Huberman Lab - Dr. Samer Hattar: Timing Your Light, Food, & Exercise for Optimal Sleep, Energy & Mood

Starting point is 00:00:00 Welcome to the Huberman Lab Podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today I have the pleasure of introducing Dr. Samer Hattar as my guest on the Huberman Lab Podcast. Dr. Hattar is the chief of the section on light and circadian rhythms at the National Institute of Mental Health in Bethesda, Maryland. Dr. Hattar has many important discoveries to his name. He was one of a handful of groups that discovered the light sensing neurons in the eye that set the circadian clock. This was a fundamental discovery made in the early 2000s that has led to an enormous number

Starting point is 00:00:46 of additional discoveries on how light regulates our sleep, our immune system, our mood, mental health, metabolism, feeding, and many other important processes. If ever there was somebody who understands how all of these processes interact and can inform best practices for our daily behaviors, it's Dr. Hattar. During our discussion today, Dr. Hattar answers questions that are absolutely essential for us to know about our health and well-being. For instance, how to align our sleep schedule with our activity schedule, such as exercise, and how to align light activity and exercise

Starting point is 00:01:26 with our feeding rhythms. He presents a new model of how light activity and feeding rhythms converge to support optimal health and when those are not aligned correctly, how our mental and physical health can suffer. It's a discussion that is rich with scientific mechanism, made clearly, of course, so everybody can understand, as well as specific protocols to deal with shifts in day length, shifts in activity, and in order to optimize sleep, metabolism, and well-being of various kinds. I learned so much from Samor as I always do. He is an absolute wealth of knowledge on all things related to light and circadian rhythms, physiology and neuroscience.

Starting point is 00:02:09 I don't think you'll find anyone else as knowledgeable about these topics as Samor, and so I'm delighted that he joined us here on the podcast to share this information. Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero cost to 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 Athletic Greens. Athletic Greens is an all-in-one vitamin mineral probiotic drink.

Starting point is 00:02:40 I've been taking Athletic Greens since 2012, so I'm delighted that they're sponsoring the podcast. The reason I started taking athletic greens and the reason I still take athletic greens once or twice today is that it helps me cover all of my basic nutritional needs. It makes up for any deficiencies that I might have. In addition, it has probiotics, which are vital for microbiome health. I've done a couple of episodes now on the so-called gut microbiome and the ways in which the microbiome interacts the ways in which the microbiome interacts with your immune system, with your brain to regulate mood, and essentially

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Starting point is 00:04:51 If you'd like to try element, you can go to drinkelement.lment.com slash huberman and you'll get a free element sample pack with your purchase. They're all delicious. Again, if you want to try element, you can go to elementlemente.com slash Hubertman. And now my conversation with Dr. Samar Hatar. Samar, thanks for sitting down with me. My pleasure. We go way back.

Starting point is 00:05:15 So you are best known in scientific circles for your work on how light impacts mood, learning, feeding, hunger, sleep, and these sorts of topics. So just to kick the ball out onto the field, so to speak, how does light impact the way we feel? So when I get up in the morning, I have the opportunity to interact with light in certain ways or to avoid light in certain ways. I have the opportunity to interact with sunlight or with artificial light. Maybe you could just

Starting point is 00:05:53 weighed us into what the relationship is between light and these things like mood and hunger etc. Sure. So I mean, you do appreciate the effect of light for vision. So when you wake up in a beautiful area, beautiful ocean, light is essential. The sun rise, the sunset, blue sky, beautiful mountains. So that's your conscious perception of light. But light has a completely different aspect that is independent of conscious vision or image forming functions. And that's how it regulates many important functions in your body.

Starting point is 00:06:24 I think the best that is well studied and well known is your circadian clock. The word circadian comes from the word circu, which is approximate and DN is day, so it's an approximate day. Why is it an approximate day? Because if I put you or any other human being who have a normal circadian clock in a constant conditions, with no information about feeding time, about sleep time, about what time it is outside, you still have a daily rhythm, but it's not exactly 24 hours. So it will shift out of the solar day because it's not exactly

Starting point is 00:06:58 24 hours and hence the name circadian. So just to ask a quick question about that, when you say you have this to us about 24 hour rhythm, how does that rhythm show up in the tissues of our body? Great. So great question. So it shows up at every level that we know we studied. It shows up at the level of the cell, it shows up at the level of the tissue and it shows up at your behavior. The most obvious for you is your sleep wake cycle. You sleep and now you're awake and sleep at 24 hour rhythms. And if you measure the sleep wake cycle of a human who are maintaining constant conditions, you will see that the period length of the

Starting point is 00:07:35 sleep rhythm on average is more than 24 hours. And a human is 24.2 hours. So you'll be drifting 0.2 hours every day out of the solar day if you don't get the sunlight. So the sunlight adjusts that approximate data on exact day. So now your behavior is adjusted to the light dark environment or the solar thing. Okay, so if I understand correctly, if I were to go into a cave or I were to be in constant light, and I didn't close my eyes in constant light, that I would still sleep in one coherent bout. And I would still be awake for more or less one coherent bout,

Starting point is 00:08:13 maybe a nap. But the total duration of my day, so to speak, would be a little bit longer than 24 hours. But if I'm in a condition like most people are, where the sun goes up and the sun goes down, and I have some understanding of that sunrise and sunset, you don't have to have the understanding. You don't have to have conscious understanding.

Starting point is 00:08:35 You have the detection. So circadian photo-entrainment is the word we use in training the circadian clock to the photo environment is completely subconscious. You're not aware of it. It's not like vision or image forming where you actually know what you're looking at. So it's all hyposelomic. It's part of the brain that is not consciously driven. So you actually do not know when it happens or when it doesn't happen. And that what we'll get into when I tell you why light affects your mood and why sometimes people don't know how to deal with light to improve their mood.

Starting point is 00:09:07 For example. Okay, so this is a subconscious vision. Yes. Okay. Before you tell us about how light impacts mood, I'm curious, what is the relevance of adjusting this clock from a little bit longer than 24 hours to 24 hours. I mean, it seems like a small difference. 24 hours and 40 minutes or 24 hours. Like, what's the relevance? I mean, why should we care about that short difference?

Starting point is 00:09:33 So let's do the math. If you shift out, point two hours a day, in five days, you're shifting out one hour. So you're literally one hour off in your social behavior in five days, in 10 days, you're two hours off. And if you're an organism that is living in the wild, shifting out of the right phase of the cycle, you could either miss food or you could become food. So it's really essential for survival. I think it's one of the strongest aspect of survival for animals to have the anticipation and the adjustment to the solar cycle.

Starting point is 00:10:05 And for humans as well, when you say animals, I'm assuming that applies to us. Absolutely. Yeah. I see. So even though it's just a short bit longer than 24, if you, if that accumulates over days, then you could find yourself very much out of phase with the rest of your, your species. Yeah. So let's say it's point two hours. So in five days, it's one hour, in 25 days,

Starting point is 00:10:28 it could be five or six hours. You could be in New York and you're feeling as if you traveled from New York to London. So you will be having jet lag in New York, even though you didn't do a jet lag travel. So it's very important for the adjustment. And if we have time, maybe we could talk about why this is important for seasonality,

Starting point is 00:10:47 because also it allows animals to anticipate the change in season, and the more you're high in the north or the south, the more that these weather changes occur very harshly, and you have to be ready for them. And that happens in us as well. I will definitely get into seasonality. Okay, so we've got this subconscious vision

Starting point is 00:11:09 that aligns us with the turn of the earth. How does that work? I mean, what's the, what is the machinery that allows that to happen? And how does that machinery work? Yeah, so we know, we knew that in mammals, including us, we are mammals' humans, that the eyes are required for this function. So if humans are born without eyes, or the optic nerves are damaged, humans are not able

Starting point is 00:11:35 to adjust to the solar cycle. So we know that the eyes are required. And since we thought we knew about the eyes a lot before 2000, we thought that before the year 2000. Before the year 2000, yes. We thought it's these photoreceptors in your retina that allow you to see. So in the human retina, there are two types of photoreceptors. They are called rods and cones because of their shapes. And these rods and cones simply take the photon energy, which light is made off, and they

Starting point is 00:12:05 change it in a way to an electrical signal that allows us to build the image of the environment in our courtesies subconsciously. Consciously, in this situation, because it's vision, right? It's image-forming vision. It's a visual cortex and association, associative courtesies, which allow you to build conscious perception of the environment. However, people have found, including me, with the work of David Persson and Ignatius Proventio, that there is a subset of ganglion cells. The ganglion cells are the cells that leave the retina, their axon, leave the retina, and project to the brain. So these words are only really

Starting point is 00:12:43 wrote down con information from the light environment to the brain. We these words have stood to only relay rod and con information from the light environment to the brain. We found that a small subset of these ganglion cells are themselves photoreceptors that were completely messed in the retina. And these are the photoreceptors that relay light environment subconsciously to the areas in the brain that have and house the circadian clock or the circadian pacemaker, which adjusts all the clocks in our bodies to the central brain clock, that allows them to train to the 24 hour light dark cycle. Incredible. So, as I recall, because I was a graduate student at the time, in the year 2000, there was this landmark discovery made by you,

Starting point is 00:13:24 you could prevent CO David Berson and others, that these cells exist that can communicate day and night information to the brain. And there's very small subset of cells. Since then, I've heard, but maybe you can confirm or refute, that this system that connects the eyes to the rest of the brain is actually the most ancient form of vision. That this is probably the form of vision that some early version of human beings had before they had patterned vision, before they could see colors and shapes and motion

Starting point is 00:13:54 and all that, and that the same cells that perform this role are actually similar to insect eyes. I think I heard David Berson say once that we actually have a little bit of the fly eye in our eye. What's he talking about? Yeah, so it's really interesting actually because these same IPRGCs we discovered they contribute a little bit to image formation and now work from TiffinishMet specifically have proven that they do contribute to image forming functions. But they contribute to very limited aspect of image formation. So it fits your hypothesis that these are an ancient photoreceptors.

Starting point is 00:14:35 The other thing that adds to that hypothesis is that they are expressed in cells that don't have any modification that make them look like photoreceptors. So the photoreceptors that I told you about that are important for vision, image formation. They have very specialized structures that allow them to pack these structures with photo pigments. These are the photo detecting proteins. So they could detect a high sensitivity of photons that pass through them. These IPRGIS, these new photosceptors don't have these specialized structures. So they just really need a lot of light at the time,

Starting point is 00:15:13 we thought they need a lot of light to be activated. So that's why we think they are ancient, and that's why I think they adjust to ancient functions that are as important as regulating your body circadian clock to the solar environment, to the solar day or to the light cycle. So you mentioned IPRGCs intrinsically photosensitive. So these are cells that connect the eye, the brain that behave like photoreceptors essentially. And then you mention melanopsin, which is the actual pigment that converts the light into the electrical signal, more or less. And my understanding is that melanopsin was identified first in frog melanophores. So does that mean that we have like little pieces of frog skin in our eyes?

Starting point is 00:15:57 So honestly, David, person say you have a fly in your eye because it sounds better. The more accurate I think is that you have a frog skin in your eye. It's not as catchy, but really, Melanopsin, really the name Melanopsin is from Melanopsite Opsin. So it's Melanopsin because it was found in the frog Melanopsites. You know, the frogs can change their color depending on light. And Melanopsin drives this response. So when Ignacio prevents you first discovered these obscenes in frogs, luckily he was smart enough to see if they are expressed in the frog eye. They were expressing the frog eye and it what appears to be retinal ganglion cells, which I

Starting point is 00:16:35 told you the one that connect the eye to the brain. He had the inside to go and see if they are expressed in the monkey eye. And he found that are also expressed in what appears to be retinal ganglion cells and really that what opened the field wide open. Then David Burson did the seminal experiment where he went to the brain where the central oscillator, the oscillator that drives circadian rhythm in the brain called the superchasmatic nucleus that has been known for many years to receive retinal input and he he labeled the cells that are project there. And then he found that even if you destroy Rhodes icons, you could get light responses from these cells. So you could imagine he nearly fainted

Starting point is 00:17:15 when he saw that these cells can respond independent, completely in the absence of Rhodes and coin input. I'll never forget reading those papers in 2000, 2001. I was at the meeting in DC when Iggy, Ignacio, Iggy, we call him Iggy, showed this image of this, basically what is frog, melanophores in the human eye. And everyone was like, oh my goodness, this is the thing. And I want to get into how light actually can control circadian rhythms. Absolutely.

Starting point is 00:17:44 But I think it's worth mentioning now that people who are patterned vision blind, so people who cannot see and no conscious vision, but have eyes. Many of them still have these cells, these melanopsin intrinsically photosensitive cells, and can essentially match or entrain, as we say say onto the light dark cycle. In fact, they possibly have no problems in circadian phototrain training. They'll have a normal sleep week cycle, but they're totally blind. But they are totally image blind. And what's really interesting is that, and this story I heard from Chuck Seisler,

Starting point is 00:18:17 so I'll give him credit that some of these people who are image blind usually, they get dry eyes and they give them a lot of pain. And doctors used to think, oh, people who are image-bride usually they get dry eyes and they give them a lot of pain and doctors used to think oh, since they are image blind and they're getting dry eye, why don't you just remove their eyes? They're not using them anymore. And the minute they would remove their eyes, they start having cyclical sleep problems indicating that now they are not entraining to the light dark cycle and are having cyclical jet lags when their clock shifts through the light dox cycle. That's really interesting. And I hear from a number of blind people,

Starting point is 00:18:51 you know, in my various aspects of my job, and a lot of them have issues with sleep, I think, in part because they don't realize that they too need to see light at particular times of day or night in order to match their schedule. Absolutely. Well, I think that's a perfect segue for us to talk about how light and viewing light can impact our sleep wake rhythms. And then we will move into some of the other ways in which light can impact other forms of bodily

Starting point is 00:19:18 function. Yeah, so I love the way you set it up because one of the most interesting and difficult aspect of trying to educate people about light effect on subconscious vision is that it's subconscious. So we're all aware of what we think is intensity because we see the room. But if you talk to people who know how to take photographs and stuff like that, they know that the intensity is varies greatly, but our system, because we have to see the same way in very bright conditions and very dim conditions, we're not very good at estimating intensity consciously.

