Barbell Shrugged - [Circadian Rhythm] How to Optimize Your Internal Sleep Clock w/ Dr. Greg Potter, Anders Varner, and Doug Larson #708

Episode Date: August 16, 2023

Dr. Potter values helping people feel great and do good. He knows how hard it can be to thrive nowadays, and lots of us try our best to understand what we should be doing to look better, perform at a high level, and be happy and well.  But, achieving this is often elusive, for many aspects of modern life — grueling work schedules, fast food, physical inactivity, social isolation, pollution and so on — are at odds with the behaviors and conditions our bodies need to function optimally.  Let’s be honest: There’s a lot of nonsense about health out there too! Dr. Potter helps empower people to make simple and sustainable lifestyle changes that add years to their lives and life to their years.  To this end, here are some of his qualifications:  He did my undergraduate and master’s degrees in exercise science at Loughborough University His PhD research at the University of Leeds focused on sleep, circadian rhythms, nutrition, and metabolism. He is qualified as a personal trainer and sports massage therapist and have worked as a coach for over a decade..   Dr. Greg Potter on Instagram  Anders Varner on Instagram Doug Larson on Instagram

Shrugged family, this week on Barbell Shrugged, we are talking to Dr. Greg Potter, which is super cool because we're talking about sleep, but most of the time when we talk about sleep performance, we don't actually ever get into kind of like your body's sleep clock and understanding circadian rhythms, why they exist, how we can optimize them, and that's exactly what we do today. And it's super cool because I'm very interested in circadian rhythms, especially the more that I track my sleep and kind of understanding what's optimal specifically for me and we dig into a lot of understanding just why circadian rhythms exist

how you can use that to optimize your sleep and then ways that you can just start to program your day from getting morning light which is good for some people not for some people getting outside during the day night time bed routines and all kinds of fun stuff related to your body's sleep clock. As always, friends, you guys can get over to rapidhealthreport.com. That's where Dan Garner and Dr. Andy Galpin are doing a free lab lifestyle and performance analysis that everybody inside Rapid Health Optimization will receive. That is over at rapidhealthreport.com. Friends, let's get into the show. Welcome to Marvel Shrugged. I'm Anders Varner, Doug Larson, Dr. Greg Potter on the show today. Yo, we're going to talk about circadian rhythm, sleep. That's what your PhD is in.

And metabolism has how it relates to sleep. But pre-show, I had cut you off because you've been in the sauna a lot. And then you went on like a dark chocolate rant and all the talks that people need to know. Why have you been in the sauna so much lately? Yeah, it's partly because people can actually lose quite a lot of certain heavy metals through the sweat. And what I was saying is that I've got a history of consuming heroic quantities of dark chocolate and cocoa. During my PhD, I used to drink about 50 grams worth of cocoa a day, which is stupid. Don't do it, especially if it's cheap, low quality cocoa. And especially if it's grown in Latin America, interestingly, because the metal content of cocoa depends obviously on the growing conditions and on the soil specifically. And cocos that are grown in Africa tend to contain less cadmium than those grown in South America.

So given that cadmium has a half-life of about 50 years and is a well-established neurotoxin, I'm quite keen to try and get rid of some of it from my system. And I've got access to a good sauna now. So I'm just tacking half an hour in the sauna on the end of my workouts and then sometimes using on off days too so i've been sweating out ridiculous quantities of cabin or so i hope those heavy metals i was gonna say you said or so i hope like are you testing that in any way is that like you can do like hair follicle analysis and see like heavy metals are? Yeah, I understand. Like how those levels are fluctuating, et cetera?

Sure. I think you can do mineral tests, but I haven't actually ever done any of that. I also don't know anything about the validity of those tests. You guys probably know more about that than I do. It could be worth doing some pre-post testing, but I'm just doing it on a whim. And regardless, I know that the sauna has a bunch of other health benefits too i'm doing my cardiovascular system some good and so on so even after you can't go wrong it's incredible how many rabbit holes you will dive down in your uh in your health

optimization life yeah no kidding the dark chocolate cadmium rabbit hole is a new one to me. That's why we had to cut you off so that people knew that that was a thing. There are good dark chocolate products out there. No affiliation with them. There's a brand over here in the UK called Montezunas. And they're 100% cocoa dark chocolate, which is the kind of stuff that makes you a man, is incredibly rich in flavanols which is the good stuff that's very good for your cardiovascular health your brain function probably for your gut

health too but very low in cadmium so if anyone ever has the chance to pick up some of that stuff go for that i love it yo i want to dig into uh some sleep which is maybe your second favorite subject around next to sauna and cadmium. I'd love, we've had many sleep scientists on, but one of the few things we, one of the things we don't talk much about is really the circadian rhythms, which is super interesting to me. And that I've been tracking a lot of things on the aura. And it always tells me kind of like when my optimal time for the middle of my night is at 3 AM and I'm usually very close to it. But then I read the, the like little blurb about it. I'm like, does that really matter? Um, but at the highest level, I would love to, uh, dig in, just walk through what a circadian rhythm is, why it's important, and kind of how it relates to getting a good night's sleep.

