The Liz Moody Podcast - How To Hack Your Circadian Rhythm To Increase Energy, Sleep Better, Improve Gut Health, Fight Jet Lag & More With Dr. Russell Foster

Episode Date: May 17, 2023

Circadian neuroscientist tips for supporting a healthy circadian rhythm and dropping the habits that could be causing insufficient sleep, low energy, & chronic disease. what a circadian rhythm is and how it impacts our biology, our mental health, our relationships and more what the three chronotypes are & how to know which one you are how our chronotype changes as we age + why teenagers struggle with early wake ups how to change your body clock to fit your schedule  how hormones + the menstrual cycle impact our circadian rhythm a simple way to hack your ability to wake up or fall asleep why you might wake up in the middle of the night + what to do about it  what the research actually says about blue light blocking glasses  how to hack your circadian rhythm to fight jet lag a genius way to feel more awake during the day the best sleep & circadian rhythm support tips for new parents + night shift workers  the best times to eat, workout, take supplements & medicine, and more during the day and so much more!   For more from Dr. Foster, check out his book Life Time: The New Science of the Body Clock, and How It Can Revolutionize Your Sleep and Health and his work at the University of Oxford.  To join the Healthier Together Podcast Club Facebook group, go to https://www.facebook.com/groups/healthiertogetherpodcast. This episode is sponsored by: Osea: get 10% off your first order at oseamalibu.com with code LIZMOODY10. RocketMoney: sign up for Rocket Money today by going to RocketMoney.com/LIZM. ZocDoc: go to ZocDoc.com/Liz and download the Zocdoc app for FREE and book a top-rated doctor today.  GreenPan: visit GreenPan.us and use code HEALTHIER30 to get 30% off your entire order plus free shipping on orders over $99.  Healthier Together cover art by Zack. Healthier Together music by Alex Ruimy. Learn more about your ad choices. Visit megaphone.fm/adchoices

Hello, friends, and welcome back to the Healthier Together podcast. I'm your host, Liz Moody, and I'm a best-selling author and long-time journalist. This podcast is all about helping you live your healthiest, happiest life, whether we're uncovering the latest research on how to support a healthy gut, getting actionable tips for making career moves, or weighing the pros and cons of having kids. And yes, those are all real episodes, so if any of those topics sound good to you, scroll on back in the archives.

You all know that I am obsessed with my daily surf walks, which are essentially walks outside in the morning to set your circadian rhythm for the day. You can find out more details about it on my Instagram highlight. So today, we get to do a deep dive into the power of our body's biological clocks with one of the world's leading circadian rhythm experts. I am so excited to welcome Dr. Russell Foster to the podcast. Russell is the director of the Nuffield Laboratory of Optomology and the head of the Sleep and Circadian Neuroscience Institute at the University of Oxford.

Yes, that Oxford. His book, Lifetime, The New Science of the Body Clock, and how it can revolutionize your sleep and health is so good. It dives into all of the research, much of which he's led personally, on our circadian health and how it impacts so many parts of our lives. Consider this episode your biological clock primer. We get into what a circadian rhythm is and how it impacts our biology, our mental health, our relationships, and more, what the three chronotypes are and how to know which one

you are. how our chronotype changes as we age and why teenagers struggle with early wakeups, how to change your body clock to fit your schedule, how hormones in the menstrual cycle impact our circadian rhythm, a simple way to hack your ability to wake up or fall asleep when you want to, why you might wake up in the middle of the night and exactly what to do about it, what the research actually says about blue light blocking glasses, how to hack your circadian rhythm to fight jet lag, a genius way to feel more awake during the day if you get like that 3 p.m. slump. This is what to do. The best sleep and circadian rhythm support tips

for new parents and night shift workers. The best times to eat, to work out, to take supplements and medicine and more during the day, and so much more. I would love to hear your thoughts and your biggest takeaways as you're listening to the episode. So definitely screenshot and tag me. I am at Liz Moody on Instagram. I really tried to use this episode to get as much clarity as possible and answer as many of our questions as I could about our circadian rhythm and how to actually work with it to live our best lives, how to wake up feeling more energized, how to sleep better, what to do if your sleep schedule feels completely out of whack, what daily practices you should and shouldn't be doing to optimize it. And Russell was an absolute font of knowledge

and it was so helpful to hear everything from one of the top researchers in the fields. If there's someone in your life who has been struggling with their sleep, who's been feeling low energy all the time or who's just looking for easy ways to up level their everyday life, please send them a link to this episode so they can benefit from all of Russell's incredible information, sending the episode to someone by text on Slack, on DM, mentioning it in real life. This is the best way to support the show and it is so, so appreciated. Okay, let's get into it with Dr. Russell Foster.

Russell, I am so excited to have you here today. I have so many questions about our circadian rhythm, which we were talking a little bit about before we got on the call, but it light, all of these things really impacts so much more than we even talk about. Absolutely. Well, first of all, lovely to join you today, Liz. It's good just to step back and think about what our biology is supposed to deliver. If you think about it, what we need is the right stuff, at the right concentrations, at the right

tissues and organs at the right time of day. and it's the circadian system, our internal representation of time, if you like, that provides that structure that allows essentially life to work. And I think we overlook that. The circadian system provides this great organizing principles for our ability to function. Can you explain as if you're talking to a five-year-old what our circadian system actually is? If you think about it as a day within, we sit on an earth that revolves once every 24 hours, and it provides the light and the dark and differences in temperature and availability of food and not.

And what's happened is that all life has evolved a response to that 24-hour world. It's able to know when morning or evening is going to occur and up and down-regulate physiology accordingly. So in anticipation of sleep, the brain is starting to switch into sleep mode. metabolism is lowering a bit. Our immune function, interestingly, is being turned off a bit whilst we sleep. Our blood pressure is dropping. And we then go into sleep and then in anticipation, even before we've woken up, our blood pressure is rising, our metabolism is rising, and essentially it's getting us ready for increased activity and all the demands of the day that's arriving. And it's our circadian system, our body clock, that is allowing this beautiful, fine adjustment to these incredibly varied demands of the day-night cycle.

So if it's based on the day-night cycle, why do different people have different circadian rhythms? Yeah, it's a great question. And why do some people have short rhythms and others' long rhythms? What's interesting about humans is that there's huge variation. If you look at, let's say, mice or birds, their chronotype when they like to get up and go to bed is really, really tight between individuals. Ours can spread almost over a 12-hour domain. There are some people that could share beds. Some are getting up while others are going to bed.

And it's not clear why we're so diverse. One explanation has been that in our recent history, we were a tribal society in danger of attack from other individuals or nature or whatever. And it might have been good to have vigilance across the day-night cycle. So that may be part of the spread, but it's even more interesting than that, because there's not only that huge difference in chronotype, but as we age our chronotype changes. So from about the age of 10, we want to go to bed later and later and later, peaks in our late teens, early 20s, males tend to want to go to bed later for longer than females. And then after that peak in our late teens, early 20s, we move slowly to a more morning chronotype.

But the bottom line is that when you're in your late 50s, early 60s, you're getting up and going to bed at about the time you got up and went to bed when you were a pre-teenager. And that is about a two-hour difference. So trying to get a teenager to get up at 7 o'clock in the morning is like getting a 55-year-old up at 5 o'clock in the morning. That's the impact. Part of it is hormonal changes. Also genetics, we understand how the clock ticks. and there are genetic differences between us. I think it's amazing.

Essentially, by their contribution to our genes, our parents are still telling us what time to get up and go to bed. But subtle changes in some of those genes can make you a morning or an evening person. But there's a third component that determines our morningness and eveningness. And that's when we see light. And that's the bit where we have quite a bit of control. Light doesn't do the same thing across the day.

So dusk light delays the clock, makes us want to go to bed later and get up later, whereas morning light advances the clock makes us want to go up earlier and go to bed earlier. So if you happen to be an extreme late type and you need to get up earlier for jobs or whatever, then you can set the alarm, try and get natural light exposure, and if there isn't much of that in the wintertime, then sit in front of a light box. And that will actually move your body clock forward in time and help you sort of better adjust to the demands of what's expected of you. I have so many things to say about that.

