Dr. Samer Hattar: Timing Light, Food, & Exercise for Better Sleep, Energy & Mood

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

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

00:00:04.880 | for everyday life.

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

00:00:10.640 | and I'm a professor of neurobiology and ophthalmology

00:00:13.360 | at Stanford School of Medicine.

00:00:15.520 | Today, I have the pleasure of introducing Dr. Samir Hattar

00:00:18.800 | as my guest on the Huberman Lab Podcast.

00:00:21.600 | Dr. Hattar is the chief of the section

00:00:23.680 | on light and circadian rhythms

00:00:25.600 | at the National Institute of Mental Health

00:00:27.560 | in Bethesda, Maryland.

00:00:29.500 | Dr. Hattar has many important discoveries to his name.

00:00:33.120 | He was one of a handful of groups

00:00:34.720 | that discovered the light-sensing neurons in the eye

00:00:38.440 | that set the circadian clock.

00:00:40.560 | This was a fundamental discovery made in the early 2000s

00:00:44.620 | that has led to an enormous number of additional discoveries

00:00:48.160 | on how light regulates our sleep, our immune system,

00:00:52.120 | our mood, mental health, metabolism, feeding,

00:00:56.440 | and many other important processes.

00:00:59.360 | If ever there was somebody who understands

00:01:01.160 | how all of these processes interact

00:01:03.680 | and can inform best practices for our daily behaviors,

00:01:07.600 | it's Dr. Hattar.

00:01:09.140 | During our discussion today,

00:01:10.460 | Dr. Hattar answers questions that are absolutely essential

00:01:13.780 | for us to know about our health and wellbeing.

00:01:16.840 | For instance, how to align our sleep schedule

00:01:20.300 | with our activity schedule, such as exercise,

00:01:22.940 | and how to align light activity and exercise

00:01:26.720 | with our feeding rhythms.

00:01:28.660 | He presents a new model of how light activity

00:01:33.060 | and feeding rhythms converge to support optimal health,

00:01:36.240 | and when those are not aligned correctly,

00:01:39.220 | how our mental and physical health can suffer.

00:01:41.960 | It's a discussion that is rich with scientific mechanism,

00:01:45.240 | made clearly, of course, so everybody can understand,

00:01:48.280 | as well as specific protocols to deal with shifts

00:01:51.720 | in day length, shifts in activity,

00:01:54.260 | and in order to optimize sleep, metabolism,

00:01:57.720 | and wellbeing of various kinds.

00:01:59.600 | I learned so much from Samer, as I always do.

00:02:02.200 | He is an absolute wealth of knowledge

00:02:04.520 | on all things related to light and circadian rhythms,

00:02:07.280 | physiology, and neuroscience.

00:02:09.320 | I don't think you'll find anyone else

00:02:10.720 | as knowledgeable about these topics as Samer,

00:02:13.040 | and so I'm delighted that he joined us here on the podcast

00:02:15.920 | to share this information.

00:02:17.460 | Before we begin, I'd like to emphasize that this podcast

00:02:19.920 | is separate from my teaching and research roles at Stanford.

00:02:22.720 | It is, however, part of my desire and effort

00:02:24.760 | to bring zero cost to consumer information about science

00:02:27.400 | and science-related tools to the general public.

00:02:30.000 | In keeping with that theme,

00:02:31.000 | I'd like to thank the sponsors of today's podcast.

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00:06:15.960 | And now my conversation with Dr. Samer Hatar.

00:06:19.640 | Samer, thanks for sitting down with me.

00:06:22.240 | - My pleasure.

00:06:23.080 | - Yeah, we go way back.

00:06:24.440 | So you are best known in scientific circles

00:06:28.760 | for your work on how light impacts mood,

00:06:32.320 | learning, feeding, hunger, sleep, and these sorts of topics.

00:06:37.040 | So just to kick the ball out onto the field, so to speak,

00:06:41.400 | how does light impact the way we feel?

00:06:45.600 | So when I get up in the morning,

00:06:47.740 | I have the opportunity to interact with light

00:06:49.760 | in certain ways or to avoid light in certain ways.

00:06:52.220 | I have the opportunity to interact with sunlight

00:06:54.120 | or with artificial light.

00:06:56.000 | Maybe you could just wade us into what the relationship is

00:07:00.560 | between light and these things

00:07:02.640 | like mood and hunger, et cetera.

00:07:04.080 | - Sure.

00:07:05.200 | So I mean, you do appreciate the effect of light for vision.

00:07:09.080 | So when you wake up in a beautiful area, beautiful ocean,

00:07:13.840 | light is essential.

00:07:15.240 | The sunrise, the sunset, blue sky, beautiful mountains.

00:07:20.120 | So that's your conscious perception of light.

00:07:23.140 | But light has a completely different aspect

00:07:25.720 | that is independent of conscious vision

00:07:28.360 | or image-forming functions.

00:07:30.480 | And that's how it regulates

00:07:32.120 | many important functions in your body.

00:07:34.680 | I think the best that is well-studied and well-known

00:07:37.940 | is your circadian clock.

00:07:39.960 | And the word circadian comes from the word circa,

00:07:42.660 | which is approximate, and dn is day.

00:07:45.200 | So it's an approximate day.

00:07:46.600 | Why is it an approximate day?

00:07:48.520 | Because if I put you or any other human being

00:07:51.080 | who have a normal circadian clock in a constant conditions

00:07:54.920 | with no information about feeding time, about sleep time,

00:07:58.900 | about what time it is outside,

00:08:01.080 | you still have a daily rhythm,

00:08:02.880 | but it's not exactly 24 hours.

00:08:04.800 | So it will shift out of the solar day

00:08:08.000 | because it's not exactly 24 hours

00:08:09.840 | and hence the name circadian.

00:08:11.340 | - So just to ask a quick question about that,

00:08:13.400 | when you say you have this about 24-hour rhythm,

00:08:17.760 | how does that rhythm show up in the tissues of our body?

00:08:20.820 | - Great, so great question.

00:08:22.520 | So it shows up at every level that we know we studied.

00:08:26.200 | It shows up at the level of the cell,

00:08:28.480 | it shows up at the level of the tissue,

00:08:30.320 | and it shows up at your behavior.

00:08:32.120 | The most obvious for you is your sleep-wake cycle.

00:08:35.360 | You sleep and you're awake and sleep at the 24-hour rhythms.

00:08:39.680 | And if you measure the sleep-wake cycle

00:08:41.720 | for humans who are maintaining constant conditions,

00:08:44.520 | you will see that the period length of the sleep rhythm,

00:08:47.040 | on average, is more than 24 hours.

00:08:49.640 | In humans, it's 24.2 hours.

00:08:51.840 | So you'll be drifting 0.2 hours every day

00:08:55.240 | out of the solar day if you don't get the sunlight.

00:08:57.540 | So the sunlight adjusts that approximate day

00:09:01.520 | to an exact day, so now your behavior is adjusted

00:09:05.040 | to the light-dark environment or the solar day.

00:09:08.020 | - Okay, so if I understand correctly,

00:09:09.640 | if I were to go into a cave or I were to be

00:09:12.280 | in constant light and I didn't close my eyes

00:09:15.880 | in constant light, that I would still sleep

00:09:19.040 | in one coherent bout and I would still be awake

00:09:22.540 | for more or less one coherent bout, maybe a nap.

00:09:25.520 | But the total duration of my day, so to speak,

00:09:30.520 | would be a little bit longer than 24 hours.

00:09:34.840 | But if I'm in a condition like most people are,

00:09:37.840 | where the sun goes up and the sun goes down

00:09:40.040 | and I have some understanding of that sunrise and sunset--

00:09:43.120 | - You don't have to have the understanding.

00:09:44.840 | You don't have to have conscious understanding.

00:09:46.580 | You have the detection.

00:09:48.160 | So circadian photoentrainment is the word we use

00:09:51.680 | in training the circadian clock to the photic environment.

00:09:55.260 | It's completely subconscious.

00:09:56.920 | You're not aware of it.

00:09:58.100 | It's not like vision or image forming

00:10:00.760 | where you actually know what you're looking at.

00:10:02.840 | So it's all hypothalamic.

00:10:05.400 | It's part of the brain that is not consciously driven.

00:10:08.560 | So you actually do not know when it happens

00:10:10.720 | or when it doesn't happen.

00:10:11.700 | And that's what we'll get into when I tell you

00:10:14.120 | why light affects your mood and why sometimes

00:10:16.400 | people don't know how to deal with light

00:10:18.160 | to improve their mood, for example.

00:10:20.240 | - Okay, so this is a subconscious vision.

00:10:22.320 | - Yes. - Okay.

00:10:23.360 | Before you tell us about how light impacts mood,

00:10:26.640 | I'm curious, what is the relevance of adjusting

00:10:30.200 | this clock from a little bit longer

00:10:33.200 | than 24 hours to 24 hours?

00:10:35.040 | I mean, it seems like a small difference.

00:10:36.440 | 24 hours and 40 minutes or 24 hours?

00:10:40.000 | Like, what's the relevance?

00:10:42.400 | I mean, why should we care about that short difference?

00:10:44.320 | - So let's do the math.

00:10:45.400 | If you shift out 0.2 hours a day,

00:10:47.560 | in five days you're shifting out one hour.

00:10:49.520 | So you're literally one hour off

00:10:52.120 | in your social behavior in five days.

00:10:54.480 | In 10 days, you're two hours off.

00:10:56.560 | And if you're an organism that is living in the wild,

00:10:59.600 | shifting out of the right phase of the cycle,

00:11:02.100 | you could either miss food or you could become food.

00:11:04.920 | So it's really essential for survival.

00:11:07.000 | I think it's one of the strongest aspect of survival

00:11:10.600 | for animals to have the anticipation

00:11:13.680 | and the adjustment to the solar cycle.

00:11:16.440 | - And for humans as well, when you say animals,

00:11:18.840 | I'm assuming that applies to us.

00:11:19.880 | - Absolutely, yeah.

00:11:21.200 | - I see.

00:11:22.040 | So even though it's just a short bit longer than 24,

00:11:25.640 | if that accumulates over days,

00:11:28.320 | then you could find yourself very much out of phase

00:11:30.880 | with the rest of your species, essentially.

00:11:33.520 | - So let's say it's 0.2 hours.

00:11:35.400 | So in five days, it's one hour.

00:11:37.800 | In 25 days, it could be five or six hours.

00:11:41.400 | You could be in New York and you're feeling

00:11:43.260 | as if you traveled from New York to London.

00:11:45.160 | So you will be having jet lag in New York,

00:11:48.360 | even though you didn't do a jet lag travel.

00:11:50.760 | So it's very important for the adjustment.

00:11:53.640 | And if we have time, maybe we could talk about

00:11:55.920 | why this is important for seasonality,

00:11:57.960 | because also it allows animals

00:11:59.780 | to anticipate the change in season.

00:12:02.280 | And the more you're high in the north or the south,

00:12:06.320 | the more that these weather changes occur very harshly

00:12:10.220 | and you have to be ready for them.

00:12:12.100 | And that happens in us as well.

00:12:15.080 | - All right, well, we will definitely get into seasonality.

00:12:17.880 | Okay, so we've got this subconscious vision

00:12:20.560 | that aligns us with the turn of the earth.

00:12:24.440 | How does that work?

00:12:25.640 | What is the machinery that allows that to happen?

00:12:31.040 | And how does that machinery work?

00:12:33.840 | - Yeah, so we knew that in mammals, including us,

00:12:36.960 | we are mammals, humans,

00:12:38.520 | that the eyes are required for this function.

00:12:40.480 | So if humans are born without eyes

00:12:43.300 | or the optic nerves are damaged,

00:12:45.360 | humans are not able to adjust to the solar cycle.

00:12:48.800 | So we know that the eyes are required.

00:12:51.040 | And since we thought we knew about the eyes a lot

00:12:53.800 | before 2000, we thought that-

00:12:55.640 | - What did you say, before the year 2000?

00:12:57.280 | - Before the year 2000, yes.

00:12:59.000 | We thought it's these photoreceptors in your retina

00:13:02.680 | that allow you to see.

00:13:03.680 | So in the human retinas,

00:13:05.620 | there are two types of photoreceptors.

00:13:08.120 | They are called rods and cones because of their shapes.

00:13:11.360 | And these rods and cones simply take the photon energy,

00:13:14.360 | which light is made of,

00:13:16.040 | and they change it in a way to an electrical signal

00:13:18.640 | that allow us to build the image of the environment

00:13:22.360 | in our cortices.

00:13:23.480 | - Subconsciously?

00:13:24.520 | - Consciously, in this situation, 'cause it's vision, right?

00:13:26.920 | It's image forming vision.

00:13:28.120 | It's a visual cortex and associative cortices,

00:13:32.520 | which allow you to build conscious perception

00:13:34.560 | of the environment.

00:13:36.320 | However, people have found,

00:13:38.860 | including me with the work of David Berson

00:13:41.280 | and Ignacio Provencio,

00:13:42.480 | that there is a subset of ganglion cells.

00:13:45.520 | The ganglion cells are the cells that leave the retina,

00:13:48.760 | their axon, leave the retina, and project to the brain.

00:13:51.720 | So these words are stored to only relay

00:13:54.360 | rod and cone information from the light environment

00:13:56.760 | to the brain.

00:13:58.040 | We found that a small subset of these ganglion cells

00:14:01.480 | are themselves photoreceptors that were completely missed

00:14:04.720 | in the retina.

00:14:05.980 | And these are the photoreceptors

00:14:08.060 | that relay light environment subconsciously

00:14:11.120 | to the areas in the brain that have and house

00:14:14.980 | the circadian clock or the circadian pacemaker,

00:14:18.060 | which adjusts all the clocks in our bodies

00:14:20.520 | to the central brain clock that allows them to entrain

00:14:23.800 | to the 24 hour light dark cycle.

00:14:27.400 | - Incredible, so in the year, as I recall,

00:14:30.040 | 'cause I was a graduate student at the time,

00:14:31.520 | in the year 2000, there was this landmark discovery

00:14:34.420 | made by you, Ignacio Provencio, David Berson, and others,

00:14:37.960 | that these cells exist that can communicate

00:14:40.320 | day and night information to the brain

00:14:42.680 | in this very small subset of cells.

00:14:45.440 | Since then, I've heard, but maybe you can confirm or refute,

00:14:49.200 | that this system that connects the eyes

00:14:52.880 | to the rest of the brain

00:14:54.340 | is actually the most ancient form of vision,

00:14:56.300 | that this is probably the form of vision

00:14:58.200 | that some early version of human beings had

00:15:01.480 | before they had pattern vision,

00:15:03.080 | before they could see colors and shapes

00:15:04.640 | and motion and all that.

00:15:06.420 | And that the same cells that perform this role

00:15:11.340 | are actually similar to insect eyes.

00:15:14.820 | I think I heard David Berson say once

00:15:16.480 | that we actually have a little bit of the fly eye

00:15:19.040 | in our eye, what's he talking about?

00:15:20.900 | - Yeah, so it's really interesting actually,

00:15:23.460 | because these same IPRGCs we discovered,

00:15:27.060 | they contribute a little bit to image formation

00:15:29.520 | and now work from Tiffany Schmidt,

00:15:31.360 | specifically have proven that they do contribute

00:15:34.160 | to image forming functions.

00:15:36.240 | But they contribute to very

00:15:38.160 | limited aspect of image formation.

00:15:41.960 | So it fits your hypothesis

00:15:43.640 | that these are an ancient photoreceptors.

00:15:45.800 | The other thing that adds to that hypothesis

00:15:48.640 | is that they are expressed in cells

00:15:50.140 | that don't have any modification

00:15:52.040 | that make them look like photoreceptors.

00:15:54.100 | So the photoreceptors that I told you about

00:15:56.340 | that are important for vision, image formation,

00:15:59.840 | they have very specialized structures

00:16:02.380 | that allow them to pack these structures

00:16:04.680 | with photopigments, these are the photo detecting proteins,

00:16:09.080 | so they could detect a high sensitivity of photons

00:16:12.160 | that pass through them.

00:16:13.680 | These new photoreceptors don't have

00:16:18.200 | these specialized structures.

00:16:20.420 | So they just really need a lot of light at the time.

00:16:24.460 | We thought they need a lot of light to be activated.

00:16:28.100 | So that's why we think they are ancient

00:16:30.100 | and that's why I think they adjust to ancient functions

00:16:33.420 | that are as important as regulating your body,

00:16:36.780 | circadian clock to the solar environment,

00:16:39.260 | to solar day or to the light dark cycle.

00:16:42.180 | - So you mentioned IPRGCs, intrinsically photosensitive.

00:16:45.280 | So these are cells that connect the eye of the brain

00:16:47.060 | that behave like photoreceptors essentially.

00:16:49.340 | And then you mentioned melanopsin,

00:16:51.740 | which is the actual pigment that converts the light

00:16:54.580 | into the electrical signal more or less.

00:16:57.560 | And my understanding is that melanopsin

00:17:00.260 | was identified first in frog melanophores.

00:17:04.180 | So does that mean that we have like little pieces

00:17:06.100 | of frog skin in our eyes?

00:17:08.020 | - So honestly, David Berson say you have a fly in your eye

00:17:10.980 | because it sounds better.

00:17:12.500 | The more accurate I think

00:17:14.020 | is that you have a frog skin in your eye.

00:17:16.060 | It's not as catchy, but really melanopsin,

00:17:19.660 | really the name melanopsin is from melanocyte opsin.

00:17:23.260 | So it's melanopsin

00:17:24.260 | because it was found in the frog melanocytes.

00:17:26.700 | You know the frogs can change their color depending on light

00:17:30.300 | and melanopsin drives this response.

00:17:32.740 | So when Ignacio Provencio first discovered

00:17:35.980 | these opsins in frogs,

00:17:37.820 | luckily he was smart enough to see

00:17:39.580 | if they are expressed in the frog eye.

00:17:41.740 | They were expressed in the frog eye

00:17:43.380 | and it what appears to be retinal ganglion cells,

00:17:45.820 | which I told you the one that connect the eye to the brain.

00:17:48.460 | He had the insight to go and see

00:17:50.300 | if they are expressed in the monkey eye.

00:17:52.620 | And he found that they are also expressed

00:17:54.420 | in what appears to be retinal ganglion cells.

00:17:56.780 | And really that what opened the field wide open.

00:17:59.480 | Then David Berson did the seminal experiment

00:18:02.920 | where he went to the brain where the central oscillator,

00:18:07.180 | the oscillator that drives circadian rhythm in the brain

00:18:09.860 | called the suprachiasmatic nucleus

00:18:11.820 | that has been known for many years to receive retinal input.

00:18:15.780 | And he labeled the cells that project there.

00:18:18.300 | And then he found that even if you destroy rods and cones,

00:18:21.260 | you could get light responses from these cells.

00:18:23.540 | So you could imagine he nearly fainted

00:18:26.340 | when he saw that these cells can respond independent

00:18:29.700 | completely in the absence of rod and cone input.

00:18:32.700 | - I'll never forget reading those papers in 2000, 2001.

00:18:36.800 | I was at the meeting in DC when Ignacio,

00:18:40.500 | we call him Iggy,

00:18:41.540 | showed this image of this basically what is frog melanophores

00:18:46.020 | in the human eye.

00:18:47.220 | And everyone was like, "Oh my goodness, this is the thing."

00:18:50.700 | And I want to get into how light

00:18:52.620 | actually can control circadian rhythms at the moment.

00:18:55.240 | But I think it's worth mentioning now

00:18:57.320 | that people who are pattern vision blind,

00:19:00.120 | so people who cannot see and no conscious vision,

00:19:03.960 | but have eyes, many of them still have these cells,

00:19:07.620 | these melanopsin intrinsically photosensitive cells,

00:19:10.080 | and can essentially match or entrain, as we say,

00:19:14.240 | onto the light-dark cycle.

00:19:16.000 | - In fact, they possibly have no problems

00:19:18.000 | in circadian photo entrainment.

00:19:19.400 | They'll have enormous sleep-wake cycle.

00:19:21.560 | - But they're totally blind.

00:19:22.580 | - But they are totally image blind.

00:19:24.140 | And what's really interesting is that,

00:19:26.620 | and this story I heard from Chuck Sizler,

00:19:28.480 | so I'll give him credit,

00:19:29.820 | that some of these people who are image blind,

00:19:32.200 | usually they get dry eyes and they give them a lot of pain.

00:19:35.620 | And doctors used to think,

00:19:37.360 | "Oh, since they are image blind

00:19:39.240 | and they're getting dry eye,

00:19:40.400 | why don't you just remove their eyes?

00:19:42.060 | They're not using them anymore."

00:19:43.640 | And the minute they would remove their eyes,

00:19:45.960 | they start having cyclical sleep problems,

00:19:48.200 | indicating that now they are not entraining

00:19:50.720 | to the light-dark cycle and are having cyclical jet lags

00:19:54.580 | when their clock shifts through the light-dark cycle.

00:19:57.960 | - That's really interesting.

00:19:58.920 | And I hear from a number of blind people,

00:20:02.480 | in my various aspects of my job,

00:20:04.560 | and a lot of them have issues with sleep,

00:20:07.440 | I think in part because they don't realize

00:20:09.960 | that they too need to see light

00:20:11.540 | at particular times of day or night

00:20:13.160 | in order to match their schedule.

00:20:15.840 | Well, I think that's a perfect segue for us

00:20:18.280 | to talk about how light and viewing light

00:20:22.280 | can impact our sleep-wake rhythms.

00:20:24.540 | And then we will move into some of the other ways

00:20:27.120 | in which light can impact other forms of bodily function.

00:20:30.320 | - Yeah, so I love the way you set it up

00:20:33.240 | because one of the most interesting and difficult aspect

00:20:37.240 | of trying to educate people about light effect

00:20:40.520 | on subconscious vision is that it's subconscious.

00:20:43.800 | So we're all aware of what we think is intensity

00:20:47.200 | because we see the room.