Starting point is 00:19:55 So when you try to tell people about intensity, you really struggle because they think they know intensities, but they really don't, you mean light intensity? So that the cones themselves have an incredible ability to adapt to different light conditions. So you can see at all different conditions, otherwise it'll be a disaster, you know, if you don't change the the setting on your camera and you go from inside the room to the outside, it becomes completely white, you don't see anything. So if your cones don't adapt to the environment, then you're not going

Starting point is 00:20:25 to be able to see in this room and on the beach, right? But the problem is your IPRGC is the cells that we talked about. They measure intensity pretty well. They really know what intensity is. They have a very good linear measurement of intensity. They don't adapt as well, they don't adapt actually that much, to be honest. So that tells you that subconsciously the system is used to measuring light intensity in a natural environment, because when you're in a natural environment, you don't have you know industrialized lighting, then you you know your system is functioning very well. But now when we change these environments, we could really mess up ourselves. So you have to teach people how to understand intensity,

Starting point is 00:21:12 and that's something that you have to explain to people. And I think I love to do it myself. I do it in what is called the lowest amount of light required to allow you to see comfortably. So you have to do this as a fun experiment. Okay, so explain to me how this goes. And maybe we could break it up in the day into three or four parts. So let's say assuming that most people wake up in the morning as opposed to night shift workers, et cetera, we could talk about later. But wake up in the morning. So let's divide the

Starting point is 00:21:41 day into quarters. What is what is the proper way to interact with light in the first part of the day? So I honestly think the easiest thing is waking up. Get as much light as you can. It's your eyes. Yeah, it's really nice. Your system is primed. If you're in trained, it's primed to get light. The sun should be out.

Starting point is 00:22:01 Most animals in the world, they actually seem to track the sun. The sun has a huge influence on life on earth. It's actually life on earth is because of sun. So that's easy. In the morning, when you wake up, you need light. Okay. So what is the behavioral practice that you recommend? Does it? Let's say somebody is in a condition where there's a lot of cloud cover. Yeah. Is it important to get outside? So I have to tell you, the cloudiest day is going to be much more brighter than your room. You could ask any photographer, a cloudy day, unless it's really dark, dark clouds. Usually cloudy days have much more bright outside than inside the room, even when you have good lighting inside the room.

Starting point is 00:22:42 So I think in the outside is usually even when it's cloudy, you're going to get enough intensity to help you adjust your cycle to the day night cycle. So how long do you... These are general rules of thumb, but how long do you recommend people go outside? So if you do it daily, you possibly need very... If you do it daily, because remember, this thing is going to happen on a daily matter. So it's like the clock is tracking it on a regular basis. Absolutely. It's spot on counting, it's tracking. I would say 15 minutes.

Starting point is 00:23:09 If you don't do it daily, you may want to increase it. And we talk about when you travel, what you could do. But yeah, 15 minutes should be fun. You do it more. It doesn't hurt. And through a window, my understanding is that through a window, it dramatically decreases the amount of light energy coming through. It depends on how thick the windows are and how dark they are.

Starting point is 00:23:29 But it's also nice to go outside and to feel the season, sunglasses off. I don't use sunglasses. But you have the Jordanian photo pigment. Yeah. Whereas my eyes are very sensitive. No, if I'm in the shade, or if it's not incredibly bright, I try to, especially in the morning,

Starting point is 00:23:51 but I'm also an early person. So we have to differentiate between early and early wake up. I wake up at 4.30 in the morning. But the sun isn't on yet. It's not out yet. So what do you do? You turn on artificial lights. I usually don't turn on artificial light

Starting point is 00:24:03 because I know the sun is going to come up eventually, but that's why I don't like the change in the timing that they do. What do you do between 4.30 a.m. and 7.00 a.m.? I just got my computer on my phone. So possibly I get enough light. But in reality, I mean, as long as you let your body get the morning sunlight, which I think is really to me. And there's no evidence but to me, this is, if you look at all animals' plants, this morning sunlight seems to be very important. And I, you know, we don't have experiments to show it, but I have got feeling that it has a huge impact on humans. Well, Jamie Zyzer's lab at the Stanford sleep lab has shown that these early morning light

Starting point is 00:24:45 flashes can adjust the total amount of sleep that one will get makes it easier to get it to sleep. Absolutely. Okay so and and Ken Wright also did this beautiful camping experiments that should maybe you should describe those because those are beautiful experiments. They are beautiful experiments. He took these, you know, college students that had a late onset of sleep and late waking time. And then he said, let's go camping and just don't use any artificial light and you could go to sleep as late or as early as you want and wake up as late as early. And he found a huge shift in their sleep pattern just by exposing them to the light dark cycle. I mean, so...

Starting point is 00:25:25 And it lasted. And it lasted. Even after they came back. Exactly. I think it was two days of camping, reset the circadian farm. Seven days, but it lasted. Yeah, it's pretty amazing. Yeah, it's really incredible.

Starting point is 00:25:35 OK, so get bright light of some sort early in the day, ideally sunlight, even on a cloudy day, it's going to be brighter than indoor light. OK, so that's easy. OK, so then. And the other thing that I would like to mention to people, if you think it's very dim outside, let's say it's very cloudy, stay longer.

Starting point is 00:25:53 So remember, intensity is only one component. Duration is also important because remember that the circadian system is not like the image system. In the image system, you have to change every second because you're looking at different objects. You have to change your perception. But for the circadian system, it's trying to figure out where am I in the day night cycle. So the more you give them the information, the better you are. So if it's very bright, you don't need a lot because it's clearly going to make you fire like crazy. But if it's not bright,

Starting point is 00:26:24 stay longer. Stay for one hour. You know, have your coffee outside or something like that. It's just going to help. I think you said something extremely important, which is that this circadian system is trying to figure out when you are in time, not where you are in space. So I said where you are in time when you are.

Starting point is 00:26:41 Oh, no, no, I wasn't correcting you. I just meant that I think fundamentally that's the incredible thing about the system that you have this clock, this 24 hour clock in your brain, but it needs to be synchronized to the outside. So could we go a little deeper into this circadian setting behavior and come up with some general rules of thumb? So let's say it's a very bright day, extremely bright.

Starting point is 00:27:06 No clouds, suns out. You said 10 minutes, 15 minutes. And I'll tell you, if you're sensitive, don't, you don't even have to go in the sun. You could be in the shade. There's going to be so many photons out there in the shade. It's going to be perfect. You don't even have to see the sun. You don't have to have the sun. You know, it's great for vitamin D. That's a different story. You could do this for your skin and protect your skin. That's not my area of expertise.

Starting point is 00:27:33 But for that effect on the circadian system, as long as you're outside in the shade and it's sunny day, 10 to 15 minutes should be ample amount. Okay. And then let's say it's kind of overcast. You know, it's not particularly brighter. There's, you know, solid cloud cover, but, you know, the obviously the sun is out, but it's not as bright. How long do you think it would take to set the

Starting point is 00:27:56 clock? 10 to 15 should be sufficient. Stay for a half an hour. Stay for 45 minutes. If it's very dark cloud, yeah, stay for longer. Okay. And if, some reason one finds himself very far north and it's very, very dense cloud cover, how long and at what point should somebody consider using an artificial light source to mimic the sunlight? Yeah, honestly, this is where we don't have a lot of information still, because this is where we're going to discuss this maybe in more detail, that if you put humans in artificial conditions, the circadian system is very sensitive to light. But in reality, in the real environment, light also is affecting other aspects that are independent of the setting of the circadian base maker. And these, which we call the direct effect of light on mood, for example.

Starting point is 00:28:48 So that is very hard to figure out what intensity you need to use. And we haven't done enough experience because the system has been discovered just recently. But I would say if you use bright light in the morning, and I mean, it's hard for me to give numbers it can get complicated but yeah I mean if you're honestly if you're that far north and you're in the winter and you want to get make sure you don't use these light boxes I would suggest that personally but that's it. I use it's actually not designed for circadian setting but I have a 930 lux light pad that I bought and I bought it. They're very affordable compared to the dawn

Starting point is 00:29:28 simulating lights, which are quite expensive, frankly. And I put it there. And so I just basically, when I wake up in the morning, I use that until the sun comes out. And then I make sure once the sun is out, I go outside. But I keep that thing on all day. And I don't know if that's good or bad, is a good or bad. I honestly, I don't think being exposed to bright light in the day is going to ever be

Starting point is 00:29:49 bad because really if you're outside in the day, unless you know, the worst going to happen, if the temperature is very high, your body is going to say, don't dehydrate and go to sleep. So you could tell actually sometimes when it's very hot, the more you get exposed to bright light, the sleepier you feel in the afternoon, when it's very hot, the more you get exposed to bright light, the sleepier you feel in the afternoon, which is counterintuitive. So you think that's the product, I see you think against dehydration.

Starting point is 00:30:12 I think if you think about the human evolution from near the equator in them, between noon and a certain time in the afternoon, it would have been very hard for you to maintain physiological homeostatic function being active at this very high temperature time. So I think napping was a way, that's why I think it has a major function, which is still napping was a way to somehow take you away from that dangerous zone. And maybe that's why people in the north, they say in the winter

Starting point is 00:30:41 we can't wake up in the morning because they don't have the strong light, so they it more at night, but in the summer they say we feel like we can't go to sleep We have to put all these dark curtains So I think you know venturing that up that much north Up north has been came up with problem because evolution was used to a certain light environment that was completely Changed with a human, with other animals, I think that lived there longer. They have come up with very interesting adaptation of actually measuring even very small changes in the light intensities that still occur. So, even if you're near the poles, even though it's always light, but there is a change in the

Starting point is 00:31:24 light intensity across the day and I cycle. So your system, if it's's always light, but there is a change in the light intensity across the day and I cycle. So your system, if it's linear, and remember, I told you that IPRGCs are incredibly linear, can still measure, oh, this is lower light than higher light, if the organism has the ability to do that. I see. It's interesting.

Starting point is 00:31:40 I've spent so much time learning from you, fortunately, about these cells. And yet, I never really appreciated until now how on the one hand, they are tracking the amount of light to understand when we are in time, relative to the 24 hour cycle, but also that you keep mentioning this, this linear measurement of intensity that they really are trying to figure out when we are in time by measuring the intensity of light.

Starting point is 00:32:05 And of course, the sun is the most intense source of light available to us. So okay, so I think we've nailed down that first part of the day. Basically, it's 10 to 30 minutes depending on how bright it is. And trying to do that as often as possible to give the system a regular. Daily is the best. This system is really about, and you'll see that, even for the effect on depression,

Starting point is 00:32:27 it's about multiple days. It's just, so you don't have to worry if you missed it one day, stay longer if you want, but if you're in a hurry and you wanna do other stuff, that's a great recommend date. So you might wanna compensate

Starting point is 00:32:40 with some extra time if you missed it a year too. And this is why I've heard you say before, it's entirely possible to get severely jet lag without traveling. Absolutely. Simply by staying in, being on your phone too much, not getting the sunlight. And you saw this during the pandemic,

Starting point is 00:32:55 a lot of people mentioned that their sleep-wake cycles suffered a lot. Because if you're not going out and if you're staying at home and you don't have big windows and you're waking late, waking up late and then you're using very bright light till late at night, your body's gonna shift. And now your day is gonna start instead of like really when the sun comes up, let's say at six o'clock in the morning,

Starting point is 00:33:18 it's gonna, your day is gonna start at 11 o'clock in the morning. That's what your body's gonna think is the beginning of the day. So then you're not gonna be able to sleep at 10 o'clock at night because now that's really for your body is completely different timing. And you could see this happen during the pandemic

Starting point is 00:33:37 at a very high scale. People get delayed in their sleep, they cycle a lot. And there is this idea of chronotypes that we all each intrinsically have a best rhythm of either being a morning person, you call yourself an early person, or a night owl, or more of a kind of standard, you know, to bed around 10, 30 up around seven type thing. And I think there are now good data, correct me if I'm wrong, from the National Institutes

Starting point is 00:34:03 of Mental Health and elsewhere, showing that the more we deviate from that intrinsic rhythm, the more mental health issues and physical health issues start to crop up. So there is great data on this, and there is a couple of things that complicate this. The first is the people who usually are late. They tell you that the society doesn't accommodate. What lit by late, what do you mean, people that wake up late and go to sleep late and wake up late? They have an overwhelmingly higher level of depression and failures. I mean clearly, I mean, the reason the people say, sleep early, wake up earlier,

Starting point is 00:34:38 better because human notice that people who wake up go to sleep early and wake up early, they do better in life, they notice that. They just perform better. They perform better. But the question is, is that intrinsic to the system or is that society because society start things usually early or late, that's a hard question. We discriminate against late rise. We, in a way, we discriminate, right?