Let's start with, it's a bi-directional relationship, right? Like our hormones are affecting our body clock and our body clock is impacting our hormones and all of the other systems in our body the same. That's right. And that's particularly clear when you look at the menstrual cycle. It's really fascinating because there are estrogen receptors within the the master clock within the brain. That's doing a couple of things. Estrogen seems to make the clock more coherent, give you a better, clearer drive, which can then impact upon your sleep wake systems.

The other things that estrogen and progesterone are doing is that estrogen has been associated with receptors in the brain that are regulating mood. So you can feel better with estrogen. and progesterone reduces anxiety. So either side of ovulation, women are feeling probably at their best because you've got high estrogen, you've got high progesterone. And before and after menace,

when those hormones are low, is when you can have more disrupted circadian rhythms, disrupted sleep wake cycles, and lower levels of mood. So there's a very interesting set of interactions, which we're only just beginning to understand. It's actually pretty scandalous that this whole area of human biology hasn't really be properly looked at in women.

So what should we do with that type of information? Does that mean if we are getting poor sleep at a point in our cycle? Can we use things like light viewing to alter that? Knowledge in a sense is power, knowing that either side, particularly premenis, mood might be lower and you may not be sleeping as well, is something we need to take on board. And in a sense, be prepared for. Speak to the people that we spend our lives with. And so I'm going into this phase. Cut me some slack here because this is what's going on. Now, it's going to be immensely variable. Some people have no effect at all. Other people are very, very sensitive. And that raises a really important point about this area of biology generally. We've talked about variation in

terms of one's chronotype. But of course, sleep, which is another 24-hour phenomenon, hugely influenced by our circadian systems, it varies. immensely between individuals. There's the sort of mantra that you've got to get eight hours of uninterrupted sleep, which is one of the reasons why I wrote the book, because I got increasingly irritated with statements like that. Healthy sleep can range from six hours, and some people need 10, maybe 11 hours of sleep per day. And what each of us have got to do is define the sleep needs that we need and then organize our life accordingly. You talk about three chronotypes. I've heard people also talk about four,

like a bear, lion, wolf, dolphin. Is that not scientifically sound? It's a different way of cutting the cake, I guess. As somebody with a biological background, when I heard the term dolphin, I thought, are they talking about unihemispheric sleep? Because when they're swimming, half of their brain goes to sleep.

And, you know, does a bear mean you're going into hibernation? So I kick back against that and have focused upon the larks, which is, what, about 15% of the population, the doves, which are 65%, and the rest, 25%, would be the outs. There's a lot of us in the middle. And of course, the key thing is we change as we age as well. So it's not a fixed thing. It can be hugely influenced by our genetics,

but our development and our light exposure will nudge it backwards or forwards. How do we know which one we are? There's a questionnaire at the back of the book, which is one of the oldest questionnaires, which has been used and validated extensively in the literature. There are lots of online questionnaires. And I think, broadly speaking, they're accurate. There's the Munich Sleep questionnaire, which is a great questionnaire.

I'd recommend that. We kind of know ourselves. Do you need an alarm clock to get you out of bed? Do you feel sleepy when you wake up? Do you need caffeine to get you going? If you ask owls, what interferes with your preferred bedtimes? Is it your work life or your social life? they'll all say it's the work life.

I just really struggle to get up in the morning. But not with a social life because, of course, they can stay out and they can party until the early hours. If you ask Larks, they say, I love going to work because I wake up, I'm refreshed, I can operate at work. The problem is for me on Friday and Saturday nights when all my friends who are sort of doves and owls want to stay partying and I want to go to bed at 10 o'clock,

I'm exhausted at 10 o'clock. So you do have these sort of slightly competing demands. What are you? I'm an owl. As a student, I was a terrible owl. And even at my advanced age, I'm still inclined to be an owl. What have you done as an owl to make our Dov Lark Society work for you? That's really easy. I struggled really hard to get as senior as I possibly could. When you sort of run an institute, you decide when the meetings will be. Hot tip. Become the boss.

We're coming in at 5 p.m. today. We'll be working until midnight. But it kind of makes sense because I work with a lot of young people and they tend to be later chronotypes. I get the best out of them and I think they get the best out of me. Our meetings may not start until 10 o'clock, but we're here. It's almost 20 past 6 in the evening and there are loads of people in the lab. We tend to work later. I will say that even if you're not the boss, you can do little things like that. like you can say, oh, I would prefer to take meetings after 10 a.m. if possible. I'm also more of an owl type. And I only do podcast interviews starting at 10 a.m. my time just because I know I won't be

able to perform as well. And I think people are much more open to that sort of discussion than they were. So the morning and dusk light viewing, the morning light viewing is going to make it so you can go to bed earlier. And then the dusk light viewing is going to push back your bedtime. Is that an instantaneous effect? Like if I view it that morning, that dusk, is it for that day? It will happen the day after. So if you get dusk light today, for example, then tomorrow you'll go to bed a bit later. It sort of takes about a day to catch up. But it kicks in pretty quickly, actually. And is it only for that day? Or like, are the effects gone by the following day? If you really want to adjust, you need to keep a stable, light, dark cycle and have it so that you're

aligned at the time that's best for you. So just one morning getting up early and getting morning light to advance the clock will be fine for the next day. But if you don't get it the following day, you're going to slide back to a later chronotype. You need to do it repeatedly. Okay. I'm going to ask you some quick fire questions about the morning light viewing because I do something called Cirque walks with my audience, which is just like get out in the morning. It's a circadian walk, see some light. And I get peppered with. questions about these. So I'm going to throw some at you. How long is the minimum amount of time to have it be effective in the morning? Good question. What we know from lab studies is that 10,000

lux, which is of intensity you get outside in the morning, for 30 minutes is very effective. So I would say 30 minutes outside is a good time, a good robust hit to the clock. You're getting your morning photon shower, which will set the clock. It's interesting. It's interesting. There's some studies suggesting that dog owners get better sleep, and that's always interpreted as well because it's a companion animal. I don't think that's true at all. I think it's because you have to get up in the morning and take your dog out for a walk, which gives you your morning light exposure. Is some better than nothing? Like if you can only do two minutes, is that better than doing none at all? It is, but it gets a bit complicated because people say, well, hang on, hang on,

there are lab studies suggesting that 200 lucks, not 10,000 lux, but 200 lucks can be effective. Well, yes, it can work, but you need to have that for seven or eight hours. What's happening is the light detecting systems are sort of light counters. You can have bright light over a short period of time or dim light over a much longer period of time. But outside, you're getting, even in the wintertime, a good thousand, two thousand, ten thousand lux. by the middle of the day, if some environments can generate 100,000 luxe. Even if it is raining, if it's overcast,

do you need to go longer? Yeah, but it's surprising. One thing that Lissas might be interested in is to get a cheap lux meter. They're about $20, and you can then get a sense of the fact that we live in dim-dark caves. By the window surface, you might get 3,000 lux.

By the time you've got to the middle of the room, you may be 50 or 100 luxe outside, it's going to be 10,000, 20,000, 50,000 luxe, even early in the day. It's a great experiment just to get a sense of how light deprived in a sense we are as a species. What is the latest cutoff to have this early in the bedtime effect? The recommendations are first thing in the morning. Six, seven o'clock in the morning will be better than eight, nine o'clock in the morning, but not by much. And particularly as nine o'clock, you're going to have a lot brighter light in the environment. So I think it's just that morning dose. I think it's fairly flexible, largely because you can titrate duration and timing

with light intensity. The brighter the light, the more effective it's going to be. Does something through a window count? Like if you're driving to work in your car, does that count? Broadly speaking, it can. You're getting quite a bit of light through the windshield. The one thing I would say, though, is you shouldn't completely detach yourself from natural light. So most glass doesn't transmit UVB light, which is the light that we need to synthesize vitamin D. And so still get out there, and then it doesn't matter what time. It's a completely different system. But you're getting the UVB to synthesize vitamin D, which of course has been associated with improved immunity, bone and calcium metabolism.

there's some interesting data suggesting that vitamin D might also help with sleep. It's probably enough to get the light through the windshield, but for the full benefits of light, then UVB is important. Of course, you've got to be careful because UVB and UVA can cause skin burns and sunburn, which can be really damaging. And people would argue that there's no safe level of having a tan. You know, you are increasing your risk of skin cancers. I need like a full face mask with just like the eye cutouts like people wear skiing and just wear that outside on your morning. I mean, you'd probably scare your neighbors, but it would be effective as a thing. It is a struggle.

