's been since we've eaten

00:29:58.180 | and ghrelin makes us hungry by stimulating

00:30:01.360 | particular neurons in our hypothalamus.

00:30:03.080 | It actually makes us really want to eat

00:30:05.220 | and in particular really makes us want to eat

00:30:07.600 | sugary and fatty foods.

00:30:09.580 | Fructose reduces the activity of the hormones

00:30:12.740 | that reduce ghrelin.

00:30:14.540 | And so the net consequence of that

00:30:16.300 | is that fructose increases ghrelin.

00:30:19.700 | So although I, and I think pretty much everyone out there,

00:30:24.300 | say for a few individuals agrees that calories in,

00:30:27.740 | calories out is the fundamental principle

00:30:29.400 | of weight loss, weight maintenance or weight gain,

00:30:32.120 | ingesting fructose shifts our hormone system.

00:30:36.160 | And as a consequence, our neural pathways within our brain,

00:30:39.860 | the hypothalamus to be hungrier,

00:30:43.120 | regardless of how many calories we've eaten, okay?

00:30:47.500 | Now I also want to be absolutely clear.

00:30:50.200 | This does not mean that eating an apple or eating a melon

00:30:53.340 | or eating a couple of apricots or something

00:30:55.660 | is going to make you hyperphagic,

00:30:58.940 | meaning it's going to make you just want to eat and eat.

00:31:00.980 | That's simply not the case.

00:31:02.240 | But if you compare fructose and you compare glucose,

00:31:05.840 | not only are they metabolized differently

00:31:07.860 | in the brain and body, but in addition to that,

00:31:10.900 | fructose has this impact of reducing the hormones

00:31:14.600 | that reduce hunger hormones and neural circuits.

00:31:17.960 | And so fructose does have this kind of twist

00:31:20.700 | in its phenotype, right?

00:31:23.560 | Or it's, I guess if fructose had a dating profile,

00:31:27.000 | this would be a kind of a red flag in that profile.

00:31:31.240 | Because fructose itself,

00:31:33.700 | while it's actually a pretty good fuel source in many ways,

00:31:38.060 | and it's often packaged in things like fruits,

00:31:40.160 | which bring along fiber and vitamins and minerals

00:31:42.460 | that I think for many of us are things

00:31:45.000 | that we should be eating more of and ingesting more of,

00:31:47.280 | it can suppress the pathways that suppress hunger.

00:31:50.920 | And as a consequence, it can increase hunger.

00:31:53.720 | So current recommendations for most people

00:31:56.960 | are to eat more fruits and vegetables.

00:31:58.760 | But for those of you that are trying to control your hunger,

00:32:02.200 | ingesting a lot of fructose

00:32:04.580 | is probably not going to be a good idea.

00:32:06.140 | Certainly ingesting it from high fructose corn syrup

00:32:08.800 | is not going to be a good idea

00:32:09.760 | because of the enormous percentages of fructose

00:32:12.580 | in high fructose corn syrup, 50% or sometimes even more.

00:32:15.700 | But even from fruit, some people will find

00:32:18.080 | that fruit really quenches their appetite.

00:32:19.880 | Other people will find that fruit stimulates their appetite.

00:32:22.760 | And I suppose if you're trying to stimulate your appetite,

00:32:24.680 | then ingesting more fruit might actually

00:32:26.960 | be advantageous to you.

00:32:28.440 | So fructose provides a bridge for us

00:32:31.340 | between a particular kind of sugar, hormone function,

00:32:35.600 | in this case, ghrelin and the hypothalamus,

00:32:39.560 | which leads us to the next question,

00:32:41.000 | which is what is it about sugar

00:32:43.800 | that makes it such an attractive thing for us?

00:32:46.020 | Why do we like it so much?

00:32:47.800 | And the obvious answer that most people arrive at is,

00:32:50.960 | well, it just tastes really, really good,

00:32:53.540 | but that's actually not the way it works.

00:32:56.800 | The rewarding properties, as we say, of sugar,

00:33:00.680 | whether or not they come in the form of sucrose or fructose

00:33:03.860 | or foods that increase glucose to a very high level,

00:33:08.660 | actually is not just related to the taste of the foods

00:33:13.020 | that produce that elevation in glucose, sucrose, or fructose.

00:33:16.080 | It is in part, but that's only part of the story.

00:33:19.340 | And the rest of the story, once you understand it,

00:33:22.340 | can actually place you in a position to much better control

00:33:25.800 | your sugar intake of all kinds,

00:33:28.380 | but also your food intake in ways that can allow you

00:33:30.600 | to make much better choices about the foods you ingest.

00:33:33.360 | And actually at this point,

00:33:34.400 | I should probably give a confession.

00:33:36.720 | I've said today, and I'll say it again,

00:33:38.800 | and I've said it on previous podcasts,

00:33:40.240 | I don't have much of a sweet tooth and indeed that's true.

00:33:42.760 | And I can kind of pass on chocolate or ice cream

00:33:45.400 | or things like that.

00:33:46.240 | It seems like with each successive year,

00:33:48.060 | sweet things are less and less appealing to me.

00:33:50.800 | Of course, savory foods,

00:33:52.660 | anything that is really fatty, salty, savory,

00:33:57.520 | those don't last long in my presence.

00:33:59.700 | But I always say I don't really like sweet things so much.

00:34:02.700 | And I don't, I like sweet people,

00:34:04.160 | but I don't tend to like sweet foods, which is true,

00:34:07.280 | but there's probably one exception and that's mangoes.

00:34:10.440 | And it turns out that mangoes have the highest percentage

00:34:13.640 | of sugar in them, in particular fructose,

00:34:16.460 | as well as other forms of sugars.

00:34:18.560 | So what I do, because I love mangoes so much,

00:34:22.600 | is I will have mangoes probably twice a week,

00:34:25.400 | but I'll have them after some sort of resistance training

00:34:28.640 | or hard run or something like that.

00:34:30.400 | Because it is the case that after you exercise hard,

00:34:33.240 | in particular exercise that is of the high intensity variety

00:34:36.980 | that your body is more efficient

00:34:38.920 | at using circulating blood sugar.

00:34:41.740 | It's able to store that or use that for fuel.

00:34:44.760 | And so what I'll typically do is just take the mango,

00:34:47.620 | actually eat the peels too.

00:34:48.960 | I know that probably some people are going to cringe

00:34:50.460 | when they hear that.

00:34:51.300 | I find them delicious.

00:34:52.140 | So I just bite into those things like apples.

00:34:53.520 | I don't eat the pits, however.

00:34:55.320 | So now I want to take us on a journey

00:34:57.340 | into the nervous system to explain the pathways

00:35:00.240 | in the brain and body that regulate our appetite for sugar.

00:35:04.460 | Now, keep in mind what I already told you before,

00:35:07.000 | which is that when we ingest foods,

00:35:08.600 | they're broken down into various components

00:35:11.420 | and glucose is going to be shuttled to the brain.

00:35:14.020 | And of course, to other neurons in our spinal cord

00:35:16.040 | and elsewhere and to our muscles, et cetera,

00:35:18.720 | in order for all of those cells and organs and tissues

00:35:22.260 | to be able to function.

00:35:23.400 | The fact that so many cells and organs and tissues

00:35:27.980 | require glucose in order to function

00:35:30.420 | has led to a situation where you have dedicated

00:35:34.100 | neural machinery, pieces of your brain

00:35:36.460 | that are almost entirely, if not entirely devoted

00:35:39.840 | to seeking out of sugar or foods that contain sugars

00:35:44.700 | and to make sure that you not only seek those out,

00:35:48.300 | but you know where those foods are

00:35:50.080 | and that you ingest more and more and more of them.

00:35:52.620 | And there are two main ways that these neural circuits work.

00:35:55.900 | In fact, we can say that there are two neural circuits

00:35:57.940 | entirely that work in parallel.

00:36:00.100 | And this is a common theme throughout the nervous system

00:36:03.340 | and that's parallel pathways.

00:36:06.100 | Parallel pathways are the ways

00:36:07.760 | that you can distinguish light from dark.

00:36:09.740 | Parallel pathways are the ways that you can distinguish

00:36:11.820 | high-pitched sounds from low-pitched sounds.

00:36:13.620 | Parallel pathways are the ways that you can

00:36:15.660 | flex your muscles versus extend your muscles.

00:36:18.220 | For instance, if you move your wrist

00:36:19.300 | closer to your shoulder, you're flexing your bicep

00:36:22.300 | and you're actually inhibiting,

00:36:23.620 | you're actually preventing the action of your tricep.

00:36:25.340 | If you move your wrist away from your shoulder,

00:36:28.560 | you are essentially using your extensor, your tricep,

00:36:31.500 | and you're inhibiting the activity of your bicep.

00:36:33.740 | So for every function in your body

00:36:35.940 | that you might think is controlled by one brain area

00:36:38.420 | or one neural circuit, almost always,

00:36:41.060 | there are two or more so-called parallel pathways

00:36:43.620 | that ensure that that particular behavior happens.

00:36:47.900 | Now, in the case of sugar consumption,

00:36:51.020 | the two parallel pathways involve one pathway

00:36:54.060 | related to the actual taste and the perception

00:36:57.420 | of sweet tastes that lead not just you,

00:37:01.280 | but every animal that we're aware of

00:37:03.580 | to seek more sweet-containing foods.

00:37:07.160 | The other parallel pathway is related

00:37:10.660 | to the nutritive component of sweet foods,

00:37:14.820 | meaning the degree to which a given food

00:37:17.620 | will raise blood glucose.

00:37:19.540 | I want to repeat that.

00:37:20.700 | One pathway in your brain and body is devoted

00:37:23.580 | to getting you to seek out sweet-tasting things

00:37:26.460 | that you perceive as sweet.

00:37:28.300 | And another parallel pathway is devoted

00:37:31.620 | to getting you to seek out foods

00:37:33.860 | that lead to increases in blood glucose.

00:37:37.160 | It just so happens that the foods

00:37:38.940 | that lead to big increases in blood glucose

00:37:41.660 | typically are associated with that sweet taste.

00:37:44.840 | Now this is distinctly different than the neural pathways

00:37:47.980 | that control seeking of savory foods or salty foods

00:37:51.620 | or spicy foods for that matter, or bitter foods.

00:37:55.180 | The sweet pathway is what we would call hardwired.

00:37:58.800 | It exists, as far as we know,

00:38:00.060 | in every mammal that even exists in fruit flies,

00:38:02.460 | hence fruit fly.

00:38:04.040 | Basically getting sweet stuff into the body

00:38:07.220 | might seem like it has a lot to do with the taste,

00:38:09.380 | but it has just as much to do

00:38:11.780 | with the nutritive components

00:38:13.860 | that sweet-tasting foods carry

00:38:15.940 | and the fact that your nervous system

00:38:17.840 | and so many cells in your brain and body run on glucose.

00:38:22.180 | If you recall earlier, I said, even if you ingest fructose,

00:38:25.520 | fructose can be converted into glucose in the liver.

00:38:28.840 | And I mentioned, of course,

00:38:30.740 | that fructose may actually work directly on the brain.

00:38:32.700 | That's still unclear for humans.

00:38:34.460 | The jury's still out on that.

00:38:35.620 | We will see.

00:38:36.880 | But the fundamental thing to understand here

00:38:39.920 | is that when you think you want a piece of chocolate

00:38:42.420 | or you think you want a piece of cake

00:38:44.120 | or you're craving something sweet,

00:38:46.780 | you are both craving the taste

00:38:48.620 | and your neurons are literally craving

00:38:51.700 | the nutritive components that arrive with that taste.

00:38:55.420 | And simply by understanding that

00:38:57.160 | can allow you to circumvent some of the sugar cravings

00:39:00.940 | that you might otherwise be a complete hopeless victim to.

00:39:05.500 | Also in this episode, I will talk about ways

00:39:07.560 | that you can sort of undermine or short circuit,

00:39:10.220 | these circuits, if you will,

00:39:11.560 | in order to reduce sugar cravings on a regular basis

00:39:14.640 | if that's your goal.

00:39:16.340 | Two parallel pathways.

00:39:18.040 | One of the parallel pathways

00:39:19.280 | has to do with conscious perception.

00:39:21.060 | So animals of all kinds, mice, rats, and humans

00:39:24.540 | will prefer sugary tastes to non-sugary tastes.

00:39:28.700 | When we eat something that tastes sweet,

00:39:33.220 | we register that sweet taste by way of sweet receptors,

00:39:37.840 | literally little ports or portals of neurons

00:39:41.860 | on our tongue and on our palate.

00:39:44.140 | A lot of people don't realize this,

00:39:45.140 | but there are a lot of taste receptors on the soft palate

00:39:48.260 | and around the mouth, so on the sides of the mouth.

00:39:50.660 | So you're actually tasting things, not just with your tongue

00:39:52.780 | but with your entire mouth and your palate.

00:39:54.820 | So when you ingest something sweet,

00:39:57.340 | very quickly there are signals sent

00:39:58.980 | from those neurons in your mouth

00:40:00.860 | to brain areas that cause you to seek out

00:40:04.260 | or at least pay attention to the source

00:40:07.220 | and the abundance of those sweet things.

00:40:08.780 | They literally change your perception.

00:40:11.400 | In fact, there are beautiful neuroimaging studies

00:40:13.940 | that show that when people ingest a sugary drink,

00:40:17.960 | their perception of images of foods change very much

00:40:22.220 | to make those foods appear more appetizing

00:40:24.780 | and not just foods that contain sugar.

00:40:28.300 | Results of those studies do show

00:40:30.020 | that there's an increase, for instance,

00:40:31.420 | in the perception of detail and images of ice cream

00:40:35.380 | after you ingest a sweet drink

00:40:36.940 | or even put like a hard candy into your mouth.

00:40:40.180 | It will make you seek out sugary things more.

00:40:42.220 | It will make sugary things look more appetizing,

00:40:44.160 | but also other foods more appetizing.

00:40:46.900 | So I think it's important that people recognize that fact

00:40:49.020 | that when you have a sweet taste in your mouth

00:40:51.700 | or when you've tasted something sweet within your mouth,

00:40:54.860 | I should say, your perception of food

00:40:57.800 | has immediately shifted.

