The ultimate guide to better sleep with Dr. Sophie, sleep scientist & Royal Marines consultant

We’ve all been there: tossing and turning, checking the clock, and stressing about not getting enough sleep. But what if the secret to a good night’s rest isn’t in a pill or a product, but in changing your mindset and daily habits?

We dive into what really happens when we don’t get enough sleep, from the psychological effects on our willpower and relationships to the physiological impacts on our long-term health.

Sophie debunks common myths about blue light, alcohol, and cheese, and explains the critical difference between occasional poor sleep and true insomnia. She also introduces us to Cognitive Behavioral Therapy for Insomnia (CBT-I), explaining why it’s a more effective long-term solution than sleeping pills.

Finally, we walk through the simple, science-backed habits you can adopt right now to improve your sleep, starting the moment you wake up.

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Transcript

Jonathan Wolf: Sophie Bostock, thank you for joining me today. 

Sophie Bostock: Thank you so much for inviting me. 

Jonathan Wolf: It's a pleasure. 

Now we like to kick off our show here at ZOE with a rapid-fire Q&A with questions from our listeners. Are you ready to give it a go? 

Sophie Bostock: I'm very nervous, but I'm ready. 

Jonathan Wolf: And you told me you often listen to the shows, so you know the rules, yes or no, unless you absolutely have to give us a sentence.

Sophie Bostock: Okay. 

Jonathan Wolf: Can eating cheese give you nightmares? 

Sophie Bostock: Unlikely. 

Jonathan Wolf: Is blue light from screens important for preventing good sleep? 

Sophie Bostock: Often overestimated. 

Jonathan Wolf: Can eating more fiber improve your sleep? 

Sophie Bostock: Yes. 

Jonathan Wolf: Is sleeping too long linked to poor health? 

Sophie Bostock: Yes. 

Jonathan Wolf: Does a lack of sleep make couples more likely to argue?

Sophie Bostock: Yes. 

Jonathan Wolf: I like that. It's another explanation from my life. Okay, and finally, what do most people get wrong about sleep? 

Sophie Bostock: I think most people underestimate the importance of our sleep beliefs and our mindset around sleep. 

Jonathan Wolf: So I was thinking this morning that I was really looking forward to this because, like most people, I feel I don't get enough sleep.

I was actually on holiday last week, and I was sleeping in, to my natural rhythm later, and it was a huge shock to wake up early enough this morning to do this podcast, Sophie. And I know I'm not alone in this. I think lots of listeners are in exactly the same place. 

Sophie Bostock: Well, and you have the advantage of all of these wonderful conversations with scientists telling you how to sleep well. If you can't get it nailed, Jonathan, what hope is there for the rest of us? 

Jonathan Wolf: Poor willpower, I think.

Sophie Bostock: Well, let's unpack that. You know, I think we often blame willpower, but when we are sleep deprived, our self-control reduces. We sabotage our own sleep by being tired.

The moment that you have a poor night of sleep, the following night, it becomes harder to switch off Netflix or whatever streaming service that you used.

And so we can get into a negative pattern. 

Jonathan Wolf: Could we actually talk about what happens if we don't get enough sleep? 

Sophie Bostock: I think everyone's probably familiar with the superficial aspects of what happens. You know, we get a bit more irritable. Our emotional control centers, no doubt, become more sensitive, more dysregulated.

You asked me earlier about do sleep sleep-deprived couples argue more, and we know that they do. Not only are they more argumentative, but also they're more accusatory in their problem-solving approach. 

We tend to increase our perception of threat when we're sleep deprived. And I think this is an incredibly important theme that will probably sort of run through this conversation because that sense of threat that is not just psychological, that is very much physiological.

So if your brain and your body are feeling on edge, then what happens? Amp up that sensitivity of the stress response. This physiological cascade which has evolved to help us to fight or flee or freeze in the face of danger. 