00:20:48.580 | But if you talk to people who know how to take photographs

00:20:52.400 | and stuff like that,

00:20:53.560 | they know that the intensity varies greatly.

00:20:56.140 | But our system, because we have to see the same way

00:20:59.100 | in very bright conditions and very dim conditions,

00:21:02.140 | we're not very good at estimating intensity consciously.

00:21:06.080 | So when you try to tell people about intensity,

00:21:08.440 | you really struggle because they think they know intensities

00:21:11.600 | but they really don't.

00:21:12.680 | - You mean light intensity.

00:21:13.720 | - Light intensity.

00:21:14.760 | So that the cones themselves have an incredible ability

00:21:18.880 | to adapt to different light conditions.

00:21:21.480 | So you can see at all different conditions,

00:21:23.520 | otherwise it'd be a disaster.

00:21:24.880 | You know, if you don't change the setting on your camera

00:21:28.000 | and you go from inside the room to the outside,

00:21:30.040 | it becomes completely white, you don't see anything.

00:21:32.640 | So if your cones don't adapt to the environment,

00:21:36.000 | then you're not gonna be able to see in this room

00:21:38.560 | and on the beach, right?

00:21:41.000 | But the problem is your IPRGCs,

00:21:44.200 | the cells that we talked about,

00:21:46.400 | they measure intensity pretty well.

00:21:48.600 | They really know what intensity is.

00:21:50.380 | They have a very good linear measurement of intensity.

00:21:53.240 | They don't adapt as well,

00:21:54.880 | they don't adapt actually that much, to be honest.

00:21:58.480 | So that tells you that subconsciously the system is used

00:22:03.320 | to measuring light intensity in a natural environment.

00:22:06.520 | Because when you're in a natural environment,

00:22:08.800 | you don't have industrialized lighting,

00:22:12.120 | then your system is functioning very well.

00:22:15.520 | But now when we change these environments,

00:22:18.120 | we could really mess up ourselves.

00:22:19.640 | So you have to teach people how to understand intensity.

00:22:23.440 | And that's something that you have to explain to people.

00:22:25.960 | And I think I love to do it myself.

00:22:27.960 | I do it in what is called the lowest amount of light

00:22:31.240 | required to allow you to see comfortably.

00:22:33.520 | So you have to do this as a fun experiment.

00:22:36.460 | - Okay, so explain to me how this goes.

00:22:38.760 | And maybe we could break it up in the day

00:22:40.600 | into three or four parts.

00:22:42.880 | So let's say, assuming that most people wake up

00:22:45.720 | in the morning, as opposed to night shift workers, et cetera,

00:22:48.560 | we could talk about later.

00:22:49.680 | But they wake up in the morning,

00:22:51.500 | so let's divide the day into quarters.

00:22:52.880 | What is the proper way to interact with light

00:22:57.040 | in the first part of the day?

00:22:59.640 | - So I honestly think the easiest thing is waking up.

00:23:02.880 | Get as much light as you can.

00:23:04.340 | - Into your eyes.

00:23:06.200 | - Yeah, it's really nice.

00:23:07.460 | Your system is primed.

00:23:08.840 | If you're in trained, it's primed to get light.

00:23:10.880 | The sun should be out.

00:23:12.640 | Most animals in the wild,

00:23:14.040 | they actually seem to track the sun.

00:23:16.280 | The sun has a huge influence on life on earth.

00:23:18.720 | It's actually, life on earth is because of sun.

00:23:21.880 | So that's easy.

00:23:24.040 | In the morning, when you wake up, you need light.

00:23:26.000 | - Okay, so what is the behavioral practice

00:23:28.040 | that you recommend?

00:23:29.960 | Does it, let's say somebody is in a condition

00:23:32.120 | where there's a lot of cloud cover,

00:23:33.940 | is it important to get outside?

00:23:35.600 | - So I have to tell you, the cloudiest day

00:23:37.900 | is gonna be much more brighter than your room.

00:23:40.120 | You could ask any photographer.

00:23:42.320 | A cloudy day, unless it's really dark, dark clouds,

00:23:45.460 | usually cloudy days have much more bright outside

00:23:48.800 | than inside the room,

00:23:49.840 | even when you have good lighting inside the room.

00:23:52.740 | So I think in the outside is usually,

00:23:55.960 | even when it's cloudy, you're gonna get enough intensity

00:23:58.560 | to help you adjust your cycle to the day/night cycle.

00:24:01.740 | - So how long do you, these are general rules of thumb,

00:24:05.000 | but how long do you recommend people go outside?

00:24:07.200 | - So if you do it daily, you possibly need very,

00:24:09.920 | if you do it daily, because remember,

00:24:11.680 | this thing is gonna happen on a daily matter.

00:24:13.480 | - So it's like, so the clock is tracking it

00:24:15.520 | on a regular basis. - Absolutely.

00:24:16.760 | It's photon counting, it's tracking,

00:24:19.600 | I would say 15 minutes.

00:24:20.680 | If you don't do it daily, you may wanna increase it.

00:24:23.600 | And we'll talk about when you travel what you could do.

00:24:25.720 | But yeah, 15 minutes should be fun.

00:24:27.960 | You do it more, it doesn't hurt.

00:24:29.840 | - And through a window, my understanding is

00:24:32.120 | that through a window, it dramatically decreases

00:24:34.440 | the amount of light energy coming in.

00:24:35.880 | - It depends of how thick the windows are

00:24:39.040 | and how dark they are.

00:24:40.720 | But it's also nice to go outside and to feel the season.

00:24:44.440 | - Sunglasses off.

00:24:46.040 | - I don't use sunglasses.

00:24:47.400 | - Yeah, but you have your Jordanian photo pigment.

00:24:50.700 | Whereas my eyes are very sensitive, right?

00:24:55.120 | But I personally, you know, if I'm in the shade

00:24:58.200 | or if it's not incredibly bright, I try to,

00:25:00.880 | especially in the morning, but I'm also an early person.

00:25:03.580 | So we have to differentiate between early--

00:25:05.160 | - What time do you wake up?

00:25:06.220 | - I wake up at 4.30 in the morning.

00:25:07.840 | - But the sun isn't out yet? - It's not out yet.

00:25:10.120 | - So what do you do?

00:25:10.960 | You turn on artificial lights?

00:25:12.120 | - I usually don't turn on artificial light

00:25:14.160 | because I know the sun is gonna come up eventually.

00:25:16.520 | But that's why I don't like the change

00:25:18.960 | in the timing that they do.

00:25:20.520 | - Wait, but what do you do between 4.30 a.m. and 7 a.m.?

00:25:23.720 | - I mean, I just got my computer and my phone,

00:25:26.280 | so possibly I get enough light.

00:25:28.720 | But in reality, I mean, as long as you let your body

00:25:31.980 | get the morning sunlight, which I think is really,

00:25:35.820 | to me, and there is no evidence, but to me,

00:25:38.080 | this is, if you look at all animals, plants,

00:25:40.840 | this morning sunlight seems to be very important.

00:25:44.360 | And I, you know, we don't have experiments to show it,

00:25:47.380 | but I have a gut feeling that it has

00:25:49.580 | a huge impact on humans.

00:25:51.680 | - Well, Jamie Zeitzer's lab at the Stanford Sleep Lab

00:25:54.360 | has shown that these early morning light flashes

00:25:57.120 | can adjust the total amount of sleep

00:25:59.640 | that one will get, makes it easier to get into sleep.

00:26:02.120 | - Absolutely, absolutely.

00:26:02.960 | - Okay, so--

00:26:03.960 | - And Ken Wright also did this beautiful camping experiments

00:26:08.240 | that showed that--

00:26:09.080 | - Right, maybe you should describe those

00:26:10.600 | 'cause those are beautiful experiments.

00:26:11.840 | - They are beautiful experiments.

00:26:13.160 | He took these, you know, college students

00:26:15.900 | that had the late onset of sleep and late waking time,

00:26:19.640 | and then he said, let's go camping and just don't use

00:26:22.160 | any artificial light and you could go to sleep as late

00:26:26.580 | or as early as you want and wake up as late as early.

00:26:29.280 | And he found a huge shift in their sleep pattern

00:26:33.000 | just by exposing them to the light-dark cycle.

00:26:35.400 | I mean, so--

00:26:36.560 | - And it lasted.

00:26:37.660 | - And it lasted.

00:26:38.500 | - Even after they came back.

00:26:39.320 | - Exactly.

00:26:40.160 | - I think it was two days of camping,

00:26:40.980 | reset the circadian clock.

00:26:41.820 | - Seven days, but it lasted, yeah, it's pretty amazing.

00:26:44.960 | Yeah, it's really incredible.

00:26:46.760 | - Okay, so get bright light of some sort early in the day,

00:26:51.400 | ideally sunlight, even on a cloudy day,

00:26:53.760 | it's going to be brighter than indoor light.

00:26:55.720 | - So that's easy.

00:26:56.580 | - Okay, so then--

00:26:57.600 | - And the other thing that I would like to mention to people,

00:27:00.060 | if you think it's very dim outside,

00:27:02.400 | let's say it's very cloudy, stay longer.

00:27:04.560 | So remember, intensity is only one component.

00:27:07.300 | Duration is also important because remember

00:27:09.620 | that the circadian system is not like the image system.

00:27:12.960 | In the image system, you have to change every second

00:27:15.340 | because you're looking at different objects.

00:27:16.980 | You have to change your perception.

00:27:19.040 | But for the circadian system, it's trying to figure out

00:27:22.120 | where am I in the day/night cycle.

00:27:24.920 | So the more you give them the information,

00:27:27.000 | the better you are.

00:27:28.000 | So if it's very bright, you don't need a lot

00:27:30.520 | because it's clearly going to make you fire like crazy.

00:27:33.680 | But if it's not bright, stay longer.

00:27:35.640 | Stay for one hour, have your coffee outside

00:27:38.680 | or something like that.

00:27:39.700 | It's just going to help.

00:27:41.180 | - I think you said something extremely important,

00:27:43.040 | which is that this circadian system is trying to figure out

00:27:46.420 | when you are in time, not where you are in space.

00:27:49.860 | - Sorry, I said where you are in time, I meant when you are.

00:27:52.540 | - Oh no, no, I wasn't correcting you.

00:27:53.700 | I just meant that, I think fundamentally,

00:27:56.060 | that's the incredible thing about this system,

00:27:59.860 | that you have this clock, this 24-hour clock in your brain,

00:28:02.780 | but it needs to be synchronized to the outside.

00:28:05.560 | So could we go a little deeper

00:28:07.840 | into this circadian setting behavior

00:28:10.460 | and come up with some general rules of thumb?

00:28:13.340 | So let's say it's a very bright day, extremely bright.

00:28:17.260 | No clouds, sun's out.

00:28:19.540 | You said 10 minutes, 15 minutes.

00:28:22.820 | - And I'll tell you, if you're sensitive,

00:28:25.020 | you don't even have to go in the sun.

00:28:26.720 | You could be in the shade.

00:28:28.120 | There's going to be so many photons out there in the shade.

00:28:31.240 | It's going to be perfect.

00:28:32.320 | You don't even have to see the sun.

00:28:34.380 | You don't have to have the sun.

00:28:36.140 | It's great for vitamin D, that's a different story.

00:28:38.300 | You could do this for your skin and protect your skin.

00:28:42.180 | That's not my area of expertise.

00:28:43.820 | But for that effect on the circadian system,

00:28:47.780 | as long as you're outside in the shade and it's sunny day,

00:28:50.980 | 10 to 15 minutes should be ample amount.

00:28:53.580 | - Okay, and then let's say it's kind of overcast.

00:28:57.280 | It's not particularly bright or there's solid cloud cover,

00:29:00.980 | but obviously the sun is out, but it's not as bright.

00:29:05.300 | How long do you think it would take to set the clock?

00:29:07.380 | - 10 to 15 should be sufficient.

00:29:09.340 | Stay for half an hour, stay for 45 minutes.

00:29:11.780 | If it's very dark cloud, yeah, stay for longer.

00:29:14.540 | - Okay, and if for some reason one finds themselves

00:29:17.600 | very far north and it's very, very dense cloud cover,

00:29:22.600 | how long and at what point should somebody consider

00:29:26.020 | using an artificial light source to mimic the sunlight?

00:29:30.200 | - Yeah, honestly, this is where we don't have

00:29:32.560 | a lot of information still, because this is where

00:29:35.940 | we're gonna discuss this maybe in more detail,

00:29:38.220 | that if you put humans in artificial conditions,

00:29:42.060 | the circadian system is very sensitive to light.

00:29:45.580 | But in reality, in the real environment,

00:29:48.860 | light also is affecting other aspects that are independent

00:29:52.620 | of the setting of the circadian basemaker.

00:29:55.680 | And these which we call the direct effect of light

00:29:58.000 | on mood, for example.

00:29:59.960 | So that is very hard to figure out what intensity

00:30:03.060 | you need to use, and we haven't done enough experiments

00:30:05.340 | 'cause the system has been discovered just recently.

00:30:07.940 | But I would say if you use bright light in the morning,

00:30:12.020 | and I mean, it's hard for me to give numbers,

00:30:14.620 | it can get complicated.

00:30:16.140 | But yeah, I mean, if you're, honestly,

00:30:20.120 | if you're that far north and you're in the winter

00:30:22.480 | and you wanna get, make sure you don't use these light boxes,

00:30:25.620 | I would suggest that personally, but that's it.

00:30:28.780 | - I use, it's actually not designed for circadian setting,

00:30:31.740 | but I have a 930 lux light pad that I bought,

00:30:35.940 | and I bought it, they're very affordable

00:30:38.060 | compared to the Dawn simulating lights,

00:30:40.860 | which are quite expensive, frankly.

00:30:43.460 | And I put it there, and so I just basically,

00:30:45.960 | when I wake up in the morning,

00:30:47.000 | I use that until the sun comes out.

00:30:48.900 | And then I make sure once the sun is out, I go outside.

00:30:51.180 | But I keep that thing on all day.

00:30:53.280 | And I don't know if that's good or bad.

00:30:55.100 | Is it good or bad?

00:30:56.100 | - I honestly, I don't think being exposed to bright light

00:30:59.340 | in the day is going to ever be bad.

00:31:00.820 | Because really, if you're outside in the day,

00:31:03.740 | unless, you know, the worst is gonna happen

00:31:06.100 | if the temperature is very high,

00:31:07.660 | your body's gonna say don't dehydrate and go to sleep.

00:31:10.340 | So you could tell actually sometimes when it's very hot,

00:31:13.940 | the more you get exposed to bright light,

00:31:15.820 | the sleepier you feel in the afternoon,

00:31:17.740 | which is counterintuitive.

00:31:19.260 | So--

00:31:21.020 | - And that's to protect us, you think, against dehydration?

00:31:23.340 | - I think if you think about the human evolution

00:31:26.020 | from near the equator in the,

00:31:28.420 | between noon and a certain time in the afternoon,

00:31:31.660 | it would have been very hard for you to maintain

00:31:34.640 | physiological homeostatic function,

00:31:36.660 | being active at this very high temperature time.

00:31:39.740 | So I think napping was a way,

00:31:42.100 | that's why I think it has a major function,

00:31:44.100 | which is still, napping was a way to somehow

00:31:47.140 | take you away from that dangerous zone.

00:31:49.220 | And maybe that's why people in the north,

00:31:51.860 | they say in the winter we can't wake up in the morning

00:31:54.140 | 'cause they don't have this long light,

00:31:55.720 | so they sleep it more at night.

00:31:57.320 | But in the summer they say we feel like we can't go to sleep,

00:32:00.380 | we have to put all these dark curtains.

00:32:02.960 | So I think venturing that much up north

00:32:07.960 | has been, came up with problem because evolution

00:32:10.660 | was used to a certain light environment

00:32:13.120 | that was completely changed with a human,

00:32:16.380 | with other animals I think that lived there longer.

00:32:19.360 | They have come up with very interesting adaptation

00:32:22.740 | of actually measuring even very small changes

00:32:26.180 | in the light intensities that still occur.

00:32:29.060 | So even if you're near the poles,

00:32:32.320 | even though it's always light,

00:32:33.940 | but there is a change in the light intensity

00:32:36.040 | across the day and night cycle.

00:32:37.200 | So your system, if it's linear,

00:32:39.060 | and remember I told you that IPRGCs are incredibly linear,

00:32:42.860 | can still measure, oh, this is lower light than higher light

00:32:46.500 | if the organism has the ability to do that.

00:32:49.780 | - I see, it's interesting, I've spent so much time

00:32:53.020 | learning from you, fortunately, about these cells,

00:32:56.580 | and yet I never really appreciated until now

00:32:59.060 | how on the one hand they are tracking the amount of light

00:33:03.180 | to understand when we are in time

00:33:05.420 | relative to the 24 hour cycle,

00:33:07.820 | but also that you keep mentioning

00:33:09.420 | this linear measurement of intensity,

00:33:11.860 | that they really are trying to figure out

00:33:13.860 | when we are in time by measuring the intensity of light.

00:33:16.500 | And of course the sun is the most intense source

00:33:18.900 | of light available to us.

00:33:21.020 | So, okay, so I think we've nailed down

00:33:24.180 | that first part of the day.

00:33:25.900 | Basically it's got 10 to 30 minutes,

00:33:27.600 | depending on how bright it is,

00:33:29.020 | and try and do that as often as possible

00:33:31.420 | to give the system a regular--

00:33:32.620 | - Daily is the best.

00:33:33.460 | This system is really about, and you'll see that

00:33:36.880 | even for the effect on depression,

00:33:38.460 | it's about multiple days.

00:33:40.560 | So you don't have to worry if you missed it one day,

00:33:43.540 | stay longer if you want, but if you're in a hurry

00:33:46.540 | and you want to do other stuff,

00:33:48.140 | that's a great recommendation.

00:33:49.980 | So you might want to compensate with some extra time

00:33:51.980 | if you missed a day or two.

00:33:53.740 | And this is why I've heard you say before,

00:33:55.900 | it's entirely possible to get severely jet lagged

00:33:58.940 | without traveling.

00:33:59.880 | - Absolutely.

00:34:00.720 | - Simply by staying in, being on your phone too much,

00:34:03.000 | not getting the sunlight.

00:34:03.980 | - And you saw this during the pandemic.

00:34:06.060 | A lot of people mentioned that their sleep-wake cycles

00:34:08.740 | suffered a lot, because if you're not going out,

00:34:12.980 | and if you're staying at home and you don't have big windows

00:34:16.380 | and you're waking late, waking up late,

00:34:18.740 | and then you're using very bright light till late at night,

00:34:21.580 | your body's gonna shift.

00:34:23.220 | And now your day is gonna start,

00:34:25.460 | instead of like really when the sun comes up,

00:34:27.620 | let's say at six o'clock in the morning,

00:34:29.340 | it's gonna, your day's gonna start

00:34:30.860 | at 11 o'clock in the morning.

00:34:32.100 | That's what your body's gonna think

00:34:33.700 | is the beginning of the day.

00:34:35.820 | So then you're not gonna be able to sleep

00:34:38.380 | at 10 o'clock at night, because now that's really,

00:34:42.180 | for your body, is completely different timing.

00:34:45.380 | And you could see this happen during the pandemic

00:34:48.060 | at a very high scale.

00:34:49.540 | People get delayed in their sleep-wake cycle a lot.

00:34:52.700 | - And there is this idea of chronotypes

00:34:54.940 | that we all each intrinsically have a best rhythm

00:34:59.140 | of either being a morning person,

00:35:00.980 | you called yourself an early person,

00:35:02.580 | or a night owl, or more of a kind of standard,

00:35:05.860 | to bed around 10, 30, up around seven type thing.

00:35:08.980 | And I think there are now good data,

00:35:11.300 | correct me if I'm wrong,

00:35:12.820 | from the National Institutes of Mental Health

00:35:14.500 | and elsewhere showing that the more we deviate

00:35:17.020 | from that intrinsic rhythm, the more mental health issues

00:35:21.260 | and physical health issues start to crop up.

00:35:23.140 | - So there is great data on this,

00:35:24.940 | and there is a couple of things that complicate this.

00:35:27.140 | The first is the people who usually are late,

00:35:30.500 | they tell you that the society doesn't accommodate.

00:35:32.980 | - What, by late, what do you mean?

00:35:34.940 | People that wake up late and go to sleep late?

00:35:36.540 | - Go to sleep late and wake up late.

00:35:38.580 | They have an overwhelmingly higher level

00:35:41.020 | of depression and failures.

00:35:43.500 | I mean, clearly, I mean, the reason that people say

00:35:46.880 | sleep early, wake up early, you're better,

00:35:49.400 | because human notice that people who wake up,

00:35:52.560 | go to sleep early and wake up early,

00:35:54.300 | they do better in life, they notice that.

00:35:56.280 | - They just perform better.

00:35:57.340 | - They perform, but the question is,

00:35:58.920 | is that intrinsic to the system, or is that society,

00:36:02.440 | because society start things usually early,

00:36:04.720 | or late, that's a hard question to ask.

00:36:06.040 | - We discriminate against late risers.

00:36:07.940 | - In a way, we discriminate, right?

00:36:09.640 | But the other explanation is Ken Wright's experiment.

00:36:12.960 | These late riser, if they were truly chronotypically late,

00:36:17.960 | why would they shift so easily when you put them in the,

00:36:21.720 | if you were really chronotypically late,

00:36:23.940 | and there is a phase relation between

00:36:26.180 | the light-dark environment and your circadian clock,

00:36:28.820 | then doing this camping experiment

00:36:30.580 | should not have caused much changes,

00:36:32.460 | because it's not that light is gonna affect you

00:36:37.260 | in a certain way, it's that this is the relationship

00:36:39.580 | that your body decided, that I'm a late sleeper,

00:36:42.460 | late waking, so I'm honestly, I'm still unable

00:36:47.060 | to figure out how much of this late waking up

00:36:50.300 | is controlled by the light environment,

00:36:52.600 | and how much is intrinsic.