I'll frame this in the context of evolution. Organisms evolved in the presence of predictable changes in the environment. The most conspicuous of those is the light-dark cycle. And we can think of that as being the environmental clock. In response to that we evolved biological clocks that produce rhythmic changes in our biology across different time scales to anticipate and adapt to changes in the environment. One of these time scales is 24 hours roughly and the type of rhythm that is relevant to this is what's called a circadian rhythm. Circadian means about 24 hours.

And these are rhythmic changes that are self-generated. So they're not just the product of behaviors such as physical activity and eating food. And instead, they're driven by some intrinsic timekeeping mechanism. And we have these in all tissues in our bodies to optimize their function according to time of day. So to give you some examples of these, obviously, with respect to the brain, we have changes in how awake we feel at different times of day and how liable we are to sleep. But we also experience changes in things like our alertness and ability to pay attention during difficult cognitively taxing tasks. Elsewhere in the body, we could look to metabolism. And there are substantial shifts in many different metabolic processes

over the course of the 24-hour day that are driven by these biological clocks. And just to use blood sugar regulation as an example you have a clock in your liver that influences gluconeogenesis or the production of glucose from precursors to that you have a clock in your pancreas that influences production of insulin each day which then shuttles glucose to appropriate tissues and also the clock in your brain that influences many other clocks in your body the so-called master clock relays information about light exposure back to the pineal gland that produces melatonin and then melatonin acts on receptors in tissues throughout your body to tell them that

it's the night nighttime and therefore to engage in nighttime activities and one of these is actually the pancreas so melatonin has metabolic roles too and that what it does is it reduces glucose stimulated insulin secretion and that's thought to be in order to maintain sufficient blood sugar levels overnight when you're not eating you don't have a source of glucose coming in. So we have all of these different types of rhythms and we could go into the immune system, gut function, musculoskeletal function, but I'll pause there because you asked about sleep specifically. And we can think about sleep as being broadly regulated by two different processes. One of these is called homeostatic sleep drive the concept is quite simple the longer

that you've been awake the greater the pressure there is in your body to sleep and we actually know quite a lot about the biological substrates of this sleep pressure the best known of them is adenosine and what happens is that while you're awake synapses in your brain that are releasing neurotransmitters will release ATP into spaces between your brain cells and that will either stay as ATP which will then produce increases in some inflammatory substances that then influence sleep circuits and promote sleep or the ATP will be broken down into adenosine, which then directly acts on sleep promoting circuits to increase their activity and also inhibits wake promoting circuits. So the longer that you've been awake, the more ATP and adenosine in the cells or between the

cells in your brain, which promote sleep. The other aspect of sleep regulation is your body's clock. And specifically, your body's clock influences what we can think of as being circadian wake drive. So it's this rhythmic change in a wakefulness drive that at some times opposes that sleep pressure so what should happen in somebody with healthy sleep is they wake up in the morning after a good night of sleep feeling refreshed and at that time of day they've paid off the sleep pressure that accumulated during the previous day so sleep pressure is very low homeostatic sleep is very low and then as they stay awake during the day the drive to sleep increases to oppose that increasing drive to sleep the body's clock produces an increasing circadian wake drive you know that dip in alertness that you feel around lunch each day that's actually due to a temporary

dip in the wake drive at that time of day which is why you feel a bit sleepy but then what happens around the time that you typically fall asleep is there's a sudden drop in that circadian wake drive. And so now you've got loads of sleep pressure, but low circadian wake drive. And then you should hopefully quickly fall asleep and stay asleep. So I realize that's quite a long preamble. Hopefully that tees up the rest of the conversation. Shrug family, I want to take a quick break. If you are enjoying today's conversation, I want to invite you to come over to rapidhealthreport.com. When you get to rapidhealthreport.com, you will see an area for you to opt in, in which you can see Dan Garner read through my lab work. Now, you know that we've been working at Rapid Health Optimization

on programs for optimizing health. Now, what does that actually mean? It means in three parts, we're going to be doing a ton of deep dive into your labs. That means the inside out approach. So we're not going to be guessing your macros. We're not going to be guessing the total calories that you need. We're actually going to be doing all the work to uncover everything that you have going on inside you. Nutrition, supplementation, sleep, and then we're going to go through and analyze your lifestyle. Dr. Andy Galpin is going to build out a lifestyle protocol based on the severity of your concerns. And then we're going to also build out all the programs that go into that based on the most severe things first. This truly is a world-class program, and we invite you

to see step one of this process by going over to rapidhealthreport.com. You can see Dan reading my labs, the nutrition and supplementation that he has recommended that has radically shifted the way that I sleep, the energy that I have during the day, my total testosterone level, and just my ability to trust and have confidence in my health going forward.