And for most of us, that means increasing adrenaline, increasing cortisol, increasing blood pressure, increasing the blood flow to the muscles, perhaps making us sweat a little bit more, mobilizing blood sugar, blood glucose, so that we're fired up for action.

So that is an evolutionary response to being in an environment where we couldn't sleep well. 

So if you think about our hunter-gatherer ancestors, you know, if they were camped out next to a den of saber-tooth tigers, there was an evolutionary advantage in being in this increased state of fight or flight. They were much less likely to get eaten. 

Over hundreds of thousands of years, our brains have learned to associate sleep loss with potential danger, and so we are more on edge. So that helps to explain those emotional responses. 

Also, the physiological responses that over time our immune system becomes dysregulated, more like exhausted almost. Because we are constantly ramping up our immune response, ready to fight infection. 

We also see that we're at increased risk of hypertension, of inflammation. These diseases, which help to increase risks of heart disease, of diabetes, disrupted blood sugar. I could go on. 

But I think the other aspect is cognitive function. So we know that the brain does a huge amount of mental processing overnight. We are consolidating memories. We are pruning back information so that we can focus on what is most important. 

So sleep is really helping us to learn and innovate. So when we're sleep deprived, that sort of brain fog, that slowness to respond, slower reaction time, that can also have knock-on effects and increased risks of accidents and things like that. 

So we've got very acute effects, and also more chronic long-term effects on health.

Jonathan Wolf: Is there a sort of real scientific evidence that if you are not sleeping as well, it's going to affect things you're talking about, like heart disease?

Sophie Bostock: It's a really good question, and we have incredibly compelling evidence that lack of sleep increases your risk for this vast number of diseases. 

And actually, a recent study came out and said there are 172 different diseases which are associated with poor sleep. 

But those types of studies typically look at a large group of people. They look at how they're sleeping, perhaps at one, maybe two or three points in time, and see who goes on to develop disease. 

So we can't say for sure, because there are so many things which impact on those disease processes, it's sometimes very difficult to really pin down the extent to which sleep is the most important driver.

I'll give you one example because there's often headlines around how lack of sleep causes dementia or cognitive decline.

There was quite a well-known study that was published a few years ago where they took 8,000 adults. It was a good quality study in the U.K. They measured sleep at several intervals when people were in their fifties and sixties. 

Over time, they showed that those people getting fewer than five hours sleep were 30% more likely to develop dementia.

And that sounds pretty scary. 

Jonathan Wolf: Yep. 

Sophie Bostock: But we've also got to remember that the absolute risk, the actual number of people that went on to go and develop dementia, I think it increased from something like 5% to 7%. 

So there was an increase of 30%, but the absolute numbers were still very low. The vast number of people who were sleeping for five hours or less didn't actually go on to develop dementia during that study.

So more often than not, we are talking about increased risk. So if there are people listening to this with really shockingly bad sleep right now, please don't despair. There are so many factors that go on to influence your risk of ill health. 

Jonathan Wolf: So it's not inevitable, you're just saying, but it is a significant increase in risk, you'd really like to make a difference. 

And it's not just like my short-term performance and how I feel, it's genuinely linked to things that could end my life, like heart disease. 

Sophie Bostock: Definitely disease process. I think the most straightforward link, the things that are easiest to notice are the links with next-day focus, concentration, reaction time, but also mood.

A lot of my interest has been around how does lack of sleep impact on mental health, but perhaps more importantly, if we improve sleep, can we improve mental health? And we know that that is the case. 

We now have data from 60, 70 different randomized controled trials, which have shown that actually if you improve someone's sleep quality, they will be less likely to be anxious, less likely to be depressed. 

So this is a bidirectional, a two-way relationship. And I think very often we talk about the negatives. You know, lack of sleep is bad for your health, but actually, when we turn that around, we have this incredibly powerful lever to improve health and wellbeing.

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Jonathan Wolf: So I think anyone listening to this is saying, Oh, it sounds like I should try and get a good night's sleep. 