00:36:53.820 | I'm sure there are differences,

00:36:55.840 | but are they as big as we see in the environment?

00:36:58.540 | Because you have people that go up to sleep at 7 p.m.

00:37:02.800 | and wake up at 1 a.m., these are clearly advanced phase.

00:37:06.220 | - So people that go to sleep at 7 p.m.

00:37:08.020 | and wake up at 1 a.m. and feel good doing that.

00:37:11.060 | - I'm not so sure they feel good,

00:37:12.740 | but a lot of the time you talk to people,

00:37:14.800 | they say they are high achievers,

00:37:17.060 | but they suffer because they go to 7 p.m.,

00:37:20.340 | wake up advanced phase sleep syndrome, they call it,

00:37:23.460 | they call it a syndrome, but then you have people

00:37:27.380 | who would not be able to sleep 'til 5 a.m.

00:37:29.820 | and not be able to wake up 'til 3 p.m., right?

00:37:33.620 | And I'm not so sure that the circadian system

00:37:35.920 | is that variable in the human population.

00:37:38.140 | I mean, clearly there are maybe some genetic factors

00:37:40.760 | that make a small percentage of like everything

00:37:43.860 | with a bell shape, but I think most of the time,

00:37:47.160 | the light environment may play a role.

00:37:49.140 | And once, as we've talked about,

00:37:51.500 | this is a long-term effect of light.

00:37:53.840 | Once you get into a rhythm, and I don't mean it as a pun,

00:37:57.420 | in reality, once you get into a rhythm,

00:37:59.440 | it's hard to break out of that rhythm,

00:38:01.820 | because if you start sleeping late and waking up late,

00:38:04.820 | you're not getting the morning sunlight.

00:38:06.780 | - Right.

00:38:07.620 | - And so you're just gonna be late.

00:38:09.640 | And if you're like me, waking up early,

00:38:11.940 | you're getting the morning sunlight.

00:38:13.300 | You're getting what Zeisler said.

00:38:14.900 | I said his last name wrong.

00:38:17.820 | The one in Stanford who did the-

00:38:21.020 | - Oh, Jamie Zeisler.

00:38:22.140 | - Zeisler. - Yeah.

00:38:22.980 | - Yeah.

00:38:23.800 | - He actually worked for Zeisler, so Zeisler and Zeisler.

00:38:27.400 | Yeah, there are a lot of Z's, E's, and I's in their names.

00:38:30.340 | - Yeah.

00:38:31.180 | - Both phenomenal scientists.

00:38:32.020 | - Yeah.

00:38:32.860 | - What it seems to me is the case

00:38:35.700 | is that the only way to really know

00:38:38.280 | if you're meant to be an early bird, as they call it,

00:38:41.460 | an early person or a late person, or somewhere in between,

00:38:44.900 | is to get morning sunlight

00:38:46.220 | and figure out whether or not that makes you feel better.

00:38:48.260 | - And to understand,

00:38:50.000 | to be educated about how to measure intensity,

00:38:54.780 | how to measure, I put it between quotation,

00:38:57.180 | 'cause you either get a measuring device,

00:38:59.740 | but you cannot depend on your eye to measure intensity.

00:39:03.580 | - Okay, so how do we do that?

00:39:04.500 | 'Cause you keep coming back to this,

00:39:06.140 | so that tells me that's important.

00:39:08.020 | - It's very important.

00:39:08.860 | - So obviously, so there are apps, like free apps,

00:39:11.500 | like LightMeter, where you can walk around

00:39:13.800 | and hold the button down and see how many lux,

00:39:16.340 | you know, are in the environment.

00:39:18.060 | - These are complicated,

00:39:18.940 | because you have to point them to specific regions.

00:39:21.240 | - So how do people start to develop an intuitive sense

00:39:25.080 | of the measurement of intensity?

00:39:27.260 | - Yeah, I think at one point I posted on Instagram

00:39:30.900 | how I keep my nighttime at home,

00:39:33.540 | and I found out that my night vision is very strong.

00:39:36.920 | So I found out that I, especially in the winter,

00:39:39.620 | I only need candle lights,

00:39:41.180 | so I literally use these tea lights,

00:39:43.620 | and I put like 15 or 20 of them.

00:39:45.820 | - How romantic.

00:39:46.700 | - And it's so nice, I could see,

00:39:48.740 | it clearly doesn't affect my circadian system.

00:39:51.140 | - You and your cats.

00:39:52.140 | - And my wife, and it's just great, it's just great, right?

00:39:55.800 | But I don't expect people

00:39:56.980 | to have the same night vision as me.

00:39:59.380 | So the simple, I mean, I tell people, do the experiment.

00:40:03.020 | So if you put three or four lights in your room,

00:40:07.240 | switch to, sit for 15 minutes, you have--

00:40:09.600 | - Switch two off.

00:40:10.440 | - Switch two off, let's say you're using five,

00:40:12.720 | and see, after 15 minutes,

00:40:14.600 | you will not recognize you switched these two off.

00:40:17.360 | My gut feeling is that most people would need

00:40:19.800 | at least 10 times less light than they use at night to see.

00:40:24.000 | The problem people use it,

00:40:25.480 | because most of the time

00:40:26.760 | they didn't see the morning sunlight,

00:40:28.280 | they are actually hungry for light without their knowledge.

00:40:31.040 | So they come switch all these lights on,

00:40:33.020 | but at the wrong time, because they woke up late.

00:40:36.180 | - Okay, now I understand.

00:40:37.820 | So this morning light viewing goes way beyond

00:40:41.280 | setting your clock. - Absolutely, absolutely.

00:40:42.940 | - It's also a way to determine

00:40:44.740 | how little light you need later in the day.

00:40:47.640 | - Exactly.

00:40:48.480 | - And we're going to talk about this in a moment,

00:40:50.120 | but how little light you get later in the day

00:40:53.220 | is a very strong determinant of things

00:40:55.040 | like when you will wake up,

00:40:56.080 | whether or not you wake up feeling refreshed, et cetera.

00:40:58.360 | Let's--

00:40:59.200 | - And that's why--

00:41:00.240 | - Yeah.

00:41:01.080 | - I'm gonna break it on your show, Andrew,

00:41:02.840 | that I'm gonna tell you,

00:41:04.000 | I think there is something else

00:41:06.020 | that people need to think about,

00:41:07.360 | which is the tripartite model.

00:41:09.540 | That this model incorporate three components

00:41:12.340 | we should talk about in details

00:41:13.840 | that allows us humans and all animals

00:41:17.760 | to incorporate the circadian clock

00:41:20.360 | and its relation to light, the homeostatic drive,

00:41:24.040 | and the direct effect of the environment,

00:41:26.160 | which includes stress, light, all kind of stuff.

00:41:29.160 | They have to be incorporated together.

00:41:31.320 | If you think, that's what I think right now,

00:41:33.540 | if you think of one alone, you will always miss something.

00:41:37.920 | And when you think of them as a whole,

00:41:39.940 | things really become clear.

00:41:41.480 | It's actually quite amazing.

00:41:43.000 | - Okay, well, we will definitely want to hear

00:41:45.520 | about your tripartite theory

00:41:47.760 | and go into detail about this homeostatic mechanisms.

00:41:50.640 | I wanna make sure that for people who are thinking now,

00:41:53.980 | I'm sure, about light and how it impacts them.

00:41:56.880 | So the morning light viewing behavior,

00:41:58.920 | I like to think we've tacked down clearly.

00:42:01.160 | And thank you for that

00:42:02.160 | because there's so much information out there

00:42:03.920 | and I've tried to relay that information.

00:42:06.040 | Of course, you're my primary source

00:42:07.260 | for all things circadian, as well as Jamie and others,

00:42:10.700 | of course, Matt Walker,

00:42:12.020 | but I think you've made that very, very clear.

00:42:15.960 | Now, let's say I've gotten my morning sunlight, okay?

00:42:20.440 | Made my bright artificial light.

00:42:21.600 | And throughout the day, you said to get a lot of light.

00:42:23.840 | So I'm working at my desk.

00:42:25.020 | Maybe I'll go out during the day a few times,

00:42:27.860 | but I'm working at my computer, I'm doing things.

00:42:30.500 | Is there anything about light viewing

00:42:32.100 | in the middle of the day that people should keep in mind?

00:42:35.520 | Or can they just sort of freestyle it,

00:42:37.640 | depending on what they're doing?

00:42:38.540 | Most people are not in a dark room throughout the day.

00:42:42.580 | - My gut feeling, if you got your morning sunlight,

00:42:45.520 | you walk from your car slowly or you walk to work,

00:42:49.700 | you didn't wear sunglasses

00:42:50.860 | when the lights were still dim in the morning,

00:42:53.380 | that you could freestyle it.

00:42:55.000 | That even if you don't get a lot of light,

00:42:57.700 | there is a way to just, you know, in the day,

00:43:01.080 | you don't have to just worry

00:43:02.340 | about getting a lot of bright light.

00:43:03.820 | But personally, I like to do that.

00:43:05.820 | So I go out at lunch and have my lunch outside as well.

00:43:09.680 | This reminds the body that here it is even brighter now.

00:43:13.560 | But the evidence is that you could literally

00:43:16.620 | help your circadian clock by giving lights at dawn and dusk.

00:43:20.380 | But again, if you think of the tripartite model,

00:43:22.860 | this may be important versus circadian clock,

00:43:25.060 | but is it important for your mood?

00:43:27.900 | So that's where I think you need, or the homeostatic drive.

00:43:31.260 | So that's where you need to think about it.

00:43:33.620 | So for the clock, for entraining your clock,

00:43:36.780 | you literally can entrain it only by the dawn sunlight.

00:43:39.820 | You actually don't need dawn and dusk.

00:43:41.580 | You can even forget that.

00:43:42.820 | - Yeah, and I appreciate that you're distinguishing

00:43:44.840 | between circadian effects and other effects of light.

00:43:47.700 | You're being very precise, which is appreciated.

00:43:51.580 | Until we hear about this tripartite model,

00:43:53.660 | which we will cover, for the sake of the discussion,

00:43:57.320 | let's treat the light viewing behavior

00:43:59.580 | as what are the benefits or drawbacks of viewing light

00:44:04.260 | for all biological purposes, not just circadian setting.

00:44:07.340 | So in the morning, it's clearly going to set the clock.

00:44:10.820 | And then during the day, if I understand correctly,

00:44:13.820 | the idea is to get as much bright light as you can

00:44:15.860 | because you're feeding, it sounds like,

00:44:17.280 | a sort of light hunger.

00:44:19.820 | - Exactly. - I see.

00:44:21.140 | - I love this way to put it.

00:44:22.220 | I think there is a weird light hunger.

00:44:24.220 | Considering that we're not photosynthetic organisms,

00:44:27.660 | there is a weird light hunger in animals

00:44:29.840 | that they need to measure, they need measure.

00:44:33.140 | And I think that relates to the season

00:44:35.100 | because the whole reproduction cycle of animals

00:44:38.180 | is gonna depend on the availability of food

00:44:41.660 | in the environment.

00:44:42.600 | And if you don't know when the season's gonna happen,

00:44:45.260 | they don't have calendars,

00:44:47.000 | it's gonna be very hard to survive.

00:44:48.700 | So I think that's why we have this light hunger.

00:44:51.060 | That's a major hypothesis, it's not been tested.

00:44:54.000 | - Interesting.

00:44:54.840 | So then afternoon and evening start to approach.

00:44:59.060 | So I've had this weird experience.

00:45:00.740 | Maybe you can psychologically

00:45:02.780 | or biologically diagnose me now, Samir.

00:45:05.220 | So where if I go into a movie in the afternoon,

00:45:07.800 | like a matinee, and I come out and it's dark,

00:45:11.500 | I notice a significant drop in my mood

00:45:15.140 | and my ability to go to sleep.

00:45:17.800 | Whereas if I get some view of the light in the evening,

00:45:21.480 | doesn't have to be the sunset, although sunsets are nice,

00:45:23.900 | but I get some light pulse in the afternoon

00:45:26.780 | that I have no trouble whatsoever.

00:45:29.200 | - And this happens on a single time to watch them?

00:45:33.000 | - More or less.

00:45:33.840 | - That's interesting.

00:45:35.520 | - And then you mentioned the camping experiment

00:45:37.240 | where when they went camping,

00:45:38.400 | they're seeing the sunrise and the sunset.

00:45:41.120 | So what should people do in the afternoon/evening time

00:45:46.400 | in terms of their light viewing behavior?

00:45:48.200 | - I mean, the best thing to do is to let the natural light

00:45:51.240 | creep in into darkness, right?

00:45:53.120 | That would be the best.

00:45:54.680 | But clearly that would be inefficient.

00:45:57.400 | You wanna go home, you wanna read,

00:45:59.740 | you wanna talk to your kids,

00:46:01.720 | you wanna talk to your family.

00:46:03.400 | So I think, you know, it's nice to extend the day.

00:46:06.000 | I don't think that's wrong.

00:46:07.140 | If you somehow can block that light

00:46:10.240 | from affecting your circadian clock.

00:46:12.080 | - So should people use blue blockers in the evening?

00:46:15.400 | - I personally do not like any blockers

00:46:19.020 | that take a single wavelength of light.

00:46:20.960 | Because again, if you think of a holistic approach,

00:46:24.240 | yes, the blue blocker is gonna prevent you

00:46:26.180 | from affecting your circadian clock very much,

00:46:29.560 | but then your vision is gonna be distorted

00:46:31.720 | because we always see in full spectrum.

00:46:34.220 | The sun has this beautiful spectrum, right?

00:46:36.840 | And then when you start seeing without the blue,

00:46:39.280 | things look yellow and it can get really weird, right?

00:46:43.740 | I mean, so I personally, I've tried the blue blocker

00:46:47.800 | and I couldn't even wear them.

00:46:49.420 | I thought they were just really horrendous to be honest.

00:46:53.000 | - Well, along the lines of blue blockers,

00:46:54.940 | I think a lot of people mistakenly wear them all day long.

00:46:58.340 | - Oh my God, that would be very bad.

00:46:59.660 | - A lot of people do that.

00:47:01.260 | A lot of people do that.

00:47:02.160 | They think that the blue light is bad.

00:47:04.060 | I think that the concept of blue light being bad

00:47:07.940 | led to a lot of product development.

00:47:10.380 | And a lot of people are just assuming

00:47:11.900 | that viewing blue light is what was giving them headaches

00:47:14.580 | when in fact, it might've just been looking

00:47:16.060 | at screens at close distance.

00:47:17.940 | - So here's the problem, right?

00:47:19.440 | I mean, the blue light got the bad reputation

00:47:22.060 | because people who gave a pure blue light

00:47:24.100 | showed that it caused a huge retinal damage.

00:47:26.980 | But again, if you're using blue light in its pure form,

00:47:30.420 | it has a lot of energy because it's shorter wavelength.

00:47:33.620 | But we're talking about full spectrum light.

00:47:36.380 | There are ways now where you could change the spectrum

00:47:39.700 | of the light and keep it white between day and night

00:47:43.300 | and change the content of the color without you noticing.

00:47:47.580 | So you don't even have to affect your vision.

00:47:49.780 | - So how would you go about doing that?

00:47:51.500 | - So you just lower the level of the blue light.

00:47:53.780 | You don't have to eliminate it.

00:47:54.940 | - So just dim the lights.

00:47:56.280 | - Dim the blue, but keep, then increase the yellow,

00:47:59.220 | but keep all the colors in a certain white.

00:48:02.860 | So you could have different warmness of white.

00:48:06.840 | And people know how to do this.

00:48:08.260 | Physicists know how to do this.

00:48:09.660 | People who work with light know how to do this.

00:48:11.580 | - Well, maybe somebody in the wellness slash,

00:48:14.260 | I don't like the word,

00:48:15.100 | but biohacking or optical community will do this.

00:48:18.620 | I think it's really important.

00:48:20.140 | I see so many people wearing blue lockers.

00:48:22.380 | - I don't know why they love blue.

00:48:24.020 | - Well, I think they're just uninformed.

00:48:25.180 | I think, frankly-

00:48:26.460 | - And to be honest, it's easy, right?

00:48:27.860 | It's easier to explain to somebody,

00:48:30.080 | if IPRCCs respond mostly to blue,

00:48:32.540 | remove blue, you'll be fine, right?

00:48:34.680 | But that's not as simple as that

00:48:36.260 | because they also receive road and cone input.

00:48:38.340 | So you want to actually, and you know,

00:48:40.900 | we could go into details that's boring for you listeners,

00:48:43.300 | but it also affects the adaptation properties

00:48:45.740 | of the whole retina.

00:48:47.140 | So you don't want to do something so drastic

00:48:49.600 | that you take just one color of the spectrum.

00:48:51.820 | It just seems very counterintuitive to me, to be honest.

00:48:56.500 | - You've told me before as well,

00:48:58.620 | that just because these intrinsically photosensitive

00:49:02.380 | circadian setting ganglion cells respond best to blue light,

00:49:07.180 | if the light is bright enough,

00:49:08.780 | because they also get input from other components of the eye,

00:49:12.380 | it doesn't matter if you block the blues.

00:49:14.940 | If you're looking at bright light at night,

00:49:16.500 | you're going to disrupt your circadian cycle.

00:49:18.500 | - And that's why I didn't want to go

00:49:19.860 | into the boring details, but themselves,

00:49:21.780 | the photoreceptors have a wide range of responsiveness.

00:49:25.320 | So they are most sensitive to blue light,

00:49:27.360 | but that doesn't mean they don't respond to green light

00:49:30.280 | or to shorter than blue light.

00:49:32.180 | They respond to very, very wide spectrum

00:49:35.300 | with different sensitivities.

00:49:37.000 | So unless you understand the system,

00:49:38.880 | just removing 480, I don't think it's going to do anything.

00:49:41.600 | - 480 nanometers, yeah.

00:49:43.480 | So your home is a cave at night, basically.

00:49:48.480 | - It's a nice cave.

00:49:49.760 | - It's a nice cave with candles, right?

00:49:52.360 | And you and your cats and your lovely wife,

00:49:56.140 | who I know who's also a phenomenal scientist

00:49:58.260 | in her own right.

00:49:59.100 | - Thank you, yeah, she is.

00:49:59.940 | - She is, but you do keep your home

00:50:03.400 | quite dim to dark at night.

00:50:06.120 | In fact, I did go to meetings with some of my friends

00:50:10.120 | who work on this, and they really struggled with me.

00:50:12.320 | They said we could have broken our legs

00:50:14.600 | living in the same light environment that you do.

00:50:17.000 | So I am an extreme, but I measured it for myself,

00:50:20.480 | and I asked Reggie, my wife, if she's okay with it.

00:50:22.960 | She also liked the dimness.

00:50:24.260 | Both of us can see well in dim conditions,

00:50:27.200 | and that helps us a lot.

00:50:29.320 | But I think you have to measure it for yourself.

00:50:32.800 | You really have to do, it's a very simple experiment.

00:50:36.520 | Just try to dim the light as much as you can.

00:50:39.040 | I call it the minimum amount of light

00:50:41.600 | you require to see comfortably.

00:50:44.280 | - And that's how you want your environment,

00:50:46.040 | ideally, at night.

00:50:47.200 | - This is what I think is the game changer.

00:50:50.000 | If you reach to a level where it's just barely,

00:50:53.440 | you're literally on the cusp of seeing uncomfortably

00:50:56.640 | versus seeing very comfortably,

00:50:58.840 | you are gonna be very much better than,

00:51:02.360 | I don't like to make it completely dark.

00:51:04.320 | I think complete darkness induce anxiety in humans,

00:51:08.160 | to be honest, so I don't like complete darkness.

00:51:10.780 | - Kids don't like complete darkness.

00:51:13.540 | They like a night light.

00:51:14.880 | - Even nocturnal animals don't like complete darkness.

00:51:17.600 | I mean, we have studies in animals that are nocturnal

00:51:21.080 | that if you put them in complete darkness

00:51:22.600 | for several weeks, they have severe anxiety

00:51:26.480 | and depression-like effect.

00:51:28.280 | So keep the light dim.

00:51:31.680 | Use red light that is very dim

00:51:34.000 | if you wanna keep the room for sleeping.

00:51:36.760 | Red light that is very dim has very small effect

00:51:40.260 | on circadian clock, and below 10 lux of red light

00:51:44.960 | literally doesn't affect sleep at all.

00:51:47.400 | So there are ways to do it.

00:51:49.320 | It's just we need to educate the public,

00:51:51.240 | and I feel like you literally need a whole lecture

00:51:55.580 | to just explain to the people how to deal with light

00:51:58.720 | because it's not as simple as people think.

00:52:01.080 | - Well, that's what we're doing here.

00:52:02.360 | We're stepping through it piece by piece,

00:52:04.000 | and the reason we're doing that

00:52:06.400 | is because it's not as simple as saying

00:52:08.160 | just block blue light or get a lot of light

00:52:09.760 | during the day and minimal at night.

00:52:10.600 | - I mean, just to put it in perspective to tell it,

00:52:13.440 | we only have three different cones in our retina

00:52:17.240 | that respond to three different colors.

00:52:20.040 | We call them red cones for simplicity,

00:52:23.120 | green cones, and blue cones.

00:52:25.260 | Yet we have only three of these,

00:52:27.100 | but we could see massive palette of colors.

00:52:30.640 | So that tells you something.

00:52:32.320 | If the system was just simply about a single color,

00:52:35.820 | and it's just removing 480 or just blue is sufficient,

00:52:39.960 | then we should only see in red, yellow, and blue.

00:52:42.480 | We shouldn't see all these different hues of color,

00:52:45.160 | but because the system is not that,

00:52:47.160 | we see all these different colors.

00:52:49.740 | And that's why it's important to remind people

00:52:52.000 | that the white light is made of many different colors.

00:52:55.560 | It's actually like the rainbow.

00:52:56.980 | That's why you see the rainbow.