I really, really hope that you're able to go over to rapidhealthreport.com, watch the video of my labs, and see what is possible. And if it is something that you are interested in, please schedule a call with me on that page. Once again, it's rapidhealthreport.com, and let's get back to the show. Related to the sleep pressure, an interesting note for the audience, isn't one of the primary mechanisms of caffeine is to block the adenosine receptors and so there's there's there's a build-up of adenosine um and so that that sleep pressure is kind of like um avoided so to speak and then uh eventually

eventually the that mechanism action wears off and then it's kind of why you get the afternoon crash because like all of a sudden the receptors aren't blocked but there's like this build-up of adenosine and then you get like this like adine dump, and then you're really, really, really sleepy. Was that said close enough to be accurate? No, very well put, Doug. It actually antagonizes all of the adenosine receptors. So like you say, it blocks the interaction of adenosine with its receptors. But something that many people in your audience won't be familiar with, which is interesting and somewhat related, is that creatine monohydrate also influences homeostatic sleep drive through a different mechanism. So whereas caffeine is blocking that interaction, what creatine is doing is it's reducing the amount of ATP and adenosine in those spaces between cells in the brain. And so as a result, where you take

creatine and caffeine at the same time, the creatine would reduce the amount of adenosine and ATP, and then the caffeine would block any of that adenosine and ATP from interacting with its receptors. And so while this hasn't been well studied in humans, there's a fascinating paper, which has barely been cited, published a few years ago and what they did was they added creatine monohydrate to the chow of rats for several weeks and they looked at how their sleep changed and what they found was that they slept less they had a smaller amount of deep sleep in particular their deep sleep was less deep and also when they subsequently deprived them of sleep what you normally see after sleep deprivation is a kind of rebound sleep where you'll sleep longer

and you'll sleep deeper too they had less of that rebound sleep when they had supplemented creatine and all of that points in the direction of the fact that creatine is reducing homeostatic sleep drive so my guess is that if you have a period coming up where you know you're going to be short on sleep creatine is something you should be taking and i think people realize they should be taking creatine for all sorts of other reasons too but maybe an underappreciated benefit of creatine is that it can really help you maintain your cognition yeah during those periods of broken sleep as in the case of parents and newborns for instance i mean chronically

though is that probably a negative if you're taking it every single day for many many years like for a long time it was kind of like five grams a day was the standard but now with now that performance all that research has kind of been done everyone knows like five grams a day can help you with explosive power and speed endurance and whatever else but now a lot of people because of the cognitive benefits are taking more like 10 grams a day 20 grams a day and if you're doing that every single day and that's limiting deep sleep is that is there a negative is there a downside there to taking treating every day from a sleep perspective then i think there are two things to mention one of them is that when you give some other animals creatine, like rats, you increase their

brain phosphocreatine stores quite a lot. In humans, you don't increase them so much. So any effects on sleep are going to be smaller, but then maybe more pertinent, going by the long-term studies of creatine that have been done and in some instances people have been taking 30 grams of creatine monohydrate a day for years in the case of certain neurodegenerative conditions when you look at whether there are any downsides to that they're basically non-existent as far as we can tell it's got a fantastic safety profile and it benefits most bodily systems obviously the musculoskeletal system increases strength of power hypertrophic responses to resistance training bone mineral density and so

on seems to be good for working memory seems to be good for some aspects of metabolic control the only thing that some people have raised a potential flag over is the prospect of it negatively affecting kidney function but frankly absent any existing renal issues i don't think there's any cause for concern any increase in creatinine that you see on a blood test is just a product of the fact that you've got more creatine coming into the system there's nothing pathological about it so the short answer doug is i don't think so i don't think there's any cause for concern whatsoever and i think what it's actually doing is it's slightly reducing actual sleep needs so when somebody is taking creatine at high doses in the long term it's like

they have a shorter sleep phenotype than they normally do because there are some people out there who do need less sleep than the rest of us yeah and the people who are true short sleepers are few and far between but there is a tiny number of very fortunate people who seem to function perfectly well on less than six hours of sleep per night and what creatine seems to be doing is pushing people in that direction a tiny bit. Yeah. I'd love to dig in a little bit on the clock idea that you had earlier.

