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Welcome to the human lab Podcast, where we discuss science and science based tools for everyday life.
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I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. This podcast is separate from my teaching and research roles at Stanford. It is however part of my desire and efforts to bring zero cost of consumer information about science and science related tools to the general public. In keeping with that theme, I'd like to thank the sponsors of today's podcast. Our first sponsor is Roca, founded by two all American swimmers from Stanford roga eyeglasses and sunglasses have really been designed with the utmost care and the utmost attention to the science of optics and the visual system. So one of the things I like so much about Roca eyeglasses and sunglasses is that they're extremely lightweight. If you get sweaty So for instance, if you wear them while running, or walking or hiking, they don't slip off. And with the sunglasses, when you're outdoors, if there's cloud cover, or if they're shadows, or if the day gets brighter or dimmer, you can still see your surroundings perfectly well. And that's because the designers at Roca really understand the way the visual system works, how it habituates how it adapts, you don't need to understand the science behind all that, but they do. And as a consequence, the eyeglasses perform extremely well, under all conditions, whether or not that's indoors or outdoors. So they put a ton of science and purpose into the design. They also happen to look really good. They have a really nice aesthetic. A lot of as you know performance. Active wear eyeglasses look rather ridiculous. But the rochat losses, I think, have a very nice aesthetic to them, that you can wear anywhere. If you'd like to check out Roca glasses, you can go to Roca, that's our okay a.com and enter the code Huberman at checkout and you'll get 20% off your first order. That's Rocha r o k.com, and enter the code Huberman at checkout for 20% off your order. today's podcast is also brought to us by insidetracker. insidetracker is a personalized nutrition platform that analyzes data from your blood and DNA to help you better understand your body and reach your health goals. I'm a big believer in getting regular blood work done for the simple reason that many of the factors that impact our immediate and long term health can only be analyzed from a blood test. And now with the advent of modern DNA tests, we can also get insight into our specific DNA makeup, and how that influences our lifestyle choices, and our health status. The problem with a lot of blood tests is that you get a lot of information back but you don't always know what to do with that information. With insidetracker, they have a very easy to use personalized dashboard platform that informs you what sorts of lifestyle nutrition exercise changes you might want to make, according to the levels of particular metabolic factors, hormone factors, etc. in your blood, and DNA. So it makes everything very simple, both in terms of where you're at health wise, and what you should or could do in order to improve your health, something I do believe most everybody would like to do with insidetracker and makes all that very easy. They also have something called the inner age test. This is a test that shows you what your biological age, and compares to that, of course, to your chronological age. And of course, your biological age is really what you want to know because it's a predictor of how long you're going to live and the quality of your life. If you'd like to try insidetracker you can visit insidetracker.com slash Huberman and if you do that, you'll get 25% off any of inside trackers plans, just use the code Huberman at checkout. Today's episode is also brought to us by helix sleep. helix sleep makes mattresses and pillows that are ideally suited to your sleep needs. Everybody needs something different in terms of what to sleep on. Some people like a hard mattress some people like a soft mattress, some people tend to run warm, some people tend to run cold. With helix sleep, you go to their website, you take a very brief two minute quiz. And you answer some questions such as Do you tend to sleep on your stomach or your side of your back? Maybe you don't know do you tend to run hot or cold etc. At the end of that quiz you match to a specific mattress. I took that quiz about six months ago and I matched to that dusk mattress and I've been sleeping on a dusk mattress from helix for the last six months. And I've been sleeping better than I ever have before. Basically, everyone's unique and helix understands that and that's built into the design of their mattresses and this two minute quiz that you take to match you to one if you'd like to try a helix sleep mattress you can go to helix sleep comm slash Huberman take their two minute quiz and they'll match you to a customized mattress. You'll also get up to 200 off and two free pillows. We are now beginning a new topic for the next four to five episodes of the Huberman lab podcast. Before we move into that I want to just breathe We touch on a couple questions that I got from the last episode, which was related to the science of endurance training, I described the four kinds of endurance training, we posted protocols of the specific four kinds of endurance training at Huberman lab.com. Just go to that episode, you can see the download, it's a zero cost PDF, I got a lot of questions about what's called concurrent training, which is how to program endurance training, if you are also interested in strength and hypertrophy training, or how to incorporate strength and hypertrophy training, which was in the previous episode, with endurance training. This can all be made very simple. Ask yourself, what are you trying to emphasize and then emphasize that for a 10 to 12 week cycle, so if you're mostly interested in endurance, I would say use a three to two ratio, maybe get three endurance training workouts per week, maybe four. And to strengthen hypertrophy workouts. If you're mainly focusing on strength and hypertrophy, get three or four workouts for strength and hypertrophy. And do two endurance workouts. Start with the minimum number of sets that's required to get the result that you want. So if you're not accustomed to doing endurance work, you would start with the minimum number that's listed on that protocol. So if it says three to five sets, you would start with three, maybe even just two, and then work your way up by adding sets each
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week.