00:52:58.040 | It's made of many colors.

00:52:59.680 | White light is never truly white.

00:53:01.600 | It's made of more of different colors.

00:53:03.800 | - It's like the Pink Floyd album cover.

00:53:05.400 | - Exactly, exactly, exactly.

00:53:08.000 | - So dim at night, maybe dim red light ideally,

00:53:12.960 | or candlelight, find that minimum required light level.

00:53:16.300 | - Just make sure when you lower the light,

00:53:19.320 | sit for at least 10 to 15 minutes, let your system adapt.

00:53:23.680 | Because if you had it bright light and you switch it off,

00:53:26.640 | surely you're gonna suffer

00:53:27.800 | because your system didn't adapt it.

00:53:29.400 | It was used to very bright light.

00:53:31.880 | So you want to engage your rods,

00:53:33.800 | which take a long time to dark adapt.

00:53:36.720 | So that's why I tell you, just wait a little bit.

00:53:39.600 | Don't just switch off the light, don't see, put it on.

00:53:42.320 | Put it off, sit down, wait for 10 minutes,

00:53:44.680 | ideally 15 minutes, and then see how you see.

00:53:48.560 | And then once you do that, you will notice that actually,

00:53:51.880 | yeah, I could see quite well, even with much less light.

00:53:57.560 | - What do you do regarding screens?

00:54:00.400 | - Yeah, that's the hardest thing.

00:54:02.480 | Again, I mean, there are beautiful programs

00:54:05.300 | that change the whole intensity and color of the screen.

00:54:08.680 | These could help dim your screen at night

00:54:11.040 | to the lowest part.

00:54:11.960 | I mean, yes, you won't see it

00:54:13.440 | when you wake up in the morning,

00:54:14.540 | but then you can increase the intensity.

00:54:16.800 | So try to decrease.

00:54:18.200 | I mean, just what we were talking about.

00:54:20.700 | Think of light intensity, duration, color, and time of day.

00:54:25.140 | You really have to keep these four things together, right?

00:54:28.740 | - We've roomed together at a couple of meetings

00:54:31.200 | from time to time, no longer, because one of us,

00:54:33.840 | not to be named, has a severe snoring issue

00:54:36.740 | that made the other one pseudo-homicidal.

00:54:39.360 | You can guess who that was.

00:54:42.780 | But I've seen you check your phone after dark once or twice,

00:54:49.300 | and you did it by sort of pointing your phone

00:54:53.140 | away from you, right?

00:54:55.060 | - And actually, I'm sort of half joking,

00:54:57.960 | and you dim it quite a bit.

00:54:59.440 | I'm sort of half joking, but it actually makes sense

00:55:01.840 | that if you shine a flashlight in your eye,

00:55:03.760 | it's much brighter than if you shine a flashlight on the--

00:55:05.000 | - Light only go in direct line.

00:55:06.440 | So if you just look on the side,

00:55:08.120 | most of the light is going to go this way,

00:55:09.840 | and you're only seeing this way.

00:55:11.600 | - Okay, and as silly as that might seem to people listening,

00:55:14.520 | I mean, what it means is that getting bright light

00:55:17.040 | in your eyes at night is something

00:55:19.360 | that you really want to avoid, but there is the reality.

00:55:23.000 | - And even when I check sometimes,

00:55:24.600 | if I have something and I check it so fast

00:55:28.180 | and switch it off so fast,

00:55:29.260 | so I'm also aware of the duration.

00:55:31.060 | - Not my messages.

00:55:32.420 | - I'm also aware of the duration, right?

00:55:34.720 | So duration, intensity, color, and time of day.

00:55:38.220 | Ideally, I should not check iPhones and iPads.

00:55:41.160 | I don't use iPad at night because it's hard

00:55:43.360 | to lower it enough 'cause it's huge.

00:55:46.440 | But even my iPhone, I try not to use it at night.

00:55:49.480 | And once it becomes 8.30 or nine, I don't look at it at all.

00:55:53.720 | - Unless it's World Cup or Euro Cup,

00:55:55.560 | in which case Sanders on 24 hours, everybody.

00:55:57.920 | - That's only every four years.

00:55:59.720 | [laughing]

00:56:00.760 | - He's a big soccer fan.

00:56:02.180 | All right, this has been incredibly, no pun, illuminating.

00:56:06.340 | Let's talk about the relationship between light

00:56:10.420 | and some of these other non-circadian

00:56:13.560 | or pseudo-circadian effects.

00:56:15.880 | And we will try and link those.

00:56:19.140 | But you had a, what I consider,

00:56:21.640 | absolutely landmark, beautiful paper,

00:56:24.240 | published in "Nature" a few years ago,

00:56:26.900 | showing that if you disrupt the exposure to light

00:56:31.900 | or the timing of the exposure to light,

00:56:34.960 | that there are dramatic effects on the stress system

00:56:38.120 | and on the learning and memory system.

00:56:40.000 | Maybe we could talk about each of those

00:56:43.040 | separately or together.

00:56:44.400 | What are the effects on stress and the effects on learning

00:56:48.040 | when light-viewing behavior and sleep-wake cycles

00:56:52.440 | are disrupted?

00:56:53.280 | - Yeah, so just to remind you, you know that,

00:56:57.560 | but to remind your listeners that I was trained

00:57:00.480 | as a circadian biologist, so I really was indoctrinated

00:57:05.200 | into thinking that light has to affect the clock,

00:57:07.660 | which then cause all these different effects.

00:57:10.160 | So that's what I believe, that's my dogma,

00:57:12.760 | that's what would have made me really happy.

00:57:14.700 | And then Tara LeGates and Kara Altimas joined the lab

00:57:18.900 | and said, and we started discussing a lot of data,

00:57:21.620 | and we said, what if there is a direct effect of light

00:57:24.200 | that we're missing independent of the circadian clock?

00:57:27.260 | So this is not an easy question to ask, to answer,

00:57:29.980 | because as we've been talking all along,

00:57:32.080 | light affects the circadian clock.

00:57:33.660 | So how could you give light at different times of the day

00:57:37.460 | and not mess up the circadian clock?

00:57:39.340 | Luckily, we came up with such a way,

00:57:41.060 | and that's why it was important to do this experiment

00:57:44.940 | the way we did them.

00:57:46.460 | And we proved that this light-dark cycle

00:57:48.900 | does not disrupt the clock,

00:57:50.340 | there is still a circadian rhythm,

00:57:52.460 | and does not cause sleep deprivation.

00:57:55.900 | And yet, surprisingly, if you give light

00:57:58.900 | at the wrong time of the day,

00:58:00.140 | even without disrupting the circadian clock,

00:58:02.760 | or without causing sleep deprivation, as you mentioned,

00:58:06.140 | you get huge mood changes in the organisms,

00:58:10.800 | and you get learning deficit.

00:58:12.740 | So this really, and at the time,

00:58:15.540 | people have really hit us hard.

00:58:17.860 | I mean, it was really hard to publish this work,

00:58:21.140 | and you could, yeah.

00:58:22.740 | - Well, it came out in nature, so in the end, you prevailed.

00:58:26.860 | But I want to make sure that I understand.

00:58:28.340 | So you're saying that, yes, there are effects of light

00:58:32.080 | on the circadian rhythm, meaning sleep and wakefulness,

00:58:36.100 | and their timing.

00:58:37.420 | However, there are direct effects of light on mood

00:58:40.840 | that can be dissociated from the effects

00:58:43.540 | on sleep and waking.

00:58:44.860 | So if I interpret that correctly,

00:58:47.160 | that could mean that when we view light

00:58:50.960 | and how much light could make us feel happier,

00:58:55.000 | or less happy, or even depressed,

00:58:56.820 | stressed, learning, et cetera.

00:58:58.560 | - Bingo.

00:59:00.480 | - Even if we're sleeping and waking up

00:59:03.000 | at the appropriate time.

00:59:03.880 | - Bingo.

00:59:04.720 | I mean, eventually, because we're talking about

00:59:07.160 | the whole system, eventually when you start having

00:59:09.620 | the other problems, you also develop sleep problems.

00:59:12.900 | But you're absolutely right.

00:59:14.180 | And in fact, now, research from Diego Fernandez

00:59:17.700 | in the lab have found that now we know

00:59:20.620 | that they actually require different brain regions.

00:59:23.120 | So we don't only have a theory,

00:59:25.180 | we don't only have a light environment

00:59:26.940 | that showed they can be dissociated.

00:59:29.240 | We know that they use completely different brain regions.

00:59:32.300 | So the SCN that I told you about earlier,

00:59:34.580 | the place where the central pacemaker is,

00:59:36.700 | the one that receives direct input from the retina

00:59:39.420 | through the iPRGCs to adjust your circadian clock,

00:59:43.100 | is not the area that receives the light input

00:59:46.020 | for mood regulation.

00:59:47.080 | It's a completely different brain region.

00:59:49.020 | - What's the brain region called?

00:59:50.180 | - So the brain region, we called it

00:59:51.720 | the perihabineular nucleus.

00:59:54.060 | I'm not so sure how good or bad the name,

00:59:55.880 | but doesn't matter, it's the PHB.

00:59:58.020 | And what's really amazing, this region also receives

01:00:00.580 | direct input from the iPRGCs,

01:00:02.740 | but projects to areas in the brain

01:00:04.520 | that are known to regulate mood, including

01:00:06.980 | the ventral medial prefrontal cortex,

01:00:10.580 | which has been studied for many years

01:00:13.200 | to be impacted in a human depression.

01:00:16.000 | So just by this amazing serendipity

01:00:19.860 | to find that a region that is so deep in the advanced brain,

01:00:24.860 | like the prefrontal cortex is your executive brain,

01:00:29.060 | one of the most elaborated in humans,

01:00:32.040 | to see that they receive input from these

01:00:34.500 | ancient photoreceptor was stunning to us

01:00:38.220 | and told us how much we didn't understand

01:00:40.380 | the importance of light on a human behavior.

01:00:43.100 | - So how does that finding inform daily protocols

01:00:47.620 | for you or for other people?

01:00:48.940 | I realize you can't leap to always from one paper

01:00:52.460 | to daily protocols.

01:00:53.660 | But if light indeed does control prefrontal cortex,

01:00:57.100 | executive function, learning, stress, and mood,

01:01:01.900 | and let's say I'm waking up each morning and I'm sleeping,

01:01:05.180 | what should I do differently?

01:01:06.680 | - That's why we came up with the tripartite model.

01:01:08.940 | Because yes, we could think about just adjusting the clock

01:01:12.160 | with lights in and being dark throughout the day.

01:01:14.880 | But that may not be important

01:01:16.400 | for your whole physiological function.

01:01:17.920 | So now if we include these other effects of light,

01:01:21.680 | that's why I prefer to still get a lot of light in the day.

01:01:24.740 | I don't wanna be in very dim light condition

01:01:26.920 | throughout the day.

01:01:27.760 | - I see.

01:01:28.580 | - So even though it doesn't affect your clock,

01:01:30.680 | as you beautifully said, Andrew,

01:01:32.140 | it may affect your mood and learning and memory.

01:01:34.780 | It may affect your alertness level,

01:01:36.600 | which is gonna allow you to learn better.

01:01:38.540 | It may affect your homeostatic drive.

01:01:41.140 | Maybe your homeostatic factor will go higher

01:01:43.500 | so you could sleep earlier.

01:01:45.260 | So it's important to think of light

01:01:47.580 | as stimulating all these brain regions,

01:01:49.840 | which means it's producing more activity,

01:01:52.340 | which in reality,

01:01:53.260 | this is how people think of the homeostatic drive,

01:01:55.620 | that the more active you are,

01:01:57.180 | the more the homeostatic drive is built up,

01:01:59.740 | the better you sleep.

01:02:01.520 | So that's why we came up with the tripartite model,

01:02:04.580 | because as a circadian biologist,

01:02:06.560 | I only thought of light through the circadian clock

01:02:08.780 | affecting behavior.

01:02:10.240 | As a sleep biologist,

01:02:11.300 | they only thought of the homeostatic drive

01:02:13.460 | affecting sleep, affecting behavior.

01:02:15.780 | And for people who study light for vision and other things,

01:02:18.620 | they thought only of the environmental input.

01:02:21.000 | But now if you put them all together,

01:02:22.860 | you get with this tripartite model

01:02:24.700 | where it's really mind-boggling and it makes so much sense.

01:02:28.320 | The organism doesn't wanna depend on a single component,

01:02:31.620 | but if you could incorporate these three together,

01:02:34.700 | you could have a beautiful system that is well-adapted.

01:02:38.080 | So let me tell you the sleep-wake cycle, right?

01:02:40.340 | So we know there is a homeostatic drive to affect sleep.

01:02:43.580 | We've had beautiful talks about that.

01:02:45.840 | - Which is basically the longer you're awake,

01:02:47.460 | the more you wanna be asleep.

01:02:48.420 | - So that's your homeostatic drive.

01:02:50.300 | We've talked about the circadian influence of sleep

01:02:52.900 | and the fact that light-dark cycle

01:02:54.680 | affect the circadian system,

01:02:56.260 | which eventually affects sleep.

01:02:58.060 | So these two components are well understood.

01:03:00.260 | Now the third factor is your direct light

01:03:03.180 | or environmental input.

01:03:04.780 | How much stress, how much light you get from there

01:03:07.280 | also can highly impact sleep.

01:03:09.640 | So even if you have a good circadian and homeostatic drive,

01:03:13.320 | if you're getting light at the wrong time of the day

01:03:15.800 | or if you're being stressed and thinking,

01:03:18.080 | then your sleep's gonna suffer.

01:03:19.820 | So you have to think of the three together

01:03:22.660 | to have a beautiful sleep-wake cycle.

01:03:25.840 | And that's why we came up with the tripartite motor.

01:03:28.120 | The same thing happens with feeding.

01:03:29.720 | I could beautifully put it to people.

01:03:31.760 | Your hunger, your energy level

01:03:33.680 | is measured by the arcuate nucleus.

01:03:36.140 | Your daily intake of food is, again,

01:03:38.300 | dependent on the SCN and light-dark input.

01:03:41.120 | We found that if food is not available,

01:03:43.960 | there is yet a third input that is not dependent on the SCN,

01:03:48.520 | not dependent on the arcuate,

01:03:49.800 | depending on a completely different brain regions

01:03:52.840 | so the animal can actually start looking,

01:03:55.020 | or the human can start looking for food when it's scarce,

01:03:58.560 | even at time when they are not supposed to be active.

01:04:01.560 | So that's how the organism think.

01:04:03.200 | They have to evaluate multiple inputs for them to decide

01:04:07.400 | what is the best physiological outcome at that moment,

01:04:10.360 | at that season.

01:04:11.340 | - I see.

01:04:12.980 | So I wanna get into arcuate and feeding,

01:04:14.720 | but just to make sure we can keep our hands

01:04:17.400 | around this tripartite model.

01:04:19.540 | So if I understand correctly,

01:04:20.680 | we've got the circadian influence,

01:04:23.040 | then you've also got the drive to sleep.

01:04:25.480 | Actually, one of the ways

01:04:27.080 | that I think that can be best understood is

01:04:29.520 | if somebody ever pulls an all-nighter,

01:04:32.060 | they get tired around 11 or 12 or so,

01:04:35.340 | and then very tired around 3, 4 a.m.,

01:04:38.480 | but then even if you stay up,

01:04:40.320 | sometime right around 7 or 8 a.m.,

01:04:41.960 | your normal wake-up time, you start to feel alert again.

01:04:44.140 | - Exactly. - And that's because

01:04:45.480 | the sleep drive is extremely strong,

01:04:47.960 | but there's a circadian rhythm

01:04:49.240 | that drives wakefulness in the morning.

01:04:51.040 | - Okay, so that's two of the components.

01:04:53.720 | Before we get into the feeding component,

01:04:55.320 | I wanna talk about these direct effects of light on mood.

01:04:58.000 | Okay, Diego Fernandez's data.

01:04:59.880 | And this perihabenular thing.

01:05:03.560 | So let's just, for the moment,

01:05:06.240 | set aside the tri part of the tripartite model

01:05:08.720 | and just focus on what are the direct effects

01:05:10.880 | of light on mood?

01:05:12.040 | And the way that I interpret what you've said so far is

01:05:14.480 | that the protocol that emerges from this,

01:05:16.600 | if one is trying to optimize their mood,

01:05:19.120 | is, yes, see light, view light, I should say,

01:05:21.960 | early in the day in order to set your circadian clock,

01:05:24.560 | maybe also in the evening as well.

01:05:26.520 | And of course, avoid light at night,

01:05:28.660 | get it as dim as possible.

01:05:30.480 | However, you said it's also a good idea

01:05:35.360 | to get as much bright light during the day as you safely can

01:05:38.880 | in order to improve your mood

01:05:40.560 | independently of regulating your sleep-wake cycle.

01:05:43.120 | - And that's a hypothesis.

01:05:44.360 | Here's the problem where it's not gonna be as satisfying

01:05:46.960 | as the circadian is that, as you know,

01:05:49.160 | this brain region has been discovered very recently.

01:05:52.040 | - Habenula.

01:05:52.880 | - The perihabenular region.

01:05:54.000 | - We've known about it a long time,

01:05:55.280 | but nobody knew what it did.

01:05:56.260 | - So we knew about the habenula,

01:05:57.760 | but that's why the name is confusing.

01:05:59.720 | It's actually not the habenula itself.

01:06:01.680 | It's the perihabenula.

01:06:02.720 | - No, near the habenula.

01:06:03.540 | - It's near the habenula.

01:06:04.380 | - Why don't you just call it the Semer-Hattar nucleus?

01:06:06.160 | - I should have, I don't know why I've done that.

01:06:08.520 | - Maybe 'cause if you do that, it's not okay.

01:06:10.480 | Okay, so for herever after, the perihabenular nucleus,

01:06:14.460 | we should probably call it the Hattar-

01:06:16.080 | - The Hattar-Fernandez.

01:06:17.360 | - How about Hattar-Fernandez-Berson?

01:06:19.480 | Okay, this is like nerdy science attribution stuff,

01:06:22.080 | but I'm just gonna call it the Hattar nucleus.

01:06:24.700 | Wikipedia, line it up.

01:06:26.060 | Okay, so this structure is taking light,

01:06:29.320 | and independent of sleep rhythms and circadian rhythms,

01:06:32.320 | it's driving changes in mood.

01:06:34.140 | How does it do that?

01:06:35.040 | Is this through the dopamine system,

01:06:36.460 | the serotonin system?

01:06:37.640 | - We still recently,

01:06:38.940 | we haven't identified this region very well.

01:06:41.120 | We don't know what light does to it.

01:06:43.160 | We don't know how it interacts.

01:06:44.680 | So this is an area that is ripe for discoveries,

01:06:47.640 | and we're working on this right now.

01:06:49.640 | But that's why I said it's not satisfying.

01:06:51.760 | This is like the function of sleep.

01:06:54.020 | Why do we sleep?

01:06:55.200 | We know sleep is very important to us,

01:06:57.040 | but we still don't have a satisfying function

01:06:59.160 | of why do we sleep, right?

01:07:00.880 | - I see, but the why questions,

01:07:03.480 | I think it's our good friend and colleague

01:07:05.640 | at University of Washington, Russ Van Gelder,

01:07:07.320 | who always says, when somebody asks why,

01:07:09.360 | the best answer is just to say,

01:07:11.120 | I wasn't consulted at the design phase, right?

01:07:13.800 | None of us really know why.

01:07:15.080 | - No, but the point is, maybe I shouldn't have said why.

01:07:17.700 | What is the function of sleep?

01:07:19.200 | It's still very hard to know.

01:07:21.340 | Why would, what is the reason organisms

01:07:24.700 | have to go offline for so long?

01:07:27.240 | You know, people assume it's for repair,

01:07:29.880 | assume it's for learning and memory,

01:07:31.440 | assume all kind of stuff,

01:07:32.720 | but there is really no clear function for sleeping.

01:07:37.240 | There is no clear function for sleeping.

01:07:39.480 | I mean, if you talk to people, there are hypotheses.

01:07:42.360 | I mean, all we know is that if you don't sleep,

01:07:44.320 | or your sleep is very fractured, you get messed up.

01:07:46.840 | - And you could die even, right?

01:07:48.440 | I mean, it's really bad if you don't sleep,

01:07:51.700 | but we don't know what is the function.

01:07:54.800 | What is that sleep have gone to organisms

01:07:58.260 | that couldn't have done with rest?

01:08:00.760 | What if you just could rest without sleeping,

01:08:03.000 | just sit down and rest?

01:08:04.120 | - Well, my lab is trying to figure out

01:08:05.800 | whether or not these non-sleep deep rest protocols

01:08:08.000 | can compensate for sleep.

01:08:10.200 | I mean, obviously sleep is better,

01:08:12.080 | but many people are not getting the sleep that they need.

01:08:14.620 | But, okay, so, and if people are sensing

01:08:18.320 | that Samir and I are about to start talking over each other

01:08:20.480 | and arguing, that's always the goal when we talk, right?

01:08:23.480 | Unlike other scientists I interact with,

01:08:25.500 | when Samir and I get together,

01:08:26.680 | it's considered a successful conversation

01:08:28.880 | if we get into a big fight and then go for a big meal

01:08:31.700 | where I pick the restaurant.

01:08:33.240 | Okay, so let's talk about food and eating and appetite.

01:08:39.080 | You had yet another, yes,

01:08:42.560 | I greatly admire your success in this way,

01:08:45.820 | yet another incredible discovery

01:08:48.160 | showing that there are direct, excuse me,

01:08:51.360 | effects of light on appetite and feeding behavior.

01:08:55.240 | Maybe you could just summarize those results for people.

01:08:58.440 | - Honestly, that paper is the one that allowed us

01:09:00.600 | to come with the tripartite model

01:09:02.120 | because we were thinking completely wrong about it.

01:09:04.880 | We wanted, this experiment,

01:09:06.920 | it'd be fun for your audience to hear

01:09:08.960 | why we started this experiment.