Like when do you put your sunscreen on for something like going outside? Exactly. It's been argued that overuse of sunscreen has meant that people aren't making vitamin D. I think we intuitively know, though, if we get our 30 minutes, bright light in the morning, when the sun isn't high, but we're still getting that. brightness to lock the clock. But if we're out during the day and it's bright light, then sunglasses and a hat makes perfect sense. And you said in the book that midday light doesn't really have any impact on our circadian clock. Not too much. It's all about dawn and dusk. And I think that's so fascinating because midday gives you no time information. It doesn't tell you when dusk and dawn is coming

through evolution. And the shape is called the phase response curve. Dusk light delays. morning light advances, that shape is the same for almost all life on the planet. It changes a bit, but basically that phenomenon of dusk versus dawn is similar whether you're a photosynthetic algae, you're some sort of snake or indeed us. I think that's so amazing. And are you actually doing this every day like in England where the weather is often less than desirable? You're actually like going outside for 30 minutes most mornings? Absolutely. What I've now done is I've always organize my timetable so that I have a good 30, 40 minute walk into work. I deliberately park outside, so I get that morning walk. And I do feel better for it. And when I've stayed at home

and I've worked, I just don't feel as good. I love that morning walk. I love the idea of integrating it into your routine, saying how can I fit this into the schedule that I already have versus trying to add it on. Because often I think, especially with wellness things we're trying to do for ourselves, it can get really overwhelming to be like, well, where do I fit this in and this and this in? And I love that you're just like, I have to get to work. I'm going to make my commute a walking commute so I can get this time in. Yeah.

So friends, for example, who are living in London and using the tubes, the underground, you could basically never see proper light. So what they'll do is get off several stops before the closest stop. So the last bit is a walk in outside. Yeah, the London, too, makes you feel like a mole rat. You're so deep undercrowned. It's like a little frightening. Kind of smells like that, too. So let's talk about dusk light for a second. If dusk light is delaying our circadian clock,

should we be consciously avoiding dusk light if we are trying to go to bed earlier? We did some studies a few years ago on university students. in Australia, in Germany, in England, in New Zealand. And we showed that the later the chronotype, the later they wanted to go to bed and get up, they missed the morning light, but they got the evening light. I think it's a really nice illustration that actually light has different effects.

And if you're going to get more dusk light, the morning light, you're going to go to bed later and get up later. If we're all trying to live in a world that is operating more on this morning light schedule, the chronotype that the world wants us to be is a little bit earlier, though. So if that is true, even if our chronotype is later, and maybe even especially if our chronotype is later, would we want to consciously avoid that dusk light? Absolutely. Yes. And if you are a late type and you want to get up earlier, then absolutely avoid the dusk light, set the alarm clock for an early

point in the morning. Let's say sort of six, seven o'clock in the morning. That'll drive you out of bed. get outside. If it's winter, then sit in front of a light box, and that morning light will advance the clock. As we discussed, you know, one's chronotype is dependent upon one's age, one's genetics. But when you see light is so important. So you're right. Avoid dusk light if you want to get up earlier. And if you see both morning light and dusk light, do they cancel each other out? They do. Yeah. When we were all agricultural workers in 1800, over 95% of the population worked outside. So we were constantly being nudged, advance forward, and then delayed back as we saw the dawn, dusk signal. So you're absolutely right. They would cancel each other out. And so we'd stay more or less

aligned to the expanding and contracting seasonal light, dark cycle. Oh, that's so interesting. So it's almost like in the world where we were outside all the time, everything balanced, because we were seeing morning light, we were seeing evening light. And it's just in the world that we're in now where maybe a lot of people go outside after work, but they're not getting the light in their eyes. Maybe they're inadvertently delaying, delaying, delaying just because of the rhythms of modern society. That's right. So many people will be commuting in the winter months in particular. You're commuting to work in the dark, so you're missing the morning light, and you're probably missing the dusk light as well, but you're not getting any light. So the clock will then start to drift

through time. For 80 to 90% of people, you'll be getting up later and later and later. Is this why sleep scientists are so opposed to the daylight savings rollback? They like the one I feel like that I don't like. I want it to be light later. This is the best time of the year. But I read something from a sleep scientist that I really admire. And she was like, no, that is not what sleep scientists on the whole like. That's right.

We don't like daylight savings time. Of course, you know, scientists will never agree completely on everything. But there's almost universal agreement that noon should be when the sun is at the highest point. in the sky. You know, time zones are really interesting. In central European time, in eastern Poland, compared to Western Spain, you see that there's a difference of almost an hour and a half in when dawn occurs. And what's so interesting is that as you cross the continent, people go from a more early chronotype to a later chronotype going from east to west. And you can link that at least partially to the different dawn time relative to the mechanical clock time.

That's so interesting. Did you follow that Spanish woman who lived in a cave to kind of live outside of clock time and see what impact it had on her circadian rhythm? It makes me want to throw away my clocks, maybe not live in a cave, but throw away my clocks and see what my body would do. Well, in a sense, that's what people with no eyes face or radical damage to the eye. because of the out the eye you can't set the clock to local time. What those individuals have is a completely free-running rhythm. And I work with profoundly blind individuals, and it's utterly devastating.

And some of these are blind veterans, both in the UK and the US. And they constantly feel as I'm being tricked by my body. There's one chap I talked to, and he was determined to have a decent garden. He was not going to let the road down by having a messy garden. So he was completely blind, but he'd worked out a way of getting to the shed to get the mower and would work out how to cut the lawn. And he was doing this, and his wife came down and tapped him on the shoulder and said, it's 3 a.m. in the morning, you're waking the neighbours. And, you know, this is what happens when you're time blind.

There's been some crazy TV programs in the UK, where celebrities have been put in complete darkness for a week. just to see what happens. And I was asked to express a view on this. And I said, well, I can sort of see why you'd want to do it. But I think if you were putting it into the context of a real world situation, talk to somebody who's lost their eyes. They can tell you how horrifying it is to spend an entire life constantly drifting,

essentially experiencing unremitting jet lag for the rest of their lives. I think it's really profound. When you work with those people, do you focus on other ways to set your circadian rhythm that aren't light? Yeah, this is the problem because there's nothing that's particularly effective. Because we've been working for so many years on how the light regulates the clock, we've now got one particular drug, we've got a series of drugs, but one particular drug mimics the light input pathway onto the clock.