Specifically when it, sleep is kind of the easy one. And I think the easy assumption would be it's based on the amount of light that is coming into our eyes, hitting our skin. Is it the light? Is it like vitamin D? What kind of triggers these clocks? And what is like, why are they so important?

Yeah. Okay. Which is probably just a massive question. Hopefully just in sleep instead of all of the clocks. Okay. Yeah. That is a massive question hopefully just in sleep instead of all of all of the clocks okay yeah that is a massive question and i'll try and only touch on the most important bits but as you can already tell i can be quite long-winded at times perfect so one concept to understand is that your circadian rhythms aren't precisely 24 hours when they're left to their own devices

so way to go and live in constant darkness devoid of any time cues so you didn't have food coming in you didn't have a clock on the wall that could give you some indication of what time it is outside and you measured your body's clockwork by looking at say your body temperature rhythm what you find is that there's a very low chance that your body's clock ticks at precisely 24 hours each day you look across people that clock is too linear for reality like it's 2 12 1 it doesn't exist like, it doesn't. The reality is a lot noisier. But in humans, on average, the body's clock ticks at about 24 hours and 12 minutes. And so you have to reset it each day because if it otherwise carried on ticking at that speed,

what you'd find is that day on day, it'd drift later and later. So sometimes you'd be in time with the light-dark cycle outdoors, but much of the time, you'd basically be nocturnal temporarily. So it has to be reset each day and it gets reset by what are called zeitgebers, time givers. And the most important of these, as you're alluding to Anders, is the light dark cycle. And you mentioned the skin and the eyes i think it's important for people to realize that the most important time cue for your master clock which influences the timing of your sleep is the pattern of light exposure at the eye specifically and regarding that light exposure we can think of three different things as being

very important one of them is the intensity of light. And intensity is measured in photometry using something called lux. One lux is the intensity of light that's emitted by one candle held one meter from the eye. And in this room right now and in most typical offices, the intensity of light might be something like 500 lux in a relatively well lit office. Way to go outdoors at midday on a sunny day, even in the UK, the intensity can be about 100,000 lux. So 200 times brighter than an office. And while your visual system

doesn't really register this, you wouldn't think that it was 200 times brighter outdoors necessarily. Your body's clockwork does. And that's one of the reasons why it's so important to spend plenty of time outdoors in daylight each day and as a general rule of thumb i typically suggest that people spend at least an hour outdoors it's easy to remember but also that is based on some science too another of these parameters that matters is the timing of light exposure and there's a concept in circadian

biology it's a little bit difficult to explain but it's called a phase response curve and people will have heard of dose response curves the idea is that how much you respond something depends on the dose of it that you get you have eight cups of coffee and you thereby have 1.2 grams of caffeine. You're going to feel more jittery than if you just had two cups of coffee. That's because of the dose. In a phase response curve, it's not just the dose that matters, but it's also the timing of the stimulus, particularly the timing relative to the timing of your body's clock. And in the case of light exposure what you find is that in the early biological morning which is around the time you wake up each day

exposing yourself to lots of high intensity light is going to accelerate your clock it's going to shift it earlier so if you're a night owl and you have to wake to an alarm clock each day and that is curtailing your sleep and that's affecting your daytime function you want to shift your clock earlier and so for someone like this it's really important to get outdoors into daylight early in the day and then at the other end of the day if you expose yourself to lots of that type of daylight shortly before bed or around bed that's going to tend to push your clock later it's going going to slow it down. And so that can actually be helpful for some people. And this is often misunderstood because there are a few people in the world of podcasts who really drill home the importance

of morning light exposure, but that can actually be detrimental for some people. Because if you think about a 70 year old whose sleep has just shifted earlier and earlier and now they're falling asleep at 6 p.m and they're waking up at 3 a.m feeling irritated and feeling lonely and misaligned with the rest of society the last advice they should be getting is get lots of light in your eyes when you wake up in the morning that's going to shift them even earlier and instead for them there's a sweet spot between about three hours before they plan to go to bed and one hour before when they should be actively trying to get more of this type of high intensity light exposure because that's going to help keep them a bit later yeah and then they don't want that immediately before

bed because light doesn't just affect your clock it also affects things like alertness and it will influence their sleep architecture which we can get into later if you want then the third aspect of light that i'll mention is the spectral composition of light. So it's different wavelengths and different wavelengths are good for different things. So if you look at sunlight it actually contains many different wavelengths. At one end of the spectrum you've got ultraviolet radiation which is best known for the fact that it can cause skin damage of course. You've then got visible light which is best known for the fact that it can cause skin damage of course you've then got visible light which is between roughly 380 and 780 nanometers and within that there is a range that most strongly affects the body's clock and it's because of how specialized cells in the eye