01:09:10.920 | Remember that when we discovered the IPRGCs,

01:09:14.080 | we figured if they are the only relay

01:09:17.240 | to entrain the circadian clock,

01:09:19.280 | then you could kill them and have an animal

01:09:22.320 | opposite to the one that we spoke,

01:09:23.960 | or a human opposite to the one that we spoke about earlier,

01:09:26.440 | where instead of having no pattern vision

01:09:29.420 | and have circadian photo entrainment,

01:09:31.560 | we could produce an animal that have pattern vision

01:09:34.000 | but no circadian photo entrainment.

01:09:36.120 | - So circadian blind.

01:09:37.600 | - Circadian blind, but pattern sighted,

01:09:40.760 | and we succeeded in that.

01:09:42.840 | The problem when you have these animals,

01:09:44.500 | which I've told you many times already,

01:09:46.820 | is that they don't adjust to the day/night cycle.

01:09:49.680 | So doing experiments on them become very complicated.

01:09:53.440 | - What is their behavior like if you don't have these cells?

01:09:55.800 | Are they awake and then asleep, awake and then asleep?

01:09:57.200 | - They just drift like the humans we've talked about.

01:09:59.800 | - They think they're in Las Vegas.

01:10:01.220 | - They drift, exactly.

01:10:02.960 | - They stay up later every night.

01:10:04.400 | - They come either, depend, they're a clock.

01:10:06.360 | If their clock is shorter, they come in earlier.

01:10:08.600 | If their clock is longer, they come in later.

01:10:10.160 | - So they're really messed up.

01:10:11.160 | - They really don't adjust to the,

01:10:12.960 | if they were in the wild,

01:10:14.120 | they'll be eliminated in a second, right?

01:10:16.000 | There is no way they'll survive.

01:10:18.000 | So me and Diego started talking and we're like,

01:10:20.900 | what if we use non-light entraining agent,

01:10:23.640 | and what is the strong non-light entraining agent?

01:10:26.880 | Food.

01:10:28.000 | So we thought that the light defective animals

01:10:32.640 | will have more sensitivity to food entrainment,

01:10:34.880 | because as you know more than me,

01:10:36.440 | this is an area that you've worked really well on.

01:10:38.880 | For vision, if you're image blind,

01:10:41.040 | you're hearing and somatosensory get improved, right?

01:10:44.880 | The lack of vision improves your hearing and sensation.

01:10:49.640 | But we found actually that if you don't have

01:10:52.120 | the light system, actually you're feeding,

01:10:56.120 | the food ability to entrain the animal

01:10:57.900 | goes completely to the ground,

01:10:59.840 | completely opposite to what we predicted.

01:11:02.760 | So light viewing and feeding behavior

01:11:06.400 | are interacting in ways that support one another.

01:11:08.840 | - And that's why we came with the tripartite model.

01:11:11.000 | We figured it's different than sensation of the environment.

01:11:14.280 | When you sense with vision, vision and hearing interact,

01:11:17.640 | but your vision is a real full modality.

01:11:20.180 | You want to see, that's what vision want to do.

01:11:23.180 | You want to hear, that's what hearing want to do.

01:11:25.600 | You want to sense, that's what sensing want to do.

01:11:28.260 | But for the circadian system, light, food,

01:11:32.340 | all these in training Asian,

01:11:33.780 | they somehow have to interact to keep a coherent system.

01:11:38.240 | You don't just assume if you remove light,

01:11:40.140 | this one is going to be stronger.

01:11:41.380 | No, they need to know each other's.

01:11:43.680 | The light informs when the animal's going to eat.

01:11:46.360 | - Well, what I like about this so much is that,

01:11:49.160 | you know, in the other, in the world outside of science

01:11:52.560 | in which I don't really exist in,

01:11:55.200 | but that I see a lot of this kind of wellness,

01:11:57.700 | you know, stuff with this,

01:11:58.600 | all this mind body integration stuff,

01:12:01.920 | it's interesting because people view the body

01:12:05.060 | more as a system, right?

01:12:06.560 | A system of organs that interact,

01:12:08.400 | as opposed to the way that standard science

01:12:11.540 | and medical profession is like,

01:12:13.140 | you work on the liver or your ear, nose and throat,

01:12:15.740 | or heart and lung or brain or, you know.

01:12:18.340 | - That's a great way of thinking.

01:12:20.060 | - But the biology is integrated.

01:12:22.060 | - Yeah.

01:12:22.900 | - I mean, and so for somebody who's interested

01:12:26.680 | in affecting their eating behavior,

01:12:29.320 | something that you are familiar with

01:12:31.620 | and that we will talk more about your experiences

01:12:33.820 | of in a moment,

01:12:34.660 | how should they use light

01:12:37.940 | in order to adjust their eating behavior?

01:12:40.660 | - Right.

01:12:41.500 | So now that I've told you about all these interaction

01:12:44.160 | between the different inputs to the circadian clock,

01:12:47.780 | just you think about it as an engineer,

01:12:49.740 | what would be the best thing?

01:12:51.300 | The best thing is to know

01:12:53.260 | when your food times happen in the day,

01:12:56.080 | when should you get light

01:12:57.340 | and where is your circadian,

01:12:58.620 | when is your circadian clock in your system, right?

01:13:02.060 | So if you eat at very specific times of the day,

01:13:05.500 | that's another signal that is telling your body,

01:13:08.140 | your clock, you're in a certain time of the day.

01:13:10.620 | So if you're having lunch at the correct time every day

01:13:13.320 | and you're getting bright light,

01:13:14.620 | now you have two systems that are informing your clock,

01:13:18.060 | your clock is gonna be better.

01:13:19.540 | - So regular meal times.

01:13:21.020 | - Regular meal times that fit your circadian clock.

01:13:24.180 | So, and in fact, if you do that,

01:13:26.380 | when I started doing this

01:13:28.380 | and it helped me lose weight,

01:13:30.100 | is that I'm exposing myself

01:13:31.700 | to the right amount of light dark cycle.

01:13:34.020 | I'm eating at regular time.

01:13:35.940 | It is amazing.

01:13:37.020 | You will be not hungry, let's say,

01:13:38.540 | let's say you eat at noon.

01:13:39.620 | You will not feel any hunger at 11.45

01:13:42.500 | and then all of a sudden the hunger jumps.

01:13:45.220 | This is clearly not an energy issue

01:13:47.100 | because it could not be that drastic.

01:13:49.380 | - Right, no, the desire to eat is mainly driven by these,

01:13:52.280 | these cues, these hormone cues

01:13:55.940 | that are very exquisitely timed to sleep-wake cycle,

01:14:00.820 | but also to light.

01:14:02.260 | - Exactly, and you know, in the wild,

01:14:04.500 | you could imagine why energy level

01:14:06.380 | through the arcuate nucleus.

01:14:08.380 | - You should explain to people what the arcuate is

01:14:10.080 | 'cause I don't think we've done that adequately.

01:14:11.900 | The arcuate nucleus is an area of the hypothalamus

01:14:14.260 | that drives hunger and feeding behavior.

01:14:16.660 | And what we're talking about is the fact that

01:14:19.020 | it's taking cues from your viewing of light,

01:14:23.080 | believe it or not, is impacting your level of hunger.

01:14:26.240 | And this is a non-trivial way

01:14:29.880 | in which your timing of hunger and amount of hunger

01:14:32.800 | is regulated by when and how much light you view.

01:14:36.740 | So let me ask you a couple of practical--

01:14:38.720 | - But can I just, this is really, before you ask me,

01:14:41.200 | sorry, Andrew, we said we were gonna fight,

01:14:43.460 | but to me, it's the interesting thing to think about it.

01:14:46.920 | In the wild, when you didn't have

01:14:48.260 | the availability of food that we have,

01:14:50.640 | the arcuate plays a huge important role

01:14:53.180 | because if you weren't successful in getting food,

01:14:57.360 | then the arc is gonna tell you,

01:14:58.580 | look, you have to take risk and go get food

01:15:01.120 | because your energy level is very low.

01:15:03.200 | And that's great, that's tons of great research about that.

01:15:06.400 | But I think what's missing is the fact in humans,

01:15:09.620 | we're not getting to a situation, most of us,

01:15:12.760 | we're not getting to a situation

01:15:14.040 | where we have low energy levels.

01:15:16.360 | Most of the time, actually, we eat not because we want to,

01:15:19.300 | because we really have low energy,

01:15:21.400 | but because we want to eat.

01:15:22.980 | So I think that's why I feel that the timing

01:15:26.320 | is very important for us

01:15:27.980 | because we always have enough energy level for us to eat.

01:15:31.480 | - Well, I mean, I enjoy eating so much that I'll eat

01:15:33.840 | just for the sensation of chewing.

01:15:35.800 | I mean, I enjoy the taste too,

01:15:38.200 | and I enjoy the social aspects when those are a part of it,

01:15:40.920 | but I literally enjoy the physical act of chewing,

01:15:44.740 | which explains a lot.

01:15:47.500 | Okay, so how regular are you,

01:15:52.500 | or do you recommend people be about meal times?

01:15:56.240 | Because what I'm hearing is that light viewing behavior

01:16:01.020 | is pretty straightforward.

01:16:01.960 | Get a lot of light in the morning and throughout the day,

01:16:03.880 | minimize it in the evening and at night,

01:16:05.720 | generally speaking, for sake of mood and circadian rhythm.

01:16:09.120 | But for sake of regulating timing and quality,

01:16:13.560 | I should also say, of food intake,

01:16:15.760 | because people clearly make better choices about food intake

01:16:18.380 | when they are anticipating a meal

01:16:20.700 | and they aren't constantly hungry.

01:16:22.700 | And so the ability to regulate hunger for particular phases

01:16:26.100 | of the circadian cycle is quite valuable for all people,

01:16:29.120 | not just people trying to lose weight, but all people.

01:16:32.300 | Are we talking about down to the minute?

01:16:33.980 | Like if I- - Absolutely not.

01:16:35.500 | - All right, so 12 noon is my normal lunch, let's say,

01:16:40.020 | plus or minus?

01:16:41.400 | - Half an hour.

01:16:42.260 | - Okay, so eat around between 11.30 and 12.30.

01:16:45.740 | If that's the time, and it depends,

01:16:48.000 | if you also do multiple meals.

01:16:49.640 | Remember, three meals, that's decision

01:16:52.020 | that somebody came up with.

01:16:53.480 | I don't know why.

01:16:54.320 | - Nowadays, fewer people are doing that, I think.

01:16:56.520 | - Yeah.

01:16:57.360 | - Given our friend Sachin Panda's work.

01:16:59.040 | - Right, I mean, so you could have two meals.

01:17:01.260 | You could have very multiple meals

01:17:04.800 | that are distributed across your active time.

01:17:07.960 | I agree with Sachin Panda's work that try to avoid eating

01:17:12.540 | when your system is supposed to be relaxing,

01:17:14.900 | when you're supposed to be at non-active time.

01:17:18.540 | So, you know, limit your eating

01:17:20.980 | to the active time of your cycle.

01:17:23.580 | And that seemed to be,

01:17:24.960 | and Joe Takahashi is doing some beautiful stuff on this.

01:17:28.180 | That seems to be incredibly important

01:17:30.100 | for aspect of the circadian.

01:17:33.300 | - And for health.

01:17:34.140 | - And for health.

01:17:34.960 | - Yeah, I mean, Sachin,

01:17:35.800 | we're referring to Sachin Panda's work.

01:17:37.520 | He wrote a beautiful book called "The Circadian Code."

01:17:39.820 | Maybe, Samir, with some luck, you'll write a book as well.

01:17:43.420 | Meaning the world would be lucky to have that book.

01:17:46.060 | But Sachin's data really strongly points to the fact

01:17:49.580 | that liver health, brain health,

01:17:52.980 | metabolic factors, and endocrine factors

01:17:56.180 | of various systems and organs all seem to benefit

01:17:59.620 | from having a period of each 24-hour day

01:18:02.240 | in which we are not eating anything

01:18:03.620 | and then eating it very regular sometimes.

01:18:05.660 | Let's talk about eating and mealtimes,

01:18:08.580 | and let's move a little bit away

01:18:10.300 | from the science for the moment,

01:18:12.140 | although we will return to it,

01:18:13.460 | and talk a little bit more about your experience

01:18:16.660 | with eating and mealtimes.

01:18:18.460 | So you're looking in good shape lately.

01:18:21.420 | - Thank you.

01:18:22.260 | - I know you've been putting work into it.

01:18:23.760 | We talk a lot, and you've been exercising,

01:18:25.900 | and you've been eating well, meaning quality food.

01:18:30.500 | You just came back from Jordan,

01:18:31.540 | where I'm assuming the food is amazing.

01:18:33.660 | - The food is amazing, and honestly,

01:18:35.420 | usually I gained a lot of weight in Jordan,

01:18:37.740 | but this time I didn't gain any weight,

01:18:39.980 | which was really nice, so.

01:18:41.820 | - Yeah, when I met you,

01:18:45.140 | you were probably about 100 pounds heavier

01:18:49.060 | than you are now.

01:18:49.900 | - Yeah, 275 pounds, I'm 219 now, it's crazy, yeah.

01:18:53.820 | - You had a lot of vigor then,

01:18:54.920 | and you have a lot of vigor now,

01:18:56.700 | but I know that you undertook a very specific protocol

01:19:01.500 | in order to lose the weight.

01:19:03.720 | Based on your understanding of the circadian system

01:19:06.280 | and of light and appetite and mood,

01:19:09.140 | maybe you could just tell us a little bit

01:19:10.520 | about what that schedule looks like,

01:19:12.280 | and we realize that this is not a prescriptive for everybody,

01:19:14.960 | but you found what worked for you.

01:19:17.440 | Maybe just describe those changes.

01:19:18.760 | - I mean, honestly, I followed my circadian cycle, right,

01:19:21.560 | of what we've talked about, right?

01:19:23.960 | So I dimmed the light at night, I slept at regular hours,

01:19:27.940 | I ate my major food in breakfast and lunch

01:19:31.020 | when I'm really active and I'm really hungry,

01:19:33.640 | and at night, when I avoid dinner

01:19:35.720 | because my circadian system really shuts off at three,

01:19:38.340 | I'm an early person, like you could give me anything

01:19:41.260 | I would eat before three.

01:19:42.380 | After three, nothing appeals to me anymore.

01:19:44.740 | My system is shut off.

01:19:46.100 | - What time are you going to sleep

01:19:47.240 | and what time are you waking up?

01:19:48.080 | - Oh, so in my case, I should have put this on.

01:19:50.460 | I mean, I go to sleep literally at 9 p.m.

01:19:53.340 | I mean, I literally, five minutes after 9 p.m.,

01:19:56.580 | I'm completely out,

01:19:58.380 | and I wake up between 4.30 and 5 a.m.

01:20:01.000 | So if I extend it, I go to 6 a.m.,

01:20:03.580 | but very rarely, depends on how tired I was.

01:20:06.600 | - And that, as I recall, was an important set of changes

01:20:10.600 | for you to be able to regulate your food intake.

01:20:12.840 | - Absolutely, because then I'm having very big breakfast at,

01:20:16.760 | and again, for different people, it's different.

01:20:19.420 | I have a big breakfast at 7 a.m. maximum.

01:20:22.840 | So I have a big breakfast, coffee, and all this stuff.

01:20:25.840 | Then I have some simple snack around 10.

01:20:29.020 | Then I have regularly lunch at noon or between noon to one.

01:20:32.800 | Then I have another snack at three,

01:20:34.360 | and the hardest time to regulate the food

01:20:36.200 | is between 12 and three.

01:20:37.440 | This is when I really feel hungry all the time.

01:20:39.520 | - This is your equivalent of kind of late evening

01:20:41.520 | for most people. - Yes.

01:20:42.360 | - So for me, it would probably be between seven and 10 p.m.

01:20:44.640 | - Exactly, exactly.

01:20:46.360 | And then at night, I'm completely not hungry,

01:20:49.000 | but usually, as you said, the enjoyment of food,

01:20:52.640 | like when my wife cooks some really beautiful Indian food,

01:20:56.080 | I eat, but I'm not hungry.

01:20:58.160 | And I notice if I eat with that, I usually gain weight.

01:21:01.120 | But if I regulate that at night, I also lose weight.

01:21:04.400 | So there is a combination of all these things

01:21:07.040 | that help you adjust the input of food,

01:21:11.280 | the input of light, the input of the clock,

01:21:13.680 | and the drive to hunger.

01:21:14.920 | - Yeah, I appreciate you sharing that.

01:21:17.480 | And I want to emphasize that some people

01:21:19.480 | are not hungry early in the day.

01:21:21.200 | They might be late-shifted people,

01:21:22.680 | in which case eating later in the day will work well.

01:21:25.080 | - It will work as long as they don't eat

01:21:26.640 | early in the morning.

01:21:27.480 | That's just, you have to work with your schedule,

01:21:29.880 | with your active schedule.

01:21:31.440 | - Yeah, you and I have been talking about this offline

01:21:33.320 | for years.

01:21:34.160 | We're finally having this discussion publicly now.

01:21:36.680 | What we're talking about really is finding

01:21:38.240 | your ideal sleep schedule.

01:21:39.800 | - Exactly.

01:21:40.640 | - And finding your ideal eating schedule.

01:21:43.120 | - Exactly.

01:21:43.960 | - And understanding how those two things interact.

01:21:46.400 | - And you know, the nice thing, as you said,

01:21:48.040 | finding them out is going to help you to understand

01:21:50.240 | how they interact because we know from the tripartite model

01:21:53.480 | that they are all interconnected.

01:21:55.840 | And for each person,

01:21:57.040 | they're going to be interconnected differently.

01:21:59.600 | So for each person, you would, you know, for me,

01:22:03.680 | if I exercise at night, I'm going to mess up my whole system.

01:22:07.000 | - So when do you exercise?

01:22:08.240 | - Morning.

01:22:09.080 | Morning works great for me.

01:22:10.440 | I mean, it's amazing.

01:22:11.800 | Morning exercise for me works great.

01:22:14.800 | I tried one time because it was easier for me

01:22:17.240 | to exercise at night before I leave

01:22:19.240 | when the traffic is there from the night.

01:22:21.360 | And I think that messed me up because I couldn't sleep well

01:22:24.640 | and I couldn't wake up well.

01:22:26.040 | And that led to more changes in my food.

01:22:27.840 | I gained weight again, actually, believe it or not,

01:22:30.840 | even though I was exercising.

01:22:32.600 | So I think this really makes me think

01:22:35.360 | that you have to think of the tripartite model

01:22:38.160 | to see where is the best times

01:22:41.320 | and what is the best interrelation

01:22:43.200 | between the different components, as you beautifully said,

01:22:45.880 | between your meal times, your light exposure,

01:22:48.320 | and your sleep that works for you.

01:22:50.800 | - Well, thank you for that.

01:22:51.640 | Usually Samir's insulting me today.

01:22:53.360 | He's complimenting me.

01:22:54.560 | I'm going to compliment him right back by saying,

01:22:57.120 | this is the first time that I've ever really understood

01:23:01.480 | how yes, light can control sleep.

01:23:04.480 | Yes, it can control mood.

01:23:06.200 | Yes, it can impact feeding,

01:23:09.040 | but that it's really about doing the self exploration

01:23:11.720 | to align those in the way that works best.

01:23:14.560 | And what I'm hearing, tell me if I'm wrong,

01:23:16.520 | but what I'm hearing is that once you understand

01:23:19.320 | what gives you the best sleep-wake cycle,

01:23:21.960 | then you should exercise during the period of time

01:23:25.480 | in which you feel most alert.

01:23:27.640 | And if it works for your schedule,

01:23:30.680 | ideally you would also eat during the time

01:23:32.920 | in which you feel most alert and then stop eating

01:23:35.800 | and stop light viewing behavior as you head towards sleep.

01:23:38.280 | - Right.

01:23:39.120 | So the only thing I would say that complicates all of this,

01:23:42.240 | and that's what makes me sad, is your light exposure.

01:23:45.080 | - Mine personally?

01:23:45.920 | No, I'm just kidding.

01:23:47.640 | - The people's light exposure, right?

01:23:49.880 | This is what complicates it

01:23:51.400 | because you're not going to be able to figure all this out

01:23:55.000 | if you're shifting yourself out of your comfort zone.

01:23:57.720 | - By viewing?

01:23:58.540 | - By viewing light at the wrong time of the day.

01:24:01.260 | So let's say if you were under an idle natural conditions,

01:24:06.260 | you're a person who would sleep later than me,

01:24:09.260 | let's say will sleep at midnight and wake up at 8 a.m.

01:24:12.980 | Let's say you don't eat anything till noon

01:24:15.020 | and as you said, you eat late in the evening,

01:24:17.860 | then this would be perfect for you.

01:24:19.620 | But now see what happens

01:24:21.420 | if now you include the light component.

01:24:23.340 | Now if you push your sleep from midnight to 4 a.m.,

01:24:26.820 | now you're waking up in the morning

01:24:29.300 | and you're actually really not the morning,

01:24:31.980 | you're working up, sorry, at noon instead of 8 o'clock

01:24:35.040 | and the time where you're not supposed to be hungry,

01:24:37.460 | now you're gonna start eating directly at noon

01:24:39.740 | or something like that or even delay it.

01:24:42.260 | And now you're shifting your whole cycle

01:24:43.980 | and you don't know if this interaction

01:24:45.680 | between your sleep feeding and the light dark environment

01:24:48.440 | are still gonna be maintained or not.

01:24:50.580 | And that's the problem that people have.

01:24:52.500 | - So as I'm hearing this, what I'm realizing is most of us,

01:24:56.700 | probably me included, are messing up at least one,

01:25:00.420 | two or three of these components.

01:25:02.460 | But that the probe, the way to figure out

01:25:06.500 | what's right for oneself

01:25:08.020 | is to start manipulating light exposure.