00:40:59.700 | These are fast neural pathways,

00:41:01.540 | then we'll get into some of the brain structures

00:41:03.000 | in a moment, but these are fast neural pathways

00:41:05.460 | that shift your entire self toward seeking more sugary stuff

00:41:10.460 | and more food generally.

00:41:12.740 | Now, does that mean that you should

00:41:14.180 | never ingest anything sweet?

00:41:15.860 | No, certainly I'm not saying that.

00:41:18.660 | Everyone has to decide for themselves

00:41:20.020 | what the appropriate amount of sugar intake is,

00:41:22.100 | but I find it remarkable when people say,

00:41:24.820 | "Oh, you know, I need to get my sugar fix,"

00:41:26.900 | or, "I need to have my chocolate,"

00:41:28.660 | or, "I need to have a little bit of something

00:41:29.940 | to just kind of take care of that sugar appetite,"

00:41:32.620 | because in taking care of that sugar appetite,

00:41:35.240 | maybe for the very disciplined of you,

00:41:36.700 | you can just have that one piece of chocolate

00:41:38.300 | and it's great and you can relish in it,

00:41:40.140 | but it does shift the way

00:41:42.500 | that you perceive other foods as well.

00:41:44.500 | And the way it does that is through our,

00:41:47.420 | probably if you're a listener to this podcast now,

00:41:49.380 | old friend, but incredible neuromodulator dopamine.

00:41:53.840 | Dopamine is a molecule that is released

00:41:55.700 | from several places in the brain.

00:41:57.740 | There's a so-called mesolimbic reward pathway,

00:42:00.000 | which is a whole set of places in the brain or circuits

00:42:02.500 | designed to get us motivated and craving

00:42:05.200 | and in pursuit of things.

00:42:06.780 | And then of course, there are areas of the brain

00:42:08.620 | that are involved in movement that are linked up

00:42:11.540 | with those areas involved in motivation.

00:42:13.620 | That makes perfect sense.

00:42:14.440 | Why would you have a brain area involved in motivation

00:42:17.220 | if you couldn't actually do something with that motivation?

00:42:19.060 | So the way that your brain is designed

00:42:20.980 | is when there's an increase in dopamine

00:42:22.920 | in the mesolimbic reward pathway,

00:42:24.380 | there are signals sent to an area of the brain

00:42:26.300 | called the striatum.

00:42:27.140 | We're going to spend a little bit of time today

00:42:28.540 | in the striatum.

00:42:29.420 | It's got a dorsal part, meaning an upper part

00:42:31.580 | and a ventral part, which means a lower part.

00:42:33.820 | And the dopamine sent to those areas

00:42:36.180 | places us into modes of action to pursue particular things.

00:42:41.180 | Sugar or sweet tastes, I should say to be more specific,

00:42:46.980 | have an incredibly potent ability

00:42:49.580 | to activate dopamine release

00:42:51.420 | within the mesolimbic reward pathway.

00:42:53.580 | This has been shown over and over and over again.

00:42:57.220 | In animal models and in humans.

00:43:00.160 | This is especially true, I should mention,

00:43:03.460 | through the ingestion of sweet liquids.

00:43:06.700 | Now, this becomes a very important point to us

00:43:08.940 | a little later on when we talk about the proliferation

00:43:12.740 | of sodas and sweet drinks,

00:43:15.300 | and dare I even say non-sugar or diet sodas.

00:43:19.460 | We're going to get into that a little bit later,

00:43:21.320 | perhaps one of the most third rail topics in nutrition.

00:43:25.060 | But when we ingest something sweet,

00:43:28.500 | the perception of that sweet taste increases dopamine

00:43:31.340 | and the mesolimbic reward pathways,

00:43:33.220 | which then are conveyed to pathways for motor behavior.

00:43:36.580 | And in general, place us into modes of focused action

00:43:39.660 | toward getting more of whatever was sweet.

00:43:42.880 | Again, for those of you that are very disciplined,

00:43:45.020 | you can probably eat that one piece of chocolate

00:43:47.740 | and be just fine.

00:43:49.420 | But if you understand the way that dopamine works,

00:43:52.720 | what you'll realize is that when this dopamine pathway

00:43:54.900 | is triggered, it tends to create not the sensation

00:43:59.320 | or the perception of satiety,

00:44:01.300 | of feeling like something is enough,

00:44:03.140 | but rather to produce the sensation of wanting more.

00:44:07.340 | As described in the episode that I hosted

00:44:09.340 | with my phenomenal colleague

00:44:11.420 | from Stanford School of Medicine, Dr. Anna Lemke,

00:44:14.060 | she's an expert on addiction and dopamine pathways.

00:44:16.620 | The dopamine circuits of the brain

00:44:20.220 | have what we call a pleasure pain balance.

00:44:23.460 | And there I'm paraphrasing what Dr. Anna Lemke has said

00:44:27.640 | and has written about in her beautiful book,

00:44:29.440 | "Dopamine Nation."

00:44:30.280 | If you haven't read that book, I highly recommend it.

00:44:32.360 | Whether or not you have issues with addiction

00:44:34.700 | or you know people that do or you don't,

00:44:37.140 | it's an incredibly important read,

00:44:39.120 | especially if you're interested

00:44:40.060 | in understanding motivated behaviors

00:44:41.960 | and ways to channel your behaviors in life

00:44:44.940 | toward healthy motivated behaviors

00:44:46.880 | and make sure that you avoid some of the common pitfalls

00:44:49.740 | that people fall into, not just addiction,

00:44:51.880 | but things like overuse of social media

00:44:55.220 | or wasting time in general, it's a phenomenal book.

00:45:00.100 | In that book and of course, within research articles,

00:45:03.280 | you will find evidence of this so-called pleasure pain

00:45:08.300 | balance that exists within our dopamine circuits.

00:45:11.400 | Nobody has dopamine circuits that allow them to escape

00:45:14.300 | this pleasure pain balance.

00:45:15.580 | And the way this works is that any time

00:45:17.380 | that we engage in a behavior or we ingest something

00:45:21.020 | that increases our levels of dopamine,

00:45:23.220 | there is a subsequent increase in the neural circuits

00:45:27.780 | that control our sense of frustration, pain and lack.

00:45:32.740 | And you can actually notice this phenomenon.

00:45:35.780 | If for instance, you're somebody who really likes chocolate

00:45:39.440 | or you really like something else,

00:45:41.460 | pay attention to the way that you experience indulging

00:45:45.140 | in that thing.

00:45:45.980 | If you eat that piece of chocolate

00:45:49.260 | and you really focus on savoring its amazing taste,

00:45:52.400 | you'll notice that it provides some quenching of your desire

00:45:57.400 | for let's say sweet stuff or chocolate or both.

00:46:01.540 | But right as you stop experiencing that,

00:46:05.200 | right as that chocolate intake tapers off,

00:46:08.420 | as you swallow it down your throat

00:46:09.900 | or you just pause for a second afterwards,

00:46:12.700 | what you'll notice is that your brain and body

00:46:15.540 | actually orient toward wanting more.

00:46:18.980 | And that wanting of more is really the action

00:46:22.300 | of the neural circuits that underlie pain

00:46:24.340 | and are pushing your dopamine levels back down.

00:46:27.860 | And when these circuits go awry, or I should say,

00:46:30.900 | when people fail to control themselves

00:46:34.940 | within the context of that pleasure pain balance,

00:46:37.460 | the typical behavior is to reach for yet another chocolate

00:46:40.340 | or to then look for something that will quench that desire

00:46:44.660 | and get dopamine levels back up.

00:46:46.400 | Now, the way these pleasure pain circuits work

00:46:49.140 | is very diabolical because it turns out

00:46:51.080 | that were you to take another piece of chocolate,

00:46:52.740 | yes, your dopamine levels would go back up,

00:46:54.720 | but not to the same extent

00:46:56.480 | that they did the first bite of chocolate that you had.

00:47:00.660 | In fact, we can say that the longer it's been

00:47:02.800 | since you've indulged in something that you really enjoy

00:47:06.140 | or would like, the greater the dopamine you will experience

00:47:10.840 | when you finally engage in that behavior

00:47:13.480 | or indulge that thing, ingest that thing.

00:47:16.180 | And the greater the dopamine increase,

00:47:18.980 | the greater the subsequent action of those pain circuits.

00:47:22.420 | So this puts you on a very complicated seesaw.

00:47:25.520 | It's a very wobbly precarious state to be in,

00:47:28.540 | which is not to say you shouldn't have a piece of chocolate.

00:47:30.380 | It's just to say that the sweet taste of sweet things,

00:47:35.220 | in particular things that we crave very much

00:47:37.240 | and we wait and wait and wait,

00:47:38.260 | and then we allow ourselves to indulge,

00:47:40.200 | those trigger changes in our neurochemistry

00:47:43.560 | and our neural circuits that place us

00:47:45.260 | in a very vulnerable place

00:47:47.680 | to either want more and more of that thing

00:47:50.180 | or to seek out other ways to fill that kind of emptiness

00:47:55.180 | that we feel or that gap like, oh, I would love more,

00:47:57.800 | but I'm not going to allow myself more.

00:47:59.600 | Now, again, I'm not saying

00:48:01.080 | that you shouldn't pursue pleasurable things.

00:48:03.000 | I mean, this molecule dopamine exists for a reason.

00:48:05.480 | It's the, frankly, because of its involvement

00:48:07.840 | in sex and reproduction,

00:48:09.240 | it's the reason we're all here in the first place

00:48:11.000 | because last time I checked,

00:48:12.120 | the only way any of us got here was one way or another,

00:48:15.640 | sperm met egg and there was conception.

00:48:18.120 | I still believe there are no exceptions to that

00:48:20.860 | that I'm aware of anyways.

00:48:22.120 | That is a process where I should say

00:48:24.980 | the events leading up to that process

00:48:26.540 | typically involve dopamine in one way or another.

00:48:28.520 | There are exceptions to that too, but you get the idea.

00:48:31.140 | These dopamine pathways are not evil, they're not bad,

00:48:33.840 | but once you understand the way they work,

00:48:36.400 | you can leverage them to your advantage

00:48:39.200 | as opposed to them leveraging you to their advantage.

00:48:42.600 | Okay, so when you ingest something sweet,

00:48:45.000 | you perceive that sweet taste

00:48:46.720 | and a cascade ensues within your brain

00:48:49.220 | that makes you want more of the sweet thing.

00:48:51.840 | That's the conscious pathway for sugar perception,

00:48:56.840 | for sweet perception.

00:48:59.580 | Now there's the second pathway.

00:49:01.180 | The second pathway is what's called

00:49:02.680 | the post-ingestive reinforcing properties of sugar,

00:49:06.300 | which is really just a fancy nerd speak way of saying

00:49:09.380 | there are events that happen within your stomach

00:49:11.900 | and below your conscious detection

00:49:14.160 | that are also driving you to seek out sweet tasting things

00:49:18.020 | independent of their taste

00:49:20.140 | and foods that increase blood glucose

00:49:23.240 | independent of their taste.

00:49:24.940 | In order to illustrate the immense power

00:49:26.620 | of these subconscious circuits for sugar seeking,

00:49:29.580 | I'd like to describe an experiment.

00:49:31.160 | And this is just one experiment of many,

00:49:33.460 | of dozens or more experiments done in animal models

00:49:36.100 | and humans, which essentially illustrate the same thing.

00:49:38.140 | And as I described this experiment,

00:49:39.780 | I think you will come to understand

00:49:41.980 | the power of these circuits.

00:49:43.620 | I'll provide a link to this study in the caption.

00:49:47.980 | The first author is Freeman.

00:49:49.860 | The paper was published in Frontiers in Bioscience,

00:49:51.820 | but there have been others papers in Nature Neuroscience,

00:49:55.300 | papers in Neuron, Cell Press Journals, et cetera,

00:49:57.280 | many, many journals, many, many papers.

00:49:59.220 | If subjects are given the choice of drinking plain water

00:50:04.440 | or a sweet tasting fluid,

00:50:06.900 | their preference for the sweet tasting fluid

00:50:08.980 | is much, much higher, right?

00:50:11.540 | Sweet things taste better than plain water,

00:50:14.040 | at least for most people and certainly for animals.

00:50:18.540 | Now, if for instance, you take an animal

00:50:22.460 | which completely lacks sweet receptors,

00:50:25.340 | and you can do this through some molecular genetic tools

00:50:28.720 | and gymnastics.

00:50:30.280 | In the laboratory, we call these knockout mice

00:50:32.080 | where you can knock out a particular receptor

00:50:33.640 | for sweet taste.

00:50:34.480 | You can confirm that there's no perception of sweet things

00:50:37.340 | or at least no preference for sweet things

00:50:39.740 | in those animals.

00:50:40.580 | In humans, you can numb the mouth.

00:50:41.800 | There are other pharmacological ways

00:50:44.100 | that you can eliminate sweet receptors in the mouth.

00:50:46.700 | And by doing that, people will tell you,

00:50:49.980 | no, I can't taste anything sweet.

00:50:51.500 | It's just, you could give them a ice cream.

00:50:54.000 | You could give them pure sucrose.

00:50:55.340 | You give them table sugar,

00:50:56.600 | and they wouldn't be able to perceive it as sweet.

00:50:58.980 | If you eliminate the perception of sweet taste in the mouth

00:51:01.460 | and you offer people or laboratory animals

00:51:05.280 | water versus some sugar containing solution,

00:51:08.440 | you eliminate the preference for the sugary solution,

00:51:12.420 | which tells us that the perception of sweet

00:51:14.480 | is important for the preference for sweet tasting drink.

00:51:19.380 | This is also true for sweet tasting foods,

00:51:21.620 | I should mention.

00:51:23.140 | However, in both animal models and in humans,

00:51:27.020 | after about 15 minutes,

00:51:30.660 | subjects start preferring the sugary water,

00:51:34.140 | even though they can't taste that it is sweeter.

00:51:37.620 | So to repeat that,

00:51:39.100 | if you eliminate the ability to sense sweet,

00:51:41.700 | to perceive sweetness in foods,

00:51:44.360 | then you eliminate the preference for sweet beverages

00:51:47.180 | or sweet foods.

00:51:48.500 | So that's not surprising.

00:51:49.480 | But if you wait about 15 minutes,

00:51:51.460 | the preference for the sweet beverage or the sweet food

00:51:55.300 | comes back.