absorb photons and that range corresponds to blue light it's basically the color of a clear sky on a sunny day which is no coincidence so if you want to maximally shift your body's clock or if you want to provide the strongest time queue that anchors the timing of each day it's important to get lots of that type of relatively short wavelength light. It doesn't have to look blue, full spectrum white light will contain plenty of that too. And then some longer wavelengths also influence our biology as well. Not the body clock so much, but actually near infrared light, for example, is used in photobiomodulation devices for all sorts of therapeutic reasons and sunlight does contain some of those long wavelengths too so it's not just that it's affecting our body's clock or

our vitamin d it's actually affecting our bodies in many different ways but i'll pause there and hopefully people just remember those three things intensity timing and spectral composition get at least an hour outdoors each day if you want want to shift earlier, within two hours of waking. If you want to shift later, between three hours before bed and one hour before bed. A practical question on that note, like if I'm in a coffee shop, and my laptop is right in front of me, and there's a huge window in front of me, out to a bright sunny day, is that the same as sitting two feet outside that window or is it still radically different than being actually outside even if

it's like the whole wall is a piece of glass and it's bright where i am still looking out at the sunshine yeah it's an important question and the intensity of light actually drops exponentially with distance away from windows so it really drops very quickly and the closer you can get to the windows the better and there is research showing that in office work in context people who sit by windows or have access to windows sleep better than people who don't they fall asleep faster they wake less frequently in for shorter periods and they sleep slightly longer too. So when possible, sit by the window when the sun's up. Yeah. Is there an effect on, say, kind of in the example, and as you're walking through,

if you were to get sun exposure late at night, it's going to push your bedtime back. Is that something to do with the body clock on when melatonin starts to get released or is there is that correct line of thinking there yes yeah it is so it's partly mediated by melatonin and it's probably just worth spelling out that the way the melatonin synthesis happens and what it does is during the daytime, you should be getting lots of light into your eyes, into these intrinsically photosensitive retinal ganglion cells. And they contain this photopigment melanopsin that I mentioned earlier. And basically, there's a quick path back to the master clock in the brain. It's called the suprachiasmatic nucleus which is like the conductor of the orchestra of circadian rhythms help keeps it helps keep all of the other players in the

circadian system in time with each other and then the master clock relays information the kind of track record of your recent light exposure history back to the pineal gland in the brain that synthesizes melatonin and so it's through this pathway that light exposure during the biological night time when your brain is producing lots of melatonin can rapidly shut off melatonin synthesis it doesn't just do that but it will actually acutely increase cortisol production which can have some alerting effects as well and then in addition to the circadian system so what you're speaking about there is light exposure around bedtime pushing your clock back light does have some independent effects on

cognition and mood too so it will acutely increase alertness that's one of the reasons why if you're ever feeling sleepy around lunchtime if you can just increase your exposure to strong overhead lighting that's going to help you perform better at work but also it can affect your mood too and people who have seasonal affective disorder will have experienced this firsthand and if you have seasonal affective disorder then you want to get yourself a light therapy lamp if you can't spend lots of time outdoors keep that about a meter from yourself have it slight to the side get one that emits at least 2 000 lux but most emit 10 000 lux and use it for 30 to 60 minutes within a couple of hours of waking in the morning that should help out so a few bonus tips there but yes it does relate to melatonin but not just melatonin it's also increasing alertness independent of that

yeah um jet lag is kind of of like the easiest example that probably everybody has experienced, but what, what happens when your body is out of its natural rhythm, circadian rhythm and kind of taking it all the way to the end jet lag being a very temporary thing where your body just needs to get aligned. But what happens when there's some sort of pathology or disorder that's actually associated with not being aligned with your circadian rhythm? Yeah that's a great question. So you can think of jet lag as being a really visceral example that most of us are familiar with and that is largely due to circadian disruption but we can think of a huge spectrum of different forms of circadian disruption. So at the severe end, we have jet lag.