Starting point is 00:34:59 But the other explanation is, can rights experiment? These late risers, if they were truly chronotypically late, why would they shift so easily when you put them in the... If you were really chronotypically late, and there is a phase relation between the light dark environment and your circadian clock, then doing this camping experiment should not have caused much changes, because it's not that, you know, light light is gonna affect you in a certain way,

Starting point is 00:35:27 is that this is the relationship that your body decided that I'm a late sleeper, late waking. So I'm honestly, I'm still unable to figure out how much of this late waking up is controlled by the light environment and how much is interesting. I'm sure there are differences, but are they as big as we see in the environment? Because you have people that go up to sleep at 7 p.m. and wake up at 1 a.m. These are clearly advanced face.

Starting point is 00:35:55 So people that go to sleep at 7 p.m. and wake up at 1 a.m. and feel good doing that? I'm not so sure they feel good, but a lot of the time you talk to people, they say they are high achievers, but they suffer because they go to 7pm wake up, advance face, leave syndrome, they call it a syndrome, but then you have people who would not be able to sleep till 5am and not be able to wake up till 3pm, right? And I'm not so sure that the circadian system is that variable in the human population. I mean, clearly there are maybe some genetic factors that make a small percentage of like everything with a bell shape. But I think most of the time the light environment

Starting point is 00:36:37 make player role. And once as we've talked about this is a long-term effect of light. Once you get into a rhythm, and I don't mean it as a pun, in reality, once you get into erhythm, it's hard to break out of that rhythm because if you start sleeping late and waking up late, you're not getting the morning sunlight, right? And so you're just going to be late. And if you like me waking up early, you're getting the morning sunlight. You're getting what size Lucette said his last name wrong. The one in Stanford who did the... Oh, Jamie Zites. Yeah. Yeah. He actually worked for the size layers of Zites or in a size layer. Yeah, there are a lot of zzzz and eyes in their names. Yeah. Both phenomenal scientists. Yeah. What it seems to me is the case is that the only way to really know

Starting point is 00:37:27 if you're meant to be an early bird, as they call it, an early person or a late person, or somewhere in between, is to get morning sunlight and figure out whether or not that makes you feel better. To understand, to be educated about how to measure intensity, how to measure, I put it between quotation, because you either get a measuring device, but you cannot depend on your eye to measure intensity. How do we do that? Because you keep coming back to this,

Starting point is 00:37:55 so that tells me that it's important. It's very important. So there are apps like Free Apps, like Light Meter, where you can walk around and hold the button down and see how many locks you know are in the environment. These are complicated because you have to point them to specific reasons. So how do people start to develop an intuitive sense of the measurement of intensity? Yeah, I think at one point I posted on Instagram how I keep my night time at home and I found out that my night vision is very strong. So I found

Starting point is 00:38:26 that that I especially in the winter, I only need candlelight. So I literally use these T-lights. And I put like 15 or 20 of them. And romantic. And it's so nice. I could see it clearly doesn't affect my circadian system. You and your cat. And my wife and wife and wife and wife and wife. It's just great, right? It's just great, right? But I don't expect people to have the same night vision as me. So the simple, I mean, I tell people, do the experiment. So if you put three or four lights in your room, switch to, sit for 15 minutes. Switch to off. Switch to off.

Starting point is 00:39:00 Let's say you're using five. And see, after 15 minutes, you will not recognize you switch these two off My gut feeling is that most people would need at least 10 times less light than they use at night to see The problem people use it because most of the time they didn't see the morning sunlight They are actually hungry for light without their knowledge So they come switch all these lights on but at the wrong time Because they woke up late. Okay, now I understand. So this morning light viewing goes way beyond setting your clock.

Starting point is 00:39:32 It's also a way to determine how little light you need later in the day. Exactly. And we're going to talk about this in a moment, but how little light you get later in the day is a very strong determinant of things like when you wake up, whether or not you wake up feeling refreshed, et cetera. Let's, let's, that's why. Yeah, I'm going to break it on your show and through that. I'm going to tell you, I think there is something else

Starting point is 00:39:55 that people need to think about, which is the tripartate model, that this model incorporates three components which we should talk about in details, that allows us humans and all animals to Incorporate the circadian clock and its relation to light the homeostatic drive and the direct effect of the environment Which includes stress light all kind of stuff. They have to be incorporated together if you think that's what I think right now If you think of one what I think right now, if you think of one alone, you will always miss something. When you think of them as a whole, things really become clear. It's actually quite amazing.

Starting point is 00:40:32 Okay, well, we will definitely want to hear about your tripartite theory and go into detail about this homeostatic mechanisms. I want to make sure that for people who are thinking now, I'm sure, about light and how it impacts them. So the morning light viewing behavior, I like to think we've tacked down clearly. And thank you for that because there's so much information out there. I've tried to relay that information. Of course, you're my primary source for all things circadian as well as Jamie and others, of course, Matt Walker. But I think you've made that very, very clear. Now let's say I've gotten my morning sunlight, okay, made my bright artificial light.

Starting point is 00:41:10 And throughout the day, you said to get a lot of light. So I'm working at my desk, maybe I'll go out during the day a few times, but I'm working at my computer, I'm doing things. Is there anything about light viewing in the middle of the day that people should keep in mind? Or can they just sort of freestyle it, depending on what they're doing. Most people are not, you know, in a dark room throughout the day. My gut feeling, if you got your morning sunlight, you walk from your car slowly or you walk

Starting point is 00:41:38 to work, you didn't wear sunglasses when the lights were still dim in the morning, that you could spree style it. That even if you don't get a lot of light, there is a way to just, you know, in the day, you don't have to just worry about getting a lot of bright light. But personally, I like to do that. So I go out at lunch and have my lunch outside as well. This reminds the body that here it is even brighter now. But the evidence is that you could literally help your circadian clock by giving lights at dawn and dusk.

Starting point is 00:42:09 But again, if you think of the tripartite model, this may be important for circadian clock, but is it important for your mood? So that's where I think you need or the homeostatic drive. So that's where you need to think about it. So for the clock, for entraining your clock, you literally can't entrainer only by the dawn sunlight.

Starting point is 00:42:29 You actually don't need dawn on dusk. Okay, but forget that. Yeah, and I appreciate that you're distinguishing between circadian effects and other effects of light. You're being very precise, which is appreciated. Until we hear about this tripartite model, which we will cover for the sake of the discussion, let's treat the light viewing behavior as what are the benefits or drawbacks of viewing light

Starting point is 00:42:53 for all biological purposes, not just circadian settings. So in the morning, it's clearly going to set the clock. And then during the day, if I understand correctly, the idea is to get as much bright light as you can, because you're feeding it sounds like a sort of light hunger. Exactly. I see. I love this way to put it. I think there is a weird light hunger, considering that we're not photosynthetic organisms. There is a weird light hunger in animals that they need to measure.

Starting point is 00:43:20 They need, they, they need measure. And I think that relates to the season season because the whole reproduction cycle of animals can depend on the availability of food in the environment. And if you don't know when the season's gonna happen, they don't have calendars, it's gonna be very hard to survive. So I think that's why we have this light hunger. That's a major hypothesis. It's not being tested. Interesting. So then afternoon and evening start to approach.

Starting point is 00:43:48 So I've had this weird experience. Maybe you can psychologically or biologically diagnose me now, Sam. So where if I go into a movie in the afternoon like a matinee, and I come out and it's dark, I notice a significant drop in my mood and my ability to go to sleep. Whereas if I get some view of the light in the evening, it doesn't have to be the sunset, although sunsets are nice, but I get some light pulse in the afternoon that I have no trouble whatsoever. And it happens in a daily, on a single time to watch them more or less. That's interesting.

Starting point is 00:44:24 And then you mentioned the camping experiment where when they went camping, they're seeing the sunrise and the sunset. So what should people do in the afternoon slash evening time in terms of their light viewing behavior? I mean, the best thing to do is to let the natural light creep in into darkness, right? That would be the best.

Starting point is 00:44:43 But clearly, that would be inefficient. You want to go home, you want to read, you want to talk to your kids, you want to talk to your family. So I think, you know, it's nice to extend the day. I don't think that's wrong. If you somehow can block that light from affecting your circadian clock. So should people use blue blockers in the evening? I personally do not like any blockers that take a single wavelength of light because again if you think of a holistic holistic approach, yes the blue blockers going to prevent you from affecting your circadian clock very much. But then your vision is going to be distorted because we always see in full spectrum.

Starting point is 00:45:23 The sun has this beautiful spectrum, right? And then when you start seeing without the blue things look yellow and it can get really weird, right? I mean, so I personally, I've tried the blue blocker and I couldn't even wear them. I thought they were just really horrendous to be honest. Well, along the lines of blue blockers, I think a lot of people mistakenly wear them all day long. Oh my God, that would be very bad. A lot of people do that. A lot of people do that.

Starting point is 00:45:51 They think that the blue light is bad. I think that the concept of blue light being bad led to a lot of product development. And a lot of people are just assuming that viewing blue light is what was giving them headaches. When in fact, it might have just been looking at screens at close distance. So here is the problem, right? I mean, the blue light got the bad reputation because people who gave a pure blue light

Starting point is 00:46:13 showed that it goes a hugely retinal damage. But again, if you're using blue light in its pure form, it has a lot of energy because it's shorter wavelength. But we're talking about full spectrum light. There are ways now where you could change the spectrum of the light and keep it white between day and night and change the content of the color without you noticing.

Starting point is 00:46:36 So you don't even have to affect your vision. So how would you go about doing that? So you just lower the level of the blue light. You don't have to eliminate it. So just dim the level of the blue light. You don't have to eliminate it. So just dim the light. Dim the blue, but keep then increase the yellow, but keep all the colors in a certain white. So you know, you could have different warmness of white. And people know how to do this, physicists know how to do this. People who work with light know how to do this. Well, maybe somebody in the wellness slash, I don't like the word, but biohacking or optical community will do this. Well, maybe somebody in the wellness slash, I don't like the word, but bio hacking or optical community will do this. I think it's a really important. I see

Starting point is 00:47:09 so many people were really long. I don't know why they love well, I think they're just uninformed. I think, frankly, to be honest, it's easier, right? It's easier to explain to somebody if IPRGC's respond mostly to blue, remove blue, you'll be fine, right? But that's not as simple as that because they also receive road and coin input. So respond mostly to blue, remove blue, you'll be fine. Right. Right. But that's not as simple as that because they also receive road and coin input. So you want to actually, and you know, we could go into details that's boring for your listeners, but it also affects the adaptation properties of the whole retina. So you don't want to do something so drastic that you take just one color of the spectrum. It just seems very counter

Starting point is 00:47:43 intuitive to me, to be honest. You've told me before as well that just because these intrinsically photosensitive circadian setting gangling cells respond best to blue light, if the light is bright enough because they also get input from other components of the eye, it doesn't matter if you block the blues. If you're looking at bright light at night, you're going to disrupt your circadian cycle. And that's why I didn't want to go into the boring details. But themselves, the photo receptors

Starting point is 00:48:11 have a wide range of responsiveness. So they are most sensitive to blue light, but that doesn't mean they don't respond to green light or to shorter than blue light. They respond to very, very wide spectrum with different sensitivity. So unless you understand the system, just removing 480, I don't think it's going to do 100,000 in and under. So your home is a cave at night, basically, with some, it's a nice cave

Starting point is 00:48:39 with candles, right? And you and your cats and your lovely wife. I know who's also a phenomenal scientist in her own, right? Yeah, she is. She is. And, but you do keep your home quite dim to dark at night. In fact, I did go to meetings with some of my friends who work on this and they really struggled with me.

Starting point is 00:49:01 They said we could have broken our legs, living in the same light environment that you do. So I am in extreme, but I measured it for myself and I asked Rajeev my wife if she's okay with it. She also liked the dimness both of us can see well in dim conditions and that helps us a lot. But I think you have to measure it for yourself. You really have to it's a very simple experiment. Just try to dim the light as much as you can. I call it the minimum amount of light you require to see comfortably. And that's how you want your environment at night.

Starting point is 00:49:36 This is what I think is the game changer. If you reach to a level where it's just barely, you're literally on the cusp of seeing uncomfortably versus seeing very comfortably. You are going to be very much better than I don't like to make it completely dark. I think complete darkness induce anxiety in humans to be honest, so I don't like complete darkness. In fact, I don't like complete darkness. They like it. Even nocturnal animals don't like complete darkness. They like it all night life. Even nocturnal animals don't like complete darkness. I mean, we have studies in animals that are nocturnal that if you put them in complete darkness for several weeks, they have severe anxiety

Starting point is 00:50:15 and depression like effect. So keep the light dim. Use red light that is very dim. If you wanna keep the room for sleeping, red light that is very dim has very small effect on circadian clock and below 10 locks of red light literally doesn't affect sleep at all. So there are ways to do it.

Starting point is 00:50:38 It just we need to educate the public. And I feel like you literally need a whole lecture to just explain to the people how to deal with life because it's not as simple as people think. Well, that's what we're doing here. We're stepping through a piece by piece and the reason we're doing that is because it's not as simple as saying just block blue light or get a lot of light during the day and minimal. I mean, just put it in perspective to tell it we only have three different cones in our retina that respond to three different colors We call them red cones for simplicity green cones and blue cones

Starting point is 00:51:14 Yet we have only three of these but we could see massive Palette of colors. So that tells you something if the system was just simply about a single color and it's just removing 4, 8, or just blue is sufficient, then we should only see in red, yellow and blue. We shouldn't see all these different hues of color, but because the system is not that, we see all these different colors. And that's why it's important to remind people that the white light is made of many different colors. It's actually like the rainbow. That's why you see the rainbow. light is made of many different colors. It's actually like the rainbow.