00:51:56.260 | Now that doesn't mean that they can perceive the sweetness.

00:51:59.120 | In fact, the way these experiments are done is very clever.

00:52:01.920 | You offer people various cups of different things

00:52:04.940 | or different food items,

00:52:06.000 | and then you just look at what they eat more of

00:52:07.640 | or what they prefer to eat more of.

00:52:09.080 | So this experiment is so crucial because what it says

00:52:13.060 | is that the preference for sugar containing foods

00:52:16.960 | is in part due to the sweetness of those foods,

00:52:19.960 | but in part due to something else.

00:52:22.420 | And this something else is what we call

00:52:24.000 | the post-ingestive effect.

00:52:26.100 | And as I mentioned before, it took about 15 minutes.

00:52:28.160 | And you've actually experienced this.

00:52:30.800 | Whether you realize it or not,

00:52:32.220 | this phenomenon of post-ingestive rewarding properties

00:52:35.420 | of sweet foods, meaning what happens in your body

00:52:39.140 | when you ingest something that increases

00:52:40.700 | your blood glucose very much,

00:52:42.420 | has no doubt controlled you from the inside

00:52:46.580 | below your awareness.

00:52:48.220 | This was happening to you and you didn't realize it.

00:52:51.240 | And here's how it works.

00:52:53.300 | We all have neurons within our gut.

00:52:55.860 | These neurons have a name, they are called neuropod cells.

00:52:58.900 | Neuropod cells were famously discovered

00:53:01.180 | by professor Dr. Diego Bajorquez at Duke University.

00:53:05.940 | And these cells respond to, among other things,

00:53:09.860 | to the presence of sugar within the gut.

00:53:12.760 | So when we ingest a sugary food or drink,

00:53:16.120 | or we ingest a food or drink that simply contains

00:53:19.560 | fructose, sucrose, glucose, or some other form of sugar

00:53:23.300 | that later, through metabolism,

00:53:26.380 | will be converted into glucose,

00:53:28.160 | the neuropod cells are able to register the presence

00:53:32.660 | of those sweet or glucose stimulating foods.

00:53:37.220 | And in response to that, send electrical signals,

00:53:41.220 | because electrical signals are the way neurons communicate,

00:53:43.540 | up to the brain via the so-called vagus nerve.

00:53:46.540 | The vagus nerve, of course, being a nerve pathway

00:53:48.700 | famous for its role in relaxation.

00:53:50.620 | That's kind of the assumption out there

00:53:53.040 | that it's always involved in relaxation.

00:53:54.400 | That's not the case.

00:53:55.320 | It's involved in a lot of things besides relaxation.

00:53:57.780 | But nonetheless, these neuropod cells

00:54:00.060 | send electrical signals through a particular highway

00:54:03.700 | within the vagus to the so-called nodose ganglion.

00:54:06.740 | This is a cluster.

00:54:07.760 | A ganglion is just a cluster of neurons.

00:54:09.660 | And then the nodose ganglion sends on information

00:54:12.860 | to the nucleus of the solitary tract.

00:54:16.060 | The nucleus of the solitary tract is an area of the brain

00:54:18.420 | that we're going to talk about extensively today.

00:54:20.620 | It's very important for understanding sugar preference.

00:54:23.940 | These neuropod cells also trigger activation

00:54:28.840 | of dopamine pathways within the mesolimbic reward pathway.

00:54:33.280 | In other words, there are signals conveyed from the gut,

00:54:36.880 | meaning stomach and intestines, to the brain

00:54:39.760 | anytime we ingest sweet foods,

00:54:42.680 | but it has nothing to do with our perception

00:54:45.200 | of them being sweet.

00:54:46.040 | It has everything to do with the fact

00:54:47.640 | that sweetness of food is almost always correlated

00:54:50.700 | with an ability to increase blood glucose.

00:54:54.180 | And the net effect of this is a parallel pathway

00:54:58.140 | by which dopamine is increased further.

00:55:01.200 | Now, the experiment that I described before

00:55:04.300 | of animals or humans ingesting something

00:55:07.500 | that contains sugar,

00:55:08.660 | but not being able to perceive its sweetness,

00:55:10.900 | and yet after a period of time,

00:55:14.060 | still preferring that food or drink to non sugar containing

00:55:18.160 | food or drinks,

00:55:19.280 | even though they can't distinguish their tastes,

00:55:21.720 | is dependent on these neuropod cells and related pathways.

00:55:26.560 | What this means for you is that anytime you eat

00:55:29.580 | something sweet, that substance is actually causing your gut,

00:55:34.580 | your stomach and your intestine,

00:55:36.880 | where to be more precise, I should say,

00:55:39.160 | that food substance is causing the neuropod cells

00:55:43.340 | in your stomach and intestines to send a parallel set

00:55:46.820 | of signals up to your brain saying, eat more of that,

00:55:50.140 | or simply eat more, eat more, eat more,

00:55:52.300 | and preferably eat more sweet foods.

00:55:54.540 | So we've all heard of hidden sugars,

00:55:56.820 | meaning the sugars that manufacturers have put into foods

00:55:59.660 | and disguise them with other flavors.

00:56:01.580 | I talked about this in the episode on salt,

00:56:03.660 | using salt to mask the taste of sweetness

00:56:06.020 | so that people ingest more sugar.

00:56:08.240 | That is not an accident that hidden sugars are often hidden

00:56:11.700 | with salt or with other flavors.

00:56:14.500 | It's done so that people will, meaning you or me,

00:56:17.940 | will want to ingest more of a particular food independent

00:56:22.660 | of how sweet that food tastes.

00:56:24.620 | And in fact, some crackers, for instance, chips,

00:56:27.460 | for instance, you might think, oh, well, you know, chips,

00:56:30.020 | they're not sweet, they're salty and savory.

00:56:33.020 | Again, I'll mention, I love salty, savory foods,

00:56:36.060 | including certain foods.

00:56:37.160 | I love kettle chips, for instance,

00:56:38.460 | I try not to walk by them in the grocery store.

00:56:41.300 | I usually have to eat one bag while I'm in the store

00:56:43.180 | and then another later.

00:56:44.540 | The savory foods are often laden with these hidden sugars

00:56:49.540 | that we can't register as sweetness,

00:56:51.920 | but trigger the neuropod cells,

00:56:53.360 | which then further trigger dopamine,

00:56:54.820 | which make us want more of them.

00:56:56.640 | Now we may be able to resist eating more of them,

00:56:59.300 | but it makes us crave more food in general.

00:57:03.580 | Now we will talk about ways to regulate this pathway,

00:57:07.340 | to sort of intervene in this subconscious pathway.

00:57:10.700 | But for now, I'm hoping that just the understanding

00:57:14.500 | that we all have this pathway,

00:57:15.800 | this is hardwired into our body,

00:57:17.960 | could potentially allow people to better understand

00:57:21.840 | why is it that their cravings are so intense,

00:57:25.420 | that it's not necessarily just about the taste of that food.

00:57:28.440 | And when you consider this in concert with the fact

00:57:33.040 | that we have this dopamine pain pleasure balance,

00:57:36.040 | excuse me, that I referred to earlier,

00:57:38.200 | you start to realize that there are multiple mechanisms

00:57:40.420 | hardwired into us that make it especially hard

00:57:43.260 | to not eat the sweet thing

00:57:45.340 | or to not eat the food that we're craving.

00:57:47.460 | And indeed that's the case.

00:57:48.800 | We have two major accelerators.

00:57:50.720 | It's like a car with two accelerators

00:57:52.980 | and we will talk about the brakes,

00:57:54.820 | but two ways that really get us into forward motion

00:57:58.060 | toward pursuing the consumption of sweet foods.

00:58:01.120 | Now, if it doesn't already seem diabolical enough

00:58:03.340 | that sweet things that we perceive as sweet

00:58:05.920 | make us want to eat more of those because of dopamine

00:58:07.980 | and then send us down this pain pleasure pathway

00:58:11.740 | that I mentioned earlier.

00:58:12.980 | And the fact that we have this subconscious circuit

00:58:15.960 | coming from the neuropod cells in our gut

00:58:18.100 | that are registering the presence of sugar

00:58:20.660 | or glucose increasing foods in our gut

00:58:22.660 | and sending those signals to the brain

00:58:23.780 | for yet more dopamine pain pleasure challenges.

00:58:27.660 | There's a third layer to this whole thing.

00:58:29.980 | And that has to do with how sugar is metabolized

00:58:33.280 | in the brain, or I should say how glucose is used.

00:58:35.780 | Without getting into too much detail,

00:58:38.260 | some of the more beautiful studies of neuroimaging

00:58:41.660 | and evaluating which brain areas are active

00:58:45.040 | when we eat certain foods were done by Dr. Dana Small's lab

00:58:48.780 | at Yale University and in some of her previous work

00:58:52.180 | when she was elsewhere and of course,

00:58:53.780 | by other laboratories too.

00:58:55.100 | And they used an approach called

00:58:56.660 | positron emission tomography.

00:58:58.620 | And they and others have used pet scanning as it's called,

00:59:02.920 | positron emission tomography.

00:59:05.500 | Along with a tool called 2-Deoxyglucose.

00:59:08.460 | 2-Deoxyglucose is actually involved in the procedure

00:59:11.460 | of seeing which brain areas are active

00:59:13.460 | when people eat foods or engage in other types of behaviors.

00:59:16.480 | But the way that 2-Deoxyglucose sometimes shortened 2DG,

00:59:21.300 | the way that it works is to block glucose uptake

00:59:25.500 | from neurons and instead bring along with it

00:59:29.660 | a marker that one can see through imaging.

00:59:32.380 | So in other words,

00:59:33.740 | a tool for looking at what parts of the brain are active

00:59:37.160 | when eating particular foods actually prevents foods

00:59:41.420 | such as sugar from allowing glucose

00:59:44.460 | to get into particular neurons.

00:59:46.900 | Now that might seem like a bad situation.

00:59:48.980 | You'd say, well, wait, you're trying to understand

00:59:50.480 | how sugar works in the brain.

00:59:52.480 | And then you block the ability for sugar glucose

00:59:56.420 | to bind to or be used by these neurons

00:59:59.700 | because of the thing that you're using for the experiment.

01:00:01.500 | Exactly, it's a huge problem.

01:00:03.380 | But it turns out to be a huge problem

01:00:04.620 | that led to a great insight.

01:00:06.060 | And the great insight is this.

01:00:08.460 | The preference for sweet tasting foods and liquids

01:00:11.940 | is actually blocked by 2-Deoxyglucose.

01:00:16.940 | What that means experimentally,

01:00:19.240 | but also in terms of what it means for you and me

01:00:21.520 | in the real world is that there's yet

01:00:23.840 | a third parallel pathway that's related

01:00:27.760 | to the use of blood sugar,

01:00:30.940 | the use of glucose by neurons

01:00:34.060 | that further reinforces our desire to eat more sweet things.

01:00:38.760 | And the preference for sweet foods

01:00:40.860 | can actually be eliminated through 2-Deoxyglucose.

01:00:45.400 | Now I definitely don't want people going out

01:00:48.340 | and consuming 2-Deoxyglucose.

01:00:49.800 | This is a laboratory tool.

01:00:51.020 | It is not something that you should be ingesting.

01:00:54.000 | So don't go look it up and try and get some.

01:00:56.100 | There might be other uses for it, but that's not the point.

01:00:58.140 | The point is that it is the sweet taste of sugary foods.

01:01:03.140 | It is the signals coming from your gut,

01:01:06.840 | from your digestive tract to your brain.

01:01:09.420 | And it's the use of the metabolic consequences

01:01:13.820 | of sugary foods that are acting as a three-pronged push

01:01:18.580 | on your desire to consume more sugary foods.

01:01:21.800 | So this car analogy that I used before

01:01:24.740 | where it's some weird car that has two accelerators,

01:01:27.020 | it actually has three accelerators.

01:01:29.340 | And so with three accelerators all pushing the system hard,

01:01:33.700 | we can say, wow, there must be something really special

01:01:36.740 | about this pathway.

01:01:37.580 | And indeed there is.

01:01:38.660 | This pathway is the quickest source of fuel for the brain

01:01:41.660 | and the rest of the nervous system.

01:01:42.720 | It's the preferred source of fuel

01:01:44.460 | for the brain and nervous system.

01:01:45.900 | And I realized as I say that all the ketonistas

01:01:48.580 | are probably going, no,

01:01:49.500 | actually ketones are the preferred source.

01:01:51.340 | Okay, I acknowledge that there are conditions

01:01:53.920 | under which you can bring your blood glucose very low

01:01:56.100 | and there are reasons to do that.

01:01:57.280 | Actually ketosis has been a terrifically successful treatment

01:02:01.260 | for a lot of forms of epilepsy,

01:02:02.680 | in particular, pediatric epilepsy.

01:02:04.900 | Many people do derive benefit from ketogenic diets,

01:02:08.540 | so I'm not knocking ketogenic diets,

01:02:10.660 | but if you were to look at what neurons normally prefer,

01:02:14.500 | meaning in a typical diet regimen, it would be glucose.

01:02:19.500 | And the fact that fructose

01:02:22.220 | is eventually converted to glucose,

01:02:23.940 | the fact that when we ingest sucrose,

01:02:25.700 | it's eventually converted into a fuel that neurons can use,

01:02:27.840 | that's very much in the glucose pathway.

01:02:30.020 | What you basically arrive at is the fact

01:02:31.940 | that your nervous system is a glucose consuming machine

01:02:34.940 | and you've got at least three pathways

01:02:37.060 | of which I've described that are pushing on your brain

01:02:40.540 | consciously and subconsciously to get you to seek

01:02:43.220 | and consume more sugar.

01:02:45.140 | Now that all sounds like a pretty depressing picture,

01:02:48.060 | at least for those of you that are trying

01:02:49.100 | to reduce your sugar intake.

01:02:50.320 | And of course we can all reduce sugar intake

01:02:53.060 | by way of sheer will.

01:02:54.380 | We can not have those foods at home.

01:02:56.440 | We can restrict ourselves from those,

01:02:58.340 | but there are some things that we all can

01:03:01.300 | and perhaps should do in order to regulate these pathways

01:03:04.980 | such that we don't feel so controlled by them,

01:03:08.380 | but rather that we control their output.

01:03:11.300 | And of course they are us and we are them.