So we've done all the preclinical work. It works spectacularly. I mean, really, it's just unbelievable. You give this an oral dose to the mouse every day, and in the complete darkness, instead of a drifting rhythm, it's beautifully aligned. And so we've done the first. in human, and it's a safe drug, no adverse effects. And so we're now looking for funding to go for

the full-blown clinical trial. I think it'll not only help the blind, of course, but there are other conditions, so neurodegenerative diseases and neurodevelopmental conditions. Some young children have appalling sleep weight because the clock is so disrupted. In mental illness, that's such as schizophrenia. We've got individuals who are again drifting through time. So I think we're going to show proof of principle in the profoundly blind. And then I think try that on. on other sorts of clinical problems. Okay, the last question I want to ask you about dusk is from the work of Andrew Huberman. He's a professor of neurobiology and ophthalmology at Stanford and the host of a really popular

podcast. And on that podcast, he said, quote, a key protocol for sleep health and wakefulness and metabolism and hormone health is viewing light in the afternoon. As we progress into the evening hours, there's a phenomenon where our retina, our eyes, become very sensitive to light, such that if we view bright light or even not so bright lights between the hours of 11 p.m. and 4 a.m. It is strongly disruptive for our dopamine production. There are ways to offset that, however. Those of you who like to stay up late on the tablet or

computer watching Netflix, if you view light as the sun is starting to go down for 20 to 30 minutes, it lowers the sensitivity of your retina in the late evening hours, which allows you to buffer yourself against the negative effects of bright light later at night. If you go outside and view sunlight in the evening hours for anywhere from 5 to 30 minutes, what happens is that your melatonin rhythm stays appropriate. Melatonin is a hormone that is prevented by light, and melatonin is the hormone that allows you to fall asleep easily. So get outside in the afternoon or evening for 10 to 30 minutes, take your sunglasses off, get some bright light, get some natural light in your eyes. That was the quote. So I'm curious how you interpret that statement, and because I've been doing afternoon light

viewing and I'm a later chronotype trying to function in an early chronotype world, and it sounds like you would say I should be avoiding afternoon light viewing, but he would say, no, no, it's buffering you in this way. And I'm very happy for him to call me, and we can discuss this. But I think he's confusing the fact that there's a shift from daylight vision to night vision, from the cones to the rods as we go from bright light to dim light. And that's being regulated by dopamine. And that's been shown by retinal biologists. But that is not the sorts of mechanisms we're talking about. out, which is essentially detection of light by the photosensitive retinal ganglion cells and their direct inputs to the circadian clock. So I think there's a little bit of confusion there.

I know where it's coming from, but it's the dopamine signal is part of the day dusk shift. And that's not going to have much of an effect upon the clock. We can say, well, hang on, if you're going to make the eye more sensitive by kicking in the rods, well, why isn't that having an effect? Well, it might do, but it'll be a mild effect. And the key thing, of course, is that vision works by grabbing light in a fraction of a second and then forgetting you've seen it. What the circadian system needs is an overall sort of calculation of light over very long periods of time. And so there may be circumstances where they say flicker and the rods and cones are very good at detecting flicker. And so they might actually feed in. And there's some evidence that they do

that, but it's basically what's the brutal overall level of light at dawn and dusk, which is the primary signal. I also felt that it was essentially describing melatonin as a sleep hormone, and it most emphatically is not. It's a mild modulator of sleep. Many people are on beta blockers, and they have a perfectly normal sleep wake cycle. It's slightly, slightly altered, but it's very little effect. And when you try and give, for example, supplementary melatonin to aged individuals, it has almost no effect on their sleep weight timing. The best studies ever done suggested that you could reduce the time it to fall asleep, the sleep latency, by 20, 30 minutes. But in many studies, there was no effect at all. So we must stop thinking of melatonin as a sleep hormone.

What it is is a biological marker of the dark. And melatonin feeds back onto the master clock. and it reinforces the light signal. So, yeah, it's a modulator. For example, there have been drugs developed which mimic the action of melatonin and going back to the blind. Those drugs have only a very moderate effect on regulating the biological clock.

That's why we're developing these new drugs, which mimic the effects of light on the clock and don't activate the melatonin pathway, which is at best weakly effective. Okay, so you said it's a modulate, later of the clock, does that mean whatever we're doing to impact the clock, melatonin is having an impact on that? Well, yeah, if we think about for jet lag, a lot of people take melatonin for jet lag. What are the data that it actually has an effect? Well, actually, it does have a mild

effect. It probably in some people, advances or reduces the time it takes to adapt to the new time zone. But the overwhelmingly important signal is when you see light in the new time zone. So when light and melatonin are acting together, it's probably synergistic. Melatonin on its own is having very little effect. If you have headaches, allergies, brain fog, skin irritation, or you've been dealing with hormone issues, you are especially going to want to listen to this ad. Every single thing that I just listed has been linked to chemicals and household cleaners. One study found that regular use of cleaning sprays was associated with a lung function decline

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I would love your best tips for finding it. Sort of like a jet lag protocol. Well, it's interesting with the dusk light delays thing, because I've flown to places like Europe many times. And when I get there, if it's the early evening or something, I will go out and go for walk because my idea is like any light in my new environment is helping me. But it actually sounds like that might be hurting me going to sleep earlier. Yeah, it is slightly complicated. Because light has different effects at different times, it's very important when you cross several time zones that you expose yourself. to light in the new time zone appropriately. The rule of thumb is when you travel west, you seek out light upon arrival in the new time zone. Now the logic here is that light will

hit your clock when it thinks it's dusk in the old time zone. And the clock will be delayed to the location you've traveled to. So take a stroll outside when you arrive in your new destination when traveling west. For example, if I was traveling from London to New York, when I arrived in New York, it would actually be dusk in London, and I then would want to delay my clock, so I'm hitting light at the right time for where my clock thinks it is. In some ways, my intuition, like you're delaying your old clock to match the new clock. Yeah, exactly. But traveling east, a bit more complicated. So you need to advance your clock, you need to drag it forward in time. And to adjust quickly, and this is again, the rule of thumb, when you arrive, and I was flying a lot to, from London, let's say, to Australia.

And what I was doing was avoiding morning light, because many people take a night flight from the UK to Australia. They arrive in the morning. But that's bad, because avoid the morning light, but then you seek out the afternoon light. Now, the explanation is, because of the morning. You're dusk in the old time zone will be morning in the new time zone, you want to avoid that morning light and then seek out the afternoon light, because by the time it's afternoon in the old time zone, it'll be morning where you were, sorry, I'll say it again. So when traveling east, the rule of thumb is you need to advance your clock, and it's a bit more complicated. So to adjust quickly, you avoid the morning light in the new time zone.

and then seek out the late afternoon light for the first few days in the new time zone. So that's the rule of thumb when travelling east. Now, this is because dusk, where you've come from, will be mourning in the new time zone. And light exposure at that time, when the body still thinks it's dusk, will delay the clock. It'll push it back. It won't drag it forward in time. Now, by the late afternoon in the eastern location, it will be morning in the old time zone, and light exposure at that time will advance the clock. You don't have to understand the mechanism.

The rule of thumb, avoid morning light in the new time zone, seek out afternoon late and early evening light, and for the first few days, and that will hit the clock appropriately. And of course, what do you do? You can't stay inside if you're Australia or New Zealand. You can do like sunglasses, right? So sunglasses can help very substantially in that regard. Which is why people always ask me when they go in their cirquarks, should I wear sunglasses? And I'm like, no, don't.

Because the sunglasses actually do have an inhibitory effect of the light hitting your eyes, right? Oh, yeah, absolutely big time. So when traveling west, seek light out. When you arrive, when traveling east, avoid morning light, but seek out late afternoon, early evening light. And I think it's helpful, at least for me, to just think about it as less like trying to match the time zone of the new place and more, am I trying to. to advance or move back my circadian clock from where I was to the new place? Like, what is the difference? Yeah, and indeed, there are apps that you can download online, which will help you.

They'll know roughly where you've come from and where you're going to, and they can calculate roughly when you need to seek out light and when to avoid light. Is there anything else you do when you're like traveling to Australia? Yes, I do try and eat at the local time. I used to try melatonin, and it really didn't work for me at all. And in fact, there's some warnings about melatonin. Pilots are not advised to use it for a start and don't. And the other thing is that if you have a family history of some psychiatric illness or migraine, you're not advised to use melatonin. It didn't work for me. It might work for others. And I know some people absolutely

swear by it. And it seems that there might be a lot of individual variation with melatonin. But when I started to dose myself with light appropriately, it worked really well. Is it fair to say that in general, you would encourage people to try other things in their arsenal? Like melatonin would be very low on your list, if on your list at all. Absolutely. Yes. The thing about light, I'd eat at local meal times because that will help drag the clock in the right direction. Now, this is all, of course, if you're going to stay more than a few days. Oh, that's interesting. So if it's a short trip, Would you want to just stay on your local circadian rhythm, perhaps? Yeah, if you're going to be there just for a few days and traveling up.