We also have ways of disrupting the circadian system that are used in experimental settings to try and work out what the effects of this disruption are, independent of other effects. Because if you think of shift work, for instance, there are all sorts of confounding variables. It's hard for shift workers to keep good relationships with other people who don't work shifts for example but those types of experiments have very clearly shown that disrupting the circadian system within just three days or so can have dramatic effects on things like

blood sugar control blood pressure pressure. It will basically invert cortisol rhythms, will reduce heart rate variability. It will affect cognition. So those are helpful because they actually clarify these are some of the things that happen when you strongly disrupt the circadian system. But thinking about other forms of the circadian disruption that are very relevant to people there are a few that are subtle but i think pernicious one of these is daylight savings time and we obviously experience that a couple of times each year here in the uk and during the spring transition when the clocks spring forward what happens is basically a small reduction in sleep duration probably a small amount of circadian disruption too that

leads to an acute but meaningful increase in heart attacks and a drop in workplace performance people engage in more of what's called cyber loafing, basically just randomly surfing the Internet and not doing anything that's related to the actual work. Judges meet out harsher penalties at this time of year to probably relate to insufficient sleep. And you also see a increase in traffic accidents, which probably relates to some of that sleep loss and interestingly that is more severe in the west of a time zone because thinking about a very minor case of this if you think about people sleeping in the east versus the west of a time zone people sleeping in the west of a time zone are going to get less sleep because even within the time zone you do see differences in sleep try sleep timing because people's clocks do somewhat track the sun so if you want to get more sleep

it's actually a good thing for you to be sleeping in the east of the time zone and during that daylight savings time transition people in the west experience more traffic accidents because of the additional sleep loss in response to that and then there are instances of entire countries being in the wrong time zone so china for instance spans over four time zones and they all follow beijing time so it's this horrible huge experiment that's taking place we actually know little about the effects of that but it's an instance where there's societal driven circadian disruption that could have really big consequences and then going to the end of the spectrum that you mentioned namely people with what are called circadian rhythm sleep wake disorders there are lots of these probably the

most pervasive and maybe the most burdensome is called shift work disorder it affects about a quarter of shift workers and basically these people are trying to sleep at times of day at which their body's clocks are promoting wakefulness and they're trying to be awake at times when their body's clocks are promoting sleep and because they never get restorative sleep they never fully pay off that pressure to sleep that's accumulated previously over recent weeks and so they're constantly sleepy during the day and then they're bothered by insomnia when they try and sleep but there are some other ones too so that doesn't relate to any intrinsic dysfunction in the clock work but there are also some intrinsic disorders where people's clocks are actually somewhat broken i spoke earlier about how if

you stick someone in constant darkness their clock will basically what's called free run over time and it will lose time of the world around them quite a large number of people who are blind visually blind have what's called non-24-hour sleep-wake rhythm disorder where the cells i mentioned in the eye earlier dysfunctional and because of that they don't respond to light the way that the rest of ours do and so they aren't able to align their clocks with the day around them and so they basically just drift across days they'll drift later and later for the most part and they won't be in time with the world around them that much of the time there are things they can do like well-timed melatonin use for instance and then i'll mention a couple more one of them is advanced sleep phase syndrome

and that is something that typically runs in families and these people have very early sleep wake timing relative to the rest of us. And we know something about the genetic contributors to that. There have been a few genes that have been identified that seem to run in those families too. And then there's delayed sleep phase syndrome. And these people have very late sleep-wake timing relative to the rest of us, which can be really crippling because they often have to try and get up on time for work each day to follow a regular schedule and they just lose a lot of sleep and again there are things that both of those groups of people can do but their sleep timing seems to be more rigid than

the rest of us it's harder to shift it back to something more reasonable. Yeah. Going back to the blind people and circadian rhythm and possibly related to Doug kind of with the glass being in front of you, people that have maybe not full blindness, but some sort of impaired vision and need to wear glasses, is that affected the amount of sunlight coming in is it on the blindness side of things is it is the uh impairment of vision not being able to get the um the light in through their pupils into their brain and then set those clocks off and do glasses um impair that or especially

sunglasses too yeah yeah so so in the case of should i take the glasses off of my daughter which is really what i'm saying and will she sleep better at night that was that's what i'm really getting at here yeah and if she sleeps better at night he'll sleep better at night that's the real but this is really about me a broad question uh really just for my own benefit yeah it all comes back to that yeah yeah so in the case of the blind person it is actually dysfunction in those intrinsically photosensitive cells but regarding people wearing glasses regular eyeglasses i wouldn't worry about that they're gonna they can get in from all of the angles i would imagine yeah exactly they're gonna they're gonna barely affect it and i think lots of people tend to major in the minors and worry about things that they just shouldn't be too fussed about and that is definitely one of them

sunglasses are interesting because they definitely are going to affect the amount of short wavelength light that is reaching the eyeball but most people wear sunglasses on really sunny days and they don't wear them the entirety of the time that they're outdoors on those days so there's probably still a substantial amount of sun hitting the eye and regarding when to use sunglasses it's difficult because people differ substantially in their sensitivity to light exposure and also in the degree to which uv radiation is likely to damage the eye but i think if you're say going down to the beach and you're spending eight hours at the beach you should definitely be wearing sunglasses a good chunk of that time because we do know that uv radiation at