01:03:12.920 | So this gets into all sorts of issues of consciousness

01:03:15.580 | and free will that I certainly don't want to cover

01:03:17.540 | in this episode.

01:03:18.860 | But nonetheless, I think once you understand

01:03:22.740 | that these circuits exist and you understand

01:03:25.600 | that there are simple substitutions and modifications

01:03:29.200 | that one can make to their food intake

01:03:31.540 | that can work within these pathways

01:03:34.780 | and even bypass some of these pathways,

01:03:37.140 | you start to realize that you have a lot more control

01:03:39.380 | over sugar intake and sugar appetite

01:03:42.600 | than you previously thought.

01:03:44.140 | Now, many of you have heard of the so-called glycemic index.

01:03:46.540 | The glycemic index is a measure

01:03:48.340 | of how quickly blood sugar rises

01:03:49.960 | after ingesting particular foods, and very broadly speaking,

01:03:53.940 | we can say that there are low glycemic index foods

01:03:56.940 | of less than 55, typically is the measurement,

01:04:00.040 | or medium glycemic index foods,

01:04:01.900 | which go from about 55 to 69,

01:04:03.900 | and then so-called high glycemic foods, which are above 70.

01:04:06.860 | And of course there's additional nuance

01:04:08.900 | related to glycemic load

01:04:10.900 | and many more features of the glycemic index.

01:04:14.940 | A couple of things to understand

01:04:16.180 | about how the glycemic index is measured.

01:04:18.720 | And then I'd like to just briefly talk

01:04:20.740 | about how the glycemic index can be leveraged

01:04:23.860 | to short circuit some of the neural circuits

01:04:27.340 | that would otherwise lead us to crave

01:04:29.740 | and perhaps even ingest sugary foods.

01:04:33.060 | First of all, measurements of glycemic indices of food

01:04:37.740 | are typically made by having people ingest those foods

01:04:40.460 | in isolation.

01:04:41.780 | And in general, we can say that anytime we ingest fiber

01:04:46.420 | and or fat lipids along with a particular food,

01:04:49.840 | it will reduce the glycemic index of that particular food,

01:04:53.840 | either the absolute level of blood glucose

01:04:57.340 | that a particular food causes

01:05:00.100 | or the rate at which that elevation in blood glucose occurs.

01:05:05.060 | And this is why there are some seemingly paradoxical aspects

01:05:09.240 | to sweet stuff in terms of the glycemic index.

01:05:11.400 | For instance, ice cream has a lower glycemic index

01:05:14.480 | provided it's ice cream that includes fat,

01:05:16.440 | which I hope it would

01:05:17.280 | 'cause that's the good tasting ice cream in my opinion,

01:05:19.400 | compared to something like mangoes or table sugar, right?

01:05:23.120 | So the glycemic index is not something to hold wholly

01:05:27.160 | in most cases because most people

01:05:28.940 | are not ingesting foods in isolation.

01:05:31.000 | And there's actually a lot of argument

01:05:32.480 | as to whether or not the glycemic index

01:05:33.920 | is really as vital as some people claim.

01:05:38.160 | There's also the context in which you ingest

01:05:40.560 | particular foods.

01:05:41.400 | As I mentioned earlier,

01:05:42.620 | after I do hard training of any kind,

01:05:45.040 | meaning training that ought to deplete glycogen,

01:05:46.860 | so hard resistance training,

01:05:48.040 | I actually make it a point

01:05:49.360 | to ingest some very sweet high glycemic foods like a mango.

01:05:53.260 | I'll also ingest some starches

01:05:54.680 | 'cause I'm trying to replenish glycogen.

01:05:56.040 | I'm also trying to spike my blood sugar a little bit

01:05:58.740 | because that can be advantageous

01:06:00.020 | in terms of certain strength

01:06:01.160 | and hypertrophy protocols, et cetera.

01:06:03.160 | But most of the time I'm avoiding these high glycemic foods

01:06:05.440 | and high sugar foods.

01:06:06.280 | I should point that out.

01:06:07.560 | Now, why am I telling you about the glycemic index?

01:06:09.680 | Well, if we zoom out and take our perspective

01:06:13.260 | on all of this discussion about the glycemic index

01:06:15.640 | through the lens of the nervous system,

01:06:18.060 | and we remind ourselves that neurons

01:06:20.340 | prefer glucose for energy,

01:06:22.220 | and that all sweet things

01:06:24.200 | or things that we perceive as sweet,

01:06:25.620 | but also sweet things that are ingested

01:06:27.860 | and registered by those neuro pod cells in our gut

01:06:30.500 | trigger the release of dopamine

01:06:32.400 | and trigger these neural circuits

01:06:34.360 | to make us want to eat more of these foods,

01:06:36.960 | what we start to realize is that a sharp rise

01:06:40.000 | in blood glucose or a very high degree of elevation

01:06:43.840 | in blood glucose is going to be a much more potent signal

01:06:47.860 | than will a more moderate rise in blood glucose

01:06:51.600 | or a slower rise in blood glucose.

01:06:54.840 | So if we think about the analogy of three accelerators,

01:06:58.200 | meaning three parallel neural circuits,

01:07:00.080 | all essentially there to get us to seek out

01:07:03.240 | and consume more sweet tasting and sugary foods.

01:07:07.220 | Well, then the glycemic index is sort of our measurement

01:07:10.960 | of how hard we are pushing down

01:07:12.920 | or how fast we are pushing down on those three accelerators.

01:07:16.440 | And so those of you that are trying to reduce sugar intake,

01:07:19.520 | and you want to do that through an understanding

01:07:22.000 | of how these neural circuits work,

01:07:23.520 | and you want to short circuit some of the dopamine release

01:07:26.580 | that's caused by ingesting sugary foods,

01:07:30.100 | it can be advantageous to ingest sweet foods,

01:07:35.100 | either alone or in combination with foods

01:07:38.940 | that reduce glycemic index or reduce glycemic load.

01:07:42.860 | So that might mean making different food choices.

01:07:45.980 | So paying attention to sweet tasting foods

01:07:48.760 | that can satisfy sugar cravings, but do not have as steep,

01:07:52.860 | or I should say, do not cause

01:07:54.300 | a steeper rise in blood sugar,

01:07:55.980 | or it could mean consuming other foods

01:07:59.220 | along with sweet foods in order to reduce the glycemic index

01:08:03.220 | and thereby slow or blunt the release of dopamine.

01:08:07.320 | You might think, well, why would I want to do that?

01:08:09.260 | I want the maximum dopamine output

01:08:11.640 | in response to a given sweet food.

01:08:13.260 | I don't just want the level 10,

01:08:15.440 | I want the level 100 output of dopamine,

01:08:18.040 | but you really don't because of the pleasure pain balance

01:08:20.560 | that dopamine causes.

01:08:21.660 | And in fact, if we consider some of the non-food substances

01:08:24.940 | that really push hard on these dopamine pathways,

01:08:27.260 | we can come up with a somewhat sinister,

01:08:29.840 | but nonetheless appropriate analogy.

01:08:31.820 | The drug cocaine causes very robust,

01:08:36.100 | potent increases in dopamine within the brain

01:08:39.480 | and typically causes people to want to ingest more cocaine

01:08:42.860 | because of those sharp increases in dopamine.

01:08:47.240 | But within the category of the drug cocaine,

01:08:50.100 | there are various modes of ingestion.

01:08:52.080 | Some people inhale it,

01:08:53.680 | some people will inject it intravenously,

01:08:57.480 | some people will smoke it.

01:08:58.860 | And those different forms of taking cocaine

01:09:02.080 | actually impact the dopamine circuits differently.

01:09:04.880 | And it turns out that crack cocaine,

01:09:07.640 | the smokable form of cocaine rock,

01:09:11.220 | increases dopamine to a very high degree,

01:09:13.900 | but also very, very quickly.

01:09:16.220 | And it is the sharp rise in dopamine over time,

01:09:20.520 | not so much the absolute level of dopamine

01:09:23.360 | that makes crack cocaine so absolutely addictive.

01:09:27.400 | So sometimes you'll hear, sugar is like crack.

01:09:30.360 | Well, and that's getting a little extreme

01:09:32.100 | because even though I don't think the measurements

01:09:34.020 | have been done in the same experiment,

01:09:36.060 | I think it's reasonable to think that

01:09:38.120 | the absolute level of dopamine caused by ingesting sugar,

01:09:42.020 | at least for most people,

01:09:42.860 | is not going to be as high as the absolute level

01:09:45.500 | of dopamine caused by smoking crack.

01:09:48.360 | Of course, it goes without saying,

01:09:49.460 | please don't do cocaine in any form, by the way.

01:09:52.840 | It is appropriate to say that the rate of dopamine increase

01:09:57.840 | over time has a profound effect on how people will,

01:10:03.840 | and if people will, go on to want to pursue more

01:10:07.520 | of what caused that increase in dopamine.

01:10:10.120 | So what I'm basically saying is,

01:10:11.720 | if you're going to ingest sweet foods

01:10:14.080 | in order to satisfy a sweet craving,

01:10:17.020 | ingesting sweet foods for which the glycemic index

01:10:21.600 | is lower or in which you've adjusted

01:10:24.600 | those glycemic index foods through the co-ingestion of fiber

01:10:28.120 | or maybe fat might be beneficial.

01:10:31.560 | So is this justification for putting peanut butter

01:10:34.440 | on that piece of chocolate or for having a bowl of ice cream

01:10:38.200 | along with the mango that you're craving?

01:10:41.160 | In some sense, yes.

01:10:42.440 | However, there's also the issue of how sweet

01:10:46.360 | and how delicious something tastes.

01:10:48.280 | Highly palatable foods, absolutely delicious foods,

01:10:51.680 | trigger that one neural circuit, that one accelerator

01:10:55.640 | that we're talking about in terms of our analogy

01:10:57.300 | of three accelerators.

01:10:58.900 | And the more delicious something tastes within our mouth,

01:11:01.800 | the further increase in dopamine.

01:11:04.620 | So if you really wanted to adjust your sugar cravings

01:11:07.860 | and you really still want to ingest some sugary foods,

01:11:12.580 | you probably would be better off combining fiber

01:11:15.500 | with that sugary or sweet food.

01:11:17.960 | Now, I do realize that it's somewhat unusual

01:11:19.900 | and you probably get some strange stares

01:11:22.240 | if you decided to consume broccoli, for instance,

01:11:25.000 | along with your chocolate or with another dessert

01:11:27.760 | that would otherwise cause a steep increase in blood sugar

01:11:30.960 | and has a high glycemic index.

01:11:32.640 | But nonetheless, if your goal is to blunt

01:11:35.880 | your sugar cravings, what you really need to do

01:11:38.380 | is blunt that dopamine increase.

01:11:40.320 | So what we're really talking about here

01:11:42.240 | is trying to reduce the dopamine signal

01:11:45.120 | that is the consequence of ingesting sweet foods.

01:11:47.720 | And we're talking about doing that

01:11:49.040 | through these different parallel pathways,

01:11:50.820 | not just by preventing sweet taste,

01:11:52.920 | but also by preventing the post-ingestive effects

01:11:55.760 | of sweet foods.

01:11:57.720 | And of course, the backdrop to all of this

01:12:00.620 | is that most of us, again, most of us, not all of us,

01:12:03.240 | should probably be ingesting fewer refined sugars.

01:12:06.760 | Certainly there are exceptions to that,

01:12:09.600 | but I think the bulk of data point to the fact

01:12:13.020 | that ingesting these highly palatable,

01:12:15.560 | certainly highly palatable, highly processed foods

01:12:17.840 | or foods that contain a lot of high fructose corn syrup

01:12:21.320 | can be really deleterious to our health, especially in kids.

01:12:24.760 | And I'm not going to cite off a bunch of statistics.

01:12:27.560 | You've all heard them before that, you know,

01:12:29.400 | for hundreds of years, we ingested, you know,

01:12:32.800 | the equivalent of a few cups or pounds of sugar per year.

01:12:36.280 | And, you know, now people are ingesting hundreds of pounds

01:12:38.820 | of sugar per year.

01:12:40.300 | The major culprit always seems to be sugary drinks,

01:12:43.680 | meaning soft drinks.

01:12:44.640 | And I think indeed that's the case.

01:12:46.440 | I do want to point out the incredible work

01:12:49.640 | of Dr. Robert Lustig, who's a pediatric endocrinologist

01:12:52.800 | at University of California, San Francisco,

01:12:54.840 | who was really early in the game of voicing the dangers

01:12:58.200 | of so-called hidden sugars and highly processed foods.

01:13:00.520 | There are other people, of course, now talking about this.

01:13:03.760 | His laboratory has done important work showing,

01:13:06.580 | for instance, that if high fructose corn syrup

01:13:10.100 | or even just fructose is replaced with glucose,

01:13:13.100 | even if the same number of calories is ingested,

01:13:16.660 | that there are important,

01:13:19.260 | meaning significant reductions in type two diabetes,

01:13:23.380 | some of the metabolic syndromes associated

01:13:25.140 | with high fructose corn syrup and on and on and on.

01:13:28.000 | And of course there are other culprits in type two diabetes.

01:13:30.640 | There are other factors that are going to lead to obesity,

01:13:33.860 | but I think the work from Lustig and others

01:13:36.400 | has really illustrated that we should all be trying

01:13:39.160 | to reduce our intake of highly refined sugars

01:13:42.380 | and high fructose corn syrup,

01:13:44.240 | and certainly trying to reduce our intake

01:13:46.620 | of very sugary drinks, not just soft drinks,

01:13:51.240 | but also fruit juices that contain a lot of sugar.

01:13:53.920 | Now, even for people that are of healthy weight

01:13:56.060 | and who don't have metabolic syndromes,

01:13:58.320 | there may be an additional reason

01:14:00.160 | to not want to ingest very sweet foods

01:14:03.640 | and highly refined sugars.

01:14:05.200 | And this has to do with a new and emerging area

01:14:08.160 | of nutrition neuroscience.

01:14:11.920 | And I want to point out that these are new data, right?

01:14:14.660 | So it's not a lock.

01:14:15.640 | The double-blind placebo-controlled studies

01:14:17.560 | in large populations have not been finished.