Starting point is 00:51:46 That's why you see the rainbow. It's made of many colors. White light is never truly white. It's made of a lot of different colors. It's like the pink Floyd album cover. Exactly. Exactly. So, dim at night, maybe dim red light, ideally, your candle light, find that minimum required light level. Just make sure when you lower the light, sit for at least 10 to 15 minutes, let your system adapt. Because if you had it bright light and you switch it off, surely you're going to suffer because your system didn't adapt it, it was used to very bright light. So you want to engage your rods which take a long time to dark at that. So that's why I tell you just wait a little bit. Don't just switch off it. I don't see put it on. Put it off. Sit down. Wait for 10 minutes. Ideally

Starting point is 00:52:34 15 minutes. And then see how you see. And then once you do that, you will notice that actually, yeah, I could see quite well, even with much less light. What do you do regarding screens? Yeah, that's the hardest thing again. I mean, there are beautiful programs that change the whole intensity and color of the screen. These could help dim your screen at night to the lowest part. I mean, yes, you won't see it when you wake up in the morning, but then you can increase the intensity. So try to decrease. I mean, just what we were talking about, think of light intensity, duration, color and time of day. You really have to

Starting point is 00:53:15 keep these four things together, right? We've roomed together at a couple meetings from time to time no longer, because one of us, not to be named, has a severe snoring issue that made the other one pseudo homicidal. You can guess who that was. But I've seen you check your phone after dark once or twice, and you did it by sort of putting your phone away from you, right? And actually, I'm sort of half joking, but phone away from you, right? Absolutely. And actually, I'm sort of half joking, but I, and you dim it quite a bit.

Starting point is 00:53:48 I'm sort of half joking, but it actually makes sense that, you know, if you shine a flashlight in your eye, it's much brighter than you shine. Light on the left side of the... You're going to be going direct. So if you'd let's look on the side, most of the lights are going to go this way and you're on the same... So you, okay. So, and as silly as that might seem to people listening, I mean, what it means is that

Starting point is 00:54:10 getting bright light in your eyes at night is something that you really want to avoid and but there is the reality that and even when I check sometimes if I you know if I have something and I check it so fast and switch it off so fast so I'm also aware of my messages. I'm also aware on the duration right so duration color, and time of day, ideally I should not check iPhones and iPads. I don't use iPad at night because it's hard to lower it enough because it's a huge. But even my iPhone, I try not to use it at night. And like once it becomes 830 or 9,

Starting point is 00:54:41 I don't look at it at all. Unless it's World Cup or Euro Cup in case, it's on 24 hours every month. That's only every four years. It's a big soccer fan. All right, this has been incredibly no pun illuminating. Let's talk about the relationship between light and some of these other non circadian

Starting point is 00:55:02 or pseudo circadian effects. And we will try and link those. But you had a, what I consider, absolutely landmark beautiful paper, published in Nature a few years ago, showing that if you disrupt the exposure to light, or the timing of the exposure to light, that there are dramatic effects on the stress system and on the learning and memory system.

Starting point is 00:55:29 We could talk about each of those separately or together. What are the effects on stress and the effects on learning when light viewing behavior and sleep wake cycles are disrupted. Yeah. So just to remind you, you know that, but to remind your listeners that I was trained as a circadian biologist. So I really was indoctrinated into thinking that light has to affect the clock, which then cause all these different effects. So that's what I believe. That's my dogma.

Starting point is 00:56:01 That's what would have made me really happy. And then Tara Legates and Kara Ultimas joined the lab and said, we started discussing a lot of data and we said, what if there is a direct effect of light that we're missing independent of the circadian clock? So this is not an easy question to ask, to answer because as we've been talking all along, light affects the circadian clock. So how could you give light at different times of the day and not mess up the circadian clock? Luckily we came up with such a way and that's why it was important to do this experiment the way we did them. And we proved that this light dark cycle does not disrupt the clock, there is still a circadian rhythm and does not close sleep, does not

Starting point is 00:56:43 go sleep deprivation. And yet, surprisingly, if you give light at the wrong time of the day, even without disrupting the circadian clock or without causing sleep deprivation. As you mentioned, you get huge mood changes in the organisms and you get learning deficit. So this really, and at the time,

Starting point is 00:57:04 people have really hit us hard. I mean, it was really hard to publish this work. And you could, yeah. Well, it came out in nature. So in the end, you prevailed. But I wanna make sure that I understand. So you're saying that yes, there are effects of light on the circadian rhythm.

Starting point is 00:57:22 Absolutely. Meaning sleep and wakefulness. Yes. And they're timing. However, there are direct effects of light on mood that can be dissociated from the effects of sleep and waking. So if I interpret that correctly, that could mean that when we view light and how much light could make us feel happier or less happy or even depressed, stressed, learning, etc.

Starting point is 00:57:48 Bingo. Even if we're sleeping and waking up at the appropriate time. Bingo. I mean, eventually, because we're talking about the whole system, eventually when you start having the other problems, you also develop sleep problems, but you're absolutely right. And in fact, now research from Diego Fernandez in the lab have found that now we know that they actually require different brain regions. So we don't only have a theory, we don't only have a light environment that showed they can be dissociated.

Starting point is 00:58:18 We know that they use completely different brain regions. So the SCN that I told you about earlier, the place where the central pacemaker is the one that received direct input from the retina, through the IPRGC's to adjust your circadian clock, is not the area that receives the light input for mood regulation. It's a completely different brain region. What's the brain region called? So the brain region, we called it the peri-habinular nucleus. I'm not so sure how good or bad the name, but it doesn't matter, it's the PHB. And what's really amazing, this region also received direct input

Starting point is 00:58:50 from the IPRGC's, but projects to areas in the brain that are known to regulate mood, including the ventral medial prefrontal cortex, which has been studied for many years to be impacted in a human depression. So just by this amazing serendipity to find that a region that is so deep in the advanced brain, like the prefrontal cortex is your executive brain, one of the most elaborated in humans, to see that they receive input from these ancient

Starting point is 00:59:24 photoreceptor, was stunning to us, and told us how much we didn't understand the importance of light on human behavior. So, how does that finding informed daily protocols for you or for other people? I realize you can't leap to always from one paper to daily protocols. But if light indeed does control prefrontal cortex, executive function, learning, stress, and mood, and let's say I'm waking up, even running it, I'm sleeping. That's why should I do differently? That's why we came up with the tripartate model. Because yes, we could think about just adjusting

Starting point is 01:00:00 the clock with lights in and being dark throughout the day. But that may not be important for your whole physiological function. So now if we include these other effects of light, that's why I prefer to still get a lot of light in the day. I don't want to be in very dim light condition throughout the day. I see. So even though it doesn't affect your clock, as you beautifully said, Andrew, it may affect your mood and learning and memory. It may affect your alertness level, which is going to allow you to learn better. It may affect your homostatic

Starting point is 01:00:29 drive. Maybe your homostatic factor will go higher, so you could sleep earlier. So it's important to think of light as stimulating all these brain regions, which means it's producing more activity, which in reality, this is how people think of the homeostatic drive, that the more active you are, the more the homeostatic drive is built up, the better you sleep. So that's why we came up with the tripartate model, because as a circadian biologist, I only thought of light through the circadian clock affecting behavior. As a sleep biologist, they only thought of the homeostatic drive affecting sleep, affecting behavior. And for people who study light for vision, and other things, they thought only of the environmental input.

Starting point is 01:01:10 But now if you put them all together, you get with this tri-partate model where it's really mind-boggling, and it makes so much sense. The organism doesn't want to depend on a single component. But if you could incorporate these three together, you could have a beautiful system that is well adapted. So let me tell you the sleep wake cycle, right?

Starting point is 01:01:29 So we know there is a homeostatic drive to affect sleep. You've had beautiful talks about that, which is basically the longer you're awake the more you want to be. So that's your homeostatic drive. We've talked about the circadian influence of sleep and the fact that light dark cycle affect the circadian system, which eventually affects sleep. So these two components are well understood. Now the third factor is your direct light or environmental input. How much stress, how much light you get from there

Starting point is 01:01:56 also can highly impact sleep. So even if you have a good circadian and homeostatic drive, if you're getting light at the wrong time of the day or if you're being stressed and thinking about it, then your sleep is going to suffer. So you have to think of the three together to have a beautiful sleep wake cycle. And that's why we came up with the tri-partitmolar. The same thing happens with feeding. I could beautifully put it to people. Your hunger, your energy level is measured by the arcoate nucleus. Your daily

Starting point is 01:02:25 intake of food is again dependent on the SCN and light dark input. We found that if food is not available, there is yet a third input that is not dependent on the SCN, not dependent on the arcoate, depending on a completely different brain regions. So the animal can actually start looking or the human can start looking for food when it scars even at time when they are not supposed to be active. So that's how the organism thing they have to evaluate multiple inputs for them to decide what is the best physiological outcome at that moment, at that season, I say. So I want to get into archaeology and feeding, but just to keep, make sure we can keep our hands around this tripartite model. So I want to get into arqueoid and feeding, but just to keep, make sure

Starting point is 01:03:05 we can, you know, keep our hands around this tripartite model. So if I understand correctly, we've got the circadian influence, then you've also got the drive to sleep. Actually, one of the ways that I think that can be best understood is if somebody ever pulls an all-nighter, they get tired around 11 or 12 or so and then very tired around 3, 4am. But then even if you stay up, sometime right around 7 or 8am, your normal wake up time you start to feel alert again. Exactly. And that's because the sleep drive is extremely strong, but there's a circadian rhythm

Starting point is 01:03:38 that drives wakefulness and more. Exactly. Okay, so those two are the components. Before we get into the feeding component, I want to talk about these direct effects of light on mood. Okay, Diego Fernandez's data. And this perihubbenular thing. Sure. So let's just, for the moment, set aside the tri part of the tri part type model

Starting point is 01:03:57 and just focus on what are the direct effects of light on mood. And the way that I interpret what you said so far is that the protocol that emerges from this, if one is trying to optimize their mood, is yes, see light, view light, I should say early in the day, in order to set your circadian clock, maybe also in the evening as well. And of course, avoid light at night, get it as dim as possible. However, you said it's also a good idea to get as much bright light during the day as you safely can in order to improve your mood independently of regulating your sleep wake cycle. And that's a hypothesis.

Starting point is 01:04:33 Here's the problem where it's not going to be as satisfying as the circadian, is that as you know, this brain region has been discovered very recently. Habaniila. The very habaniila. We've known about it a long time, but nobody knew what it did. So we knew about the habinula, but that's why the name is confusing. It's actually not the habinula itself. It's the perihabinula.

Starting point is 01:04:51 It's near the habinula. It's near the habinula. Why don't you just call it the summer hot tar nucleus? I should have. I don't know why. Maybe because if you do that, it's not okay. Okay, so for here ever after, the perihabinula nucleus, we should probably call it the hot,

Starting point is 01:05:05 hot, or, hot, or none does. Hot, hot, or none does burst. Okay, this is like nerdy science attribution stuff, but I'm just gonna call it the hot, or nucleus, Wikipedia line it up. Okay, so this structure is taking light and independent of sleep rhythms and circadian rhythms.

Starting point is 01:05:21 It's driving change, it's a new, how does it do that? Is this through the dopamine system? The serotonin system. We still recently we haven't identified this region very well. We don't know what light does to it We don't know how it interacts. So this is an area that is right for discoveries and we're working on this right now But that's why I said it's not satisfying. This is like the function of sleep. Why do we sleep? We know sleep is very important to us, but we still don't have a satisfying function of

Starting point is 01:05:48 why do we sleep, right? We have the wide questions. The wide questions, I think it's our good friend and colleague at University of Washington in Rustman, G elder who always says, when somebody asks why, the best answer is just to say, I wasn't consulted at the design phase. Exactly. Right, none of us really know. No. But the point is, maybe I shouldn't have said,

Starting point is 01:06:06 why, what is the function of sleep? It's still very hard to know. Why would, what is the reason organisms have to go offline for so long? People assume it's for repair, assume it's for learning and memory, assume all kind of stuff, but there is really no clear function for sleeping. There is no clear function for sleeping.

Starting point is 01:06:28 I mean, if you talk to people, there are hypotheses. I mean, all we know is that if you don't sleep or you're sleep is very fractured, you get messed up. And you could die even, right? I mean, it's really bad if you don't sleep. But we don't know what is the function? What is the, What is that sleep have gone to organisms that couldn't have done with rest? What if you just could

Starting point is 01:06:50 rest without sleeping? Just sit down on rest? Well, my lab is trying to figure out whether or not these non-sleep deep rest protocols can compensate for sleep in. I mean, obviously sleep is better, but many people are not going getting the sleep that they need. But, okay. So, and if people are sensing that Sam or an I are about to start talking over each other and arguing, that's always the goal when you talk, right? Unlike other scientists I interact with, when Sam or an I get together, it's considered a successful conversation if we get into a big fight and then go for a big meal where

Starting point is 01:07:21 I pick the restaurant. Okay. So, let's talk about food and eating and appetite. You had yet another, yes, I greatly admire your success in this way, yet another incredible discovery showing that there are direct effects of light on appetite and feeding behavior. Maybe you could just summarize those results. Honestly, that paper is the one that allowed us to come with the tripartate model because we were thinking completely wrong about it.