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I do suggest that people get at least one complete rest day per week, although I know a lot of people don't like that. I benefit from that I actually benefit from having to complete rest days, each week, I just continue to make progress that way, whether or not it's for strength, and hypertrophy or for endurance. I am a big believer in rest days, other people are not and those could be active rest days hiking, relaxing, etc. After a 10 to 12 week cycle. Then I also suggest taking anywhere from five to seven days completely off, you can still enjoy life and do things I know for you addicted exercisers that you're going to loathe to do that. But that's one way to stay injury free. Keep your joints and tissues healthy over time and continue to make progress. If you don't want to do that week off, don't do it. None of this is holy. None of it is a strict prescriptive. Just ask yourself, what are you going to emphasize and emphasize that in terms of the total volume of workouts that you do, and work up incrementally, and then move into another cycle. That's what I suggest. So go to Huberman lab comm you can get the protocol there, we are now going to move into a new topic unrelated to physical performance, starting with this episode. And for the next four to five episodes, we're going to talk all about the senses. That's sight, eye sight, hearing, touch, taste, smell. And we are also going to talk about this critical sense that we call interoception, or our sense of our internal real estate. Now, the reason that we are talking about the senses, is because if you understand how the senses are perceived, what they're about what the underlying cells and connections are about, you will be in a terrific position to understand the month's topic that follows, which is all about mental health. Now, I want to emphasize that if you're somebody who doesn't have any trouble seeing, hearing, tasting, smelling, and has an excellent sense of interoception, I do believe that these episodes will still be very relevant to you, because they have everything to do with how you move through the world, how you make sense of information, and how you organize your thoughts and your emotions. I also want to emphasize that we're going to cover a lot of practical tools. So today's episode is going to be all about vision and eyesight, a topic that's very near and dear to my heart, because it's the one that I've been focusing on for well over 25 years of my career. But we're not just going to get into the mechanistic details about how light is converted into electrical potentials and things like that. We are going to talk about practical tools that you can and should use to help maintain the health of your visual system and your eyesight. Very often, young people will say What should I do? You know, you're always talking about, you know, neural plasticity and how it tapers off over time. But I'm a young person, what should I do? You should absolutely train and support your eyesight. In fact, if you're a young person and you see perfectly, or you feel as if you see the world perfectly, you are in the best position to bolster to reinforce that visual system so that you don't lose your vision as you age. In addition, you can leverage your visual system for better mental and physical performance. And we're going to talk about that. If you're somebody who suffers from a clinical disorder of vision, you have trouble seeing or if you need corrective lenses in order to see this episode is definitely for you. And while of course I can't make clinical diagnoses, I can't have a one on one conversation with any of you in this format. Nor am I a clinician I'm a scientist, not a physician. I did consult with With our Chair of ophthalmology, Dr. Jeffrey Goldberg at Stanford University School of Medicine, as well as several other people to really vet the information and make sure that the protocols that I'm describing are consistent with the clinical literature. If you have a severe eye problem, you should be working with a really good ophthalmologist, and or optometrist, but certainly an ophthalmologist who's a medical doctor. But I do believe that the information that we're going to discuss today is going to be relevant to everybody. And we'll set the stage for the month on mental health, and mental performance. So let's get started. When we hear the word vision, we most often think about eyesight, or our ability to perceive shapes and objects and faces and colors. And indeed, vision involves eyesight, our ability to see shapes and objects and faces and colors, and so forth. However, our eyes are responsible for much more than that, including our mood, our level of alertness, and all of that is included in what we call vision. So I just want to take about three, maybe four minutes and talk about how the visual system works, how it's built, and how you are able to so called see things around you.