01:14:20.280 | So I want to make sure that that's clear,

01:14:23.380 | but I also want to make clear

01:14:25.320 | what some of the really exciting data

01:14:27.340 | coming from Dana Small's lab at Yale

01:14:29.720 | and from other laboratories are showing.

01:14:32.000 | And this has to do with what's called

01:14:33.880 | conditioned taste preference.

01:14:36.040 | Using a kind of Pavlovian paradigm,

01:14:38.620 | what they do is they have people,

01:14:40.920 | and these studies were done in people,

01:14:42.760 | ingest maltodextrin, which increases blood glucose.

01:14:45.920 | Doesn't have much flavor,

01:14:46.960 | but even if it does have a little bit of subtle flavor,

01:14:49.760 | the maltodextrin is cloaked by some other flavor.

01:14:53.640 | And by cloaking it with that other flavor

01:14:56.280 | or pairing it with that other flavor,

01:14:57.900 | what they find is that over time,

01:14:59.840 | because the maltodextrin increases blood glucose

01:15:02.340 | and they're ingesting a particular flavor

01:15:04.000 | along with that maltodextrin,

01:15:06.000 | they can then remove the maltodextrin

01:15:09.260 | and the flavor will induce an increase in insulin.

01:15:13.800 | The increase in insulin, of course,

01:15:15.320 | is the consequence of the fact

01:15:16.960 | that anytime there's a rise in blood glucose,

01:15:18.740 | provided the person isn't diabetic,

01:15:20.380 | there's a parallel increase in insulin.

01:15:25.220 | Now, this is very interesting

01:15:26.880 | because what it says is, well, at a first pass,

01:15:29.500 | it says that we are very Pavlovian

01:15:31.600 | in terms of our physiological responses to foods

01:15:34.880 | and particular flavors come to be associated

01:15:37.620 | with particular patterns of blood glucose increase

01:15:41.220 | and hence patterns of insulin increase

01:15:44.280 | because of course insulin manages glucose in the bloodstream,

01:15:47.240 | as I mentioned earlier.

01:15:48.440 | This also has implications

01:15:51.400 | for understanding things like artificial sweeteners.

01:15:53.840 | And here, I want to highlight

01:15:54.720 | that this is still very controversial work,

01:15:57.360 | needs more data, but nonetheless,

01:15:58.880 | I'd like to share it with you for consideration.

01:16:01.280 | The small laboratory has done studies in humans,

01:16:06.620 | both in adults and in children,

01:16:08.600 | showing that if the flavor of artificial sweeteners

01:16:13.020 | is paired with maltodextrin,

01:16:14.800 | and then the maltodextrin is removed,

01:16:17.400 | that the artificial sweetener taste itself

01:16:20.880 | can subsequently increase insulin in the bloodstream.

01:16:24.440 | In other words, taking something that increases blood sugar,

01:16:29.000 | attaching a flavor experience to that,

01:16:31.880 | having children or adults ingest that thing

01:16:36.120 | allows the nervous system to associate that flavor

01:16:39.680 | with that increase in blood glucose,

01:16:41.540 | but then you can remove the glucose increasing substance

01:16:45.140 | and the flavor alone will increase insulin

01:16:47.580 | because insulin typically follows blood glucose.

01:16:50.160 | So this is a conditioning effect.

01:16:52.000 | Now, the reason these data are controversial

01:16:53.960 | is several fold.

01:16:54.800 | First of all, the landscape around,

01:16:58.180 | the discussion around artificial sweeteners

01:17:01.220 | is definitely what I would call a barbed wire topic.

01:17:04.640 | And I want to preface what I'm about to say next

01:17:06.560 | by saying I actually ingest artificial sweeteners.

01:17:09.220 | I will have the occasional diet soda, not every day,

01:17:12.280 | maybe, I don't know, once or twice a month.

01:17:13.980 | I don't particularly like the taste,

01:17:15.080 | but I'll do it just 'cause it's around

01:17:16.480 | and I want some caffeine and I like the carbonation

01:17:18.880 | if I'm on a plane or something.

01:17:20.560 | I do ingest plant-based non-caloric sweeteners.

01:17:24.480 | To my knowledge, there have not been high quality studies

01:17:27.440 | of plant-based non-caloric sweeteners

01:17:29.480 | in the context that I'm referring to here, okay?

01:17:32.440 | Nonetheless, these studies show that,

01:17:34.440 | particular flavors can be conditioned

01:17:36.880 | to cause an insulin increase.

01:17:38.800 | And the flavor associated

01:17:40.800 | with certain artificial sweeteners

01:17:42.600 | is included in that category of flavors

01:17:46.160 | that can induce insulin even in the absence

01:17:48.800 | of something that can increase blood glucose.

01:17:50.660 | Now, the simple takeaway from these studies

01:17:54.620 | would be the following.

01:17:56.520 | And this is actually the one interpretation

01:17:58.680 | that Dana Small has offered to her data,

01:18:00.880 | but she offers other interpretations as well.

01:18:02.920 | One interpretation is that if people

01:18:05.760 | are going to ingest artificial sweeteners

01:18:08.440 | and they do that along with foods

01:18:10.680 | that very sharply increase blood glucose,

01:18:14.100 | then there is the potential, highlight,

01:18:16.640 | the potential for those same artificial sweeteners

01:18:19.920 | to increase insulin even in the absence of food.

01:18:24.720 | In other words, let's just draw the scenario out

01:18:26.600 | in the real world.

01:18:28.820 | You're having a diet soda along with a cheeseburger and fries.

01:18:33.820 | You do that every day for lunch, okay?

01:18:37.880 | Somewhat extreme example, but natural world example.

01:18:39.940 | You do that every day for lunch

01:18:41.040 | and then you just have a diet soda alone.

01:18:43.500 | The extreme interpretation of the data

01:18:47.660 | that they've collected says, well,

01:18:49.340 | that diet soda alone will increase insulin

01:18:51.420 | even though there's no increase in blood glucose

01:18:53.860 | because you have an ingested food with it

01:18:55.020 | because you conditioned that taste of artificial sweetener

01:18:58.580 | to the experience of a rise in glucose and hence insulin.

01:19:02.180 | Now, the counter argument to this would be,

01:19:04.780 | well, that's a very unusual situation.

01:19:06.740 | Maltodextrin causes big increases in blood glucose.

01:19:10.060 | So that's not really a fair experiment

01:19:12.740 | or it's not a natural world experiment.

01:19:14.340 | And I think that's a decent assessment.

01:19:16.280 | Although I will point out that one of the reasons

01:19:19.260 | why this study is so controversial

01:19:21.760 | or why these data are so controversial

01:19:23.400 | is that the experiment actually had to be stopped.

01:19:26.200 | And particularly the experiment in children had to be stopped

01:19:29.040 | because the changes in insulin that were observed

01:19:33.520 | early in the study were so detrimental

01:19:36.480 | that the institutional review board quite appropriately said,

01:19:40.040 | we can't do this to these kids.

01:19:41.300 | They're experiencing these odd shifts in insulin

01:19:44.600 | that are not healthy for them

01:19:46.720 | when they're just ingesting artificial sweeteners

01:19:48.760 | in the absence of these glucose increasing foods.

01:19:51.800 | So once again, I do ingest artificial sweeteners.

01:19:55.040 | I'm not saying that they are dangerous.

01:19:56.280 | I'm not saying that they are not dangerous.

01:19:58.620 | I'm saying that you have to decide for yourself.

01:20:00.900 | In previous episodes,

01:20:01.820 | I've highlighted that artificial sweeteners have been shown

01:20:05.580 | in studies of animals that when given in very high doses,

01:20:09.880 | sucralose in particular,

01:20:11.880 | there can be fairly robust disruption to the gut microbiome,

01:20:16.400 | which is vital for immune health and brain health,

01:20:18.520 | et cetera, et cetera.

01:20:20.120 | But thus far our knowledge of how artificial sweeteners

01:20:24.040 | negatively impacts or positively impacts, I should say,

01:20:26.760 | the microbiome and other deleterious effects on the body

01:20:31.760 | has mainly been explored in animal studies.

01:20:36.080 | Again, the work by Dana Small has been done in humans.

01:20:39.360 | There's some parallel work by others in animal models.

01:20:42.000 | I bring it up today to illustrate the following point.

01:20:45.540 | Normally we have a pathway

01:20:49.240 | that we don't have to condition at all.

01:20:51.000 | It's there from birth whereby ingestion of sweet foods

01:20:55.120 | causes increases in dopamine.

01:20:57.600 | And there are parallel pathways by which neurons in our gut

01:21:02.000 | and elsewhere in our body

01:21:03.520 | trigger further increases in dopamine.

01:21:05.820 | So there's no need for a conditioned response

01:21:10.240 | or to become Pavlovian about this, right?

01:21:12.600 | You're hardwired to want to eat sweet things

01:21:15.540 | by at least two and probably three parallel pathways.

01:21:18.580 | Now, the work from Dana Small's lab and others

01:21:21.600 | that have illustrated this conditioned flavor preference,

01:21:24.860 | I think beautifully show that any flavor

01:21:27.980 | that's associated with a glucose spike

01:21:30.640 | or a long sustained increase in glucose

01:21:34.340 | can also be conditioned.

01:21:35.900 | In other words, the circuits for dopamine

01:21:38.020 | that reinforce the desire to eat particular things

01:21:40.540 | is not unique to the sugar pathway.

01:21:42.380 | And this is one of the reasons I believe

01:21:45.460 | why ingestion of sweet foods

01:21:47.820 | doesn't just lead us to want to eat more sweet foods.

01:21:50.580 | I think that is absolutely clear

01:21:52.200 | based on animal data and on human data.

01:21:54.540 | I think that's robust.

01:21:55.500 | It's actually the stuff of textbooks now.

01:21:57.540 | But in addition, ingesting sweet foods

01:22:01.820 | and or foods that raise blood glucose,

01:22:03.940 | but that we don't perceive as sweet.

01:22:05.780 | So for instance, foods with hidden sugars,

01:22:08.300 | sugars that have been masked by salty or spicy tastes

01:22:10.980 | increases our desire for glucose elevating foods

01:22:14.900 | and food generally.

01:22:16.900 | I think that's the only logical interpretation of the data

01:22:20.060 | that I can arrive at.

01:22:21.580 | So for people that struggle with regulating their appetite

01:22:23.800 | or with regulating their sugar appetite,

01:22:26.220 | I think the understanding of conditioned flavor preference

01:22:29.100 | while a little bit complicated ought to be useful

01:22:32.100 | in trying to navigate reducing sugar cravings

01:22:34.700 | and sugar intake.

01:22:35.780 | As a segue into tools to control sugar intake

01:22:38.380 | as a means to both regulate sugar intake itself,

01:22:42.520 | as well as food intake overall

01:22:44.380 | and steer us towards healthier choices,

01:22:47.240 | I'd like to talk about some of the special populations

01:22:50.400 | out there that might want to be especially wary

01:22:52.880 | of having a dysregulated sugar appetite system.

01:22:57.680 | And the group I'm referring to specifically

01:23:00.000 | are those with attention deficit hyperactivity disorder,

01:23:03.200 | or I should say, and or people who have issues

01:23:06.960 | with focus and attention generally.

01:23:08.960 | And I think more and more nowadays,

01:23:10.280 | I'm hearing that people are having a hard time focusing.

01:23:13.040 | This probably has something to do with our interactions

01:23:15.980 | with electronic devices.

01:23:17.240 | As I always say, if a picture is worth a thousand words,

01:23:19.600 | a movie is worth a million pictures.

01:23:22.520 | And the fact that we can access so many movies

01:23:25.200 | in just by scrolling with our thumb

01:23:27.140 | is something that the nervous system

01:23:28.240 | has just never contended with before in human history.

01:23:30.780 | I'm confident in that.

01:23:32.320 | And it's not that it can't deal with it.

01:23:34.240 | The question is what's the trade-off?

01:23:36.320 | What are the consequences of that?

01:23:38.620 | So attention and ability to focus is obviously key

01:23:42.620 | to success in school, success in relationships,

01:23:45.080 | success in the workplace, and success in life.

01:23:48.360 | We could probably even go so far as to say

01:23:50.140 | one's ability to succeed in anything

01:23:53.420 | is proportional to one's ability to focus

01:23:55.600 | and then deliberately defocus

01:23:57.280 | when the time comes to defocus, right?

01:23:58.940 | 'Cause we all need rest and we need to disengage

01:24:00.820 | and then re-engage.

01:24:01.740 | If you look at the sum total of the meta-analyses

01:24:07.880 | and the clinical data on ADHD and nutrition,

01:24:12.100 | you arrive at a pretty clear answer,

01:24:14.160 | which is that sugar consumption,

01:24:16.160 | in particular highly refined sugars,

01:24:18.020 | is just not good for people with ADHD

01:24:21.080 | or with attentional issues.

01:24:22.780 | Now, as I say that, I also want you to recall

01:24:25.420 | the earlier study that I referred to

01:24:27.140 | whereby the tuning of neurons in the brain

01:24:29.420 | is highly dependent on glucose.

01:24:30.980 | So this doesn't mean consuming no glucose

01:24:34.080 | is going to be a good idea.

01:24:35.100 | It doesn't mean that the ketogenic diet

01:24:37.560 | is necessarily the best diet for ADHD,

01:24:40.340 | although there are some people pursuing that

01:24:42.500 | and exploring that, and we'll do yet another episode

01:24:45.120 | on ADHD at some point that goes a little bit deeper

01:24:47.260 | into that because there's some new data.

01:24:48.860 | I did do a very long and fairly extensive episode on ADHD.

01:24:53.860 | You're welcome to look that up if you like in our archive,

01:24:57.860 | excuse me, in our archive at hubermanlab.com.

01:25:01.060 | It's all timestamped.

01:25:03.480 | So, you know, because a number of people said,

01:25:05.720 | oh, you know, it's an episode on ADHD

01:25:07.440 | and you made it two and a half hours long.

01:25:08.680 | Yes, we did because we wanted it to be as comprehensive

01:25:11.640 | as we could at the time, but it is timestamps.

01:25:14.220 | You can just jump to the particular topics of interest

01:25:16.160 | in their short little cassettes there.