So what do you do to override being out of sync? Well, first of all, be aware that you're much more likely to make mistakes. And you're much more likely to be irritable, less empathetic, and do stupid and unreflected things. You need to wear like a sign, a T-shirt that's like, watch out, I'm off my circadian clock. Be nice to me. I think it's a great idea. That would certainly sell. I'm surprised one of the airlines haven't done that.

So what do you do? Well, in the conference rooms, you keep the light as bright as you can because that will increase levels of alertness. And coffee, as we all know, will have an acute effect and increase levels of alertness and override sort of the sleepiness that you will have accumulated by not actually having slept properly. And then you can fly back and you'll be adjusted for work and family. So the light works in these acute moments as well. Like bright light in an acute moment will wake you up in that. moment. Absolutely. Light is having two effects in that sense. It's obviously interacting with the clock, but actually it has a very quick and direct effect on alerting the brain. So absolutely, if you can't turn the lights up in the room as far as you can, sit by a window, make sure you're getting that light. And that will help. It's not going to be completely, but it will actually help. I love the idea of acute doses of light. I had a doctor on the podcast once, and I asked her what she did before big presentations to be very, like, focused and ready for it. And I love the idea. And she said to go for a walk outside.

And she'd studied focus effects and meditation and things like that. But it makes sense that that quick dose of bright light in your eyes would increase your alertness and make you more on point for a presentation as well. This is good. And actually, while we are talking about melatonin, many people have said that, oh, well, what light is doing is suppressing melatonin. Let's say at night when melatonin is high. And two points is that light will increase levels of alertness actually during the day

when melatonin is low. and also the acute effects of light kick in before you've changed circulating levels of melatonin. So we need to divorce that relationship. Exactly. Melatonin might have some mild modulation on alertness, but it's not the primary way in which light is impinging upon alertness. So let's go to the root cause, essentially. The root cause and the root solution. Exactly, yeah.

So you often hear people say they're a good sleeper or a bad sleeper. Are some people innately good sleepers or bad sleepers, or do they likely have different lifestyle factors that they don't even realize are impacting their sleep? Lifestyle factors are really important. Clearly, there are people with abnormalities in their sleep and in the circuitry within the brain regulating their sleep wake cycle. Most are not. Most people get bad sleep because they're either anxious or stressed.

And what's so fascinating is that sleep anxiety is now a defined condition. where people are getting anxious that they're not going to get to sleep, and if they wake up, they'll never get back to sleep. And of course, that's a self-fulfilling prophecy. Winding down at the end of the day, by whatever means, is absolutely crucial. The other thing is that it's an appreciation that we're already told it's this solid block of sleep. Well, actually, that's not the case. The default state for humans seems to be what's called polyphasic or biphasic sleep,

which is you go to sleep, you wake up, you may be awake for a short period of time, you'll then fall back to sleep again. And then you may do this several times over the night. We're doing it. And most of us are waking up, but we're not aware that we've woken up. But if you do become conscious and you're anxious and you've got a whole bunch of stress stuff going on, you'll think, oh my God, I'll never get back to sleep. And the worries of the world descend upon you. part of it is knowing that it's perfectly fine to wake up. If you stay calm, if you keep the lights low, if you read a few pages of your favorite Jane Austen or some favorite music or whatever it is, then stay relaxed. You may want to leave the bed and then return to it. But

agonizing over not getting back to sleep is the killer. I mean, that's the real problem. It's such a good point that the shame and the criticism and the fear around waking up in the middle of the night is like the thing that's actually keeping you up. And if you can eliminate that and just be like, this is a natural part of my sleep cycle, it can create, I wake up often in the middle of the night. I'll read my book for a little bit. It's like, it's almost become like my sacred reading time, because it's when I can fit in reading the most. And it's this magical little portion of my night. And then I go back to sleep for a few hours. I usually get in a full sleep cycle on my sleep tracker after that. And then I wake up and I feel great. Yeah. There's almost like sleep shaming.

Many elderly people, their pattern of sleep changes. And many elderly people I've spoken to say, look, I've never had better sleep in my life. It's completely different to the sleep I had when I was 30, but I don't have to worry about work. I don't have to worry about the kids. But don't you dare ring me before 11 o'clock in the morning. I know one person who was getting up at 10 o'clock or whenever, they were going to bed late, getting up late. And the neighbor said to them, oh, didn't see your curtains being drawn. you were sleeping in, and so they went and slept in the back bedroom, so the neighbors wouldn't

criticize their sleep. But isn't it fascinating that we're somewhat judgmental about sleep? It's still part of that. If you're asleep, you can't be working, and therefore, by definition, sleep is bad. That's so interesting. And I think there's this idea that we want to be doing everything we're doing, like, perfectly and with maximum productivity. And so people want to have their sleep be ideal and optimized in the same way that we're trying to optimize every other facet of our lives. And of course, it's immensely dynamic. It's so very variable. Some wonderful experiments were done which looked at the value of sleep. And I think we'll all be aware that, you know, good night of sleep helps you consolidate memory. But perhaps people will be less familiar

with the fact that a good night of sleep actually helps you come up with innovative solutions to complex problems. Lovely experiment was done in Germany, where one, one group of individuals were introduced to a difficult task in the morning and then had to perform the task that afternoon. And about 20% of the group solved the problem. Next group introduced in the morning and then performed it the following afternoon, but they had no night of sleep, no sleep at all. And again, 20% solved the problem. The really interesting one, introduced to the task in the morning, performed it the following afternoon, good night of sleep. 60 to 70% solved the problem. I think that's such a brilliant illustration, that sleep is not an indulgence or a luxury. It's actually allowing us

to be human, which is problem-solving and coming up with innovative solutions to complex problems. So we need to embrace it. And perhaps our leaders and business community should take a lesson out of the value of sleep in lots of ways. So in the middle of the night when I do wake up and read, I'm reading on my Kindle. I'm reading it on the most yellow setting, pretty low-light setting. how bad is it knowing the impact of light on our circadian rhythm to be reading on an e-reader? The impact of screens and these screens that shift from blue to red, there's no strong data that's having any effect at all. If you look at the data from Kindles, as a paper published a few years ago, showing that individuals were on the highest setting of the Kindle, which is about 31 Lux, they had to read a Kindle for four hours, just before sleep on five consecutive nights.

And that just statistically delayed sleep onset by under 10 minutes, which, as one of my colleagues said when the data were presented, that may be statistically significant, but it's biologically meaningless. So the evidence that those low lights before bed are having an impact because of the light they emit and the effect it's having on our clock is very low. what they do do if you're doing social media, if you're doing gaming, if you're doing all that kind of stuff, you're alerting the brain and therefore delaying sleep onset. So we've got to disentangle the light effects versus the alerting effects that social media and multimedia can have on the brain.

If the Kindle is a great way for you to relax and read, then that's fine. It's part of the reason I wrote Lifetime. I was fed up with people saying, oh, you mustn't read a Kindle before you go to sleep. Well, the data behind that statement is weak at the very best. Well, I read something online that was like the amount of light quantity I would be getting if I turn on a light would be significantly more than the amount I'm getting from my Kindle, which feels very true to me. Like the room feels generally so much darker, which feels more conducive to my sleep. Would you say it's more about the quantity of the light,

or people say there's like this difference between back light and front light. and how that's impacting your eyes. That's a really good point. But the first point to make is that there's the visual comfort you'll get from the visual system, the rod and the cone light sensors. And of course, we discovered that there's a third light sensor within the eye, which is completely different from the rods and the cones. So there are these light sensitive ganglion cells.

So the cells in the eye whose projections go out of the eye and form the optic nerve, about one out of every hundred of those cells is directly light sensitive. And they are the receptors that are picking up light and feeding it directly into the master clock within the brain. Relatively speaking, they need a lot of light for a long duration. And so it's trying to tease apart those different effects. Now, having said that, we do know that the rods and cones can modify the behavior of those light sensitive ganglion cells. but in ways we don't fully understand.