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I also want to describe the ways in which your eyes and your visual system impact your mood and your level of alertness. And then we are going to get right into some protocols, some specific things that each and all of you should do, if you want to enhance your vision, and maintain your vision as you get older. And again, if you're a 15 year old or a 12 year old, this episode is especially for you because your nervous system is far more plastic than mine is it's much more amenable to change. So you can really build a very strong visual system. And in doing that, and if you adopt specific behaviors at any age of light viewing at particular times in particular ways, then you can build an emotional system that's also reinforced by your visual system. So let's talk about vision. What is vision? Well, vision starts with the eyes, we have no what's called extra ocular light perception. While it feels good to have light on our skin. While it feels good to be outside in the sunlight. For most people, the only way that light information can get to the cells of your body is through these two little goodies on the front of your face. And for those of you listening, I'm just pointing to my eyes. As many of you have heard me say before on this another podcast, your eyes in particular, your neural retinas are part of your central nervous system, they are part of your brain, they're the only part of your brain that sits outside the cranial vault. In other words, you have two pieces of your brain that deliberately got squeezed out of the skull during development. And placed in these things we call eye sockets. There's a genetic program for the specific purpose of making sure that three little layers of neurons, nerve cells got squeezed out and form what are called your neural retinas. Now the eyes have a lot of other goodies in them that are very important. And those are the goodies that we're going to focus on a lot. today. There's a lens to focus light precisely to the retina. If you're somebody who requires eyeglasses or contacts, chances are you don't do that correctly. And that's why you use other lenses like eyeglasses or contacts. There are also other pieces of the eye that are designed to keep the eye lubricated. You also have these things that we call eyelashes, most people don't know this, but eyelashes are there. to trigger the blink reflex. If a piece of dust or something gets in front of your eye. It's a beautiful adaptation of nature. They aren't just aesthetically nice. Costello happens to have very long eyelashes, he gets compliments about this all the time. Maybe you have long eyelashes, I don't have particularly long eyelashes, but the eyelashes are there so that if a piece of dust or something starts to head towards the cornea, the eye blinks very, very fast. It's the fastest reflex you own is your eye blink reflex. We also have these things called eyelids. Now eyelids might seem like the most boring topic of all, but they are incredibly fascinating. Today, we're going to talk about how you can actually use your visual system to increase your levels of alertness based on the neural circuits that link your brainstem with your eyelids. And no, we are not going to have a blinking contest because I would win and you would lose. And that wouldn't be fun for you. So let's talk about what the eyes do for vision. Basically, the entire job of the eyes is to collect light information and send it off to the rest of the brain in a form that the brain can understand. Remember, no light actually gets in past those neural retinas. It gets to the neural retina. And we have specific cells in the eye, called photoreceptors. They come in two different types rods and cones. cones are mainly responsible for daytime vision. And the rods are mainly responsible for vision at night or under low light conditions, generally speaking. So basically what happens is, if your eyelids are open, light comes into the eye, the lens focuses that light. Light is also just called photons light energy onto the retina. These photoreceptors, the rods and cones have chemical reactions inside them that involve things like vitamin A.
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And that chemical reaction converts the light into electricity. Now that might seem incredibly abstract. But the way to think about this is very similar to for instance, you have touch receptors on your skin. And when you press on those touch receptors, they convert pressure, physical pressure into electrical information in those neurons send it up to your spinal cord, and brainian can register that somebody or you are touching the top of your hand, as I'm doing now, with the eyes and the retina is just that light gets converted into electrical information within the eye within the retina there then a series of stages of processing. And that information eventually gets sent into the brain by a very specific class of neurons. I would like you to know the names of these neurons. They're called retinal ganglion cells. So the only thing you need to know about the neuroscience of the eye at this point are that they're rods and cones. The cones are involved in bright daytime vision. And rods are involved in more dusk or nighttime vision. And you've got these cells called retinal ganglion cells that send the information off to the rest of the brain. Now, here's what's incredible, I just want you to ponder this for a second, this still blows my mind. Everything you see around you, you're not actually seeing those objects directly, what you're doing is you're making a best guess about what's there based on the pattern of electricity that arrives in your brain. Now, that might just seem totally wild and hard to wrap your head around. But think about it this way. Because this is the way it actually works. Let's take a example of a color, like green or blue, you have cones in your eye that respond best to the wavelength of light, that is reflected off, say a green apple. So you don't actually see the green apple, what you see is the light bouncing off that green apple and goes into your eye. And you see it and perceive it as round and green. But not because you see anything green, no green light arrives in your brain, what happens is, your brain actually compares the amount of green reflection coming off that Apple to the amount of red and blue around it. Well, you might say, well, the green apples sitting on a brown table or a white surface, well, then it will appear very green. Because the amount of wavelength of light for green is very high, and the amount for red is very low. And so it looks very green. Okay, so we don't actually see anything directly. What the brain is receiving is a series of