01:25:18.480 | Now, if you'd like to know upon what I'm basing

01:25:21.220 | the statement that sugar consumption

01:25:23.900 | and highly refined sugar consumption

01:25:25.800 | is potentially bad for ADHD,

01:25:28.300 | basing this mainly on the conclusions of a really nice paper

01:25:33.020 | that the title of the paper is Sugar Consumption,

01:25:35.940 | Sugar Sweetened Beverages

01:25:37.280 | and Attention Deficit Hyperactivity Disorder,

01:25:39.320 | A Systematic Review and Meta-analysis.

01:25:41.220 | And this is a paper and we'll put a link to this

01:25:44.380 | in the caption.

01:25:45.600 | This was publishing complimentary therapies in medicine,

01:25:48.720 | which is a bit of an atypical journal in some sense,

01:25:51.000 | but I really like this meta-analysis.

01:25:53.400 | The sum total of this meta-analysis is really that when,

01:25:58.400 | especially kids get beyond four sugary drinks per week,

01:26:04.220 | so four sodas of, you know, typical 12 ounce soda,

01:26:07.100 | when they get past four 12 ounce sugary sodas,

01:26:10.100 | they didn't, as far as I know,

01:26:11.500 | look at artificial sweetened sodas,

01:26:14.140 | that's when you start to see a shift

01:26:16.320 | towards more negative outcomes,

01:26:18.900 | more symptoms of existing ADHD.

01:26:21.940 | Now, where the controversy comes in

01:26:24.020 | is whether or not sugar consumption

01:26:26.180 | can actually trigger or cause ADHD.

01:26:29.020 | And I don't think we can conclude that at all at this time.

01:26:32.140 | And this review, if you decide to check it out,

01:26:35.260 | review slash meta-analysis, I should say,

01:26:37.260 | if you decide to check it out,

01:26:38.420 | goes into some of the nuance around that.

01:26:40.820 | What's also interesting in terms of ADHD and sugar intake,

01:26:45.260 | and probably has relevance to all of us,

01:26:47.120 | is that they also cover some of the interesting data

01:26:49.620 | showing that supplementation with omega-3 fatty acids

01:26:53.980 | can actually be beneficial

01:26:55.860 | for people and particular kids with ADHD.

01:26:59.320 | I've talked before about the utility of omega-3s

01:27:02.420 | that's been shown in various studies

01:27:03.800 | that have compared omega-3 fatty acid intake

01:27:06.420 | to say prescription antidepressants, like SSRIs,

01:27:09.860 | like Prozac, Zoloft, and similar, fluoxetine.

01:27:12.740 | And the results of those studies are pretty clear,

01:27:15.140 | at least to me, that provided that one gets

01:27:18.380 | at least one gram of EPA essential fatty acids,

01:27:21.620 | so it's not just getting one gram per day,

01:27:23.380 | but one or more grams per day

01:27:25.860 | of the EPA form of essential fatty acid

01:27:28.520 | can rival some prescription antidepressants

01:27:30.820 | and/or decrease the amount of antidepressants

01:27:35.180 | that's required to take, which for a lot of people

01:27:37.040 | can be a very useful thing

01:27:38.920 | because of the side effect profile

01:27:40.400 | of many of those antidepressants.

01:27:41.540 | Of course, talk to your psychiatrist, talk to your doctor,

01:27:43.520 | but the omega-3s are no doubt powerful.

01:27:46.260 | And then of course, there's a whole story

01:27:47.460 | about omega-3s and heart health.

01:27:49.500 | And of course, like anything else,

01:27:51.100 | there's some controversy around omega-3s,

01:27:52.780 | but I think the data are clear enough to me

01:27:54.580 | around mood and cardiovascular health

01:27:56.020 | that certainly I personally ingest them,

01:27:57.740 | but as always, I always say,

01:27:59.780 | anytime you're going to add or remove anything

01:28:01.980 | from your nutrition, supplementation, exercise,

01:28:03.980 | or otherwise your lifestyle,

01:28:06.280 | definitely consult with a board-certified physician.

01:28:08.260 | I don't just say that to protect me.

01:28:09.540 | I say that to protect you.

01:28:11.320 | You are responsible for your health ultimately.

01:28:13.860 | So omega-3 supplementation has been shown

01:28:16.380 | to be beneficial for ADHD.

01:28:18.380 | Why am I talking about this in the context of an episode

01:28:20.640 | on sugar and the nervous system?

01:28:22.300 | Well, if you remember those neuropod cells,

01:28:24.940 | those cells in your gut that respond to sugar

01:28:27.100 | and send signals up to the brain

01:28:28.620 | to cause the release of dopamine,

01:28:30.380 | well, it turns out that neuropod cells also respond to

01:28:34.540 | amino acids and to fatty acids,

01:28:37.380 | in particular, essential fatty acids.

01:28:40.260 | So the cells that we call neuropod cells have three jobs.

01:28:45.260 | One is to detect levels of sugar in the gut.

01:28:47.940 | The other is to detect levels of amino acids

01:28:51.060 | and to detect levels of particular essential fatty acids

01:28:54.740 | and communicate that information to the brain.

01:28:58.340 | And I should point out,

01:28:59.180 | when I say communicate that information,

01:29:00.540 | they're not actually saying,

01:29:01.380 | "Hey, there's amino acids here,"

01:29:02.740 | or, "Hey, there's sugar here,"

01:29:04.500 | or, "Hey, there's essential fatty acids,"

01:29:06.100 | because the language of these cells is somewhat generic.

01:29:09.140 | It's just the firing of electrical potentials.

01:29:11.700 | But that's the key point.

01:29:12.740 | It's generic and all three, or any of those three,

01:29:16.540 | sugar, essential fatty acids, or amino acids

01:29:19.460 | will trigger these neurons to signal to the brain

01:29:22.360 | to increase dopamine.

01:29:23.220 | And it is not coincidental

01:29:24.940 | that omega-3 fatty acid supplementation

01:29:27.460 | can help ameliorate some of the symptoms of ADHD

01:29:30.420 | by way of presumably increasing dopamine

01:29:34.940 | in this neuropod to dopamine pathway

01:29:37.140 | that we talked about earlier.

01:29:39.180 | The whole thing has a very nice logical structure to it

01:29:41.900 | and points to, yet again,

01:29:43.860 | the immense value of bringing the proper amounts,

01:29:47.580 | maybe even supplementing the proper amounts

01:29:49.540 | of omega-3 fatty acids

01:29:50.820 | and the proper amounts of amino acids into the gut

01:29:53.980 | as a way to supplant some of the stimulation

01:29:57.200 | of these pathways that would otherwise be caused by sugar.

01:30:00.100 | There's actually a version of this where one could say,

01:30:04.080 | if you want to reduce sugar cravings,

01:30:06.780 | you might consider increasing certain forms

01:30:10.580 | of amino acid intake or certain forms of fatty acid intake.

01:30:13.780 | So what are some ways that we can reduce our sugar cravings?

01:30:17.180 | And ideally, ways that we can do that

01:30:20.000 | that also benefit us in other ways,

01:30:22.540 | both nutritionally and from the neuroscience standpoint?

01:30:25.380 | Well, these neuropod cells that respond to

01:30:29.240 | and signal the brain when we ingest sugar,

01:30:32.720 | as I mentioned, also respond to amino acids

01:30:34.600 | and essential fatty acids.

01:30:36.220 | We already talked about the essential fatty acids.

01:30:38.740 | I make it a particular point to ingest anywhere

01:30:40.760 | from one to three grams, that's grams,

01:30:43.960 | of EPA essential fatty acid per day.

01:30:47.180 | I make it a point to do that

01:30:48.020 | with the ingestion of high quality omega-3s.

01:30:51.060 | For me, the simplest way to do that,

01:30:53.100 | and I think for most people, the lowest cost way to do that

01:30:56.420 | is to use some liquid form of fish oil

01:30:58.340 | or some capsule form of fish oil.

01:31:00.080 | You really do have to see how much essential fatty acid

01:31:03.100 | in the form of EPA is in those.

01:31:05.260 | If you try and do that only through capsules,

01:31:07.980 | it can get kind of expensive

01:31:09.100 | depending on which particular brands you use.

01:31:12.560 | Some have more EPA, some less.

01:31:14.260 | You can, of course, also do this through foods.

01:31:16.120 | You can do this with non-fish sources

01:31:17.740 | through things like algae, and there's some other forms.

01:31:20.180 | You can look it up online now,

01:31:21.800 | plant-based sources of EPAs.

01:31:24.180 | You can do this with high quality fish oil.

01:31:26.780 | In any case, that does seem,

01:31:30.000 | at least based on a modest amount,

01:31:32.820 | but nonetheless solid literature,

01:31:35.380 | to reduce sugar cravings somewhat,

01:31:38.400 | but that could easily be by mere replacement of calories.

01:31:41.960 | So we don't know yet, based on human studies,

01:31:44.620 | whether or not the ingestion of those EPAs

01:31:46.440 | is specifically activating the neuropod cells,

01:31:48.840 | which specifically activates dopamine release

01:31:51.620 | and bypasses the need for, or the craving for sugar.

01:31:55.160 | We don't know that yet,

01:31:56.160 | but logically it holds up to assume that.

01:32:00.580 | The fact that these neuropod cells,

01:32:02.200 | and I should say other neurons within the gut,

01:32:04.640 | respond very robustly to the presence

01:32:07.920 | of particular amino acids is also a potential lever

01:32:12.920 | by which one could reduce sugar cravings.

01:32:14.760 | And there's an interesting literature

01:32:16.740 | around the amino acid glutamine,

01:32:18.560 | in particular supplementing with the amino acid glutamine,

01:32:21.460 | as it relates to sugar cravings.

01:32:23.760 | And certainly as it relates to other aspects of the gut,

01:32:27.680 | in particular leaky gut.

01:32:29.560 | The use of supplemental glutamine

01:32:31.440 | to try and treat leaky gut is not a new phenomenon.

01:32:34.280 | There are other approaches too, of course,

01:32:36.260 | but there are many people who are experimenting

01:32:39.300 | with supplementing with glutamine,

01:32:41.680 | several grams per day,

01:32:43.180 | often even five grams distributed

01:32:46.060 | through three or four different servings throughout the day

01:32:49.360 | as a way to blunt their sugar cravings.

01:32:51.560 | Now, there has not yet been a large-scale clinical trial

01:32:55.900 | using glutamine to reduce sugar cravings,

01:32:57.760 | but the results of the few studies that I looked at,

01:33:01.320 | as well as my understanding of the logic

01:33:03.620 | of these neural circuits, including the neuropod cells,

01:33:06.420 | brings us to a conclusion that it makes sense why,

01:33:10.680 | if there's a population of neurons within our gut

01:33:13.240 | that responds very robustly to the presence of sugar,

01:33:15.940 | fatty acids, or amino acids,

01:33:18.480 | that the intake of particular amino acids

01:33:21.160 | would allow the dopamine pathways

01:33:23.680 | that might otherwise be triggered by sugar

01:33:26.320 | to be triggered by something like glutamine,

01:33:28.600 | which has very few or no calories.

01:33:31.160 | And in fact, having talked about this previously,

01:33:34.180 | a number of people that I know went out and tried this.

01:33:37.640 | Now, this is, of course, is what I call anecdata, right?

01:33:40.320 | This is not a quality peer-reviewed study.

01:33:43.540 | This is anecdata.

01:33:45.680 | Many of them have reported back that they actually feel

01:33:48.720 | as if their sugar cravings are reduced.

01:33:50.980 | I know some people who actually take glutamine

01:33:53.080 | and mix it with full fat cream

01:33:54.460 | and take it kind of like a shot of full fat cream,

01:33:56.040 | which sounds absolutely delicious, by the way.

01:33:57.640 | Glutamine is a little bit chalky,

01:33:58.800 | so it's not that great tasting to ingest with sugar.

01:34:01.960 | I should mention, if you do try and take this approach

01:34:03.960 | of ingesting glutamine to reduce sugar cravings,

01:34:06.780 | you want to increase the amount of glutamine

01:34:08.360 | that you take somewhat gradually.

01:34:09.900 | It can create some gastric distress.

01:34:12.000 | If you just, you know,

01:34:12.840 | I certainly wouldn't take a big tablespoon of it,

01:34:14.480 | throw it in water and chug it down three times a day.

01:34:16.520 | Some of you with very hearty stomachs

01:34:17.920 | can probably tolerate that.

01:34:19.400 | You know, if you're like my, you know, my bulldog,

01:34:22.660 | which unfortunately passed away, but Costello,

01:34:24.440 | I always imagined that if ever we did an autopsy on him,

01:34:26.480 | he'd have like a license plate

01:34:27.640 | and like a human being in his gut,

01:34:29.440 | 'cause it seemed like he could ingest anything

01:34:31.020 | with no issues.

01:34:31.860 | But of course, many people have kind of sensitive guts.

01:34:34.480 | So if you're going to try taking glutamine

01:34:37.240 | as a means to reduce sugar cravings,

01:34:38.960 | just know that the studies are still ongoing.

01:34:41.280 | Some people have achieved benefit.

01:34:43.440 | Please also realize that there's an entire literature

01:34:45.740 | devoted to the potential hazards of increasing glutamine

01:34:49.720 | if you have a preexisting cancer.

01:34:52.400 | So if you have cancer or you're cancer prone,

01:34:54.600 | I would really discourage you from this approach.

01:34:56.640 | And in any case, as always, talk to your doctor.

01:34:59.800 | The logic nonetheless is there,

01:35:01.400 | why increasing amino acid intake or fatty acid intake

01:35:05.760 | might decrease sugar craving.

01:35:08.680 | Now, there are other ways to reduce sugar craving,

01:35:11.700 | and there are certainly ways to reduce the sharp rise

01:35:15.300 | in blood glucose that can occur

01:35:17.380 | when we ingest sugary sweet foods,

01:35:19.580 | or even just an abundance of carbohydrate foods.

01:35:22.440 | And there are a huge number of these things.

01:35:24.560 | I'm going to sort of layer up through the ones

01:35:27.040 | that you might find in your cupboard or at the grocery store

01:35:29.000 | and then get into some of the more extravagant,

01:35:31.720 | or I should say esoteric ones.

01:35:34.080 | Many of which, however, can be quite potent.

01:35:36.560 | The first of which is simple lemon juice, right?

01:35:40.960 | Or lime juice.