the eye does contribute to things like macular degeneration age-related eye pathology but the rest of the time i wouldn't necessarily recommend wearing sunglasses maybe absent the person who's trying to avoid light at certain times of day so go back to the older adult who's trying to shift her clock later if she was going out for a walk in the morning because she had to go and get some groceries or something she was trying to avoid light at that time of day knowing that it would accelerate her clock and keep her early she might wear sunglasses at that time of day so she can actually use them to help shift her clock in the right direction so that's the kind of instance where you might use them but all of this brings up the subject of trade-offs and also the idea that

people shouldn't just be thinking about their biological rhythms when considering light exposure because light affects us in so many different ways and if you look at the eye for instance we know that people getting insufficient daylight are more prone to short-sightedness to myopia and this is one of the reasons why that is at epidemic levels now in young people it's not just that they're spending lots of time doing close work it's that they're spending more time indoors than they used to and that seems to affect how the eye changes in shape over time which relates to signaling of the neuromodulator dopamine within the eyeball itself so getting sufficient light exposure isn't just important to your body's clock it's also important to actually other

aspects of your eye health but at the same time too much light exposure isn't just important to your body's clock it's also important to actually other aspects of your eye health but at the same time too much light exposure particularly from sunlight can damage the eyes over time so there's a middle ground as is often the case which people should be aiming for yeah uh you mentioned trade-offs a second ago it seems there is likely many benefits to watching the sunrise just just starting your day, being all the way awake and, you know, focused throughout the day, especially if you're not, quote unquote, a morning person. What are the tradeoffs of watching the sunrise and or what are the what are the especially the downsides to potentially watching the sunset? Do you want to be staring at the sun late in the day like that? You know, depending on the time of year, it could be, you know, five five o'clock depending on where you live or it could be nine o'clock so there may be differences there but what are the pros and cons of watching the sunrise or the sunset

yeah in the case of watching the sunrise let's just make a couple of stipulations to start so let's say that we're talking about people who are living somewhere quite close to the equator and i just say that because if you're at a really high latitude then in the summer your your days might be 20 hours long and in the winter your days might be two hours long so if we just talk about people who are not that far from the equator and if we think about society at large many people now have quite late sleep-wake timing certainly much later than what they would have in more natural settings and we see this when people go camping there have been these beautiful experiments by ken wright at the university of boulder in colorado where people

went into the rockies for several days and they did this at two different times of year the first experiment had people do this during the summer the second one four years later people do it during the winter and what they found was that within a few days people's body clocks and their sleep timing quite closely aligned with the natural light dark cycle and for most people that meant that their sleep shifted way earlier because in the modern electrically lit environment we get lots more light at night from electric lighting and we get less light exposure during the day and because our body's clocks are slightly longer than 24 hours on average that's going to push us later so for most people seeing sunrise is going to be a good thing because most people stand to benefit from shifting their clocks and hence their sleep

a little bit earlier it's going to give them a longer sleep opportunity if they're waking to an alarm clock in the morning as about 80 percent of people do but for a minority of people it's not necessarily going to be beneficial and you shouldn't necessarily be looking directly at the sun even around twilight the intensity of light from the sun can be around 10 000 lux so it's still quite strong it's a lot stronger than what you get indoors in a well-lit office for the most part and then regarding sunset a really important idea is that how much evening light exposure affects your clock on your sleep depends on your prior light exposure and people get up in arms about using phones using ipads using kindles watching tv

using laptops shortly before bed and they think oh i must avoid that short wavelength high intensity light at all costs because it's going to shift my clock later it's going to wake me up and it's going to just decimate my sleep and the reality is that's just not the case for most people, or at least it's not because of the light exposure, provided they've had plenty of time outdoors during the day. And if we think about evening light exposure, if you were out in the morning too, then you gave your body a really strong time cue at that time of day. And that helped anchor your clock at a relatively early setting. So then watching the sunset isn't going to affect your clock that much. It's not really going to shift it that much.