01:25:10.660 | - And I'm gonna be honest, I'm biased

01:25:13.880 | 'cause I believe that light is the strongest time giver.

01:25:18.020 | And a lot of people disagree.

01:25:19.620 | Some people think feeding is.

01:25:21.100 | - I always thought that light was the primary zeit-giver,

01:25:23.420 | the primary--

01:25:24.260 | - Yeah, but a lot of people think it's food.

01:25:25.860 | A lot of people even sometimes mention social interactions.

01:25:28.620 | - And they read the literature?

01:25:29.980 | - I agree with you.

01:25:31.060 | I totally agree with you.

01:25:32.440 | - I mean, my understanding is that light

01:25:33.940 | is the most powerful driver of the things we're talking about.

01:25:36.020 | - That's why I think we need to regulate this first

01:25:38.660 | and everything else fits.

01:25:40.420 | And you know, the nice thing is that your sleep-wake cycle

01:25:43.360 | and exercise tell you really bluntly

01:25:45.820 | if you're doing it right or not.

01:25:47.220 | - Tell me more about that.

01:25:48.120 | - I'll tell you more.

01:25:48.960 | When I shifted my exercise, honestly,

01:25:52.140 | things fell apart like never before.

01:25:54.280 | - When you moved from exercising

01:25:56.060 | early in the day to late in the day.

01:25:56.900 | - In the morning, yeah.

01:25:57.740 | It completely fell apart for me.

01:25:59.480 | I didn't enjoy exercise at night.

01:26:01.480 | My pain tolerance for exercise wasn't as good.

01:26:04.260 | I'm talking with N equals one and I'm aware of this.

01:26:06.500 | I've never tested this empirically.

01:26:08.700 | But at least to me, it really messed up everything.

01:26:12.340 | I started having problems

01:26:13.500 | 'cause my body temperature will go up

01:26:15.540 | and that will affect my sleep.

01:26:16.980 | I possibly was running in the gym with a lot of lights,

01:26:19.460 | so maybe the light was a component.

01:26:22.260 | But for me, exercising in the morning,

01:26:24.680 | it's so much better for me.

01:26:26.520 | But a lot of people can't even think

01:26:28.200 | of exercising in the morning.

01:26:29.760 | So it depends on when you feel comfortable

01:26:31.960 | in your sleep-wake cycle and your exercise.

01:26:34.160 | I think that tells you if your system

01:26:35.880 | is in synchrony with one another.

01:26:38.480 | - That's really interesting.

01:26:39.480 | You know, we're good friends.

01:26:41.120 | Our friend Pat Dossett, right, that we both know,

01:26:43.660 | you know, did nine years in the SEAL teams

01:26:45.720 | and he's one of these people.

01:26:47.120 | He says, you know, he's happy to go for a run or swim

01:26:49.360 | anytime between 4.30 a.m. and 6 a.m.

01:26:52.540 | And he'll train in the afternoon too,

01:26:54.180 | 'cause, you know, he's a SEAL team guy

01:26:55.780 | and they'll do whatever anytime.

01:26:57.380 | That's part of the phenotype.

01:26:58.820 | But he feels best doing that, right?

01:27:01.480 | I'm a mid, I like to exercise mid-morning.

01:27:04.340 | And I'm happy to skip eating until 12 or one.

01:27:08.180 | And I like to go to sleep around 11.30, 12,

01:27:10.180 | 'cause I'm a normal human being rather than you

01:27:12.020 | who goes to bed at 9 p.m.

01:27:12.860 | - What about Pat, actually?

01:27:14.100 | I've never asked him what time.

01:27:15.980 | - So Pat's ideal to sleep time,

01:27:18.060 | I've asked him this would be around 8.30 or 9.

01:27:20.800 | - Oh, I sound like Pat.

01:27:21.800 | - No, but he has, yes, but he has two young children,

01:27:25.880 | two years old and a newborn.

01:27:27.600 | And so the cycle is disrupted, right?

01:27:29.720 | - Yeah, but that's known, right?

01:27:31.320 | I mean, the effect of childbearing.

01:27:33.460 | And I think we could talk about this,

01:27:35.600 | that's more complicated, but that's pretty much, yeah.

01:27:39.080 | - Yeah, I mean, I think we need to come up with a new name

01:27:41.520 | for a chronotype because chronotype implies

01:27:44.840 | that it's just about sleep and wake.

01:27:47.000 | Being an early bird or a night owl.

01:27:48.820 | And what we're also talking about is how exercise

01:27:51.220 | and eating match onto those.

01:27:52.980 | - And the phase of relation between them.

01:27:54.980 | - Right.

01:27:56.860 | - And the phases between different components, as you said.

01:27:59.400 | - 'Cause they interact.

01:28:00.380 | - Because they interact.

01:28:01.220 | - Right.

01:28:02.040 | - And they don't have to be in the same phase.

01:28:03.480 | Like let's say my light and food

01:28:05.520 | could be very close to each other's,

01:28:06.960 | your light and food could be different, right?

01:28:09.300 | The phases don't have to be, they can be plastic.

01:28:11.820 | So you have to find this for yourself.

01:28:14.100 | You may be a person who eats late at night,

01:28:17.000 | exercises late at night,

01:28:18.900 | or you may be a person who exercise early, eat later.

01:28:21.460 | So it doesn't, as long as the phase is good,

01:28:25.180 | that's what you have to find out.

01:28:27.300 | - Okay, and if I understand correctly,

01:28:28.860 | when you're talking about phase relationship,

01:28:30.300 | it means you want to lump exercise, feeding, and light for--

01:28:34.080 | - And sleep.

01:28:34.920 | - And sleep in a way that as a coherent and total system

01:28:39.580 | makes you feel really good.

01:28:41.140 | - Temporally in a great order.

01:28:43.260 | - Uh-huh.

01:28:44.100 | - Absolutely.

01:28:44.920 | - Yeah, that's, and I think that--

01:28:45.760 | - And I could tell you to me,

01:28:47.500 | is literally getting exposed to sun,

01:28:50.180 | clearly in the morning, clearly at noon I go out,

01:28:53.940 | I keep my windows in the office completely open,

01:28:57.380 | eating mostly in the early time of the day and exercising,

01:29:00.500 | and literally at the end part of the day,

01:29:03.380 | I'm literally in a more thoughtful vegetative state.

01:29:07.580 | Like I really can't, like after five, I tell my students,

01:29:11.180 | if you want to tell me anything complicated,

01:29:13.100 | you're wasting your time.

01:29:14.340 | My brain just doesn't function.

01:29:16.340 | So even though I only sleep at night,

01:29:17.900 | but I'm really starting to shut off, ramp down,

01:29:21.140 | really, I mean, it's, you know, I could send the email,

01:29:24.420 | talk about brainless stuff, but my power,

01:29:27.640 | my energy to do powerful stuff really dropped tremendously.

01:29:32.300 | So all my students who know me very well,

01:29:34.340 | they put the meetings with me early in the morning

01:29:36.980 | 'cause they know this is when I'm,

01:29:38.620 | so everything for me, and for me it's very tight,

01:29:41.620 | so it could be different, but it's very clustered

01:29:44.020 | in the morning, it's all tied together,

01:29:45.940 | and literally the remaining part seems to be just a,

01:29:48.860 | you know, vegetative state.

01:29:50.260 | - Yeah, you and my bulldog Costello,

01:29:54.640 | who unfortunately passed away recently, had that in, yeah.

01:29:57.380 | - I did not, that's so sad. - Yeah, Sam and Costello

01:29:58.960 | were good friends, yeah, sorry to break it to you here.

01:30:01.540 | Yeah, he had a good long life and he went easy,

01:30:04.420 | but he had a circadian clock

01:30:06.220 | that basically would just sleep around 24 hours a day.

01:30:09.740 | - Minimal activity interspersed every third day or so.

01:30:12.840 | You do have this morning vigor.

01:30:15.760 | - Yes.

01:30:16.600 | - I think other people are gonna have

01:30:18.780 | more of an afternoon vigor.

01:30:19.860 | Do you think that this can change across the lifespan?

01:30:23.020 | It's, the rumor is that teenagers

01:30:26.460 | naturally want to sleep in later and stay up later.

01:30:29.400 | Do you think that's social rhythm

01:30:30.820 | or do you think that that's actually biological?

01:30:32.500 | - Yeah, that's a tough question.

01:30:33.840 | I mean, it could be both.

01:30:37.380 | One thing that worries me is that it seems

01:30:40.460 | that if anything with age,

01:30:41.960 | this morning rigor gets stronger.

01:30:44.740 | - You mean you want people to become more of morning?

01:30:46.580 | - More of morning. - Why is that worry you?

01:30:47.900 | I think that's good.

01:30:48.960 | - Because for me, I'm already a very shifted morning.

01:30:51.720 | I don't wanna be one of these 7 p.m. to 1 a.m. sleepers

01:30:55.060 | at some point.

01:30:55.900 | - Yeah, on the other hand, it's also kind of nice

01:30:57.600 | because it's quiet and you can get work done.

01:30:59.420 | - Yeah, but honestly, from 4.30 to 7.30

01:31:02.300 | when my wife wake up, it can be very lonely.

01:31:05.780 | Yes, you achieve a lot, but it's quiet outside.

01:31:08.900 | It's, you know, so I don't wanna be at 1 a.m.

01:31:12.120 | Let's put it this way.

01:31:12.960 | - You can tell Samara is more social than I am.

01:31:15.540 | - That's right.

01:31:16.380 | That is true.

01:31:17.220 | - But we should touch on that actually.

01:31:18.580 | So your wife is, she follows a different schedule.

01:31:22.060 | - Yeah.

01:31:22.900 | - And so the social rhythm is important.

01:31:26.300 | I think, what should we do?

01:31:27.860 | How should we conceptualize

01:31:29.740 | and how should we adjust ourselves

01:31:31.680 | according to the social rhythm?

01:31:32.520 | - And I honestly love this hypothesis

01:31:35.340 | that people came up with and Pat's kids reminded me of.

01:31:39.300 | Because kids are really gonna disrupt

01:31:41.820 | your sleep-wake cycle.

01:31:42.880 | It seems like there is a chrono attraction

01:31:46.660 | that usually people who attract each others

01:31:48.980 | have actually different sleep-wake schedule.

01:31:51.860 | And the idea being is that this allows them

01:31:54.180 | to take care of their kids throughout the day-night cycle.

01:31:57.500 | - And have a peaceful marriage.

01:31:58.740 | - And have a peaceful marriage in a way, right?

01:32:01.240 | So, I mean, we didn't have kids me and Rachel,

01:32:03.460 | so maybe this is, but it seems like evolutionary.

01:32:06.540 | It makes sense that if you wanna protect your kids,

01:32:09.940 | you don't want everybody to be mourning rigor

01:32:12.060 | and then the kids don't have,

01:32:13.660 | so you want the distributed across.

01:32:15.860 | It makes sense.

01:32:16.700 | - It's a reasonable argument.

01:32:17.860 | I've heard that one of the reasons

01:32:20.180 | that people think that the clock is not exactly 24 hours,

01:32:24.640 | but is 24 hours plus or minus 20 minutes or so,

01:32:28.420 | is because we believe that we evolved in clans or groups

01:32:33.380 | or villages, whatever, that we're about 100 to 200 people.

01:32:37.060 | And in order to have protection

01:32:39.540 | around the early morning hours

01:32:41.740 | when we're vulnerable to predation

01:32:43.900 | and in the late night hours

01:32:45.460 | that you would want some individuals of our species

01:32:48.140 | to be naturally more like night owls

01:32:50.040 | and some more like early people.

01:32:51.260 | So your theory of parenting is similar in that way.

01:32:56.260 | The social rhythm is a powerful rhythm though.

01:32:59.140 | Meaning if I go out and I'm tired,

01:33:02.460 | let's say I'm tired at like 9.30,

01:33:03.980 | I don't wanna go out, I'm gonna need it.

01:33:04.820 | - So can I just say something about that?

01:33:06.860 | I think the social rhythm is powerful at the obvious levels

01:33:11.380 | like it affects your sleep,

01:33:13.240 | it affects how much you wake up or eat,

01:33:15.860 | but I'm not so sure it's as powerful

01:33:17.740 | as people think on the clock.

01:33:19.740 | Now, eventually it will mess up the clock

01:33:21.760 | because now if you're doing a lot of social at night,

01:33:24.720 | getting enough light, eating at the wrong time of the day,

01:33:27.020 | eventually you're gonna have an effect.

01:33:29.780 | But I don't think that's the social interactions themselves

01:33:33.840 | have been shown to affect your clock very strongly

01:33:36.260 | for some reason.

01:33:37.380 | - That's good to know.

01:33:38.580 | Well, for people hearing this,

01:33:40.560 | they're probably getting the impression

01:33:42.220 | like I'm the night owl

01:33:43.540 | and then Samara is the one that's in bed at nine

01:33:46.420 | and then wakes up at four.

01:33:48.860 | But having attended many meetings with Samara,

01:33:51.300 | I can tell you that he's the party animal.

01:33:53.500 | So let's talk about that.

01:33:55.980 | I mean, let's talk about the fact that you're the partier

01:33:58.640 | who's up until two dancing at these various meetings,

01:34:01.820 | which I've seen, actually a good dancer I'm told.

01:34:05.620 | But what should we do when we do stay up very late

01:34:10.620 | for whatever reason?

01:34:11.880 | Could be because we had to take a midnight trip

01:34:13.740 | to the hospital, unfortunate reason,

01:34:15.620 | or it could be because you're in the presence of people

01:34:18.360 | that you don't see very often

01:34:19.620 | and you go out for a really nice night out on the town

01:34:22.940 | and you get to sleep around 2.30 or three in the morning.

01:34:27.180 | How should one get back on schedule?

01:34:29.120 | Do you force yourself to then get up and view light

01:34:31.320 | at the normal time that you would get up and view light

01:34:33.440 | or do you allow yourself to sleep in?

01:34:35.000 | What's the optimal protocol?

01:34:36.320 | - I would allow myself to sleep in

01:34:37.780 | and remember this is a long-term effect.

01:34:39.980 | This is something that you live with for a long period.

01:34:42.600 | And remember I told you about the experiments

01:34:45.200 | we did with the mood.

01:34:46.260 | These require two weeks of that light schedule

01:34:48.920 | to cause mood disturbances.

01:34:50.520 | So these don't happen just in a single day.

01:34:52.740 | - So this is the way you justify staying out late

01:34:55.060 | every once in a while.

01:34:55.900 | - Well, in the meetings you've seen me

01:34:58.060 | and I've done this for five or six days continuously,

01:35:00.640 | but what you didn't see that when I came back to my home,

01:35:03.440 | it took me two weeks as if I did a jet lag.

01:35:05.960 | So I really do suffer for two weeks

01:35:08.280 | after doing a six crazy night of staying up at night,

01:35:12.160 | drinking at the wrong time of the day.

01:35:14.040 | So it's not that I'm completely okay with it.

01:35:16.920 | When I go back, everything goes back.

01:35:18.560 | It takes me actually literally two weeks to recover

01:35:21.360 | from the circadian rhythm meeting

01:35:23.240 | that you've seen me partying at some point.

01:35:25.900 | - Which is kind of ironic, the circadian rhythm meeting,

01:35:28.420 | people are totally disrupting the circadian cycle,

01:35:30.600 | but scientists are human beings too.

01:35:33.380 | - So I think if you do it at very little occasions,

01:35:38.380 | I think you should not worry too much

01:35:40.980 | that this will have lasting impact.

01:35:42.860 | And the good news is that if you readjust your schedule,

01:35:45.980 | you could come back to it.

01:35:47.200 | The problem is when you maintain these wrong schedule

01:35:50.320 | for prolonged team and becomes chronic prolonged periods

01:35:53.900 | of time, that's when you have the problems

01:35:56.000 | and the accumulation of the problems.

01:35:58.160 | So when you have sleeping problem,

01:36:00.360 | you produce metabolic problem.

01:36:01.760 | When you have metabolic problems,

01:36:03.000 | you produce lack of exercise

01:36:04.860 | and you could see how things can spiral out very quickly.

01:36:08.380 | And then it would be hard to come back to it.

01:36:11.080 | - Well, certainly sleep disruption is both a symptom of

01:36:14.000 | and a cause of almost all mental health disorders, right?

01:36:19.720 | And certainly the metabolic syndromes

01:36:22.040 | that people are talking about nowadays and all of this,

01:36:25.080 | it all funnels back to light.

01:36:28.040 | This is what's so remarkable.

01:36:30.040 | And so we have these devices and I use my phone

01:36:33.200 | and I use my computer,

01:36:35.160 | but do you think that the mere dimming of the screen

01:36:38.480 | or not interacting with screens with say 90 minutes

01:36:43.480 | or two hours before bedtime,

01:36:45.760 | according to what we're saying today,

01:36:48.920 | this should have a profound effect

01:36:50.560 | on all these factors. - And it does.

01:36:52.120 | And I really believe it does.

01:36:53.520 | And again, I think as Pat did these inventions

01:36:58.520 | where you get a pouch,

01:37:00.360 | where you put your phone in a pouch.

01:37:02.880 | - So what Samra's referring to is our friend, Pat,

01:37:06.120 | this former SEAL team member who's also a very impressive

01:37:10.280 | person in the landscape of business and family, et cetera.

01:37:12.760 | A real superhuman by any regard has this habit

01:37:18.040 | of taking his phone

01:37:19.000 | and putting it into a sealed pouch in the evening.

01:37:21.620 | So it's basically--

01:37:22.560 | - And in his program, he sends you actually these seal,

01:37:26.180 | you know, batches.

01:37:27.020 | And so that I think is a great idea

01:37:30.280 | because not only it will take away the light from you,

01:37:33.400 | but it also take away the distraction

01:37:35.200 | because you wanna repair and recover and sleep does that.

01:37:39.860 | And if you have your phone dinging all the time

01:37:42.280 | or the light flashing from it,

01:37:45.000 | you're just not getting enough sleep

01:37:46.640 | and you're causing yourself major problems.

01:37:49.100 | - I never asked you this,

01:37:51.960 | but I realize now that I should have long ago,

01:37:56.960 | but I'll ask you now.

01:37:58.200 | Why and how did you get into all this stuff?

01:38:02.360 | - Yeah, I mean, honestly, I, first of all,

01:38:05.100 | I wanted to become a, you know, I wanted to study genetics

01:38:08.620 | and I knew I wanted to do PhD in genetics,

01:38:11.820 | but I only got accepted in one university at the time.

01:38:14.480 | And I joined the learning and memory lab

01:38:16.820 | and I liked learning and memory.

01:38:18.100 | At the beginning, I worked in the snails

01:38:19.800 | and aplasia californica

01:38:21.280 | and started looking at learning and memory.

01:38:23.160 | But then the same lab was looking at these daily variation.

01:38:26.680 | I was really struck,

01:38:28.400 | like you never think about it outside of science.

01:38:31.000 | It really struck me that organisms can measure day

01:38:36.000 | biologically, that was very shocking to me.

01:38:39.100 | And I just really got attracted

01:38:41.120 | and I wanted to see why does this happen?

01:38:44.520 | What is the effect of different times of day?

01:38:46.360 | And I just stuck with it.

01:38:47.680 | It's just, it was mind blowing for me

01:38:50.100 | who was in medical school

01:38:51.960 | that I've never heard about it before.

01:38:54.360 | You know, it's really amazing medicine.

01:38:56.160 | I think still now,

01:38:57.920 | we are very good at looking at stuff spatially,

01:39:01.120 | but we're very bad at looking at temporal aspects.

01:39:04.600 | So we always, you know, like to see images, static images,

01:39:08.260 | spatial information.

01:39:09.480 | - Take an X-ray, measure a temperature,

01:39:11.280 | measure a blood pressure.

01:39:12.120 | - Exactly, but we don't think of temporal.

01:39:14.840 | And, you know, you talk to John Huganash right now

01:39:17.440 | and he's telling you the importance of chrono medicine

01:39:20.440 | or chrono pharma, pharma two, whatever the word is.

01:39:24.000 | And it just, it really just getting the drugs

01:39:27.640 | at the right time of the day

01:39:28.940 | is gonna be essential for our health.

01:39:31.440 | - Do you think that's gonna come from using better trackers

01:39:33.920 | like aura rings, whoop straps, these kinds of things?

01:39:37.280 | - I love the trackers,

01:39:38.360 | but I think there's even more exciting discoveries.

01:39:40.840 | Now you could take a single blood sample

01:39:42.920 | and measure many biological components

01:39:45.600 | and figure where you are in the circadian clock,

01:39:48.160 | something that was very hard to do before.

01:39:50.640 | So if you have a marker to know where you are in the clock,

01:39:53.480 | you could actually understand more the effect of everything,

01:39:56.780 | exercise, feeding, light input.

01:39:58.800 | - What is the marker?

01:40:00.000 | - So there are some papers from, what's her name,

01:40:03.480 | Phyllis Z and from Achim Kramer,

01:40:07.000 | where they measure multiple RNAs that are known

01:40:09.800 | to tell you what phase of the clock is

01:40:11.900 | or multiple proteins or biological reactions.

01:40:16.700 | And depending on a combination of factor,

01:40:19.200 | not a single factor, you could tell where you are

01:40:21.520 | in the circadian clock.

01:40:23.400 | So they could, instead of just measuring temperature

01:40:25.920 | or melatonin, just one measurement,

01:40:27.900 | and melatonin specifically is also complicated

01:40:29.920 | by the fact that melatonin is affected by light.

01:40:32.800 | And temperature, your temperature and sleep

01:40:36.180 | can be easily dissociatable, right?

01:40:38.320 | When you travel across different times on your sleep,

01:40:40.360 | at different times in the temperature cycle.

01:40:43.320 | So having multiple components measured

01:40:46.040 | will give you a better determination of your circadian phase

01:40:49.820 | and understanding your circadian phase in humans

01:40:53.240 | will tell you what is the effect of giving certain drugs

01:40:56.040 | at certain times of the circadian phase.