Starting point is 01:07:54 We wanted this experiment, it'd be fun for your audience to hear why we started this experiment. Remember that when we discovered the IPRGCs, we figured if they are the only relay to entraing the circadian clock, then you could kill them and have an animal opposite to the one that we spoke or a human opposite to the one that we spoke about earlier. Where instead of having no patterned vision and half circadian photoentrainment, we could produce an animal that have pattern vision, but no circadian phototentraiment. So circadian blind, circadian blind, but pattern sighted. And we succeeded in that. The problem when you have these animals, which I've told you many times already, is that

Starting point is 01:08:36 they don't adjust to the day-night cycle. So doing experiments on them become very complicated. What is their behavior like if you don't have these cells? Are they awake and then asleep? They just drift like the humans we've talked about. They think they're in Las Vegas. They stay up later every night. They come either, depending on their clock. If it's the clock is shorter, they come in earlier. If their clock is longer, they come in. So they're really messed up. They really don't adjust to the, if they were in the wild, they'd be eliminated in a second.

Starting point is 01:09:05 There is no way they'll survive. So me and Diego started talking, we're like, what if we use non-light in training agent? And what is the strong, non-light in training agent? Food. So we thought that the light defective animals will have more sensitivity to food in training. Because as you know more than me,

Starting point is 01:09:25 this is an area that you've worked really well on. For vision, if your image blind, you're hearing and and so on to sensory, get improved, right? The lack of vision improves your hearing and sensation. But we found actually that if you don't have the light to system, actually you're feeding the food ability to entrain the animal goes completely to the ground, completely opposite to what we predicted. So light viewing and feeding behavior are interacting in ways that support one another.

Starting point is 01:09:58 And that's why we came with the tripartite model. We figure it's different than sensation of the environment. When you sense with vision, vision and hearing interact, but your vision is a real full modality. You want to see. That's what vision want to do. You want to hear. That's what hearing want to do. You want to sense. That's what sensing want to do.

Starting point is 01:10:17 But for the circadian system, light, food, all these entraining agents, they somehow have to interact Ag to keep a coherent system. You don't just assume if you remove light, this one is going to be stronger. No, they need to know each other's. The light informs when the animal is going to eat. What I like about this so much is that, you know, in the other, in the world outside of

Starting point is 01:10:41 science in which I don't really exist in, but that I see a lot of this kind of wellness, you know, stuff with this, all this mind-body integration stuff. It's interesting because people view the body more as a system, right? A system of organs that interact as opposed to the way that standard science and medical profession is like you work on the liver or your ear, nose, and throat or heart and lung or brain or that's a great way of thinking. Yeah, but the biology is integrated. I mean, and so for somebody who's interested in affecting their eating behavior, something that you are familiar with and that we will talk more about your experiences of in a moment.

Starting point is 01:11:29 How should they use light in order to adjust their eating behavior? Right. So now that I've told you about all these interaction between the different inputs to the circadian clock, just you think about it as an engineer. What would be the best thing? The best thing is to know when your food times happen in the day, when should you get light and when is your circadian clock in your system? Right? So, if you eat at very specific times of the day, that's another signal that is telling your body, your clock, you're in a certain time of the day. So, if you're having lunch at the correct time every day and you're getting bright light, now you have two systems that are informing you o'clock, your clock is going to be better. So regular meal times, regular mean times that fit your circadian clock. So and in fact, if you do that when I started doing this and it helped me lose weight,

Starting point is 01:12:19 is that I'm exposing myself to the right amount of light dark cycle. I'm eating at regular time. It is amazing. You would be not hungry, let's say, let's say you eat at noon. You will not feel any hunger at 11.45. And then all of a sudden the hunger jumps, this is clearly not an energy issue

Starting point is 01:12:36 because it could not be that drastic. Right. No, the desire to eat is mainly driven by these, these cues, these hormone cues that are very exquisitely timed to sleep wake cycle, but also to light. Exactly. And in the wild, you could imagine why energy level through the acuity is, it's nucleation. You should explain to people what the arqueoid is, because I don't think we've done that

Starting point is 01:13:00 adequately. The arqueoid nucleus is an area of the hypothalamus that drives hunger and feeding behavior. And what we're talking about is the fact that it's taking cues from your viewing of light, believe it or not, is impacting your level of hunger. And this is a non-trivial way in which your timing of hunger and amount of hunger is regulated by when and how much light you view. So, let me ask you a couple of practices. But can I just... This is really... Before you ask me, sorry, Andrew, we said we're gonna fight. But to me, it's the interesting thing to think about it.

Starting point is 01:13:36 In the wild, when you didn't have the availability of food that we have, the arcoid plays a huge important role. Because if you're not... If you weren't successful in getting food, then the arcoid is going to tell you, look, you have to take risk and go get food because your energy level is very low. And that's great. That's tons of great research about that. But I think what's missing is the fact in humans, we're not getting to a situation,

Starting point is 01:14:00 most of us. We're not getting to a situation where we have low energy levels. Most of the time actually we eat, not because we want to, because we are really have low energy, but because we want to eat. So I think that's why I feel that the timing is very important for us, because we always have enough energy level for us to eat. Well, I enjoy eating so much that I'll eat just for the sensation of chewing. True. I mean, I enjoy the taste much that I'll eat just for the sensation of chewing. True. I mean, I enjoy the taste too, and I enjoy the social aspects.

Starting point is 01:14:28 I'm sure you are a part of it, but I literally enjoy the physical absolutely chewing, absolutely, which explains a lot. Okay, so how regular are you, or do you recommend people be about meal times? Because what I'm hearing is that light viewing behavior is pretty straightforward. Get a lot of light in the morning and throughout the day, minimize it in the evening and at night, generally speaking. For sake of mood, insurcated rhythm. But for sake of regulating timing and quality, I should also say a food intake, because people clearly make better say a food intake,

Starting point is 01:15:05 because people clearly make better choices about food intake when they are anticipating a meal and they aren't constantly hungry. And so the ability to regulate hunger for particular phases of the circadian cycle is quite valuable for all people, not just people trying to lose weight, but all people. Are we talking about down to the minute?

Starting point is 01:15:23 Like, if I'm... All right, plus or so, 12 noon is my normal lunch, let's say, plus or minus half an hour. Okay. So eat around between 1130 and 1230. If that's the time and it depends if you also do multiple meals. Remember, three meals, that's a decision that somebody came up with. I don't know why nowadays people are fewer people are doing that. I think given our friends such in pandas work. Right.

Starting point is 01:15:49 I mean, so you could have two meals. You could have very multiples meals that are distributed across your active time. I agree with Sachin's plan does work that try to avoid eating when your system is supposed to be relaxing, when you're supposed to be at non-active times. So, you know, limit your eating to the active time of your cycle. And that seemed to be, and John Takahashi is doing some beautiful stuff on this.

Starting point is 01:16:17 That seemed to be incredibly important for aspect of the circadian and for health. And for health. Yeah, I mean, we're referring to such in pandas where he wrote a beautiful book called the circadian code, maybe Samar with some luck, you'll write a book as well. Meaning the world would be lucky to have that book. But Sachin's data really strongly pointed the fact that liver health, brain health, metabolic factors and endocrine factors, and various systems and organs, all seem to benefit from having a period of each 24 hour a day in which we are not

Starting point is 01:16:52 eating anything, and then eating it very regularly. Let's talk about eating and meal times, and let's move a little bit away from the science for the moment, although we will return to it, and talk a little bit more about your experience with eating and meal times. So you're looking good, shape lately. Thank you. I know you've been putting work into it. Yeah. We talk a lot and you've been exercising and you've been eating well, meaning quality food. You just came back from Jordan where I'd assume in the food is amazing. It's the food is amazing. And honestly, usually I gain a lot of weight in Jordan, but this time I didn't gain any weight, which was really nice.

Starting point is 01:17:30 So, yeah, you've, you've, when I met you, you were probably about a hundred pounds heavier than you are now. Yeah, 275 pounds. I'm 219. That's crazy. Yeah. You had a lot of vigor then and you have a lot of

Starting point is 01:17:44 vigor now. But I know that you undertook a very specific protocol in order to lose the weight. Based on your understanding of the circadian system and of light and appetite and mood, maybe you could just tell us a little bit about what that schedule looks like. And we realized that this is not a prescriptive for everybody, but you found what worked for you. Yeah. Maybe just to describe those. I mean, honestly, I followed my circadian cycle, right? What we've talked about, right? So I dimmed the light at night, I slept at regular hours. I ate my major food in breakfast and lunch when I'm really active and I'm really hungry. And at night, when I avoid dinner because my circadian system really shuts off at 3.

Starting point is 01:18:27 I'm an early person. Like, you could give me anything I would eat before 3. After 3, nothing appeals to me anymore. My system is shut off. But what time are you going to sleep and what time are you waiting for? Oh, so in my case, I should have put this up. I mean, I go to sleep literally at 9 p.m.

Starting point is 01:18:42 I mean, I literally five minutes after 9 p.m. I mean, I literally, five minutes after 9 p.m, I'm completely out. And I wake up between 4.30 and 5 a.m. So if I extend it, I go to 6 a.m. But very rarely, it depends on how tired I was. And that, as I recall, was an important set of changes for you to be able to regulate your food intake. Absolutely.

Starting point is 01:19:02 Because then I'm having very big breakfast at and again, for different people, it's different. I have a big breakfast at 7 a.m. maximum. So I have a big breakfast, coffee and all this stuff. Then I have some simple snack around 10. Then I have regular lunch at noon or between noon to one. Then I have another snack at three. And the hardest time to regulate the food is between 12 and three. This is what I'm, I really feel hungry. This is the equivalent of kind of lay evening for most people. Yes.

Starting point is 01:19:31 So for me, it would probably be between seven and 10 p.m. Exactly. Exactly. And then at night, I'm completely not hungry, but usually, as you said, the beauty, the enjoyment of food. Like when my wife kicks cook some really beautiful Indian food, I eat, but I'm not hungry. And I notice if I eat with that, I usually gain weight, but if I regulate that at night, I also lose weight. So there is a combination of all these things that help you, adjust

Starting point is 01:19:57 these, these, the input of food, the input of light, the input of the clock, and the drive to hungry. Yeah, I appreciate you sharing that. And I want to emphasize that some people are not hungry early in the day. They might be late shifted people in which case eating later in the day will work well. As long as they don't eat early in the morning, that's just you have to work with your schedule, with your active schedule. Yeah, you know, I've been talking about this offline for years. I'm glad we're finally having this discussion publicly now But we're talking about really is finding your ideal sleep schedule exactly and finding your ideal eating schedule exactly and Understanding how those two things interact and you know the nice thing as you said finding them out is going to help you to understand

Starting point is 01:20:39 How they interact because we know from the tripod that model that they are all interconnected. And for each person, they're going to be interconnected differently. So for each person, you would, you know, for me, if I exercise at night, I'm going to miss up my whole system. So when do you exercise? Morning. Morning works great for me. I mean, it's amazing. Morning exercise for me works great.

Starting point is 01:21:03 I tried one time because it was easier for me to exercise at night before I leave when the traffic is there from the election. I think that missed me up because I couldn't sleep well and I couldn't wake up well and that led to more changes in my food. I gained weight again, actually. Believe it or not, even though I was exercising. So I think this really makes me think that you have to think of the tripartite model to see what is the best times and what is the best interrelation between

Starting point is 01:21:32 the different component, as you beautifully said, between your meal times, your light exposure, and your sleep, that works for you. Well, thank you for that. Usually, Sam is insulting me today. He's complimenting me. I'm going to compliment him right back by saying, this is the first time that I've ever really understood how yes, light can control sleep, yes, it can control mood, yes, it can impact feeding, but that it's really about doing the self-exploration to align those in the way that works best.

Starting point is 01:22:03 And what I'm hearing, tell me if I'm wrong. But what I'm hearing is that once you understand what gives you the best sleep wake cycle, then you should exercise during the period of time in which you feel most alert. And if it works for your schedule, ideally you would also eat during the time in which you feel most alert and then stop eating and stop light viewing behaviors you had towards sleep. So the only thing I would say that complicates all of this and that's what makes me sad is your light exposure. Mine personally. Sorry, I'm just kidding.

Starting point is 01:22:37 The people's light exposure, right? This is what complicates it because you're not going to be able to figure all this out if you're shifting yourself out of your comfort zone by viewing by viewing light at the wrong time of the day. So let's say, let's say you're if you were under an idle natural conditions, you're a person who would sleep later than me. Let's say we'll sleep at midnight and wake up at 8 a.m. Let's say you don't eat anything till noon and as you said you eat late in the evening. Then this would be perfect for you. But now see what happens if you now you include the light component. Now if you push your sleeve from midnight to 4 a.m.

Starting point is 01:23:15 Now you're waking up in the morning and you're actually really not the morning you're working up, sorry, at noon instead of 8 o'clock and the time where you're not supposed to be hungry now you're working up, sorry, at noon instead of eight o'clock. And the time where you're not supposed to be hungry, now you're going to start eating directly at noon or something like that, or even delay it. And now you're shifting your whole cycle and you don't know if this interaction between your sleep feeding and the light dark environment is still going to be maintained or not. And that's the problem that people have. So, you know, as I'm hearing this, what I'm realizing is most of us,

Starting point is 01:23:45 probably me included, are messing up at least one, two or three of these components. But that the probe, the way to figure out what's right for oneself is to start manipulating light exposure. And I'm gonna be honest, I'm biased because I believe that light is the strongest time giver. And a lot of people disagree, some people think feeding is. I always thought that light was the primary zeitgeber, the primary light.