It's turning out to be a very complicated sensory system. And it's further complicated by the fact is that we've got really very little idea of the ecology of human light exposure and what that does to us. So there's a lot of extrapolation from lab studies, which is fine. But we've now got to get out there and take the empirical measurements and find out what's really going on. And, you know, recommendations are flying all over the place. but they're in my view not really strongly supported by the science. But if it's low light, it really doesn't matter. What these receptors have a bell-shaped response curve.

They may be maximally sensitive in the blue, but they're still sensitive either side into the shorter blue and the longer green red. So if the light is bright enough, it won't matter what the wavelength is. If it's very dim, then the wavelength the color will matter. So in theory, it makes sense to move it away from the blue into, let's say, green and orange and red, which the visual system can see perfectly well.

But as I say, the data supporting that impact is not very strong at all. So blue blocking glasses, there's no evidence that they actually work. I feel like a lot of people's hearts just broke when you said that. Sorry, it'll be a heartbreaker. But you raise a very interesting point, because, there is going to be a placebo effect. But is it the blue blocking versus just the reduction in the overall amount of light, which is essentially what's going on? I always feel like that makes the biggest difference for me. My overall space feeling dark impacts my ability to feel calm and

start to go to sleep so much more than even if I'm on my phone, but the rest of the room is dark versus if the overhead lights are on and I'm on a book. I feel so much more sleepy if I'm on my phone. I was just talking to a colleague. He's a young father and he settles his sun down in the darkness of the nursery, and he says he falls asleep within minutes. And the baby's sort of awake still because it's darkness. We did get a lot of questions from listeners who are new parents, who are having problems with their own sleep, and we're worried about the impacts of their sleep on their health. What would you say to a new parent?

You raise an incredibly important point, and we should just backtrack a bit. So if you look at the way that child rearing occurred 50 years ago, then most people were part of an extended family. So the childcare was disseminated between the parents, between grandmothers and sisters and aunts and all the rest of it. Within a relatively short few generations, we've become nuclear families, where the childcare is a responsibility of the parents and usually the mother. And that's completely abnormal. If you look at the primates, the great apes, the monkeys, they all have distributed parental care for their offspring. So what the advice is that maybe says is, oh, just sleep when the child is sleeping. Well, that often doesn't work for the mother.

And of course, as a result, mothers get tired. They feel as that they're failing and they're not coping. And of course, they've never evolved to be the sole caregiver. So before a child arrives into the household, you've got to get some. set up a support structure whereby if you need that nap, you can call a friend or a relative or whomever and say, look, I need two hours of sleep. Can you just come and do some babysitting for me? And not be afraid to have that support structure in place and certainly not feel a shame, ashamed that you're chronically tired and may actually be more emotional and be more depressed as a

result of that chronic sleep loss. So part of the problems we're facing is because of the way society is shifted. And to some extent, not for everybody, I appreciate, can compensate by getting a support network in place. And you must do that. Again, not to feel guilty and to try and get as much support as you can. You seem sort of anti-napp, though, in your book. You don't seem like you're the biggest nap fan. I'm not the biggest nap fan. I guess it's all about moderation. So a short, 20-minute nap, occasionally, it's fine. Certainly the data suggests that you can have a more productive second half of the day with a short 20 minute nap. Where you need to be careful, and we see this in our teenagers, is that they have very shortened

nighttime sleep, they're delayed chronotype, they're doing social media and all the rest of it. So the alarm clock is driving them out of bed early. They struggle through school, some actually falling asleep at their desk, and then they'll get home from school, and then they'll take a two-hour sleep. Now that is fairly close to bedtime. That pushes back the sleep pressure that night, meaning you're going to further delay sleep. And so the next day you're going to wake up tired, you're going to need a longer nap, and I think you have to be careful you don't fall into that longer naps, shorter nighttime sleeps, because ideally our sleep should be during the night

phase. My view would be short 20 minute nap. Okay, perhaps don't be too dependent upon it. It's an indication that you're probably not getting the sleep that you need at night. and therefore look to what you might do in that context, just watch the fact that it might get longer and longer. That's my concern about naps. Our stomachs and our metabolic systems also function on a circadian rhythm. Oh, absolutely. Yeah. Can you share a little bit about the effects of eating at different times of the day and how that can impact all parts of our bodies?

If you think about the metabolism while we're awake, we're taking in calories, we're eating, we're taking in that food and we're burning it as we're active during the day. But at night, to survive, we're mobilising stored calories. So we've got completely different metabolic states. And that's important to appreciate. One of the other interesting bits of information is that during the 1100s, the main meal of the day was breakfast. By the Tudor times, so let's say 1,500s, 1550s, the meal had shifted to a bit later, so it was sort of lunchtimeish and with relatively small meals before bedtime.

And of course with industrialisation, where the home and the workplace are completely separated, we've changed our eating habits so that we're now in a rush for the long commute into work, so we often don't have time for breakfast or for the school bus to arrive, so we have minimal breakfast, we have a rushed lunchtime, and then we finally get home in the evening. we put the food into the microwave and it's high fat, it's high sugar, and we love it because we're hungry and in fact, tiredness promotes hunger. So our eating habits have changed radically and our biology is not caught up with it. So we are programmed to sort of essentially utilize food and glucose during the

first half of the day rather than the second half of the day. Some really nice experiments from the University of Chicago, looked at individuals who had had an infusion, a single glucose meal, breakfast, lunchtime, and evening. And it was cleared rapidly during the morning, pretty rapidly at lunchtime, and then for the evening, the glucose hangs around for a much longer period of time than during lunchtime and breakfast. So you've got high levels of glucose before you go to bed, and that is much more likely to be laid down as fat, of course, and of course the high levels of glucose predisposed to type 2 diabetes and other metabolic abnormalities such as obesity. So our feeding time across the day really matters. And certainly since I saw those data, we've now

shifted our main meal of the day where we can much earlier and very sensitive not to eat large meals later in the day. What would you say to people who say, I'm never hungry when I wake up in the morning. Like, I just am not hungry until later in the day. I get that. I often feel like that, but I try and have some sort of a breakfast in the morning, some cereal, something, you know, nutty, milky that is sort of high fiber will sort of fill the stomach and be digested. It's really tricky because we live such pressurized lives. We shift that late evening meal. And it's also a social time when the family often gets together or partners get together. have that bonding meal in the evening. So it's really tough to break that habit. But I can remember from

my grandparents, my grandfather used to come home for lunch. And it was a big lunch. And it was always a much lighter supper, you know, afternoon tea or a really light supper. It's like child care. It's something that's changed really rapidly. And our biology hasn't caught up with it. I very rarely get genuinely excited about skincare, but this is one of the most innovative products that I have come across in years, and I'm so obsessed with it. I've been telling all of my friends to get it, so now I need to tell you guys. Here's some science first. Your skin isn't just getting older. It's being actively broken down by something called senescent cells. These are cells that have stopped functioning but refused to die. They sit there releasing inflammatory

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metabolism. And there's even evidence that they can interact and communicate with the brain. And what's phenomenal is that these bacteria have circadian clocks. Their clocks communicate with the clocks in the lining of the gut. And they work together in harmony to optimize metabolism. And if you destroy those gut bacteria, you can set up major metabolic problems. I think it's one of the great revolutions, in a sense, that there's that intimate association via clocks between a bacteria and us. It's wild. And again, that's a bidirectional relationship. So something like your morning light viewing would ostensibly be helping your microbiome and something like keeping your microbiome as robust as possible would be helping your circadian

clock? Yeah, that's a really good point, but that's the problem with night shift workers. They have completely disrupted circadian biology. And of course, worth bearing in mind, higher rates of type 2 diabetes, higher rates of obesity, and all of those issues, metabolic issues, and of course, that will be acting against their gut biota. Can I get your best tips for night shift workers? Well, there's an increasing part of the population is doing night shift work. We need to think as a society whether we have to do night shift work on every occasion. But I think it's a genie. The 24-7 society is a genie that's out of its bottle.