signals, electrical signals. And it's comparing electrical signals in order to come up with what we call these perceptions. Like I see something green, a green apple, or I see red. Let me give you a slightly different example. If you were to play a key on the piano, let's say you play I'm not a musician, but I'm gonna so I'm hopefully I won't get this too, too incorrectly. But let's say you, you have like e sharp and maybe it's on Ting Ting Ting Ting Ting. If the brain gets that signal, it doesn't actually know he. That's what it doesn't recognize it until you were to play it another key nexrad dun dun dun dun dun. And what it does is does the math, it does the subtraction. And it compares those two. So when we see something green, or we see something red or we see something blue, we're not actually seeing it directly the brain is making a guess about how green or red or blue that thing is by comparing what's around it. Okay, and if that seems hard to wrap your head around, don't worry, because we will explain it in more depth going forward. But I really want people to understand this, that vision, eyesight is not looking at things directly. And that information getting directly into your brain it is translated, light information is transformed into electrical signals that your visual system exquisitely understands. Now, what does this mean? Why should you care about this? Well, if you have a dog like I do, or a cat, they are not colorblind, but they lack the cones that respond to red meaning long wavelength light. So what does that mean? That means that when they see green, it's different than the green you see.
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Not because that Apple is invisible to them, but because they aren't able to compare it to red and you are As a consequence, when they look at a green lawn, it looks more brownish or orange to them. When you wear a red shirt in front of your dog, or cat, if you see a stop sign and they see a stop sign, they see orangish Brown, and you see red presuming that you are trichromatic, meaning you have three color vision. So this is all to say that every animal sees the world differently depending on whether or not they have one or two or three of these different cones, the red, blue or green cones. If you are a mantis shrimp, of all things, you see hundreds of colors that human beings can't see. Okay, many animals see into Visual ranges that you and I can't see. And so for instance, a pit viper senses heat emissions, it literally sees the heat coming off of you, or of an animal that they want to eat. If you are a ground squirrel, you can see ultraviolet light, this is gonna sound kind of weird. But ground squirrels actually signal one another by standing up outside and shining sunlight off each other's stomachs to each other signaling at a distance. Just like you know, you could signal somebody with a mirror in sunlight at distance. There are a species of primates, this isn't very pleasant to think about that urinate on their hands, and then wipe it all over their stomach, and then use that sunlight to reflect different signals to each other. I don't know what they're saying, we always assume it's something cute and nice, but maybe they're insulting each other. So this actually gets right down to the heart of these bigger questions like consciousness, what do we see what's out there, how much of life is really accessible to us. And I could go on and on, you know, this used to be kind of an obsession of mine, when I was coming up in the field of visual neuroscience to understand how different animals see the world compared to us. I'll give one more example a diving bird, you know, a bird that flies over the ocean, it has an incredible task, it has to both view the horizon, and it has to view schools of fish, and then it has to make a trajectory down into the water and grab one of those fish to eat. And the water has what's called a refractory index, it actually shifts like a prism, the impression or the perception of where that fish is, right, if the bird sees the fish right below it, it has to know it has to adjust its diving trajectory, just right, because it knows that that fish actually isn't where it sees it, it's probably a few inches ahead or to the side of that because of the way that water diverts the image. If you've ever dropped a coin to the bottom of a pool, if you go straight down looking at that location, if you are looking from the top of the pool, and you dive straight down with your eyes closed, you will miss because the water refracts, it shifts the visual image. Well, diving birds have an arrangement of these retinal cells that communicate to the brain that's both a streak to view the horizon because they need to know where they are relative to the horizon. And they have a pupil like we do on the bottom of their eye so that they can make very accurate dive and attacks on these schools of fish and catch fish and eat those fish. We just have pupils in the middle of our eyes. So there's a ton about the optics of the eye and the way that it communicates with the brain that allows us to see, we could spend hours talking about this. But what I'd like to embed in your mind is that what you experience in the outside world is bottlenecked. It's limited by which wavelengths which colors, if you will of light that you can see that your brain is coming up with a best guess about what's there, it doesn't actually know what's there. And that your vision is distinctly different from say, the vision of a dog or from the vision of somebody who's a dichromatic, meaning they don't have a red cone, a lot of people in particular about one in 80 males lacks a red cone and therefore sees the world much the same way that Costello does, although he sees it from just much lower toward the ground. So that's what I'd like you to understand about the way the eye communicates with the brain. I would also like you to understand that the brain itself is making these guesses and that those guesses are largely right. How do I know that? Well, they're right. Because when you reach out to grab a glass, most of the time you grab the glass and you don't miss right. Most of the time when you make judgments about the world around you based on your visual impression of them. It allows you to move functionally through the world. But let me give you some examples of where this guessing is happening right now. And it's so incredible that to this day, this still blows my mind cover one eye with one hand, if you're driving, maybe don't do this. If you're viewing the world around you, presumably you can see everything that's out there. I could do this with one eye or the other eye. You probably see better out of one or the other and we'll talk about that.