Starting point is 01:24:13 A lot of people think it's food, a lot of people even sometimes mention social interact. I actually read the literature. I agree with you. I totally agree with you. I mean, my understanding is that light is the most powerful driver of the things we're talking about. That's why I think we need to regulate this first and everything else fits. And you know, the nice thing is that your sleep or cycle and exercise tell you really bluntly if you're doing it right or not. Tell me more about that.

Starting point is 01:24:37 I tell you more. When I shifted my exercise, honestly, things fell apart like never before. When you moved from exercising early in the day. In the morning. Yeah, it completely fell apart for me. I didn't enjoy exercise at night. My pain tolerance for exercise was as good. I'm talking with N equals one.

Starting point is 01:24:54 And I'm aware of this. I've never tested this empirically. But at least to me, it really messed up everything. I started having problems because my body temperature would go up and that will affect my sleep. I possibly was running in the gym with a lot of lights, so maybe the light was a component. But for me exercising in the morning, it's so much better for me. But a lot of people can't even think of exercising in the morning. So it depends on when you feel comfortable in your sleep wake cycle and your exercise, I think that tells you if your system is in synchrony with one another.

Starting point is 01:25:27 That's really interesting. I, we're good friends, our friend Pat Dawson, that we both know, did nine years in the SEAL teams and he's one of these people, he says, he's happy to go for a runner swim anytime between 4.30 a.m. and 6.00 a.m. And he'll train in the afternoon too because he's a SEALime guy and they'll do whatever

Starting point is 01:25:45 anytime, that's part of the phenotype. But he feels best doing that, right? I'm a mid, I like to exercise mid-morning and I'm happy to skip eating until 12 or one. Great. And I like to go to sleep around 11, 32, because I'm a normal human being rather than you who goes to bed at 9am.

Starting point is 01:26:02 What about that, actually? I've never asked him what time. So Pat ideal to sleep time, I've asked him this would be around 8.30 or 9pm. Except, no. Oh, not that. No, but he has, yes, but he has two young children, two years old and a newborn. And so, the cycle is disrupted, right? Yeah, but that's known, right? I mean, the effect of child bearing, and I think that we could talk about this that's more

Starting point is 01:26:25 complicated but that's pretty pretty much. Yeah I mean I think we need to come up with a new name for a chronotype because chronotype implies that it's just about sleep and wake being an early birder and Idaal and what we're also talking about is how exercise and eating match on to those. And the phase relation between them. And the phases between different components, as you said, because they interact. Because they interact. And they don't have to be in the same phase. Like, let's say my light and food

Starting point is 01:26:54 could be very close to each other. So your light and food could be different, right? The phases don't have to be, they can be plastic. So you have to find this for yourself. You may be a person who eats late at night, exercises late at night, or you may be a person who exercises early, eat later. So it doesn't, as long as the phase is, is good. That's what you, that's what you have to find out. Okay. And if I understand correctly, when you're talking about phase relationship, it means you

Starting point is 01:27:19 want to lump exercise feeding and light for and sleep and sleep in a way that as a coherent and total system makes you feel really good. Temporally in a great order. Absolutely. Yeah. And I think that and I could tell you to me is literally getting exposed to some, you know, clearly in the morning, clearly at noon, I go out, I keep my windows in the office completely open, eating mostly in the early time of the day and exercising and literally at the end

Starting point is 01:27:51 part of the day, I'm literally in a more thoughtful, vegetative state. Like I really can't like after five, I tell my students, if you want to tell me anything complicated, you're wasting your time. My brain just doesn't function. So even though I only sleep at night, but I'm really starting to shut off, ramp down. Really, I mean, it's, you know, I could send the email, talk about brainless stuff, but my power, my energy to do powerful stuff, really drop tremendously. So all my students who know me very well, they put the meetings with me early in the morning because they know this is when I'm, so everything for me and for me is very tight.

Starting point is 01:28:30 So it could be different. It's very clustered in the morning, it's all tied together. And literally the remaining part seems to be just, you know, vegetative state. Yeah, you and my Bulldog Costello, who unfortunately passed away recently, had that in, yeah, yeah, yeah. Yes, Samardog Costello who unfortunately passed away recently had that in. Yeah, Sam and Costello were good friends.

Starting point is 01:28:48 Yeah, sorry to break it to you here. Yeah, he had a good long life and he went easy, but he had a circadian clock. The basically would just sleep around 24 hours a day. Minimal activity interspersed every third day or so. You do have this morning vigor. Yes. And I think other people are going to have more of an afternoon vigor. Do you think that this can change across the lifespan? The rumor is that teenagers naturally want to sleep in later and stay up later.

Starting point is 01:29:18 Do you think that social rhythm or do you think that that's actually biological? Yeah, that's a tough question. I mean, it could be both. One thing that worries me is that it seems that if anything with age, this morning rigor gets stronger. So people become more of mourning. More and more. Why is that?

Starting point is 01:29:36 Where are you? I think that's good. Because for me, I'm already very shifted morning. I don't want to be one of these 7 PM to 1 AM sleepers at some point. Yeah, on the other hand, it's also kind of nice because it's quiet and you can get work on. Yeah, but honestly, from 4.30 to 7.30 when my wife wake up, it can be very long. Yes, you achieve a lot, but it's quiet outside. I don't want to be at 1am. Let's put this right. You can tell Samar is more social than I am. That's right. That is true.

Starting point is 01:30:06 Well, we should touch on that, actually. So your wife is, she follows a different schedule. Yeah. And so the social rhythm is important. I think what should we do? How should we conceptualize and how should we adjust ourselves according to the social rhythm? Honestly, love this hypothesis that people came up with and and Pat's kids reminded me off because kids are really gonna disrupt your

Starting point is 01:30:31 sleep week cycle. It seems like there is a crono attraction that usually people who attract each others have actually different sleep weeks schedule. And the idea being is that this allows them to take care of their kids throughout the day, night cycle. And have a peaceful marriage. And have a peaceful marriage in a way, right? So, I mean, we didn't have kids me and Regis. So maybe this is, but it seems like evolution, it makes sense that if you want to protect your kids, you don't want everybody to be mourning rigor and then the kids don't have. So you want to distribute it across. I mean, it's a reasonable argument. I've heard that one of the reasons that people think that the clock is not exactly 24 hours, but it's 24 hours plus or minus, you know, 20 minutes or so,

Starting point is 01:31:17 is because we believe that we evolved in clans or groups, villages, whatever that were about 100 to 200 people. And in order to have protection around the early morning hours when we're vulnerable to predation, and in the late night hours that you would want some individuals of our species to be naturally more like night owls and some more like early people. So your theory of parenting is similar in that way. Right. The social rhythm is a powerful rhythm, though, meaning if I go out and I'm tired, let's say I'm tired at like 930, I don't want to go out. I can't just say something about that. I think the social rhythm is powerful at the obvious levels like it affects your sleep, it affects how much you wake up or eat. But I'm not so sure it's as powerful as people think on the clock. Now eventually it will mess up the clock because now

Starting point is 01:32:11 if you're doing a lot of social at night, getting enough light, eating at the wrong time of the day, eventually you're going to have an effect. But I don't think that's the social interactions themselves have been shown to affect your clock very strongly. For some reason, that's good to know. Well, for people hearing this, they're probably getting the impression, like I'm the night owl, and then Samar is the one that's in bed at nine,

Starting point is 01:32:35 and then wakes up at four, but having attended many meetings with Samar, I can tell you that he's the party animal. So let's talk about that. I mean, let's talk about the fact that you're the party who's up until too dancing at these various meetings, which I've seen. Yeah. Actually, a good dancer, I'm told.

Starting point is 01:32:55 But what should we do when we do stay up very late for whatever reason? Could be because we had to take a midnight trip to the hospital, the unfortunate reason, or it could be because you're in the presence of people that you don't see very often and you go out for a really nice night out on the town and you get to sleep around 2.30 or 3 in the morning. How should one get back on schedule? Do you force yourself to then get up and view light at the normal time that you would get up in view light, or do you allow yourself to sleep in? What's the optimal path? I would allow myself to sleep in and remember this is a long term effect. This is something that you live with for a long period. And remember I told you about

Starting point is 01:33:33 the experiments we did with the mood. These required two weeks of that light schedule to cause mood disturbances. So these don't happen just in a single day. So this is the way you justify staying out late everyone. So well, in the in the meetings you've seen me, I've done this for five or six days continuously, but what you didn't see that when I came back to my home, it took me two weeks as if I did a jet lag. So I really do suffer for two weeks after doing a six-crazy night of staying up at night, drinking at the wrong time of the day. So it's not that I'm completely okay with it. When I go back, everything goes back. It takes me actually literally two weeks to recover from the circadian rhythm meeting that you've seen me party at some point.

Starting point is 01:34:14 Which is kind of ironic, the circadian rhythm. I know rhythm meeting people are totally disrupting the circadian cycle, but scientists are human beings too. Right. So I think if you do it scientists are human beings too. Right. So I think if you do it at very little occasions, I think you should not worry too much that this will have lasting impact. And the good news is that if you readjust your schedule, you could come back to it. The problem is when you maintain these wrong schedule for a prolonged team, it becomes chronic prolonged periods of time. That's when you have the problems and the accumulation of the problems. So when you have sleeping problem, you produce metabolic problem, when you have metabolic problems, you produce lack of exercise, and you could see how things can spiral out very quickly. And then it would be hard to come back to it.

Starting point is 01:35:00 Well, certainly sleep disruption is both a symptom of and a cause of almost all mental health disorders. And certainly the metabolic syndromes that people are talking about nowadays and all of this, it all funnels back to light. This is what's so remarkable. And so we have these devices and I use my phone and I use my computer. But do you think that the mere dimming of the screen or not interacting with screens after, you know, with it say 90 minutes or two hours before bedtime? According to what we're saying today, this should

Starting point is 01:35:38 have a profound effect on all these things. And I really believe it does. And I, you know, again, I think Aspat did these inventions where you get a pouch, where you put your phone in a pouch. So what Sam is referring to is our friend Pat, this former Celty member that was also a very impressive person in the landscape of business and family, et cetera, a real a superhuman from a by any regard. Has this habit of taking his phone and putting it into a sealed pouch in the evening. So it's basically, and in his world, he sends you actually these, these seal, you know, batches.

Starting point is 01:36:16 And so that, I think, is a great idea because not only it will take away the light from you, but it also takes away the distraction because you wanna repair and recover and sleep does that. And if you have your phone dinging all the time or the light flashing from it, it's you're just not getting enough sleep and you're causing yourself major problems. I'd never ask you this, but I realize now that I should have long ago, but I'll ask you now,

Starting point is 01:36:48 why and how did you get into all this stuff? Yeah, I mean, honestly, I, first of all, I wanted to become a, you know, wanted to study genetics, and I knew I wanted to do PhD in genetics, but I only got accepted in one university at the time, and I joined the learning and memory lab. And I liked learning and memory at the beginning I worked in the snails on Applesia, California, and started looking at learning and memory. But then the same lab was looking at these daily variation.

Starting point is 01:37:15 I was really struck. Like you never think about it outside of science. It really struck me that organisms can measure day biologically. That was very shocking to me. And I just really got attracted. And I wanted to see why does this happen? What is the effect of different times of day? And I just stuck with it.

Starting point is 01:37:36 It was mind blowing for me who was in medical school that I've never heard about it before. You know, it's really amazing medicine. I think still now, we are very good at looking at stuff spatially, but we're very bad at looking at temporal aspects. So we always like to see images, static images, spatially information. Right.

Starting point is 01:37:59 Take an X-ray, measure a temperature, measure a blood pressure. Exactly. But we don't think of temporal. And you know, you talk to John Hoganash right now, and he's telling you the importance of Chrono medicine or Chrono, pharma, pharma to whatever the word is. And it just, it really just getting the drugs at the right time of the day is going to be essential for our health. Do you think that's going to come from using better

Starting point is 01:38:22 trackers like, or rings, whoops, traps, these kinds of things? I love the trackers, but I think there's even more exciting discoveries. Now you could take a single blood sample and measure many biological components and figure where you are in the circadian clock, something that was very hard to do before. So if you have a marker to know where you are in the clock, you could actually understand more the effect of everything, exercise, feeling, light input. What is the marker?

Starting point is 01:38:49 So there are some papers from what's in a Phyllis Z and from a chemcramer where they measure multiple RNAs that are known to tell you what phase of the clock is or multiple proteins or biological reactions. And depending on a combination of factors, not a single factor, you could tell where you are in the circadian clock. So they could instead of just measuring temperature or melatonin, just one measurement. And melatonin specifically is also complicated by the fact that melatonin is affected by light.

Starting point is 01:39:22 And you know, and temperature, your temperature and sleep can be easily dissociatable, right? When you travel across different times, when you sleep at different times in the temperature cycle. So having multiple components measured will give you a better determination of your circadian phase. And understanding your circadian phase in humans will tell you what is the effect of giving certain drugs at certain times of the circadian phase. So will tell you what is the effect of giving certain drugs at certain times of the circadian phase. So in the future, this is going to be studied at a much higher level when you can determine the phase in relation to all the other stuff.