But for somebody else who's been indoors all day in a dimly lit room, who then goes out and watches the sunset, and let's say it's the middle of the summer and the sun is setting at 9pm, that is going to push their clock later. And if they have to wait to an alarm clock that's not going to be good for them so it is context dependent but basically you just got to bear in mind that getting some daylight is going to buffer you against light at night and that's one more reason why i drill home the importance of spending at least an hour outdoors and daylight

each day um we can now get back more into my privileged life of a decade living in the most beautiful place that i think in the entire world called san diego at the beach um over that decade i noticed uh my reliance on wearing sunglasses and like training your eyeballs, um, kind of in, in that overall exposure. Um, and every time now I'm outside and people go, you should be wearing sunglasses. And I'm like, it's not even bright out here. Is there a difference in say living in San Diego for a decade and how you would go about approaching some of these concepts if you lived in Alaska, where a couple of months a year, it just never is bright. Obviously, those are kind of some extremes. But how much does like just your environment and your body adapting to that

environment kind of change some of these concepts? I don't think it's going to affect how your body responds to light exposure at different times of day that much provided there's no obvious damage to your eyeballs and i doubt there's been much if any so probably not that much however this does raise an important point which is that people differ substantially in their sensitivity to light exposure and in different ways too obviously you see this with skin light exposure some people tan incredibly easily some people don't tan at all and just get burned and that obviously relates to melanin content in the skin but in the case of the eyes some people are very sensitive to light and its effects on non-visual functions including shifting your body's clock around and this is one of the reasons why teens have later sleep than

most others and actually some people have proposed that we can use sleep timing as a marker of physical development because basically people keep getting later and later and later until the end of physical maturation until the end of adolescence and then from that point they get earlier and earlier and this is one of the reasons why men end up slightly later than women on average at least until around the menopause because boys continue developing longer because they go through puberty slightly later so they get later for a longer period of time. So their peak lateness is slightly later than women. And that probably also relates to the fact that if you look across many generations, on average, men are about seven years later than their female spouses. tangent aside during adolescence people are very sensitive to the

clock delaying effects of light at night and at the other end of life so if you think about somebody who's in his 80s who hasn't had eye surgery and now the lens is quite clouded and that influences how light diffracts through the lens they're not going to be so sensitive to the effects of light and you were speaking also about how it just influences your perception of brightness and what you can tolerate in terms of visual comfort obviously there's going to be some difference there too between people and maybe some adaptation as you're alluding to so i would just distinguish between your visual comfort and the effects on your clock and in your case i doubt that how your clock responds to light has shifted that much over time

but then related to that we've just got to bear in mind that people do differ a lot in their sensitivity yeah yeah it's been uh you you brought up uh the skin and tanning and like the melanin um it's almost they've been very similar and living in socal one i think everybody should just do it because it's great life um but it's such a great life because you're outside you're always in the sun and you can't even understand how good your body feels until like it's just perfectly sunny, cloudless days for 300 days a year. And you wake up every day and it's perfect outside. It's like it's all the perfect sunlight. All of the inconsistencies

that many of the other places in the country or world can, that they have. I feel like you should get a cut from the San Diego tourist board. Nobody could, nobody wants their taxes to go up higher out there, which is why everyone moves. It's not the sunshine. We are not going to have all of the time that i wanted to uh to dig into um digging into metabolism and how it relates to sleep so we're definitely gonna have to have you back on man this was fantastic i really

appreciate you coming on the show pleasure yeah great to meet you both yeah uh where can people learn more you have a podcast give us all the details on the podcast. Yeah. I launched a podcast recently. Thanks for asking. It's called Reason and Wellbeing. And it covers many subjects I think will be interesting to people tuning into this. And actually, I just did the first part in a multi-part series on your body's clock and how it works. But other subjects that we've touched on so far include things like how to build healthier habits how to improve brain function and that was with tommy wood who i think you guys have had on the show so awesome yeah yeah and then i've also done a couple

of episodes on workplace performance and then most recently couple on back pain with steve mcgill another of your previous guests. And basically, it's about what you can do to sustainably feel and function better while being good to other beings. And in the future, I'd like to open up the breadth of it and cover a range of other subjects, too. But really enjoying that so far. So check that out. And you can find that obviously anywhere you can find podcasts including youtube and then otherwise social media at greg potter phd on instagram that's probably the best place to follow me um do you do you have remote coaching what what is how do people work with you

i do yeah a little bit and i'm quite strapped for time at the moment because i'm i'm spinning a few different plates and working with multiple startups. But yes, they can get in touch. And if you're interested in that, then do ping me a message on Instagram as well. Fantastic. Awesome, my man. Doug Larson. You bet.

On Instagram, Doug with C. Larson. Greg, appreciate you coming on the show, man. I'm going to check out your podcast as well. It was fun. Yeah, this was great, man. Fantastic. I'm Anders Varner. At Anders Varner. We are Barbell Shrugged to Barbell underscore Shrugged. Make sure you get over to rapidhealthreport.com. That's where Dan Garner and Dr.

Andy Galpin are doing a free lab lifestyle and performance analysis that everybody inside Rapid Health Optimization receives. You can access that over at rapidhealthreport.com. Friends, we'll see you guys next week.