And we're never going to put it back in. So what we've got to do is find ways to mitigate some of the problems that you see. So after an extended period of work, the drive home. Study a couple of years ago from the UK showed that 57% of junior doctors after the night shift had either had a crash or a near-miss driving home. So why aren't we advising all of our night shift workers to have an app on their phone, which is detecting a head nod or a movement of the car, to wake them up if they're starting to fall asleep? Because that's sort of easy.

Knowing that night shift workers have higher rates of metabolic abnormalities, but also cancer and coronary heart disease, it's worth bearing in mind that the World Health Organization, looking at the data that has stated that night shift work is a probable carcinogen, higher rates. of breast cancer, colorectral cancer, and a metrial cancer in women night shift workers. So why aren't we having higher frequency health checks in that group before these problems become chronic? And it's worth bearing in mind that there are things you can do about it. It's amazing data has shown that if you have an unhealthy lifestyle as a night shift worker versus a healthy with lots of exercise, you know, low fat, low sugar food, you can reduce the chances

of developing type 2 diabetes considerably. And we're not making that education and that advice available. Knowing, for example, that the divorce rate in some sectors is six times higher in night shift workers compared to day shift workers. We should not only be advising our night shift workers about the issues that they may encounter, but also their partners. It's not that your partner has turned into a monster. This is an inevitable consequence of driving your biology,

outside of its normal biological range. Another area which I think could be useful, and it goes back to where we started, which is the chronotype. It might be useful to match the chronotype of the workforce. So when you're young, you tend to be a later chronotype and some of us are very late. So I'd have been great on the night shift. I'd have been hopeless on the morning shift. And so we should maybe, where possible, match the chronotype of the individual to the demands of working at night. The other thing that is important to appreciate is that the big health problems, the cancers, the coronary heart disease and all the rest of it, build up over years. I don't have the data to back this up, but I wonder if you limited night shift work to five

years, let's say, and then you cycled out of it for five years, whether you wouldn't turn back, as it were, the clock about some of these problems. However, having said all that, I think we've also got to take on board that night shift work, and poor sleep in general is almost a hallmark of lower socioeconomic groups. People don't want to do night shift work, but to get enough income, they'll do it because it pays better. These are usually the groups that are least supported. So I think there's a real socioeconomic issue here too.

If somebody is listening and they have to do night shift work and they're a little bit freaked out at this point, what are some of those things they can do on? a daily basis, like integrate into their lives right now to feel as good as possible and to mitigate some of this damage? There is a lot. I mean, we've sort of touched on exercise and we've touched on good nutrition. That has a big impact upon the problems that you will face as a night shift worker. Other issues would be to make sure that when you get home, you go straight to sleep and get the

sleep then, rather than waiting, doing the chores, washing up or whatever it is, than later in the day. because that's when you will be your most tired. As the day increases, the biological clock gives you a stronger and stronger drive for wakefulness. So that's why it's important to get your sleep in early on. The other thing that many night shift workers do is to have a good long nap immediately before going on to the night shift.

So they're pushing back the sleep pressure, which gives them a bit extra wakefulness time. When you're working, keep the lights as bright as you. can because that will increase levels of alertness and reduce drowsiness and therefore less likely to fall asleep. And certainly when you get back home and, you know, the sleep pressure is really high and the clock isn't kicking in just yet saying you've got to be awake, you've got to be awake, keep the lights low, minimize alertness and then you'll have a better chance of getting a better sleep as soon as you get back from the night shift. If you are a night shift worker, is it better to sleep on a normal schedule on your non-work days, or is it better to maintain your night shift schedule

for consistency? We don't know for sure in the same way that we don't know what's the ideal night shift schedule. And of course, it'll vary enormously, depending upon your chronotype and all the other things. Because the body clock doesn't shift with the demands of working at night, I would stick to a normal, regular sleep wake cycle as if you were a day-active individual. You have a better chance of getting better sleep there. And it's also restorative sleep. So irrespective whether you're a night shift worker or not, many people will have chronic sleep deprivation throughout the week when they're working and then try and catch up at the weekend. It helps a bit, but you can't fully compensate for chronic sleep deprivation during the week. So it's best if you

can maintain a stable sleep week schedule. That makes sense. The other thing that I really want to Sean is how our biological clock impacts diseases. I found that that graph that you had about the various times of day that like diseases would peak was so fascinating. So you said osteoarthritis pain is worse in the early evening. Exema and psoriasis itching peaks during the late evening and overnight. Migraines tend to happen in the morning if you have a morning chronotype and in the evening if you have an evening chronotype. Can you share a little bit about why that would be and then any action steps that you think we should be taking, having that information? Yeah, we're very different creatures across the 24-hour day.

So no great surprise that our vulnerability to illness changes across the day. You know, between 6am and 12 noon, there's a 50% greater chance of having a stroke or a heart attack than any other time of the day. So being aware that we have this variation in pain thresholds, in the chances of having a migraine, in dementia, for example, sundowning, all of these sorts of issues, means that when we think about a medical intervention, can we time that intervention most appropriately? This is the whole field of chrono-pharmacology, which is giving a medication when it's best able to have its effects.

So osteo versus rheumatoid arthritis, when do you take your pain medication for those different bone conditions? Some studies from Spain a few years ago suggested that taking your anti-hypertensives if you've got high blood pressure before you go to bed versus first thing in the morning when you've woken up can reduce your chance of having a stroke by almost 50%. Now that's huge. Now, why is that? It's all about the half-life of these drugs. That dangerous window for 18m and 12 noon. You wake up, you put it around a bit, you do something, or you think, oh, I better take the anti-hypertensives. And the time they kick in, you're almost past the danger zone,

because they have a long time to get processed and they have a long half-life. But if you take them before you go to bed, then eight hours later, the drugs still are going to be in a high concentration and will intersect with that sharp rise in blood pressure, which is underpinning a stroke and heart attacks in those individuals who are vulnerable. There's a lot of evidence now emerging about when to take your drugs. One fascinating area is in anti-cancer, in chemotherapy. So a study on childhood leukemia looked at morning chemotherapy versus early evening chemotherapy.

The kids who had the evening, 75% were still alive at the end of the study period versus those that had it in the morning. It was 35%. So this is huge. Bill Horeski has done some work in ovarian cancer. Same drug, same concentration, two times of day. After five years, one group, 40%. percent were still alive. In the other group, 10 percent were still alive. Timing is really important.

Some studies looked at the flu vaccine a few years ago in 70-year-olds, and the antibody response in these 70-year-olds was three times greater if the vaccination had taken place in the morning versus the afternoon. And so it sort of underpins our dynamic biology, and are we integrating this information into our healthcare services, broadly not. I think there's got to be a radical rethink about integrating this knowledge into our healthcare sector. I'm an optimist, and I think it will happen. But it's going to be slow. I mean, there'll be a combination of the doctors we're training now, who will be more familiar with this stuff, and of course, the pressure from patients. Just asking the question, what time do I take my medication? Often the response will be, oh,

with a meal and you say, well, why? And they'll say, oh, well, it's compliance because most people forget to take their medication. That may have nothing to do with the best time to take that medication biologically. So one action step could just be if you are taking something regularly to Google if there is a time of day effect. Absolutely, yes. And then how you can take advantage of that. For example, proton pump inhibitors. We are often told to take them before you go to bed because that's when acid reflux happens. But actually, they're activated by food in the stomach. And so therefore, once those pumps are turned off by the PPIs, they're turned off for 36 hours. So you take them in the morning when you've just eaten, ideally you've had a breakfast, and then they're turned off.

And so at the time you get to the evening time, those pumps aren't producing so much acid, and therefore acid reflux will be reduced. What are some ways that we can use exercise to entrain or circadian rhythms. Yeah, that's interesting. We do know from animal studies that exercise can help set the clock. It's not as powerful as light. And so exercise and light together seem to act synergistically. So some studies in humans have shown that if you exercise in the morning outside, it's better for the sleep wake cycle. If we're going to work out inside, does it matter if we do it in the morning, in the evening, in the middle of the afternoon? It does.