Starting point is 01:39:56 It's striking to me that in all animals, besides humans, if they deviate too much from the appropriate exposure to light and light dark cycle, they essentially don't mate and or die and or get killed off. But in humans, we are able to override that at least to some extent. But the ways in which we suffer appear to be things like obesity, metabolic syndromes, reproductive syndromes that are accompanied the other syndromes, you know, endocrine syndromes, and mood and depressive disorders. Is there any effort at the level of the nationally

Starting point is 01:40:34 or laboratories that you're aware of to try and use light in order to improve mood and mental health? I mean, honestly, this is my moochia. This is the thing that I think people because it's I say don't take a pill, take a photon and not I mean you take pills, it's important. I'm just making it that really we have an opportunity right now with the incredible advances of LED lights, of changing spectra of light, of regulating intensities.

Starting point is 01:41:05 And just to, just for simple changes, you could really improve sleep-wake cycle productivity. And still you could actually get more done because as we've talked about, when you have all these messed up, now you have to sleep more, but your sleep is fragmented. It's not very good. And you can't focus. And you can't focus and you can't focus

Starting point is 01:41:25 We don't have alertness when you need the alertness So having all these you could allow you to do even more actually at the end that less and that's the exciting part of it One of the questions I get asked most often about is about ADHD You know, I think there's a lot of self-prescribed as well as clinically prescribed ADHD. People are having a tremendously difficult time focusing and not just because they're sleepy, they just can't seem to anchor their attention. And there could be multiple reasons for this, but there are now several clinical trials ongoing using light to try and anchor people's attention and mood and well-being for sake

Starting point is 01:42:00 of focus. And I think that while I love this saying that you mentioned, you know, take a photon, not a pill, and with due respect to the need for pharmacology, for certain people, I think most people just haven't really dialed in their relationship to light in a way that allows them to rule out whether or not they need a medication. Absolutely, that's the best way to put it.

Starting point is 01:42:21 I can't add to that. Let's talk about jet lag. but not in the context of, okay, if somebody's traveling from Europe to Japan or from the East Coast, because that varies tremendously, right? I mean, there's as many different variations on travel as there are individuals out there and with goals and jobs, et cetera. But rather, let's talk about what are the two or three things that people can do to adjust their schedule quickly.

Starting point is 01:42:48 Yesterday I called you and said, look, I know somebody who's traveling six hours. I won't even mention in which direction because I don't want people to anchor to that example. And you described some very simple tools of viewing light a little bit earlier than normal and getting on the local food schedule, et cetera, that would allow them to shift more quickly. And the reason I want to have this conversation is yes for the travelers and for the shift workers, but mostly because of the fact that you've proven again and again that people are disrupted in their circadian behavior at home.

Starting point is 01:43:25 So, aside from what we've already talked about, how can one adjust quickly to a new schedule? Like, let's say fall classes are starting. You start a new job where you have a baby or a puppy or whatever. What is the best way to shift the clock quickly? So, it's very simple as we've talked yesterday. So, imagine you're in the outside

Starting point is 01:43:44 with no environmental, with no industrial light. If you, if your body thinks you're in early evening and you see a bright light, what does this tell you? Oh, wait, this is not early evening yet. It's still early afternoon or late afternoon. So I have to delay my clock to go back to late afternoon. So if you get light early in the evening, it delays your clock. So what does that mean?

Starting point is 01:44:10 That makes you want to go to sleep later. Yes, it delays your clock. So you're in New York, right? People in Italy have an advanced clock because they are six hours ahead of us. So if you're in New York and you get light early in the evening, you delay even further from Italy. So now you're delaying away from Italy. Now the same thing happens, let's say you thought don't came up and you thought it's already done, but it was let's say three o'clock in the morning or four o'clock in the morning and then you get a bright light and you say,

Starting point is 01:44:41 oh wait a minute, don't it's not up yet? So I should advance my clock or at night, but I'm getting bright light, so I should run because dawn is already up. So then later in the night, later in your night, and actually it just happens that the humans you get a temperature in the year later in the night, low temperature in your body. After that, light start advancing your clock. So if

Starting point is 01:45:09 you want to go to Italy instead of getting light early in the evening, you want to get light after the temperature low. So you could advance your clock even before you go to Italy and you're catching up to the Italians just by using light. It's as simple as that. So you could do it for every region. You could calculate how much they are advanced of you. You could know how much these light shifts happen per day. And you can calculate what you need to do, very simple math, to adjust either in direction of delaying.

Starting point is 01:45:39 If you're going from New York to California, you want to delay your clock, or advancing if you're going from New York to Italy. So in order to make that a visual and because a lot of people are listening to this not looking at our own video, we will put a zero cost downloadable figure of this on the Hubertman Lab.com website related to this episode. But I think I can summarize it in language as well. If I understand correctly what you're saying is,

Starting point is 01:46:06 if your typical wake up time is say 7am, then your low point in temperature probably occurs somewhere around 5am. And if you light right around then, it's going to essentially advance your clock. Because then your body thinks, oh, it's seven o'clock, so that's at about 7 o'clock by one to two hours. But if I were to view light, say at three a.m.,

Starting point is 01:46:29 then it would probably delay my clock. Yeah. Okay. Yeah. So, and then let's say I land in a new schedule. I want to adjust to a new schedule. Let's say I didn't manage to do anything with my light viewing before I went and I didn't I didn't anticipate the trip. Suddenly, I'm on a new schedule. I was told that one of the ways to help shift the clock and to avoid gastrointestinal issues is to eat on the local schedule, to start basically behaving like a local, even though your circadian clock will take a little bit of time to catch up. Absolutely.

Starting point is 01:47:02 But you have to remember the light, right? So let's now that we explained it very simply. Let's take a very simple example, right? New York to Italy. That's a simple example. New York time, Italy time, six hour difference, right? So let's say you fly from New York at night, you reach Italy at eight o'clock in the morning. What is the time in your New York time? Although you reach six hours back, six hours back. It's two a.m. So when you land Italy, you wanna avoid light like the plague. Yeah, you could eat, but you really don't wanna get a lot.

Starting point is 01:47:34 Right, because otherwise it's gonna delay. It's gonna delay you. It's gonna send you to California instead of sending you to Italy. Right, and so this is such a key point. If anyone's confused about this, we will put some diagrams up. But what Sam is saying is so crucial, just because getting bright light in your eyes early in the

Starting point is 01:47:49 day is really beneficial when you're at home, when you travel to a new time zone, you have to take into account what your body thinks, what, excuse me, you have to take into account where your body thinks you are. And so if you're looking at the Italian sunrise having just flown from New York to Italy and you didn't prepare for that trip by waking up a little bit earlier in anticipation. Multiple days. And if you light it, excuse me, at six or seven a.m. Italian time, beautiful Italian sunrise, you are going to delay your clock, you're going to basically throw yourself back to California, but you are in Italy.

Starting point is 01:48:24 You're going to throw your biology back to California, but you are in Italy. You're going to throw your biology back to California, and you are going to be up in the middle of the Italian night, and you're going to be miserable. I'll tell it brief, and it took, because I called Sam or in desperation, a few years ago, I traveled to Abu Dhabi, NYU Abu Dhabi to give a seminar. 12 hours out of phase. It's a 12 hour flip.

Starting point is 01:48:42 And I thought I could just muscle it. I thought, I'll get up, just view sunlight when the sun comes up. And I fell apart mentally and physically. And Samur came to my rescue. I called him, I said, I don't know what to do. And he said, go to the gym, at the local dawn, work out, eat,

Starting point is 01:49:04 and then view sunlight starting the next day. And that basically got me on the schedule. So I used food and exercise to adjust myself because my light viewing activity was just completely out of whack. Yeah, I mean, and we talked about other details, so you have to calculate it, but you're absolutely right. I mean, it's very important to avoid getting the wrong light information when you're trying to adjust your body because otherwise it shifts you to the other to the other side.

Starting point is 01:49:30 Absolutely. Well, you are one of these people that has such vigor. It's one of these things where having known you all these years, you have a tremendous capacity for work and for soccer and for arguing respectful arguing and you know sometimes you know getting worse with the age. Yeah, well we could talk about that offline but I think a lot of your vigor and a lot of your ability to work hard and focus and really do so many things at an impressive level is because you think about these issues and you you think about when you're going to be optimal for focus when you're going to be optimal for exercise, and the when is the key.

Starting point is 01:50:09 And I think a lot of people live in the landscape of feeling like there's something broken inside them because they can't focus or they can't. Subconscious, right? Remember, it's all subconscious. These effects and you're absolutely right. Now, honestly, joking aside about age, I really agree with you that I think part of the reason I'm continuing to be able to do this, that I really think about it and I make sure that I keep everything aligned and that actually helps me a lot. Like, I don't

Starting point is 01:50:38 suffer in sleep, I don't suffer in waking up, I never use a timer to wake up. I mean, people say, aren't you scared? Like, you have to give a lecture at 8 or 7 30. I was like, there is no way I'm going to go beyond that. It just, even if I try, I can't sleep beyond 6 a.m. in my regular times. It's just, it's not going to happen. By 4.30, my eyes are wide, I pay awake and I'm in bed. It's just, system is so aligned.

Starting point is 01:51:02 It works. A lot of times people will say, how come I go to sleep? I fall asleep fine, but then I wake up at 3 or 4 It's just system is so aligned, it works. A lot of times people will say, how come I go to sleep, I fall asleep fine, but then I wake up at three or four in the morning and you can't fall back asleep. Is it possible that those people were supposed to go to bed at 8 p.m.? It's possible, I mean, it is possible.

Starting point is 01:51:17 It is also possible that sometimes people will wake up and go back to sleep, but yeah, I mean, it is possible, or it's possible that their clock is completely misaligned that they are getting maybe in nap time at night when they are supposed, and then they possibly feel so sleepy in the day. So all these are possible combinations.

Starting point is 01:51:36 That's an interesting idea and considered. So what they think is their sleep, their body is so out of whack with the light our cycle that it's actually a nana, or the weaker part of the sleep. I mean, you see this in when you travel to different times on before you adjust, you go to sleep really well, but two hours later, you're fully out.

Starting point is 01:51:55 Two hours. If you were so tired and this is your regular sleep, there's no way you're going to wake up in two hours. So then you feel very sleepy later in the day or something like that. So it depends of how your whole system is aligned to the invite. That's a very interesting idea.

Starting point is 01:52:13 I think that's going to resonate with a lot of people. I wake up every morning around three or four, generally use the bathroom, and then I fall back to sleep very, very deeply. It doesn't seem to disrupt my daytime wakefulness. And I think a lot of people obsess over that waking up and worry there's something wrong. Provided they can go back asleep. Exactly. It's okay. If you can go use the bathroom, go back sleep, that should not be a problem. Maybe some people when they go to use the bathroom, they use

Starting point is 01:52:39 very bright light and then they get an alerting signal. So if you maybe that could be as simple as that, that affects you. Maybe when you wake up you put tons of light or you start reading your iPad. So there's all these combination that we still don't know about, that could be affecting their sleep algorithms and their sleep maintenance. Do you use melatonin? Do you take melatonin? I don't need it to be honest. In my case, there is no reason to use it because I could guarantee you that by maybe eight o'clock my melatonin has already started to go up and by the time I sleep my melatonin is very high because I don't use a lot of mites after sunset. At light inhibits melatonin. And life's really blanx melatonin level.

Starting point is 01:53:22 But you hear this myth that the pineal gland calcifies as we get older. Is that, do you know anything about that? I mean, I've heard about that, but I don't know what does, I mean, there's not very clear evidence that affects the sleep. I don't know much about it, to be honest. Yeah. The evidence that I've seen is that, yes, there's some calcification around the pineal, just because of where it sits in the brain, it's close to some bony structures, but I don't think there's any evidence that it has negative effects.

Starting point is 01:53:50 I mean, if you still have, you could measure Minatoan and that should tell you if it has negative, it's such an easy thing to do. I think this is more of an internet wellness thing that got outside the cage. You're absolutely right. Yeah. It sounds terrible calcification of the thing, right?

Starting point is 01:54:09 The hard thing, right? Yeah, exactly. Let's talk about seasonality a little bit. I learned, and I don't know if this is still true, but that most suicides occur in April, in the spring. I think there's a poem that says April is the cruelest month. I think it is the poem begins. Are there data that suicides are more frequent, it's a particular times of year, and if so is the spring that time of year?

Starting point is 01:54:40 Yeah, I mean, a lot of people talk about this. And one of the hypothesis that is that the winter months that are very bad for moon make people not wanting to do anything. And they get into such deep level of depression that when the sun comes up, they get actually the energy to act under depression, which sounds really terrible. And it's terrible. It's terrible. So that's the idea that the lack of light throughout the winter

Starting point is 01:55:06 caused them to go into such depression that they don't feel like doing anything. And when the light comes in with rigor in the spring, it gives them that after all the depression they suffered, gives them that push to take that sad final act, I guess. What other seasonal effects have been demonstrated in human? Yeah, I mean, I think in humans, it's not very clear because we don't think about seasonality, but if you start thinking about us, I think we go through major seasonal changes. I really do.