01:40:57.720 | So in the future, this is gonna be studied

01:41:00.320 | at a much higher level when you can determine the phase

01:41:03.640 | in relation to all the other stuff.

01:41:07.020 | - It's striking to me that in all animals, besides humans,

01:41:12.020 | if they deviate too much from the appropriate exposure

01:41:15.280 | to light and light-dark cycle,

01:41:16.860 | they essentially don't mate and/or die and/or get killed off.

01:41:21.860 | But in humans, we are able to override that

01:41:25.060 | at least to some extent.

01:41:26.600 | But the ways in which we suffer

01:41:29.660 | appear to be things like obesity, metabolic syndromes,

01:41:33.960 | reproductive syndromes that accompany the other syndromes,

01:41:36.820 | you know, endocrine syndromes,

01:41:38.360 | and mood and depressive disorders.

01:41:41.220 | Is there any effort at the level of the nationally

01:41:45.600 | or laboratories that you're aware of

01:41:47.620 | to try and use light in order to improve mood

01:41:51.340 | and mental health?

01:41:52.380 | - I mean, honestly, this is my moon shot.

01:41:54.500 | This is the thing that I think people,

01:41:57.180 | because I say don't take a pill, take a photon.

01:42:01.340 | I mean, you take pills, it's important.

01:42:02.980 | I'm just making it that really we have an opportunity

01:42:06.860 | right now with the incredible advances of LED lights,

01:42:10.420 | of changing spectra of light, of regulating intensities.

01:42:15.420 | And just for simple changes,

01:42:19.000 | you could really improve sleep-wake cycle, productivity,

01:42:22.900 | and still you could actually get more done.

01:42:25.540 | Because as we've talked about,

01:42:27.500 | when you have all these messed up,

01:42:29.540 | now you have to sleep more, but your sleep is fragmented.

01:42:32.880 | It's not very good.

01:42:34.060 | - And you can't focus.

01:42:35.100 | - And you can't focus when you don't have alertness

01:42:37.420 | when you need the alertness.

01:42:39.300 | So having all these could allow you to do even more,

01:42:43.140 | actually, at the end than less.

01:42:45.220 | And that's the exciting part of it.

01:42:47.940 | - One of the questions I get asked most often about

01:42:50.380 | is about ADHD.

01:42:51.820 | You know, I think there's a lot of self-prescribed

01:42:54.120 | as well as clinically prescribed ADHD.

01:42:56.220 | People are having a tremendously difficult time focusing,

01:42:58.860 | and not just because they're sleepy.

01:43:00.540 | They just can't seem to anchor their attention.

01:43:02.240 | And there could be multiple reasons for this,

01:43:04.140 | but there are now several clinical trials ongoing

01:43:06.800 | using light to try and anchor people's attention

01:43:09.900 | and mood and wellbeing for sake of focus.

01:43:11.980 | And I think that while I love this saying

01:43:14.500 | that you mentioned, you know, take a photon, not a pill,

01:43:17.640 | and with due respect to the need for pharmacology

01:43:21.480 | for certain people, I think most people

01:43:24.580 | just haven't really dialed in their relationship to light

01:43:27.160 | in a way that allows them to rule out

01:43:28.680 | whether or not they need medication.

01:43:30.580 | - Absolutely, that's the best way to put it.

01:43:32.620 | I can't add to that.

01:43:33.860 | - Let's talk about jet lag, but not in the context of,

01:43:39.460 | okay, if somebody's traveling from Europe to Japan

01:43:42.640 | or from the East Coast, because that varies tremendously,

01:43:44.820 | right, I mean, there's as many different variations

01:43:46.980 | on travel as there are individuals out there

01:43:49.640 | and with goals and jobs, et cetera.

01:43:52.420 | But rather, let's talk about what are the two or three things

01:43:55.820 | that people can do to adjust their schedule quickly?

01:43:59.400 | Yesterday, I called you and said,

01:44:01.320 | "Look, I know somebody who's traveling six hours."

01:44:04.040 | I won't even mention in which direction

01:44:05.440 | 'cause I don't want people to anchor to that example.

01:44:08.120 | And you described some very simple tools of viewing light

01:44:13.120 | a little bit earlier than normal

01:44:15.780 | and getting on the local food schedule, et cetera,

01:44:18.560 | that would allow them to shift more quickly.

01:44:20.740 | And the reason I want to have this conversation is yes,

01:44:22.920 | for the travelers and for the shift workers,

01:44:25.800 | but mostly because of the fact that you've proven

01:44:30.160 | again and again that people are disrupted

01:44:33.620 | in their circadian behavior at home.

01:44:36.280 | So what are the, aside from what we've already talked about,

01:44:39.000 | how can one adjust quickly to a new schedule?

01:44:42.320 | Like let's say fall classes are starting,

01:44:44.080 | you start a new job or you have a baby

01:44:45.760 | or a puppy or whatever.

01:44:47.600 | What is the best way to shift the clock quickly?

01:44:50.200 | - So it's very simple as we've talked yesterday.

01:44:52.560 | So imagine you're in the outside with no environmental,

01:44:56.400 | with no industrial light.

01:44:58.100 | If your body thinks you're in early evening

01:45:02.060 | and you see a bright light, what does this tell you?

01:45:04.940 | Oh, wait, this is not early evening yet.

01:45:07.600 | It's still early afternoon or late afternoon.

01:45:11.160 | So I have to delay my clock to go back to late afternoon.

01:45:14.880 | So if you get light early in the evening,

01:45:18.120 | it delays your clock.

01:45:20.040 | So what does--

01:45:20.880 | - Meaning that makes you want to go to sleep later.

01:45:22.840 | - Yes, it delays your clock.

01:45:24.000 | So you're in New York, right?

01:45:27.760 | People in Italy have an advanced clock

01:45:29.760 | because they are six hours ahead of us.

01:45:33.000 | So if you're in New York and you get light

01:45:36.480 | early in the evening, you delay even further from Italy.

01:45:39.420 | So now you're delaying away from Italy.

01:45:42.060 | Now the same thing happens.

01:45:43.560 | Let's say you thought dawn came up

01:45:45.680 | and you thought it's already dawn,

01:45:47.680 | but it was, let's say, three o'clock in the morning

01:45:49.760 | or four o'clock in the morning,

01:45:50.800 | and then you get a bright light and you say,

01:45:52.760 | oh, wait a minute, dawn is not up yet,

01:45:55.760 | so I should advance my clock.

01:45:57.360 | Or I'm at night, but I'm getting bright light,

01:46:01.360 | so I should run because dawn is already up.

01:46:04.600 | So then later in the night, later in your night,

01:46:09.200 | and actually it just happens that the humans,

01:46:11.880 | you get a temperature in a day or later in the night,

01:46:14.800 | low temperature in your body.

01:46:16.520 | After that, light start advancing your clock.

01:46:20.020 | So if you wanna go to Italy,

01:46:21.560 | instead of getting light early in the evening,

01:46:23.440 | you wanna get light after the temperature low.

01:46:26.680 | So you could advance your clock even before you go to Italy

01:46:30.020 | and you're catching up to the Italians just by using light.

01:46:32.920 | It's as simple as that.

01:46:34.360 | So you could do it for every region.

01:46:36.680 | You could calculate how much they are advanced of you.

01:46:39.960 | You could know how much these light shifts happen per day,

01:46:43.000 | and you can calculate what you need to do,

01:46:45.920 | very simple math, to adjust either in direction of delaying,

01:46:49.880 | if you're going from New York to California,

01:46:51.760 | you wanna delay your clock,

01:46:53.360 | or advancing if you're going from New York to Italy.

01:46:56.300 | - So in order to make that a visual,

01:46:58.560 | and because a lot of people are listening to this,

01:47:00.200 | not looking at it on video,

01:47:01.800 | we will put a zero cost downloadable figure of this

01:47:06.960 | on the Hubermanlab.com website related to this episode.

01:47:10.260 | But I think I can summarize it in language as well.

01:47:14.400 | If I understand correctly, what you're saying is,

01:47:17.500 | if your typical wake up time is say 7 a.m.,

01:47:21.120 | then your low point in temperature probably occurs

01:47:23.840 | somewhere around 5 a.m.

01:47:25.240 | And if you view light right around then,

01:47:29.320 | it's going to essentially advance your clock.

01:47:31.360 | - Yeah, because then your body thinks,

01:47:33.780 | oh, it's 7 o'clock,

01:47:34.620 | so it'll advance your clock by one to two hours.

01:47:37.020 | - But if I were to view light, say at 3 a.m.,

01:47:40.780 | then it would probably delay my clock.

01:47:42.700 | - Yeah. - Okay.

01:47:43.900 | Yeah, so, and then let's say I land in a new schedule.

01:47:47.180 | I wanna adjust to a new schedule.

01:47:48.340 | Let's say I didn't manage to do anything

01:47:50.020 | with my light viewing before I went,

01:47:51.460 | and I didn't anticipate the trip.

01:47:53.500 | Suddenly I'm on a new schedule, okay?

01:47:56.220 | I was told that one of the ways to help shift the clock

01:47:59.760 | and to avoid gastrointestinal issues

01:48:02.060 | is to eat on the local schedule,

01:48:05.240 | to start basically behaving like a local,

01:48:08.220 | even though your circadian clock

01:48:10.380 | will take a little bit of time to catch up.

01:48:11.940 | - Absolutely, but you have to remember the light, right?

01:48:15.380 | So let's, now that we explained it very simply,

01:48:17.960 | let's take a very simple example, right?

01:48:20.820 | New York to Italy, that's a simple example.

01:48:23.860 | New York time, Italy time, six hour difference, right?

01:48:26.780 | So let's say you fly from New York at night.

01:48:29.620 | You reach Italy at 8 o'clock in the morning.

01:48:31.860 | What is the time in your New York time?

01:48:34.820 | Although you reach-- - Six hours back.

01:48:36.220 | - Six hours back. - It's two a.m.

01:48:37.300 | - It's two a.m.

01:48:38.500 | So when you land Italy, you wanna avoid light,

01:48:41.240 | like the plague.

01:48:42.140 | Yeah, you could eat,

01:48:43.180 | but you really don't wanna get a light.

01:48:44.940 | - 'Cause otherwise it's gonna delay you.

01:48:45.780 | - It's gonna delay you, it's gonna send you to California

01:48:48.300 | instead of sending you to Italy.

01:48:49.660 | - Right, and so this is such a key point.

01:48:51.540 | If anyone's confused about this,

01:48:52.940 | we will put some diagrams up,

01:48:54.260 | but what Samir's saying is so crucial.

01:48:57.740 | Just because getting bright light in your eyes

01:49:00.120 | early in the day is really beneficial when you're at home.

01:49:02.420 | When you travel to a new time zone,

01:49:04.940 | you have to take into account what your body thinks,

01:49:09.480 | what, excuse me, you have to take into account

01:49:11.940 | where your body thinks you are.

01:49:13.460 | And so if you're looking at the Italian sunrise,

01:49:15.540 | having just flown from New York to Italy,

01:49:17.860 | and you didn't prepare for that trip

01:49:19.420 | by waking up a little bit earlier in anticipation.

01:49:21.600 | - Multiple days, yeah.

01:49:22.440 | - And you view light at two a, excuse me,

01:49:24.660 | at six or seven a.m. Italian time,

01:49:27.560 | beautiful Italian sunrise,

01:49:29.360 | you are going to delay your clock.

01:49:31.060 | You're going to basically throw yourself back to California,

01:49:33.900 | but you are in Italy.

01:49:35.180 | You're gonna throw your biology back to California,

01:49:37.220 | and you are gonna be up in the middle of the Italian night,

01:49:39.980 | and you're gonna be miserable.

01:49:42.380 | I'll tell a brief anecdote,

01:49:44.100 | 'cause I called Samir in desperation.

01:49:46.740 | A few years ago, I traveled to Abu Dhabi, NYU Abu Dhabi,

01:49:49.980 | to give a seminar, 12 hours out of phase.

01:49:51.980 | It's a 12-hour flip, and I thought I could just muscle it.

01:49:55.140 | I thought I'll get up, just view sunlight

01:49:56.860 | when the sun comes up.

01:49:58.300 | And I fell apart mentally and physically.

01:50:02.020 | And Samir came to my rescue.

01:50:04.280 | I called him.

01:50:05.120 | I said, "I don't know what to do."

01:50:06.040 | And he said, "Go to the gym,

01:50:08.720 | went at the local dawn,

01:50:12.540 | work out, eat,

01:50:14.940 | and then view sunlight starting the next day."

01:50:18.340 | And that basically got me onto schedule.

01:50:19.880 | So I used food and exercise to adjust myself

01:50:22.160 | because my light viewing activity

01:50:24.040 | was just completely out of whack.

01:50:25.500 | - Yeah, I mean, and we talked about other details.

01:50:28.100 | So you have to calculate it, but you're absolutely right.

01:50:31.020 | I mean, it's very important

01:50:34.100 | to avoid getting the wrong light information

01:50:36.760 | when you're trying to adjust your body,

01:50:38.340 | because otherwise it shifts you to the other side.

01:50:41.800 | Absolutely right.

01:50:43.200 | - Well, you are one of these people that has such vigor.

01:50:47.420 | It's one of these things where,

01:50:49.060 | having known you all these years,

01:50:50.220 | you have a tremendous capacity for work and for soccer

01:50:53.860 | and for arguing, respectful arguing.

01:50:56.980 | And, you know, sometimes, you know-

01:50:58.500 | - It's getting worse with age.

01:50:59.860 | - Yeah, well, we could talk about that offline,

01:51:01.800 | but I think a lot of your vigor

01:51:04.420 | and a lot of your ability to work hard and focus

01:51:06.840 | and really do so many things at an impressive level

01:51:10.180 | is because you think about these issues

01:51:11.780 | and you think about when you're going to be optimal

01:51:14.920 | for focus, when you're going to be optimal for exercise,

01:51:17.420 | when, and the when is the key.

01:51:19.860 | It's, and I think a lot of people live in the landscape

01:51:22.460 | of feeling like there's something broken inside them

01:51:25.140 | because they can't focus or they can't do it.

01:51:27.140 | - Subconscious, right?

01:51:27.980 | Remember, it's all subconscious.

01:51:29.980 | These effects, and you're absolutely right.

01:51:32.140 | Now, honestly, joking aside about age,

01:51:35.180 | I really agree with you that I think part of the reason

01:51:37.940 | I'm continuing to be able to do this,

01:51:39.980 | that I really think about it

01:51:42.120 | and I make sure that I keep everything aligned.

01:51:45.340 | And that actually helps me a lot.

01:51:47.620 | Like I don't suffer in sleep.

01:51:49.900 | I don't suffer in waking up.

01:51:51.140 | I never use a timer to wake up.

01:51:53.560 | I mean, people say, aren't you scared?

01:51:55.140 | Like you have to give a lecture at eight or 730.

01:51:57.940 | Honestly, I was like,

01:51:58.780 | there is no way I'm going to go beyond that.

01:52:01.080 | It just, even if I try,

01:52:02.500 | I can't sleep beyond 6 a.m. in my regular times.

01:52:05.680 | It's just, it's not going to happen.

01:52:07.400 | By 4.30, my eyes are wide awake and I'm in bed.

01:52:10.720 | It's just, system is so aligned, it works.

01:52:14.540 | - A lot of times people will say, how come I go to sleep?

01:52:18.320 | I fall asleep, fine.

01:52:19.400 | But then I wake up at three or four in the morning

01:52:21.160 | and can't fall back asleep.

01:52:22.720 | Is it possible that those people

01:52:24.200 | were supposed to go to bed at 8 p.m.?

01:52:26.320 | - It's possible.

01:52:27.200 | I mean, it is possible.

01:52:28.760 | It is also possible that sometimes people will wake up

01:52:31.560 | and go back to sleep.

01:52:32.720 | But yeah, I mean, it is possible.

01:52:35.480 | Or it's possible that their clock is completely misaligned,

01:52:38.560 | that they are getting maybe a nap time at night

01:52:41.500 | when they are supposed,

01:52:42.340 | and then they possibly feel so sleepy in the day.

01:52:44.400 | So all these are possible combinations.

01:52:46.880 | - Well, that's an interesting idea and considered.

01:52:48.600 | So what they think is their sleep,

01:52:50.680 | their body is so out of whack with the light-dark cycle

01:52:53.520 | that it's actually a nap.

01:52:55.160 | - Or the weaker part of the sleep.

01:52:57.080 | I mean, you see this when you travel to different time zones

01:53:00.640 | before you adjust.

01:53:02.240 | You go to sleep really well,

01:53:03.920 | but two hours later, you're fully up.

01:53:06.360 | Two hours.

01:53:07.320 | If you were so tired and this is your regular sleep,

01:53:09.840 | there's no way you're gonna wake up in two hours.

01:53:13.260 | So then you feel very sleepy later in the day

01:53:16.360 | or something like that.

01:53:17.260 | So it depends on how your whole system is aligned

01:53:20.620 | to the environment.

01:53:21.580 | - That's a very interesting idea.

01:53:23.100 | I think that's gonna resonate with a lot of people.

01:53:26.860 | I wake up every morning around three or four.

01:53:30.580 | I generally use the bathroom

01:53:32.460 | and then I fall back asleep very deeply.

01:53:34.700 | It doesn't seem to disrupt my daytime wakefulness.

01:53:37.360 | And I think a lot of people obsess over that waking up

01:53:40.340 | and worry there's something wrong.

01:53:41.780 | Provided they can go back to sleep, it's okay.

01:53:43.780 | - If you can't go use the bathroom, go back to sleep,

01:53:46.540 | that should not be a problem.

01:53:48.100 | Maybe some people, when they go to use the bathroom,

01:53:50.300 | they use very bright light

01:53:51.540 | and then they get an alerting signal.

01:53:53.660 | So if you, maybe that's, it could be as simple as that,

01:53:57.120 | that affects you.

01:53:57.960 | Maybe when you wake up, you put tons of light

01:54:00.380 | or you start reading your iPad.

01:54:02.460 | So there's all these combination

01:54:04.140 | that we still don't know about

01:54:05.660 | that could be affecting their sleep wake rhythms

01:54:08.020 | and their sleep maintenance.

01:54:10.380 | - Do you use melatonin or do you take melatonin?

01:54:13.460 | - I don't need it, to be honest.

01:54:14.700 | In my case, there is no reason to use it

01:54:16.900 | because I could guarantee you that by maybe eight o'clock,

01:54:20.820 | my melatonin has already started to go up.

01:54:23.100 | And by the time I sleep, my melatonin is very high

01:54:25.600 | because I don't use a lot of lights after sunset.

01:54:29.100 | - And light inhibits melatonin.

01:54:30.660 | - And life really blocks melatonin level.

01:54:33.480 | - You hear this myth that the pineal gland

01:54:36.460 | calcifies as we get older.

01:54:38.300 | Is that, do you know anything about that?

01:54:39.660 | - I mean, I've heard about that,

01:54:40.980 | but I don't know what does, I mean,

01:54:42.700 | there is not very clear evidence that affects the sleep.

01:54:45.460 | I don't know much about it, to be honest.

01:54:47.500 | - The evidence that I've seen is that, yes,

01:54:49.100 | there's some calcification around the pineal,

01:54:51.220 | just because of where it sits in the brain.

01:54:53.800 | It's close to some bony structures,

01:54:57.740 | but I don't think there's any evidence

01:54:59.500 | that it has negative effects.

01:55:01.620 | - I mean, if you still have, you could measure melatonin

01:55:04.580 | and that should tell you if it has any,

01:55:06.060 | it's such an easy thing to do.

01:55:08.060 | - I think this is more of a internet wellness thing

01:55:11.100 | that got outside the cage.

01:55:14.380 | - I think you're absolutely right.

01:55:15.440 | - Yeah, it sounds terrible calcification

01:55:18.060 | of the thing, right?

01:55:20.140 | - The hard thing, right?

01:55:21.260 | - Yeah, exactly.

01:55:22.380 | Let's talk about seasonality a little bit.

01:55:26.060 | I learned, and I don't know if this is still true,

01:55:31.240 | but that most suicides occur in April, in the spring.

01:55:37.160 | I think there's a poem that says,

01:55:38.780 | "April is the cruelest month."

01:55:40.460 | I think it is the poem begins.

01:55:42.220 | Are there data that suicides are more frequent

01:55:47.220 | at particular times of year?

01:55:48.620 | And if so, is the spring that time of year?

01:55:50.820 | - Yeah, I mean, a lot of people talk about this.

01:55:53.060 | And one of the hypothesis is that the winter months

01:55:57.040 | that are very bad for mood,

01:55:59.600 | make people not wanting to do anything.

01:56:02.020 | And they get into such deep level of depression

01:56:05.540 | that when the sun comes up,

01:56:07.100 | they get actually the energy to act on their depression,

01:56:09.960 | which sounds really terrible, and it is terrible.

01:56:12.760 | - It's terrible.

01:56:13.840 | - So that's the idea that the lack of light

01:56:16.100 | throughout the winter caused them to go into such depression

01:56:19.100 | that they don't feel like doing anything.

01:56:21.720 | Then when the light comes in with rigor in the spring,

01:56:25.060 | it gives them that, after all the depression they suffered,

01:56:28.220 | gives them that push to take that sad final act, I guess.

01:56:33.220 | - What other seasonal effects

01:56:36.020 | have been demonstrated in humans?

01:56:37.460 | - Yeah, I mean, I think in humans, it's not very clear

01:56:40.500 | because we don't think about seasonality.

01:56:42.520 | But if you start thinking about us,

01:56:45.480 | I think we go through major seasonal changes, I really do.

01:56:48.760 | I think our eating pattern change across the year,

01:56:51.760 | I could tell you that me thinking about this,

01:56:54.600 | there's a clear changes that happens to me across the year.

01:56:58.520 | But for animals, this is really essential.