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You have a giant blind spot in the middle of your visual field. It's called your blind spot. It is the spot in which the connections the wire From all those retinal ganglion cells exit the back of the eye and head off toward the brain. In other words, you are blind for a huge spot of your central vision, the part of your vision that's highest acuity highest detail. And yet, you don't see that ever. You cover one eye and you see perfectly fine. And it's not just because your eyes moving around really quickly, your brain is guessing what's in that spot, which is absolutely incredible. And so you don't see that blind spot. This is happening all the time. Now, when you have two eyes open, the way that your eyes are positioned in your head, and the way they view the world is such that they fill in each other's blind spots. So it's pretty convenient. But if you cover one eye, that's impossible, and yet, you still see the world as complete. So the brain is doing these incredible things. It's also creating depth, a sense of depth, even though what arise from the retina is essentially a readout of a two dimensional flat image. So it can sense depth. How do you know depth? Well, this is very simple. Things that are closer to you tend to be larger than things that are far away. Things that are closer to you tend to look like they're moving faster. If you ever been in a train, and you look to your side, the rungs on a fence or the train tracks going by you look like they're going very fast. If you look off in the distance, they look like they're moving very slowly. And there are differences between what's close to you and what's further away. So a little house on the horizon, you don't look at and say Oh, that must be a tiny little house, you have some prior knowledge that things further away are smaller. So that's the main way that you do that. And you compare the location at which information about light lands on the two eyes, so your eyes are slightly offset from one another. So that For instance, if I look at you, if you were standing right in front of me right now, and I were to look at you, the image of your face, the light bouncing off your face to be more precise lands on one eye in a slightly different location than it does in the other eye. And then the brain does math. It basically does the equivalent of geometry and trigonometry, and essentially figures out how far away you are from me, which is just incredible. So the brain does all this very, very fast. And the brain uses about 40 to 50% of its total real estate. For vision, that's how important vision is. Now for those of you that are blind or low vision or no vision, that real estate in the brain will be taken over by neurons that control a sense of touch, and a sense of hearing. And you're indeed hearing and touch are much better higher acuity and faster in blind people. But for most of you who I presume are sighted, this is how it works. So that's kind of vision from eye to brain. In a nutshell, there are a bunch of different stations in the brain that do different things that's eyesight. Now, I want to talk about the other aspect of vision, which is the stuff that you don't perceive the subconscious stuff. And then we'll transition directly into how you can use light and eyesight to control this other stuff. Because it's very important in that other stuff is mood, sleep and appetite. And there are ways in which you can use the same protocols that I will describe in order to preserve and even enhance your vision, your ability to see things and consciously perceive them. So the protocols we will describe have a lot of carryover to both conscious eyesight, and to these subconscious aspects of vision. And I just want you to understand a little bit more about the science of seeing of eyesight and vision, and then all the protocols will make perfect sense. So as amazing as eyesight is, it actually did not evolve, for us to see shapes and colors and motion and form the most ancient cells in our eyes. And the reason we have eyes is to communicate information about time of day to the rest of the brain and body. Remember, there's no extra ocular photoreception there's no way for light information to get to all the cells of your body. But every cell in your body needs to know if it's night or day. I talked a little bit about this on the in the episodes on sleep. And this episode is not about sleep. But I want to emphasize that there is a particular category of retinal ganglion cell remember the neurons that connect the retina to the brain
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that is involved in a special kind of vision that has nothing to do with conscious perception of what's around you. And it's happening right now. It's happening all the time. These are so called melanopsin retinal ganglion cells named after the option that they contain within them. They are essentially photoreceptors remember, before I said there are photoreceptors and then these ganglion cells well these melanopsin cells, as the name suggests melon opsin have their own photoreceptor built inside them. The option that they contain is actually very similar to the melanopsin that is present in the skin of some amphibians. And that causes those amphibians to change their skin color in different light conditions. So you have, believe it or not a little bit of frog skin in your eye, so to speak. Okay, not exactly, but you essentially have the equivalent of what frogs