Starting point is 01:55:38 I think our eating pattern change across the year, I could tell you that me thinking about this, there's a clear changes that happens to me across the year, I could tell you that me thinking about this, there's a clear changes that happens to me across the year. But for animals, this is really essential, because for animals, they have to time their mating behavior, with when they deliver their their progeny in the most abundant amount of food. An artificial light is causing major disruption, because if you change the way these animals are receiving the light information, they either start mating much earlier or much later

Starting point is 01:56:11 and their numbers dwindle and they get into the dangers of really completely getting eliminated or extinct. Well, human birth rates are definitely going down. I mean, in the US, in particular areas, not others. Not others. But are there other effects of seasonality on humans that we are aware of? I honestly like you could see it, honestly, you could see it perfectly, I think, in Scandinavia.

Starting point is 01:56:37 I mean, you could talk to people who live in, they get seasonal depression. What season depression is one, but actually when you start asking them questions, they tell you like in the winter, they barely could wake up, they barely have the energy before even depression, even people who don't get seasonal depression, they'll tell you our energy level is lower, our ability to go to work is not the same.

Starting point is 01:57:00 And in the summer, most people actually sleep very little. They tell you we really can, we feel like we're manic, we have all this energy, and not in a negative way in a funny way, right? I mean, but if you want to sleep, we have to put this curtain. I think in these situations, you could really appreciate the seasonality of a human. I think we kind of destroyed our seasonality because we don't get exposed to that much natural light. We have all this artificial light. But I think honestly, one of the things that is going to happen if they follow your recommendations about giving

Starting point is 01:57:37 light at the same time, giving food, giving away, let's be clear, those are your recommendations. No, I'm just fair at yourution. What I'm saying is that this is going to cause them to also experience some changes across the season because now they're going to see the sun differently. If you're going to go out in the morning, in the summer you're going to get the much brighter. That's why I don't like the change in time. I know people think, oh, because you're biased, you, because I think, wait, wait, wait, sorry, the change, are you talking about daylight savings? Daylight saving. It's such a bad idea because it disrupts that rhythm that you're having. Because I think your body, if you keep that

Starting point is 01:58:15 rhythm, you will see the whole seasonality. And I look at it from a different aspect than other people. It's really, and people say I'm biased because I'm a morning person, and it may be true, but there's a situation. It can conspiracy about morning people. Yeah. But there is, if you think about it, Andrew, there is a situation where you're getting like perfectly well, and then all of a sudden they delayed by one hour, because, and then even though it's the summer, your body now, if you're still not adjusting, think, oh, wait, what happened?

Starting point is 01:58:46 What kind of happened? Well, I'm glad you're bringing this up because I always thought, you know, what's the big deal? One hour, right? One hour shift, you know, spring forward, all that. Just one hour. But the, but this goes back to the beginning of our discussion. It's not just one hour.

Starting point is 01:59:02 Right. Because it's one hour across that one day. But there's this cumulative effect on the clock and these three elements of your tripartite model. Exactly. The homestatic sleep and the light direct effects on the moon. And when it's so close, it's sometimes hard to figure out how to adjust it perfectly. Because we're already sleep deprived in our society. And then you shift it, so it all accumulates and it has no benefit. Well, you work at a major government organization,

Starting point is 01:59:32 National Institute of Mental Health. Why don't we campaign for... Honestly, I have no idea. I mean, it makes no sense. Why don't we go campaign? Yeah, I would love to. I mean, it makes no sense to have the summer light goes up at 9 p.m. The light goes down the summer light goes up at 9pm.

Starting point is 01:59:45 The light goes down where I live in Baltimore at 9pm. And then all of a sudden, when you really want to see the light longer in the day, you now shift the other way. And now it goes, or if it's not 6pm, why do you do these drastic changes? Well, let it blend across the whole season. You know, yes, later, earlier at night, but it's at least consistent. It goes in a very consistent manner.

Starting point is 02:00:09 I just don't understand why they do this. It makes no sense. Well, I think that the reason they do it is because they don't understand the biology. Because one hour seems trivial, unless you understand that the repercussions of that one hour shift. Because what's also clear now, based on what you're saying, is that that one hour shift, because what's also clear now,

Starting point is 02:00:26 based on what you're saying, is that that one hour shift is taking you out of alignment with the natural light dark cycle in exactly the wrong direction. It's pushing people to get even later. In the summer, when light is going to push you later, anyway, it doesn't make sense. You put it beautifully. I just rambled and this is, you no, you made it you made it clear I mean, it's like literally it made you it made people who are having problem Having an advanced sleep rhythm because they are delayed now you give them this hour to make them even more delayed

Starting point is 02:00:57 You push them even later in the day night cycle. It just doesn't make sense at all. I Think 2022 should be the year that we abolish bad deal. I would say the day for me, honestly, well, it's said, well, also if it has a positive effect on the, what is essentially an epidemic of mental health issues and other issues related to improper interactions with light, that I think is a well worth while cause.

Starting point is 02:01:25 Absolutely. And we can explore. So for once we're going to fight with some, with another group, a common battle, I was opposed to one of them. I mean, the Circadian people, honestly, to give them credit, have been trying for years to abolish daylight saving. Yeah, the problem is they all go to sleep at 9 p.m. and wake up at 4 a.m. so we never see them. That's right. No, the circadian community has done an amazing job of figuring out what we need.

Starting point is 02:01:52 And then the challenge, of course, is making sure that people get what they need. And making sure that at a societal level, we're not involving ourselves into the role of our environment. The biggest problem is that the late waking people, they think that really, and I'm gonna try to put it in a better way now, they think, oh, because you're a morning person, you wanna see the sun early,

Starting point is 02:02:13 so you want me to suffer it dropping late. But that's not the case, because what happens is when they shift it back after the daylight saving, now they're gonna make you suffer really badly, because now it's gonna be earlier in the fall. In the fall when there's not enough light. If they keep it the same way, so try to convince them that actually this at the end

Starting point is 02:02:36 goes it more trouble when you need the light for your late schedule in the fall when they shift it back. Then they say keep it daylight saving all the time. That has been proven that it's very bad. Like people have done studies that literally two areas close to each others and areas that work the whole year on daylight saving has much more problems, even in cancer rates and depression.

Starting point is 02:03:01 So you don't want to do that. So that's what trying to convince people that you need to prevent that switch and you don't need daylight saving at all. That's where the problem happens. Interesting. I had not thought about that, but yes, you late risers in the fall

Starting point is 02:03:19 when they fall back, as they say, spring forward, fall back, you dial back the clock. It's really compounding the problem that all of it exists. And it's really nice if you keep it consistent. In the spring, you get the long, you know, when you get the equinox and then the days start going up and then even in the summer start going down

Starting point is 02:03:39 and then the fall, you get the other equinox and go back. So it's very symmetrical, right? It goes into short day, longer, longer, and then short day again. But now you're getting these bumps in both sides of the spring and fall. Why would you do that? Something that is beautifully symmetrical, beautifully smooth, you're putting bumps into it. Well, and we're not just beautiful because it's there, but evolved. I mean, essentially, this is the system we evolved in for hundreds of thousands of years. Even apart from the exact equator, every part of the earth has seasonality.

Starting point is 02:04:14 I want to briefly touch on something which is individual and genetic variation in sensitivity to light. Yeah. So not chronotype, but first of all, a very basic question. Do people with light eyes, light colored eyes, are they more sensitive to light than people with darker pigmented eyes? I mean, honestly, it makes sense. They will be more because if you think of how my dark pupil, it's blocking more light. So if you have light pupil, yes, for vision, it may not be very obvious, but for something that is measuring the amount of light, you're getting more light than me. So you're probably need less light to be effective as somebody who's darker.

Starting point is 02:04:57 And that maybe could explain why sometimes lighter people say, I don't want to go into very bright conditions because it's really bright. Yeah, I can't, I can't even be at a cafe without one of these reflective tables, like a metal table, unless I have very dark sun glasses on that show bright. It's painful. Right. Right. When some people like you, we've sat outside and have meals and you're like, fine, I assume it was kind of Jordanian toughness versus, you know, it's really the pupil blocks more light. So I think it is possible that it's as simple as the pupil blocking more light can have sensitivity.

Starting point is 02:05:28 But your question is also goes deeper. Are there more sensitivity differences? And my understanding would be, I would think that it may be, it depends on how effective your cells are in responding to light, how healthy your IPRGCs are. So I would, but there's not many studies to show that. What is really clear that is happening is that patients

Starting point is 02:05:51 with bipolar, they seem to have different sensitivities to light. So it seems that at least people who have psychological changes, they may have differences to the sensitivity of light. So where are those differences in a particular direction? I don't remember the exact... We'll have to we can look at it. Yeah, yeah, yeah. You know, and people have heard me say this ad nauseam to the point where they actually roll their eyes, but you know, these are the only two pieces of brain, you know, I'm pointing to my eyes, folks,

Starting point is 02:06:22 that are outside the cranial vault. They are two pieces of brain that it basically inform the brain about whether or not to be alert or asleep. But you can imagine that those two little pieces of brain that we call eyes would have genetic variations, of course, eye colors genetically, modulate, is that determined, that there would be genetic variations based on whether or not your ancestry evolved near the equator further from the equator. I mean, you see more blue eyes and Scandinavia than you do with your voice. I mean, it's the lack of light that said

Starting point is 02:06:53 you need more less inhibition because there's not enough light, right? So that's the idea of the change in color. So yeah, I totally agree with you. I mean, I think this is an area that will be studied later and will be empirically determined. The problem we have in this field right now, which I think is the biggest problem,

Starting point is 02:07:13 is we don't have a way to measure the IPRGC sensitivities in humans. So, we still, like it's easy to measure your rot-con function if you go to an optometrist, they measure all the details, right? Contrast details. You look at the chart, you look at the account list, the SNL and chart, you look at the letters at the DMV. But for the none subconscious, we still don't have a good measuring systems to figure out what is Andrew's sensitivity,

Starting point is 02:07:39 what is Samar's sensitivity, what is this person's sensitivity. And I think we're starting to work on something like that to hopefully develop these techniques, but till we develop them, it's going to be very hard to figure out if there is a sensitivity difference, how do they relate and on men and women, you know, dark and unlight and all that, you know, normal versus psychologically, on effect and stuff like that. Fascinating. And every time you talk, I learn so much. It's like, in the best way, the best sense of the term,

Starting point is 02:08:13 it's a waterfall of knowledge. As a final question, I have a question about sensitivity of a whole other kind. And that's the sensitivity to spicy food. Now, the reason I'm asking this question, what seemingly out of the blue is that I made the mistake once of having Samar cook for me. And I said not too spicy, and he said, okay, not too spicy. Yeah, she said, okay, not too spicy. She said, okay, not too spicy. And it almost killed me. Like it was like two or three days.

Starting point is 02:08:47 So you know a lot about biology outside the visual system light, et cetera. You've been around a while. Are there known genetic or inherited of any kind sensitivities to spicy food, to things like red peppers and capsaicin? Because what you call mild, my friend, almost put me into the hospital.

Starting point is 02:09:09 I think this is similar to you swimming in the ocean and I need to get developed. Okay, true, true. I like cold water swims and say there's not a fan. But that's gonna change. It's a doubt to look at. That's gonna change. That's my village.

Starting point is 02:09:21 Before I met Raysia, I once liked you. And once I started eating a lot of spicy food, I lost touch of how spicy my food is. So I nearly killed you, and I apologize. I forgive you. So basically what you're saying is that marriage toughened you out. Definitely. Maybe that's the solution. Sam, this has been an amazing march through the importance of light, not just for regulating sleep and wakefulness, but also for food timing, the interactions with mood, the interactions with exercise. I'm certain that people are going to start thinking about how to change their relationship with light as a way to anchor everything that they do and that's important to their health.

Starting point is 02:10:05 And I just, on behalf of all of them, and just directly from me as your friend and as a colleague for many years now, I just wanna say thank you for the incredible work you're doing and for sharing it with us. Thank you so much. And I actually now thinking about all of this, and you said I should write a book,

Starting point is 02:10:21 I should write a book, and call it the Tripart 8 model. I think that would put all these components together would be very interesting to do at some point. You should write a book. They'll probably try and change the title to like, Food, Mood, and You, or something, because you can put in little print on the Tripart model or whatever. But regardless of what it's called,

Starting point is 02:10:44 you absolutely should write a book. So if you'd like Samar to write a book or if you'd like to learn more about them, let's talk a little bit about where people can find you. Your laboratory is at the National Institutes of Mental Health. He is head of the chronobiology unit. All these things, as I've mentioned earlier. You are active on Twitter and Instagram, right? So what is your Twitter handle? It's at Sam or Hattar and we will provide a link for that in the show notes. Sorry, yes, the Twitter at Sam or Hattar and I think the same for Instagram. Yeah, actually, and Sam has been coaxed on Instagram, so he does post from time to time, mostly pictures of food that is incredibly spicy

Starting point is 02:11:24 but also pictures of food that is incredibly spicy. But also information about chronobiology. He comes on for an Instagram live every once in a while with me. So definitely give him a follow-through there and on Twitter. I'm sure that he'll be happy to answer questions and entertain any and all discussions about chronobiology. Absolutely. Yeah. Unlight. Yeah. Great. Thank you, Samology. Absolutely. Yeah, and light.

Starting point is 02:11:45 Yeah. Great, thank you, Samar. Awesome. Thank you, Andrew. Thank you for joining me for my conversation with Dr. Samar Hatar. I hope you found it as interesting and informative as I did. If you're enjoying this podcast and we're learning from it,

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Huberman Lab - Dr. Samer Hattar: Timing Your Light, Food, & Exercise for Optimal Sleep, Energy & Mood

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