01:35:42.360 | There was an old lore and actually some papers

01:35:45.500 | pointing to the idea that the ingestion of vinegar,

01:35:48.840 | either white vinegar or wine vinegar

01:35:51.900 | could somehow blunt blood glucose

01:35:54.620 | after the ingestion of sugary foods

01:35:56.240 | or the ingestion of a lot of carbohydrate foods

01:35:58.400 | or even just a big meal.

01:36:00.220 | Actually, Tim Ferriss, I should say the great Tim Ferriss,

01:36:02.960 | 'cause I do have great respect for the fact

01:36:04.480 | that he seems to be about 10 years ahead of everything,

01:36:08.040 | both in terms of nutrition and skill learning

01:36:10.140 | and things of that sort.

01:36:10.980 | Many of the things that he predicted in his books,

01:36:13.500 | the four hour body and the four hour chef

01:36:15.720 | actually turned out to be true based on scientific data,

01:36:19.280 | some of which only exists in the animal models,

01:36:21.220 | but now also some predictions that played out to be true

01:36:26.220 | in both the animal models and the human model.

01:36:28.500 | So I think that Tim certainly deserves a hat tip

01:36:33.500 | for the fact that he experimented with these methods

01:36:36.140 | and reported his experiences with those methods

01:36:39.280 | and that now some of them, many of them have been validated

01:36:42.560 | by what I perceive to be quality science.

01:36:45.220 | He talked about the fact that,

01:36:46.800 | at least in his experiments on himself,

01:36:49.620 | the ingestion of vinegar did not seem to blunt blood glucose

01:36:54.040 | and he was using continuous glucose monitors.

01:36:56.080 | These incidentally,

01:36:57.120 | another example of where Ferriss was early to the game

01:37:00.400 | and the rest of us are kind of just in his wake,

01:37:02.680 | he talked about the use of blood glucose monitors.

01:37:05.740 | Those I think at the time were implanted below the skin.

01:37:07.920 | Nowadays, they're less invasive blood glucose monitors,

01:37:11.040 | things like levels and so forth,

01:37:12.280 | and these are actually becoming pretty popular.

01:37:14.080 | I've worn one of these before,

01:37:15.200 | they're actually pretty informative.

01:37:17.360 | I learned, for instance, that when I go in the sauna,

01:37:19.880 | that I experienced a sharp rise in blood glucose

01:37:23.320 | and that makes sense because of the dehydration associated

01:37:27.180 | with being in the sauna, a lot of sweating,

01:37:28.800 | concentration of sugar in the bloodstream goes up.

01:37:31.360 | So there's some other things that certain foods

01:37:33.080 | affect my blood glucose one way or another.

01:37:34.660 | It's kind of an interesting and fun experiment

01:37:36.920 | that some of you might be interested in doing as well.

01:37:39.840 | Regardless, there are now data pointing to the fact

01:37:43.560 | that lemon juice and lime juice,

01:37:46.340 | a couple of tablespoons or so,

01:37:48.460 | if ingested before or even during

01:37:50.300 | or even after consumption of sugary foods,

01:37:53.300 | or I should say foods that sharply increase blood glucose

01:37:57.080 | or large carbohydrate meals can actually blunt

01:37:59.480 | the blood glucose response.

01:38:00.840 | And I did see that when I did my own experiments on myself

01:38:04.240 | with continuous glucose monitor.

01:38:06.560 | It was kind of fun to do those experiments.

01:38:09.620 | I preferred to do those experiments

01:38:11.020 | by eating somewhat larger meals

01:38:12.680 | of things that didn't contain a lot of sugar.

01:38:14.760 | I saw some big increases in blood glucose

01:38:16.580 | in certain instances.

01:38:17.460 | And then I would ingest some lemon juice or lime juice,

01:38:20.240 | typically mixed in with water.

01:38:21.700 | And sure enough, you could see a blunting

01:38:23.380 | of the blood glucose response.

01:38:24.620 | And of course, this was real time blood continuous,

01:38:27.800 | hence continuous blood glucose monitoring.

01:38:30.920 | So for those of you that are interested

01:38:32.960 | in blunting your blood sugar response, certain foods,

01:38:37.220 | that's a simple low cost way to do that

01:38:39.300 | if you want to explore it.

01:38:40.140 | I will say if you are fasting

01:38:42.960 | and you already have low blood glucose

01:38:45.140 | and you ingest lemon juice,

01:38:47.720 | or I should say it's some lemon juice and water

01:38:49.480 | or lime juice and water,

01:38:51.240 | be careful because you can actually become hypoglycemic,

01:38:54.680 | for the very same reasons that lemon juice and lime juice

01:38:58.260 | can blunt blood glucose

01:38:59.640 | when your blood glucose levels are moderate to high.

01:39:02.480 | You can also reduce blood glucose levels even further

01:39:04.960 | when blood glucose levels are low.

01:39:06.700 | Now that's lemon juice and lime juice there,

01:39:10.120 | but we can't say that has to do with acidic things generally.

01:39:14.160 | And just as a side point,

01:39:16.080 | many of you have probably seen in the store,

01:39:17.920 | so-called adjusted pH waters or foods and drinks

01:39:21.380 | that are supposed to adjust your pH.

01:39:22.960 | Hate to break it to you,

01:39:23.880 | but your pH is very tightly regulated

01:39:26.440 | throughout your brain and body.

01:39:27.900 | You do not want this to change.

01:39:29.640 | It is entirely impossible, at least in any safe way,

01:39:33.760 | that you would become "more alkaline"

01:39:35.960 | by ingesting an alkaline water or something like that.

01:39:38.360 | It is true that the pH, your alkalinity and acidity

01:39:42.120 | varies in different compartments in your body.

01:39:43.840 | That's important.

01:39:45.220 | Unless you are hemorrhaging or vomiting

01:39:48.180 | or there's something badly wrong with you health-wise

01:39:50.680 | and you're in a really dire circumstance,

01:39:52.760 | you don't want big shifts in your body pH

01:39:54.780 | and your body has all sorts of ways

01:39:56.220 | of buffering against changes in pH.

01:39:59.360 | So I encourage you not to fall on the,

01:40:02.400 | or hop on the bandwagon of adjusting pH

01:40:05.040 | and becoming less acidic and that kind of thing.

01:40:06.680 | When you ingest lemon juice or lime juice,

01:40:08.740 | the mechanism by which it blunts blood glucose

01:40:11.500 | is probably twofold.

01:40:13.240 | One is probably through the post-ingestive effects

01:40:17.160 | of glucose in the gut,

01:40:18.520 | meaning the way in which sugars are interacting

01:40:22.800 | with neurons and other components of your gut circuitry

01:40:26.300 | to impact things like gastric emptying time,

01:40:30.440 | to impact things like the firing of those neuropod cells

01:40:34.100 | and their signaling to the brain.

01:40:35.800 | But almost certainly it has something to do also

01:40:40.080 | with the perception of sour taste on the tongue.

01:40:43.240 | We didn't go into this too much today,

01:40:45.260 | but you of course don't just have sweet taste receptors

01:40:49.380 | in your mouth, you also have bitter taste receptors,

01:40:51.220 | you have salty taste receptors,

01:40:53.040 | you have sour taste receptors in your mouth

01:40:55.320 | and of course that means your tongue and palate,

01:40:58.480 | and those are interacting.

01:41:00.340 | If you ingest a substance that's just sweet

01:41:03.500 | or mostly sweet, that causes a certain set of effects

01:41:07.920 | on your blood glucose, but also your brain,

01:41:09.980 | dopamine and the other neural circuits of your brain.

01:41:12.600 | If you also ingest something that's sour,

01:41:15.740 | like lemon juice or lime juice,

01:41:17.800 | it adjusts the output of those neural circuits in your brain.

01:41:21.820 | So again, we have a situation,

01:41:23.580 | we have two parallel pathways.

01:41:25.240 | One that's post-ingestive coming from phenomenon

01:41:27.800 | within our gut, neurons,

01:41:29.980 | but also things like gastric emptying time,

01:41:31.620 | the clearance and the transfer of food

01:41:35.380 | and the conversion of food into particular nutrients

01:41:38.440 | and the circulation of glucose in your bloodstream

01:41:41.340 | and how it gets into the brain,

01:41:42.660 | but also simply by ingesting something sour,

01:41:45.940 | you are changing the way that sweet things

01:41:49.080 | impact your brain.

01:41:50.260 | And so I think it stands to reason that the lemon juice,

01:41:54.240 | lime juice effect is not going to be magic.

01:41:57.060 | It's going to have everything to do with the way

01:41:58.760 | that ingesting sour foods can adjust the taste,

01:42:02.500 | excuse me, can adjust the neural response

01:42:05.580 | to taste of sweet foods.

01:42:06.980 | And in fact, we know based on the beautiful work

01:42:09.320 | of Charles Zucker at Columbia Medical School,

01:42:13.100 | that that's exactly what happens.

01:42:14.840 | They've measured the activity of neurons

01:42:17.120 | at various locations in the so-called taste pathways

01:42:19.620 | of the brain.

01:42:20.460 | And they found that when particular tastes

01:42:23.420 | like just sweet or just bitter or just sour

01:42:25.800 | evoke certain ensembles of neurons to fire

01:42:28.660 | in particular sequences,

01:42:30.300 | when sweet and sour are co-ingested,

01:42:32.800 | when bitter and sour are co-ingested,

01:42:35.500 | you get distinct ensembles,

01:42:37.500 | meaning distinct patterns of activity of those neurons.

01:42:39.980 | And of course, distinct patterns of downstream activity

01:42:43.220 | within the brain and body.

01:42:44.380 | So while it is still somewhat mysterious

01:42:47.440 | as to how exactly things like lemon juice and lime juice

01:42:50.640 | can reduce our blood glucose spikes

01:42:53.700 | when we ingest those with sweet foods

01:42:56.480 | or carbohydrate-laden foods or with big meals,

01:42:59.700 | you can use this as a tool with the understanding

01:43:01.640 | that there's a grounding in the biology

01:43:03.620 | of the way these circuits work.

01:43:05.100 | Now, some of you have probably heard that cinnamon

01:43:07.180 | can be a useful tool for controlling blood sugar.

01:43:09.320 | And indeed that's the case.

01:43:10.900 | It's very clear that cinnamon can adjust the rate

01:43:14.080 | of glucose entry into the bloodstream,

01:43:16.460 | possibly by changing the rate of gastric emptying.

01:43:19.880 | It might slow the rate of gastric emptying

01:43:22.820 | and thereby also reduce the glycemic index

01:43:26.180 | of particular foods.

01:43:27.200 | So I suppose if I were going to eat a mango

01:43:29.680 | and I hadn't just done a bunch of hard training,

01:43:31.580 | I might sprinkle some cinnamon on it here.

01:43:33.540 | I always enjoy kind of coming up with new ideas

01:43:35.360 | of ways that I can eat foods during these podcasts.

01:43:38.160 | In any event, there's some debate out there.

01:43:39.920 | If you look online as to whether or not

01:43:41.220 | Saigon cinnamon, Cassia cinnamon,

01:43:42.880 | or Ceylon cinnamon is best

01:43:46.040 | for purposes of blunting blood glucose spikes.

01:43:49.580 | But I think the, at least by my read of the data

01:43:54.340 | and from what I found, it doesn't really matter

01:43:56.340 | provided it's real cinnamon.

01:43:57.780 | And you have to actually look and make sure

01:43:59.620 | that it's real cinnamon because a lot of cinnamon

01:44:01.780 | that you buy is not real.

01:44:03.340 | I do want to provide a cautionary note

01:44:05.220 | about cinnamon however.

01:44:06.580 | Cinnamon contains something called Coumadin,

01:44:09.220 | which can be toxic at high levels.

01:44:12.220 | So you don't want to ingest more than about a teaspoon,

01:44:15.620 | maybe a teaspoon and a half of cinnamon per day

01:44:18.820 | because you'll start to exceed the threshold

01:44:20.460 | at which cinnamon could start to be problematic.

01:44:23.340 | But certainly if you're going to have a big meal

01:44:26.540 | or a meal that has a lot of sugar in it

01:44:29.100 | or a lot of carbohydrate laden foods

01:44:31.580 | and you don't want an increase in blood glucose,

01:44:34.060 | you could put cinnamon in a beverage,

01:44:36.920 | you could put cinnamon on food

01:44:38.220 | in order to blunt that blood glucose increase,

01:44:41.540 | reduce the glycemic index

01:44:42.780 | by way of reducing gastric emptying time.

01:44:44.660 | Again, just making sure that you don't get out past

01:44:47.120 | that one and a half teaspoons per day

01:44:48.980 | 'cause you really don't want to start dealing

01:44:51.380 | with any of the toxicity related to Coumadin.

01:44:53.300 | So we've talked about lemon juice and lime juice

01:44:55.540 | and cinnamon, these are kind of commonplace

01:44:57.160 | in many kitchens.

01:44:58.160 | Then of course we can venture into the more esoteric

01:45:03.040 | or I would say the more advanced tools

01:45:04.840 | for adjusting sugar intake.

01:45:07.680 | And the one that comes to mind is of course berberine.

01:45:11.900 | Berberine is a derivative of tree bark

01:45:14.560 | and is a very, very potent substance

01:45:17.140 | for reducing blood glucose.

01:45:18.300 | So much so that is on par with metformin or glibenclamide

01:45:22.460 | which are prescription drugs specifically used

01:45:25.400 | to reduce blood glucose.

01:45:27.380 | So using berberine is a serious step,

01:45:30.580 | you should absolutely talk to your doctor about it.

01:45:32.940 | I know of a number of people that use it

01:45:34.300 | to lower blood glucose when they eat really large meals.

01:45:37.700 | I know the number of people that are using it

01:45:39.640 | to get to some of the other effects of metformin

01:45:43.540 | that people have discussed things like activating

01:45:46.840 | or tapping into the so-called AMPK pathway, reducing mTOR.

01:45:50.280 | These are people that are aiming their activities

01:45:54.020 | at increasing longevity,

01:45:55.940 | a somewhat controversial approach still

01:45:58.020 | but I know many people are doing it.

01:46:00.660 | It is true that if you ingest berberine

01:46:03.100 | your blood glucose will plummet.

01:46:05.420 | And I point that out because I've actually tried it before,

01:46:08.060 | it gave me brutal headaches and I felt really dizzy

01:46:11.660 | and I felt like I couldn't see straight

01:46:13.740 | and actually I couldn't see straight.