So our core body temperature rises throughout the day, peaking in the late afternoon, early evening, which is when, for example, the finals of all the Olympic events take place, because they know that you'll get the best results. As we go through the day, your core body temperature goes up and your muscular efficiency increases and your ability to exercise more vigorously and longer increases. So peak exercise increases throughout the day. It will depend upon your chronotype to some extent. And there's some really interesting late people, for example,

doing the same exercise first thing in the morning versus late afternoon, early evening can be 28% more efficient in the evening compared to the morning. Of course, morning people are more effective early in the day. So exercise for longer and with greater vigor later in the day, as body temperature goes up. However, if you want to burn calories, then exercise before breakfast is a very useful strategy because you're still on nighttime metabolism. You haven't taken any calories in, and so you're dependent upon stored calories that you're burning up to keep yourself going. So what some people do is have exercise first thing in the morning before breakfast.

it's usually morning people can do that because they can get out of bed and they can do all this stuff before breakfast. Now, it has to be slightly careful that you don't go too close to bedtime because you can increase core body temperature too far and that can inhibit you getting to sleep because part of sleep initiation is a drop in core body temperature and if you block that drop in core body temperature, it's been shown it's more difficult to get off to sleep. So sure, exercise later in the day, greater power, greater sort of efficiency, but not too close to bedtime because that may delay sleep onset. If you're just like listening to this episode, you're like, my sleep schedule is terrible. I want a total reset. What can you do to get that? We've talked about morning light. We've talked about naps, making sure they're not longer than 20 minutes.

Exercise, we've talked about the importance of that, but not too close to bedtime. Food intake, again, shift it to earlier in the day. avoiding caffeine in the afternoon, and then during the end of the day, you're taking time to step back. You're de-stressing. You're getting out of that work mode, which is driving, you know, potentially anxiety and stress. All those things you can do during the day.

Before bed, reduce light levels, because the higher the light, the greater the alertness, and that will delay sleep. Stop using electronic devices, at least 30 minutes before you want to go to sleep. smartphones, I mean computers, I mean gaming, I mean all of it. But not my Kindle?

If the Kindle helps, then that's fine, and it's not a Stephen King novel or something that's going to terrify you. But as long as it's relaxing, that's fine. Ideally, avoid prescription drugs. Don't use alcohol. One of the things that many individuals are now doing is that they are routinely using alcohol as a sedative. And it's really important to think about what the Zed drugs and alcohol

are doing. They are sedatives. They do not provide a biological replacement for sleep. So some of the important stuff going on, like memory formation, processing of information, coming up with good ideas, can actually be inhibited by those sorts of sedatives. One thing that I think is really important is, you know, before bed, you avoid the discussion of stressful topics. And it's ironic. This is the time of the day when many couples have time together and to talk about kind of the stuff that's important to them. But actually, it can spiral out of control into a very stressful situation. We ban in our household any discussion of family finances before bed. And again, transition. You can't possibly flip a switch and go from the consciousness into the sleep state.

So have a series of things that you do. The bedroom itself shouldn't be too warm. I mean, 18 degrees would be around the recommendation because if it's too hot, you can't lose that core body temperature and therefore it's more difficult to get to sleep. Obviously keep it quiet. White noise can help if you've got noisy neighbours or whatever. Keep it dark. Again, minimising levels of alertness. And it's been very difficult, I know, but try and make the bedroom a haven for sleep. Remove all of the TVs and all of that stuff. And of course it's been difficult during COVID, so many bedrooms became offices. But try and convert them back into these wonderful cacoons of sleep. Don't clock watch. It's really interesting that if you have an illuminated

clock and if you wake up at night, the first thing you see is, oh goodness, I've only got two hours before the alarm goes off. And you get all stressed. So either cover it up or just use something else. You know, an old mechanical one. Because it doesn't matter how long you've got. It's when the alarm goes off. And as we've been talking about, 20 minute naps can be really useful. So two hours before the alarm goes off is really useful, productive sleep that you can have. It's worth bearing a mind. None of the sleep apps currently are endorsed by the Sleep Federations, and none are FDA approved. Now, that's coming. They're getting better, but really, they're not properly validated. We're early in that process. I think so, yeah. In the same way that if you want to lose weight,

you change your eating behavior, you weigh yourself in the morning, and you see a change in weight that reinforces your changed eating behavior. And of course, an app could be useful in that context. You've changed your sleep habits. You see you're getting more sleep or earlier sleep or whatever you want, and that can reinforce your behavior. So they have a potential use, but they're not there yet. And finally, in bed, try and keep to a routine. We've touched on that, free days and work days. I've worked in the States for eight years, and I did get the sense that Americans are more willing to spend money on their bed and their mattresses and their pillows, and I think that's a really healthy sign. A third of your lives will be in bed,

so why not invest in something that makes you just comfortable and wonderful? And I think it's worth investing if you can. Keep the bedside lights low. One thing that people use, and the evidence base, again, is not great, is things like lavender oil and other sort of smells, really to define the sleeping space. You smell that lavender and then you associate it with sleep. And in fact, some people will take, you know, the smell that they have in their bedroom or their partner's perfume or after shape and take it to a hotel and try and, you know, to define the sleeping space. And it makes sense, and there's some data emerging. It's not a huge amount of strong data above placebo. One very important point is if your partner snores. And this is a big issue. The first thing

you need to work out is whether they've got obstructive sleep apnea, which means that they're stopping breathing for a short period of time, then they're waking up gasping. That's a serious condition and it can be almost always resolved using these masks which force air, CPAP, for example. If they don't have, and so see a practitioner if that's a problem, if earplugs don't work and they don't for many, then find an alternative sleeping space if you've got it. Again, we've talked about sort of people getting shamed about things associated with. with sleep. It's no reflection on the strength of your relationship if you're sleeping in separate rooms. Chances though, it's a new relationship because you'll get better sleep. You'll be happier,

you'll be funnier, you'll be more empathetic, you'll enjoy each other's company more. If you wake up, then stay calm, find something that relaxes you and then go back to sleep. That is not necessarily the end of sleep. Now, the other thing is, of course, one shoe size does not fit all. Work out for yourself what works for you and then stick to it. And don't be made anxious by, you know, the sergeant majors of sleep shrieking that you must get eight hours or you must do this or you mustn't do that. If it works for you, fantastic, embrace it. Love that. Well, thank you so much, Russell. You are just a font of information, both in this conversation and in your book, which is absolutely brilliant. It has so much science, but it's just written in this way that's

incredibly accessible and readable and fun to read. So I appreciate you writing it and I appreciate you taking the time to chat with me today. Well, thank you, Liz. It's been a great pleasure and I hope we can chat again sometime. This is definitely going to be one of those episodes where I need to listen again and again and take notes because Russell shared so many ways to optimize our sleep that I want to be implementing. I also love how he's following the science and not just giving advice to basically freak out about things or to spend unnecessary money if the research isn't there and doesn't support it. Please share a link for this episode with anyone you think would benefit or just anyone you want

to talk about this stuff with. I am so glad that more people are talking about circadian rhythms and how important they are. So maybe you can discuss it with a friend over a cirque walk. And if you're new here, make sure that you're following the podcast on whatever platform you like to listen on. Just go to the main podcast page, the one that lists all of the healthier together episodes. You will see the word follow under the logo on Spotify. And then there's a little follow with a plus sign button on the top right of that same page on Apple Podcasts.

That way, all of the new episodes will show up right into your feed. So you will never miss out on one. And we have some incredible episodes coming up, including an episode about the societal pressures that we face as women and how to claim your power within all of that. And one all about how to stop dieting and land at your happy weight. So make sure that you're following so you do not miss out. Okay, I love you and I will see you next week on the next episode of the Healthier Together podcast. When it comes to wellness, you're going to get the best results by focusing on the big needle movers. A lot of us spend a lot of time trying to optimize that last 1%, which creates a ton of stress and it actually doesn't help our health that much.

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