01:57:00.880 | Because for animals, they have to time their mating behavior

01:57:05.360 | was when they deliver their progeny

01:57:08.000 | in the most abundant amount of food.

01:57:10.760 | And artificial light is causing major disruption

01:57:13.980 | because if you change the way these animals

01:57:16.640 | are receiving the light information,

01:57:19.020 | they either start mating much earlier or much later,

01:57:22.120 | and their numbers dwindle and they get into the dangers

01:57:25.860 | of really completely getting eliminated or extinct.

01:57:29.020 | - Well, human birth rates are definitely going down.

01:57:31.480 | I mean, in the US in particular.

01:57:33.940 | - Some areas, not others.

01:57:35.320 | - Not others, right.

01:57:36.440 | But are there other effects of seasonality on humans

01:57:41.380 | that we are aware of?

01:57:42.820 | - Honestly, like you could see it.

01:57:44.380 | Honestly, you could see it perfectly, I think,

01:57:46.820 | in Scandinavia.

01:57:48.300 | I mean, you could talk to people who live in.

01:57:51.300 | - Sure, they get seasonal depression.

01:57:53.080 | - What seasonal depression is one,

01:57:54.620 | but actually when you start asking them questions,

01:57:56.980 | they tell you like in the winter,

01:57:58.580 | they barely could wake up.

01:58:00.580 | They barely have the energy before even depression.

01:58:03.500 | Even people who don't get seasonal depression,

01:58:05.940 | they'll tell you our energy level is lower.

01:58:08.060 | Our ability to go to work is not the same.

01:58:11.260 | And in the summer, most people actually sleep very little.

01:58:14.980 | They tell you we really can, we feel like we're manic.

01:58:19.220 | We have all this energy.

01:58:21.260 | And not in a negative way, in a funny way, right?

01:58:23.700 | I mean, but if you wanna sleep, we have to put this curtain.

01:58:27.100 | I think in these situations,

01:58:29.140 | you could really appreciate the seasonality of humans.

01:58:32.580 | I think we kind of destroyed our seasonality

01:58:35.580 | because we don't get exposed to that much natural light.

01:58:39.740 | We have all this artificial light.

01:58:41.420 | But I think, honestly,

01:58:43.260 | one of the things that is gonna happen

01:58:45.380 | if they follow your recommendations

01:58:47.320 | about giving light at the same time,

01:58:49.640 | giving food, giving exercise.

01:58:51.100 | - Let's be clear, those are your recommendations.

01:58:52.660 | - Well, I mean. - No, I'm just,

01:58:54.220 | I'm just in fair attribution.

01:58:56.060 | - What I'm saying is that this is gonna cause them

01:58:58.500 | to also experience some changes across the season.

01:59:01.660 | Because now, they're gonna see the sun differently.

01:59:04.900 | If you're gonna go out in the morning,

01:59:07.400 | in the summer, you're gonna get a much brighter,

01:59:09.500 | that's why I don't like the change in time.

01:59:11.180 | I know people think, oh, because you're biased, you,

01:59:14.620 | 'cause I think-- - Wait, wait, wait, wait.

01:59:16.060 | Sorry, the change now,

01:59:16.900 | are you talking about daylight savings?

01:59:18.180 | - Daylight savings, it's such a bad idea

01:59:20.500 | because it disrupts that rhythm that you're having.

01:59:24.160 | 'Cause I think your body, if you keep that rhythm,

01:59:27.040 | you will see the whole seasonality.

01:59:28.820 | And I look at it from a different aspect than other people.

01:59:32.180 | It really, and people say I'm biased

01:59:34.180 | because I'm a morning person, and it may be true.

01:59:37.140 | But there's situation-- - Secret conspiracy

01:59:39.900 | about morning people. - Yeah, but there is,

01:59:42.240 | if you think about it, Andrew, there is a situation

01:59:44.980 | where you're getting light perfectly well,

01:59:47.620 | and then all of a sudden, they delay it by one hour.

01:59:50.640 | And then, even though it's the summer,

01:59:53.020 | your body now, if you're still not adjusting,

01:59:55.620 | think, oh, wait, what happened?

01:59:57.380 | What kind of happened?

01:59:58.500 | - Well, I'm glad you're bringing this up

01:59:59.740 | because I always thought, what's the big deal?

02:00:03.080 | One hour, right?

02:00:04.180 | One hour shift, spring forward, fall back.

02:00:05.780 | - It's so hard to adjust to one hour action.

02:00:07.980 | - But this goes back to the beginning of our discussion.

02:00:11.660 | It's not just one hour. - Right.

02:00:13.700 | - Because it's one hour across that one day,

02:00:16.120 | but there's this cumulative effect on the clock

02:00:18.500 | and these three elements of your tripartite model,

02:00:22.900 | the homeostatic, sleep, and the direct effects on mood.

02:00:25.880 | - And when it's so close,

02:00:27.220 | it's sometimes hard to figure out how to adjust it perfectly

02:00:31.140 | because we're already sleep deprived in our society.

02:00:34.580 | And then you shift it by,

02:00:36.700 | so it just, it all accumulates and it has no benefit.

02:00:40.700 | - Well, you work at a major government organization,

02:00:42.820 | National Institute of Mental Health.

02:00:44.220 | Why don't we campaign for-

02:00:46.080 | - Honestly, I have no idea.

02:00:47.580 | I mean, it makes no sense.

02:00:48.420 | - No, I'm saying, why don't we go campaign?

02:00:50.020 | - Yeah, I would love to.

02:00:51.000 | I mean, it makes no sense to have the summer light

02:00:54.420 | goes up at 9 p.m., the light goes down

02:00:57.820 | where I live in Baltimore at 9 p.m.,

02:00:59.820 | and then all of a sudden,

02:01:01.320 | when you really want to see the light longer in the day,

02:01:04.860 | you now shift the other way,

02:01:06.540 | and now it goes all of a sudden at 6 p.m.

02:01:08.380 | Why do you do these drastic changes?

02:01:10.060 | Well, let it blend across the whole season.

02:01:14.060 | Yes, later, earlier at night,

02:01:16.140 | but it's at least consistent.

02:01:17.980 | It goes in a very consistent manner.

02:01:20.120 | I just don't understand why they do this.

02:01:22.060 | It makes no sense.

02:01:23.360 | - Well, I think that the reason they do it

02:01:25.840 | is because they don't understand the biology,

02:01:28.320 | because one hour seems trivial

02:01:30.260 | unless you understand the repercussions

02:01:33.040 | of that one hour shift,

02:01:34.480 | because what's also clear now based on what you're saying

02:01:37.760 | is that that one hour shift is taking you out of alignment

02:01:41.020 | with the natural light-dark cycle

02:01:42.660 | in exactly the wrong direction.

02:01:44.820 | - It's pushing people to get even later in the summer

02:01:48.260 | when light is going to push you later anyway.

02:01:51.000 | It doesn't make sense.

02:01:52.160 | You put it beautifully.

02:01:53.120 | I just rambled, and this is-

02:01:55.300 | - No, no, you made it clear.

02:01:56.820 | - I mean, it's like literally it made you,

02:01:59.420 | it made people who are having problem

02:02:02.060 | having an advanced sleep rhythm because they are delayed.

02:02:05.220 | Now you give them this hour to make them even more delayed.

02:02:08.140 | You push them even later in the day-night cycle.

02:02:10.860 | It just doesn't make sense at all.

02:02:13.280 | - I think 2022 should be the year

02:02:16.620 | that we abolish bad daylight savings.

02:02:18.980 | - That would be the day for me, honestly.

02:02:20.480 | - Well, also if it has a positive effect

02:02:24.060 | on what is essentially an epidemic of mental health issues

02:02:28.940 | and other issues related to improper interactions

02:02:31.860 | with light, that I think is a well worthwhile cause.

02:02:36.860 | - Absolutely, absolutely. - And we can explore.

02:02:38.900 | So for once, we're going to fight with some,

02:02:41.040 | with another group, a common battle

02:02:43.260 | as opposed to with one another.

02:02:44.100 | - I mean, the circadian people, honestly,

02:02:46.100 | to give them credit have been trying for years

02:02:48.340 | to abolish daylight savings.

02:02:49.980 | - Yeah, the problem is they all go to sleep at 9 p.m.

02:02:52.400 | and wake up at 4 a.m. so we never see them.

02:02:54.400 | - That's right, that's right.

02:02:55.720 | - No, the circadian community has done an amazing job

02:02:59.200 | of figuring out what we need.

02:03:02.840 | And then the challenge of course is making sure

02:03:05.520 | that people get what they need

02:03:07.360 | and making sure that at a societal level,

02:03:09.720 | we're not vaulting ourselves into the wrong direction.

02:03:12.120 | - The biggest problem is that the late waking people,

02:03:16.440 | they think that really,

02:03:18.200 | and I'm going to try to put it in a better way now,

02:03:20.660 | they think, oh, because you're a morning person,

02:03:22.680 | you want to see the sun early,

02:03:24.100 | so you want me to suffer it dropping late.

02:03:27.300 | But that's not the case,

02:03:29.020 | because what happens is when they shift it back

02:03:32.740 | after the daylight saving,

02:03:34.620 | now they're going to make you suffer really badly

02:03:36.780 | because now it's going to be earlier.

02:03:39.420 | - Right, in the fall.

02:03:40.340 | - In the fall when there's not enough light.

02:03:42.220 | If they keep it the same way,

02:03:43.800 | so try to convince them that actually this at the end

02:03:47.260 | causes more trouble when you need the light

02:03:50.100 | for your late schedule in the fall when they shift it back.

02:03:54.440 | Then they say keep it daylight saving all the time.

02:03:56.980 | And that has been proven.

02:03:59.200 | That is very bad.

02:04:00.660 | Like people have done studies

02:04:02.160 | that literally two areas close to each other

02:04:05.240 | and areas that were the whole year on daylight saving

02:04:08.460 | has much more problems,

02:04:10.520 | even in cancer rates and depression.

02:04:12.580 | So you don't want to do that.

02:04:14.080 | So that's what trying to convince people

02:04:16.840 | that you need to prevent that switch

02:04:20.240 | and you don't need daylight saving at all.

02:04:22.800 | That's where the problem happens.

02:04:25.080 | - Interesting.

02:04:26.180 | I had not thought about that,

02:04:27.860 | but yes, you late risers that in the fall,

02:04:30.260 | when they fall back, as they say,

02:04:32.860 | spring forward, fall back, you dial back the clock,

02:04:35.240 | it's really compounding the problem that already exists.

02:04:39.520 | - And it's really nice if you keep it consistent.

02:04:42.360 | In the spring, when you get the equinox

02:04:45.880 | and then the days start going up

02:04:47.920 | and then even in the summer start going down

02:04:50.000 | and then the fall, you get the other equinox and go back.

02:04:52.420 | So it's very symmetrical, right?

02:04:54.600 | It goes into short day, longer, long, long, long,

02:04:57.880 | then short day again.

02:04:59.440 | But now you're getting these bumps

02:05:01.340 | in both sides of the spring and fall.

02:05:04.120 | Why would you do that?

02:05:05.160 | Something that is beautifully symmetrical,

02:05:07.440 | beautifully smooth, you're putting bumps into it.

02:05:10.000 | - Well, and we, not just beautiful because it's there,

02:05:13.080 | but evolved.

02:05:14.880 | I mean, essentially this is the system we evolved in

02:05:16.640 | for hundreds of thousands of years.

02:05:18.800 | - Even apart from the exact equator,

02:05:21.320 | every part of the earth has seasonality.

02:05:23.660 | - I want to briefly touch on something

02:05:26.740 | which is individual and genetic variation

02:05:29.720 | in sensitivity to light.

02:05:31.840 | So not chronotype, but first of all, a very basic question.

02:05:36.840 | Do people with light eyes, light colored eyes,

02:05:42.200 | are they more sensitive to light

02:05:43.760 | than people with darker pigmented eyes?

02:05:46.000 | - I mean, honestly, it makes sense they will be more

02:05:48.640 | because if you think of my dark pupil,

02:05:51.320 | it's blocking more light.

02:05:52.760 | So if you have light pupil, yes, for vision,

02:05:56.640 | it may not be very obvious,

02:05:58.000 | but for something that is measuring the amount of light,

02:06:00.440 | you're getting more light than me.

02:06:02.380 | So you'll probably need less light to be effective

02:06:06.340 | as somebody who's darker.

02:06:08.600 | And that maybe could explain why sometimes lighter people

02:06:11.680 | say I don't want to go into very bright conditions

02:06:14.040 | because it's really bright.

02:06:15.460 | - Yeah, I can't even be at a cafe

02:06:18.120 | without one of these reflective tables, like a metal table,

02:06:20.800 | unless I have very dark sunglasses on.

02:06:22.560 | - Exactly. - It's so bright,

02:06:23.400 | it's painful for me.

02:06:24.540 | Whereas some people like you,

02:06:25.800 | we've sat outside and had meals and you're like, fine.

02:06:28.200 | I assumed it was kind of Jordanian toughness versus...

02:06:31.280 | - It's really the pupil blocks more light.

02:06:33.440 | So I think it is possible that it's as simple

02:06:36.200 | as the pupil blocking more light can have sensitivity.

02:06:39.040 | But your question also goes deeper.

02:06:41.480 | Are there more sensitivity differences?

02:06:44.520 | And my understanding would be,

02:06:45.900 | I would think that it may be,

02:06:47.880 | it depends on how effective your cells are

02:06:50.760 | in responding to light, how healthy your IPRGCs are.

02:06:54.860 | So I would, but there's not many studies to show that.

02:06:58.160 | What is really clear that is happening

02:07:00.400 | is that patients with bipolar,

02:07:03.480 | they seem to have different sensitivities to light.

02:07:06.000 | So it seems that at least people who have

02:07:09.880 | psychological changes,

02:07:12.360 | they may have differences to the sensitivity of light.

02:07:15.420 | So...

02:07:16.920 | - Where are those differences in a particular direction?

02:07:20.000 | - I don't remember the exact...

02:07:21.400 | - We'll have to, we can look it up.

02:07:22.440 | - Yeah. - Yeah.

02:07:23.540 | - Yeah, yeah.

02:07:24.380 | - And people have heard me say this ad nauseum

02:07:27.440 | to the point where they actually roll their eyes,

02:07:29.240 | but that these are the only two pieces of brain,

02:07:32.160 | I'm pointing to my eyes folks,

02:07:33.320 | that are outside the cranial vault.

02:07:35.020 | They are two pieces of brain that basically inform

02:07:37.720 | the brain about whether or not to be alert or asleep.

02:07:40.920 | But you can imagine that those two little pieces of brain

02:07:43.080 | that we call eyes would have genetic variations.

02:07:46.520 | Of course, eye color is genetically modular,

02:07:49.200 | is that determined?

02:07:50.380 | That there would be genetic variations

02:07:53.280 | based on whether or not your ancestry evolved

02:07:55.960 | near the equator or further from the equator, right?

02:07:59.020 | I mean, you see more blue eyes in Scandinavia

02:08:01.200 | than you do in the equator. - Absolutely.

02:08:02.040 | I mean, it's the lack of light

02:08:03.400 | that said you need less inhibition

02:08:06.020 | because there's not enough light, right?

02:08:07.620 | So that's the idea of the change in color.

02:08:10.020 | So yeah, I totally agree with you.

02:08:13.680 | I mean, I think this is an area that will be studied later

02:08:16.840 | and will be empirically determined.

02:08:19.580 | The problem we have in this field right now,

02:08:22.160 | which I think is the biggest problem,

02:08:24.360 | is we don't have a way to measure

02:08:26.700 | the IP RGC sensitivities in humans.

02:08:29.200 | So we still, like it's easy to measure your rod cone function

02:08:33.300 | if you go to an optometrist,

02:08:35.040 | they measure all the details, right?

02:08:36.960 | Contrast detection. - You look at the chart,

02:08:38.680 | you look at the Snellen chart,

02:08:40.420 | you look at the letters of the DMV, yeah.

02:08:42.260 | - But for the non subconscious,

02:08:44.560 | we still don't have a good measuring systems

02:08:47.640 | to figure out what is Andrew's sensitivity?

02:08:50.600 | What is Samer's sensitivity?

02:08:51.900 | What is this person's sensitivity?

02:08:53.380 | And I think we're starting to work on something like that

02:08:56.560 | to hopefully develop these techniques,

02:08:58.320 | but till we develop them,

02:09:00.260 | it's gonna be very hard to figure out

02:09:02.440 | if there is a sensitivity difference,

02:09:04.140 | how do they relate on men and women,

02:09:07.560 | you know, dark and light and all that,

02:09:10.060 | you know, normal versus psychologically effect

02:09:13.240 | and stuff like that.

02:09:14.480 | - Fascinating.

02:09:16.120 | And every time you talk, I learned so much.

02:09:19.940 | It's like in the best way, the best sense of the term,

02:09:24.440 | it's a waterfall of knowledge.

02:09:27.420 | As a final question,

02:09:28.780 | I have a question about sensitivity of a whole other kind.

02:09:32.500 | And that's the sensitivity to spicy food.

02:09:36.500 | Now, the reason I'm asking this question,

02:09:38.960 | what seemingly out of the blue is that

02:09:41.460 | I made the mistake once of having Samer cook for me.

02:09:45.300 | And I said, not too spicy.

02:09:48.420 | And he said, okay, not too spicy.

02:09:50.640 | He actually said, okay, not too spicy.

02:09:52.600 | And it almost killed me.

02:09:55.700 | Like it was like two or three days.

02:09:57.940 | So you know a lot about biology

02:10:00.740 | outside the visual system, light, et cetera.

02:10:02.860 | You've been around a while.

02:10:04.200 | Are there known genetic or inherited of any kind sensitivities

02:10:10.380 | to spicy food, to things like red peppers and capsaicin?

02:10:14.200 | Because what you call mild,

02:10:17.040 | my friend almost put me into the hospital.

02:10:20.420 | - I think this is similar to you swimming in the ocean

02:10:23.000 | and I need to get developed.

02:10:24.420 | - Okay, true, true.

02:10:25.460 | I like cold water swims and Samer's not a fan,

02:10:27.680 | but that's going to change.

02:10:29.180 | It's adaptable, that's going to change.

02:10:31.380 | - That's my belief.

02:10:32.680 | Before I met Reiji, I was like you.

02:10:34.720 | And once I started eating a lot of spicy food,

02:10:37.480 | I lost touch of how spicy my food is.

02:10:40.560 | So I nearly killed you, Andrew, and I apologize.

02:10:43.240 | - I forgive you.

02:10:44.080 | So basically what you're saying is that marriage

02:10:45.460 | toughened you up.

02:10:46.320 | - Toughened me up, exactly.

02:10:48.240 | - Maybe that's the solution.

02:10:49.700 | - That's what you need, yeah.

02:10:51.380 | - Samer, this has been an amazing march

02:10:55.240 | through the importance of light,

02:10:57.240 | not just for regulating sleep and wakefulness,

02:10:59.520 | but also for food timing, the interactions with mood,

02:11:03.560 | the interactions with exercise.

02:11:05.580 | I'm certain that people are going to start thinking

02:11:08.760 | about how to change their relationship with light

02:11:11.240 | as a way to anchor everything that they do

02:11:14.700 | and that's important to their health.

02:11:16.240 | And I just, on behalf of all of them,

02:11:18.480 | and just directly from me as your friend

02:11:20.800 | and as a colleague for many years now,

02:11:23.420 | I just want to say thank you

02:11:24.400 | for the incredible work you're doing

02:11:26.160 | and for sharing it with us.

02:11:27.560 | - Thank you so much.

02:11:28.400 | And I actually now thinking about all of this,

02:11:30.840 | and you said I should write a book.

02:11:32.600 | I should write a book and call it the tripartite model.

02:11:35.640 | I think that would put all these components together

02:11:38.440 | would be very interesting to do at some point.

02:11:41.400 | - You should write a book.

02:11:42.960 | You should write, they'll probably try and change the title

02:11:44.640 | to like "Food, Mood and You," you know,

02:11:47.160 | or something because, but you can put in little print

02:11:50.000 | on the tripartite model or whatever.

02:11:52.520 | But regardless of what it's called,

02:11:55.220 | you absolutely should write a book.

02:11:57.020 | And so if you'd like Samir to write a book,

02:12:00.440 | or if you'd like to learn more about him,

02:12:01.780 | let's talk a little bit about where people can find you.

02:12:03.640 | Your laboratory is at the National Institutes

02:12:05.220 | of Mental Health.

02:12:06.360 | He is head of the Chronobiology Unit,

02:12:07.960 | all these things that I've mentioned earlier,

02:12:09.980 | but you are active on Twitter and Instagram.

02:12:13.480 | - Right.

02:12:14.320 | - So what is your Twitter handle?

02:12:15.920 | - It's @samirhattar.

02:12:18.480 | - And we will provide a link for that in the show notes.

02:12:20.760 | - Sorry, yes, the Twitter @samirhattar,

02:12:23.640 | and I think the same for Instagram, actually.

02:12:26.020 | - And Samir has been coaxed onto Instagram,

02:12:28.580 | so he does post from time to time,

02:12:30.400 | mostly pictures of food that is incredibly spicy,

02:12:34.140 | but also information about chronobiology.

02:12:37.840 | He comes on for an Instagram Live every once in a while

02:12:40.020 | with me, and so definitely give him a follow there

02:12:42.560 | and on Twitter, and I'm sure that he'll be happy

02:12:46.880 | to answer questions and entertain any and all discussions

02:12:52.240 | about chronobiology.

02:12:53.720 | - Absolutely, yeah, and light, yeah.

02:12:57.240 | - Great, thank you, Samir.

02:12:58.340 | - Awesome, thank you, Andrew.

02:12:59.880 | - Thank you for joining me for my conversation

02:13:02.200 | with Dr. Samir Hattar.

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Dr. Samer Hattar: Timing Light, Food, & Exercise for Better Sleep, Energy & Mood | Huberman Lab #43

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