01:46:15.620 | Why did it do that?

01:46:16.460 | Well, it made me hypoglycemic,

01:46:18.540 | it actually drove my blood glucose down too far.

01:46:21.800 | And the reason it did that is that I took berberine

01:46:24.280 | on an empty stomach.

01:46:25.780 | I know some people can tolerate it.

01:46:27.500 | I would say be very cautious about ingesting berberine

01:46:30.940 | on an empty stomach or if you are in a low carbohydrate diet

01:46:34.160 | unless you really know what you're doing

01:46:35.620 | and you have a medical professional

01:46:36.940 | to kind of guide you through that.

01:46:39.620 | If I took berberine along with a very large meal

01:46:43.620 | that include a lot of carbohydrates,

01:46:45.740 | I can recall the days in which Costello and I

01:46:47.660 | would eat a couple of pizzas

01:46:49.820 | and then we might get ice cream, that kind of thing.

01:46:51.900 | Then I felt perfectly fine on even up to 750 milligrams

01:46:55.740 | or a gram of berberine.

01:46:57.380 | It has the kind of unique property

01:46:59.260 | of making you feel not overwhelmed

01:47:02.140 | by the amount of blood glucose increase

01:47:04.520 | that you're experiencing from eating a big meal.

01:47:06.340 | I don't quite know how else to describe it.

01:47:08.520 | It's almost as if you can keep eating

01:47:10.140 | and eating and eating.

01:47:10.980 | And of course you have to protect your gastric volume, right?

01:47:15.580 | I mean, you only have so much space in your stomach

01:47:17.400 | to ingest food.

01:47:19.100 | I wasn't using it to gorge on food.

01:47:20.820 | I just heard about it.

01:47:21.700 | I was interested in experimenting with it.

01:47:23.080 | I don't have any chronic blood sugar issues.

01:47:25.720 | But again, when I took it on an empty stomach,

01:47:27.580 | it made me hypoglycemic on a low carbohydrate intake,

01:47:31.400 | hypoglycemic, not a good experience.

01:47:34.500 | And again, an experience I think to avoid

01:47:37.820 | but provided there's a lot of glucose in your bloodstream.

01:47:40.460 | And certainly if you are of the experimental type

01:47:44.020 | or you're trying to regulate blood glucose,

01:47:45.780 | berberine might be a good option.

01:47:47.500 | But again, talk to your doctor.

01:47:49.540 | It does have some other interesting effects

01:47:51.220 | in terms of lowering total cholesterol

01:47:53.580 | that are research supported

01:47:55.600 | of reducing insulin a little bit.

01:47:58.460 | Well, that's not surprising.

01:47:59.400 | If you reduce blood glucose,

01:48:00.420 | you're going to reduce insulin

01:48:01.640 | because of course insulin manages blood glucose

01:48:04.040 | in the bloodstream.

01:48:05.460 | So I would place berberine

01:48:06.960 | and of course metformin and glibenclamide

01:48:09.260 | in the kind of the heavy hitting potent tools

01:48:12.540 | for regulating blood glucose.

01:48:14.920 | Now, this is an episode not about sugar per se,

01:48:17.800 | but sugar viewed through the lens of the nervous system.

01:48:20.660 | And what's interesting about berberine,

01:48:22.060 | metformin, glibenclamide and related substances

01:48:25.300 | is that some of the effects are of course

01:48:28.780 | on gastric emptying or buffering blood glucose

01:48:31.060 | within the bloodstream, et cetera.

01:48:33.820 | But there appear to also be some neural effects

01:48:37.280 | of having chronically low glucose

01:48:40.840 | or blunting blood glucose through things like berberine.

01:48:44.520 | And some of those neural effects

01:48:45.880 | include longstanding changes in the hormonal cascades

01:48:50.880 | that are the consequence of having low blood sugar

01:48:53.360 | and thereby changes in the neural circuits

01:48:56.700 | that manage blood glucose overall.

01:48:58.860 | The simple way of saying this

01:49:00.220 | is that by maintaining low to moderate blood glucose,

01:49:03.800 | either by not ingesting heavily carbohydrate-laden foods,

01:49:07.520 | so here I'm speaking to the low carb

01:49:09.160 | and to the ketogenic types,

01:49:10.740 | or by blunting blood glucose

01:49:12.880 | through things like metformin or berberine,

01:49:15.600 | even if ingesting carbohydrates, maybe even some sugars,

01:49:18.420 | over time it seems that there's a adjustment,

01:49:21.660 | what we call a homeostatic regulation of the neural circuits

01:49:24.900 | that control things like sugar craving.

01:49:26.680 | And indeed, some people report

01:49:28.740 | feeling fewer sugar cravings over time.

01:49:31.680 | Now, I didn't use berberine for a very long period of time.

01:49:34.900 | I've never used metformin.

01:49:36.520 | I have experienced a somewhat odd but welcome phenomenon

01:49:40.120 | of with each progressive year of my life,

01:49:42.880 | I have fewer and fewer sugar cravings.

01:49:45.720 | Why that is, I don't know.

01:49:46.960 | I suspect it might have something to do with my sleep,

01:49:49.400 | and I'll talk about that in a few minutes.

01:49:51.240 | But if you're going to explore berberine

01:49:53.080 | or metformin or otherwise,

01:49:54.120 | in addition to working with a doctor,

01:49:56.040 | I think you should understand why you're doing it, right?

01:49:58.680 | I think that many of the effects can be quite potent.

01:50:01.760 | They can happen in both the immediate term,

01:50:04.100 | in terms of regulating blood glucose,

01:50:05.820 | they can send you hypoglycemic if you aren't careful.

01:50:09.240 | They can also cause longstanding changes

01:50:12.300 | to the neural circuitry that regulates blood sugar over time,

01:50:15.000 | some of which might be welcome changes, right?

01:50:16.920 | Reduce sugar cravings, for instance.

01:50:19.000 | And if you're really, really serious

01:50:21.660 | about modulating blood glucose through things like berberine,

01:50:25.360 | the typical dose range, again,

01:50:26.840 | is anywhere from half a gram to 1.5 grams daily.

01:50:30.520 | That's the typical dosages that have been explored.

01:50:33.200 | And there are some other substances like sodium cuprate,

01:50:37.560 | which are known to augment the effects of berberine

01:50:40.120 | via the AMPK pathways.

01:50:42.200 | They basically can increase the ability for berberine

01:50:45.160 | to have its glucose-lowering actions.

01:50:47.320 | But that, of course, is getting into the really potent,

01:50:49.800 | what I would call sharp blade tools

01:50:51.600 | for controlling blood glucose.

01:50:53.560 | And listen, anytime you're dealing with blood glucose,

01:50:56.820 | you are dealing with the brain's preferred source of fuel.

01:51:00.100 | And anytime you're dealing

01:51:00.940 | with the brain's preferred source of fuel,

01:51:03.280 | you have to be especially cautious

01:51:04.780 | about depriving the brain of what it needs.

01:51:07.000 | So whether or not you're low-carb, high-carb,

01:51:09.240 | keto, vegan, carnivore,

01:51:12.400 | these substances like berberine are very, very potent,

01:51:15.020 | and you need to take them seriously.

01:51:16.680 | There is yet another tool for controlling sugar cravings

01:51:19.960 | and the neural circuits that regulate sugar craving

01:51:23.720 | and its downstream consequences.

01:51:26.280 | And this tool is what I would call a high-performance tool,

01:51:30.220 | but it's one that you probably didn't suspect,

01:51:33.840 | and that's sleep.

01:51:35.980 | I've done extensive episodes about sleep,

01:51:38.660 | and we actually have an episode called Master Your Sleep.

01:51:41.980 | You can find that episode easily at HubermanLab.com.

01:51:44.440 | It's available in all the various formats,

01:51:46.000 | YouTube, Apple, Spotify, et cetera,

01:51:47.880 | and provides a lot of tools.

01:51:49.660 | And on social media, I provide a lot of tools.

01:51:51.620 | Often we have a newsletter that provides tools

01:51:53.340 | on how to maximize sleep.

01:51:56.160 | What is the role of sleep in sugar metabolism, sugar hunger,

01:52:01.160 | and the way that the brain regulates those things?

01:52:04.620 | Well, there's a really exciting study

01:52:07.240 | that came out just last year.

01:52:09.940 | This study was published in the journal Cell Report,

01:52:11.920 | Cell Press Journal, excellent journal.

01:52:14.080 | And the reason I love this study so much

01:52:16.080 | is it involved having people,

01:52:17.440 | so yes, this was done in humans,

01:52:19.200 | sleep in the laboratory.

01:52:20.520 | That's not unusual.

01:52:21.560 | There's a sleep lab at Stanford.

01:52:22.720 | There's sleep labs elsewhere.

01:52:24.380 | But what they did was they actually measured

01:52:27.740 | from the breath of these people

01:52:30.220 | and they extracted from their breath the metabolites

01:52:34.520 | that would allow them to understand

01:52:36.760 | what sorts of metabolism was occurring

01:52:38.980 | in these people's bodies at different phases of sleep.

01:52:42.140 | And this is a really remarkable study.

01:52:44.160 | They actually did this every 10 seconds

01:52:47.640 | throughout the entire night.

01:52:48.760 | So in little tiny 10 sec bins,

01:52:50.840 | meaning at very high resolution,

01:52:52.420 | they could evaluate what is the metabolism in the brain

01:52:54.640 | and body that people experience as they go from REM sleep,

01:52:57.640 | rapid eye movement sleep, to slow wave sleep and so on.

01:53:00.740 | And I'll go deeper into the study again in the future

01:53:03.520 | because it's so interesting and I think so important.

01:53:05.760 | But what they discovered was that each stage of sleep

01:53:09.400 | was associated with a very particular signature pattern

01:53:12.400 | of metabolism and particular phases of sleep

01:53:16.100 | are associated with sugar metabolism

01:53:18.580 | or more with fat metabolism

01:53:20.460 | or more with other aspects of metabolism.

01:53:23.160 | And the reason why I think this study is important

01:53:26.180 | to discuss in the context of today's discussion

01:53:28.580 | about sugar in the brain is that many people

01:53:32.000 | have experienced the effects of disrupted sleep

01:53:36.000 | on their appetite.

01:53:36.920 | And in particular, it's been reported

01:53:38.980 | that when people are sleep deprived

01:53:40.800 | or the quality of their sleep is disrupted,

01:53:43.640 | that their appetite for sugary foods increases.

01:53:46.760 | Now that was always assumed to be due

01:53:49.580 | to some metabolic need that was triggered

01:53:52.980 | by the sleep deprivation or by the poor sleep.

01:53:55.540 | But in reading over this study,

01:53:56.740 | some of the more important points made by the authors

01:53:59.080 | relate to the fact that, well,

01:54:00.660 | sleep is known to have incredibly important effects

01:54:03.520 | on brain and body for a variety of systems,

01:54:05.880 | immune system, neural functioning, et cetera.

01:54:08.840 | This very organized sequence of particular forms

01:54:12.840 | of metabolism being active

01:54:14.840 | during particular phases of sleep,

01:54:16.520 | which are very, very well orchestrated as we know,

01:54:18.880 | slow wave sleep and REM sleep being orchestrated

01:54:21.600 | in 90 minutes, so-called ultradian cycles

01:54:23.580 | and so on and so forth,

01:54:24.720 | is thought to perhaps set up the brain and body

01:54:29.160 | to be able to regulate itself in the waking hours.

01:54:32.360 | And therefore, when people are sleep deprived

01:54:35.080 | or deprived of certain forms or states within sleep,

01:54:38.760 | such as rapid eye movement sleep,

01:54:42.020 | that it creates a disruption

01:54:43.920 | in a particular set of metabolic pathways.

01:54:46.620 | Now, we don't want to leap too far from this study

01:54:48.740 | to sugar metabolism and the neural circuits

01:54:50.600 | controlling sugar metabolism, but I will say this.

01:54:53.680 | If you look at the sum total of the data on obesity

01:54:58.920 | or on type two diabetes or on metabolic syndromes

01:55:01.880 | of any kind, you almost always see disruptions in sleep.

01:55:06.520 | Now, some of those could be due to sleep apnea

01:55:09.240 | caused by even just the size of somebody's neck

01:55:11.960 | or the weight of their body.

01:55:13.400 | In other words, we don't know the direction of the effect.

01:55:17.240 | Metabolic syndromes could disrupt sleep,

01:55:19.000 | which disrupt metabolic syndromes.

01:55:20.740 | And indeed, the authors point out quite appropriately

01:55:23.800 | that they don't understand the direction of the effects

01:55:26.380 | that they observe either.

01:55:28.140 | But there is now a plethora of data pointing to the fact

01:55:32.320 | that getting quality sleep each night

01:55:34.480 | helps regulate not only appetite,

01:55:37.280 | but also the specific forms of metabolism

01:55:39.720 | that drive specific appetites.

01:55:42.140 | So the takeaway is while there are extravagant

01:55:46.920 | and potent and interesting ways to regulate blood glucose,

01:55:50.940 | everything from cinnamon to lemon juice to berberine

01:55:53.160 | to sodium caprate to behavioral tools

01:55:56.140 | to the mere understanding of how the direct

01:55:58.660 | and indirect pathways go from the gut to dopamine, et cetera.

01:56:02.000 | If you're not establishing the firm foundation

01:56:06.340 | of proper metabolism, all of those things

01:56:09.840 | are going to be sort of rearranging deck chairs

01:56:12.960 | on the Titanic as it's sometimes described.

01:56:15.880 | So we can't overstate the importance

01:56:17.240 | of getting regular sufficient amount of high quality sleep

01:56:21.260 | at least 80% of the time,

01:56:22.600 | not just for sake of immune system function,

01:56:24.960 | for clear thinking, et cetera,

01:56:26.240 | but also for properly regulating our metabolism,

01:56:30.160 | including our sugar metabolism.

01:56:32.040 | Thank you for joining me for this discussion

01:56:33.560 | about sugar and the nervous system

01:56:34.920 | and how they are regulating each other

01:56:36.720 | in both the brain and body.

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01:58:51.380 | [upbeat music]

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Controlling Sugar Cravings & Metabolism with Science-Based Tools | Huberman Lab Podcast #64

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