have in their skin in your eye. If you are low vision, or no vision, as long as you have retinas, it's very likely you still have these cells, even though you can't see or you don't see, well. These cells, retinal ganglion cells communicate to areas of the brain, when particular qualities of light are present in your environment, and signal to the brain, therefore, that it's early day or late in the day. These melanopsin ganglion cells are sometimes also called intrinsically photosensitive cells, because they behave like photoreceptors. What do these cells respond to? And why should you care about them? Well, you should care about them because they regulate when you'll get sleepy when you'll feel awake, how fast your metabolism metabolism is, excuse me, your blood sugar levels, your dopamine levels, and your pain threshold. There are other factors that impact those things, but they are one of the if not the most powerful determinant of those other things like mood and pain threshold, sleepiness, wakefulness, etc. These melanopsin ganglion cells have been shown by the night's group, and I Tz up at the University of Washington, and by Samara, tars lab and David persons lab and a number of other people's labs such in Panda, you prevents you, etc, a number of excellent labs in neuroscience to set the circadian clock and to respond best to the contrast between blue and yellow light of the short that lands on the cells. When you view the sun when it's a so called low solar angle when it's low in the sky, either in the morning, or in the evening. What does all this mean? It means and here's the first protocol. And you've probably heard me say this before, but is appropriate to this episode to say it again. If you are not viewing the sun, sunlight, even through cloud cover for two to 10 minutes, in the early part of the day, when the sun is still low in the sky. And doing the same thing again in the evening. You are severely disrupting your sleep rhythms, your mood, your hormones, your metabolism, your pain threshold, and many other factors, including your ability to learn and remember information. The most central and important aspect of our biology. And perhaps our psychology as well, is to anchor ourselves in time to know when we exist. Okay, it sounds a little bit abstract, and philosophical, but it's not. And we don't know time as a real thing. Because of watches and clocks. We know time at a biological level, based on where the sun is, and where, which of course, is where we are relative to the sun, because the Earth is spinning around. Now. What does this mean for a protocol, it means See, get that light in your eyes early in the day. And anytime you want to be awake. So try and get as much sunlight in your eyes during the days you safely can. We'll talk about eye safety, this episode in depth, and the blue light. And the contrast of that blue yellow. Remember, we don't see blue. This is all subconscious. This is blue reflections coming off of sunlight blue light, we've been told is so terrible. For us. It is absolutely essential and wonderful for waking up the brain for triggering all sorts of positive biological reactions. But it needs to be viewed early in the day. If you can't see sunlight, because it's the thick cloud cover of say in a, you know, you're in the UK and it's winter, then artificial lights, especially blue lights would be very beneficial to you in a lot of this light and it's contrast with yellow in order to trigger these melanopsin cells which are then triggered to your circadian clock, which sits above the roof of your mouth which will signal every cell in your body including temperature rhythms, etc. So first things first, your visual system was not for seeing faces, motion, etc. The most ancient cells in your eye, which are there right now as we speak, are there to inform your body and brain about time of day. So you want to get that bright light early in the day absolutely essential to to 10 minutes, you can download the light meter app if you want to measure Lux. When we when I explained how to do that in earlier episodes, it got a little convoluted. Get that two to 10 minutes ideally without sunglasses. Now Here's another reason to do this. And I've never spoken about this before on any podcast, which is that there have been several studies now in 1000s of subjects, exploring what can be done to prevent myopia, nearsightedness and other visual defects. And it turns out in a series of large clinical trials, the conclusion is emerged, that getting two hours a day of outdoor time without sunglasses, blue light, this blue light, that everyone is demonized, getting that sunlight during the day for two hours, even if you're reading other things, and doing other things outside has a significant effect on reducing the probability that you will get myopia nearsightedness. Now whether or not that's also due to the fact that myopia can be caused by viewing things up close to too much. So if you're indoors, we tend to be looking at things more closely, right, unless you have a very large house with walls that are very far away from you. But the effect does seem to be directly related to getting sunlight and not just to the distance that you're viewing. I'm going to describe this study just briefly. But this is a second protocol. So we have one protocol about getting sunlight to set your circadian clocks, meaning wake you up, establish your sleep will occur about 12 to 16 hours later, that's all in the sleep episode, but also to enhance your mood to enhance your metabolism to optimize your hormone levels. And to optimize learning and dopamine levels this feel good neuromodulator that's essential to not getting depressed for etc. But now's a second protocol, which is ideally, and this includes children as long as they're not very small infants. Ideally, we're all getting two hours at outdoor time, even if there's cloud cover. Remember, we evolved mostly under outdoor conditions, not indoor conditions. And no artificial blue light will not replace this aspect of your visual system and offsetting myopia. So I just want to briefly describe this study, because it's a very important one. And I don't think it's discussed often enough. There are many studies exploring this, but one of the ones I liked the most looked at
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693 students. And a subset of them were encouraged to spend 11 hours a week outdoors. Okay, so most kids are in school five days a week or so. So they're spending 11 hours a week outdoors, they are sometimes reading outdoors, they're not always just playing outdoors, they might be reading books, etc. They use eight different schools. And the reason they did this study I probably should have mentioned is that myopia, nearsightedness is a global epidemic. At least that's how it was referred to in the study. I don't know who decides what's an epidemic or not, I think there are thresholds for that. This paper published in the Journal of ophthalmology in 2018, described the fact that being outdoors for two hours a day could could significantly reduce the probability that these children would develop nearsightedness. And it turns out, based on other studies, that adults who spend two hours a day outside that would be reading outside talking outside, no, it does not include light coming through the windshield of your car. I'll explain why in a few moments. offset the the formation of myopia. Now myopia, or nearsightedness has to do with the way that the lens focuses light onto the retina. I don't want to get into a long description of this now. But basically, the lens has to bring light to the retina, not in front of it, not behind it. If it brings light to a position in front of the retina, then you won't see clearly you will need corrective lenses. If it brings light directly to the retina, then you will see clearly that should be intuitive why that makes what makes sense. So you might say why would being outside getting this blue lighter, this beaut blue yellow contrast from sunlight actually offset myopia? Well, it probably and I want to emphasize probably has to do with the fact that these melanopsin ganglion cells is intrinsically photosensitive ganglion cells are not just responsible for sleep and talking to your circadian clock and that sort of thing. They also make connections within the retina, they connect to things like this is for the aficionados the ciliary body, the iris, the muscles, and the structures within the eye that actually move the lens and allow you to adjust your vision to things up close or far away. And in doing so, they increase or improve the health of the little tiny muscles within the eye that move the lens. And they probably again, this needs a little bit more work in order to really tamp down the mechanism. They're probably also involved in in bringing growth factors and blood supply to the muscles and to the neurons that are responsible for this focus. mechanism within the eye. So remember, your eye is an optical device, you were born with lenses, you don't have to use glasses, or maybe you do because you have lenses in your eyes. And those lenses need to move. It's not a, it's not a rigid lens, like a glass lens, it's a dynamic lens, it has little muscles that pull on it and squeeze it and make it thicker or thinner. As you look at things close and far away. And I'll describe how that works in a moment. These melanopsin cells and their activation by sunlight, completely subconsciously unaware, you're unaware of this, promote the health of this system within the eye and allow you to offset the myopia, nearsightedness. In other words, getting outside for two hours a day, each day, on average, even if there's cloud cover, without sunglasses on, will allow you to offset the formation of myopia. Now you might still form myopia, if you have certain structural features or genetic basis for that, we will talk about things that you can do as well. But for everybody, we should be doing this. And that might seem like a lot. But this is the way that your visual system works. staying indoors, just getting artificial light. And looking at things up close, leads to visual defects. Okay, it's a form of kind of like visual obesity, right? the posture of your visual system, if you will, is going to be unhealthy. If you're just indoors, and you're not getting sunlight early in the day, and for at least two hours per day, I want to talk a little bit more about how our eyes adjust to things that are close to us or far away. This is an absolutely brilliant consequence of our nature and our design. And whenever I say nature and design, people always ask me, you know, what are you really trying to say? Are you trying to talk about creators? Are you talking about intelligent design? Look, I want to be very frank with you. I wasn't consulted at the design phase, and neither were you. And so that is all very interesting, but it's not the topic of this discussion.
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