Sophie Bostock: Actually, we can't really try and have a good night's sleep. This kind of comes onto the mindset point, but if you go to bed thinking, I really need to try and have a good night's sleep, there is pretty good evidence that that will not improve your sleep.

You know, the harder you try, the worse your sleep comes. This is why I am always trying to moderate people's sort of perception of risk around sleep. 

The more we think lack of sleep is really bad for us, it's incredibly important that I get very good quality sleep, the more anxious about it we become.

If that anxiety leads to quite a rigid belief that I must sleep well, otherwise there are going to be terrible consequences that is pretty much a hallmark sign of insomnia. 

And that is a belief that sleep is so important that tomorrow is going to be wrecked if you don't get a good night's sleep. 

The more sort of rigidly we believe that, the more tense we become when we get into bed at night and the slightest thing can kind of set us off.

You know, there's a noise, we're a bit too hot, and we start to become more worried we're not going to sleep well. And sleep quality can decline. 

Jonathan Wolf: It's interesting, I'm listening to thinking about an analogy with what we do about nutrition, and of course we say that the food you eat is the most important thing for your health, but also we absolutely believe that nothing is off the table.

You don't need to be perfect, and in fact, that trying to be perfect actually is the enemy of having this long-term successful attitude. 

Sophie Bostock: This is incredibly similar to good sleep health. I'll give you an example: for a client that I worked with, he said, My sleep habits are pretty shocking. I'll be on my phone before bed, maybe I don't get enough natural light, probably don't get enough exercise, and I wake up a lot during the night. 

And he said, But then I went on holiday and I fell [00:10:15] asleep really easily and I slept through the night and I hadn't changed any of my other sleep habits. 

So he'd still be in on his phone before bed, but actually, he'd slept through the night, and most of us can kind of see, Ah, maybe there was a difference there in his sort of stress levels during the day.

Perhaps his mindset around sleep. If he was quite a high-powered executive, you know, he's thinking, I need to sleep well so I can perform well at my job. Suddenly, he goes on holiday, that pressure is removed. He's changed none of his habits, but he sleeps well. 

Jonathan Wolf: What I'm picking up is you're saying that anxiety about sleep might be my worst enemy.

Sophie Bostock: I would probably say the number one reason for insomnia is anxiety about not sleeping well. And very often there will be a broader, more generalized anxiety that's linked to poor sleep.

But as insomnia progresses, it's that worry about not sleeping well that can push people and perhaps maintain greater levels of arousal.

Jonathan Wolf: So Sophie, if we stop doing podcasts about sleep and you stop talking about it, are you telling me that everyone will sleep better? 

Sophie Bostock: Ah, so this is the interesting split. 

We have a general population, and if you imagine, I like to think of perhaps 10% or 20% of people. Those who are vulnerable to insomnia, those are the ones who perhaps worry about sleep a little bit too much. And this is where the podcast might be a little bit unhelpful sometimes, where we're putting more pressure on people's sleep. 

But then we've got another group, probably 50% to 60% of the population who potentially aren't worrying about sleep enough, and those are the people who are maybe skimming through a little bit less sleep than they need, getting away with poor quality sleep, but not functioning at their best.

Jonathan Wolf: Let's talk about that 50 to 60%, because you did describe that not sleeping has a lot of impact and I've definitely felt this in my own life. 

I'm sure that anyone who's ever had small children would've almost had that experiment right where you slept normally. You decide to have children and then you suddenly discover what it was like to never get more than four hours sleep at a time.

Sophie Bostock: Yeah. And I would perhaps say that in that 50% to 60%, this is a rough estimate, most surveys suggest that maybe one in three people are routinely getting fewer than the recommended seven hours of sleep. 

People often go through a journey where they have occasional periods of poor sleep. Depending on which survey you look at, that's anything between a third to 50% or 60% of the population.

There are some groups that are at greater risk. So, of course, you mentioned parents of young children. I would also put women going through perimenopause and menopause.

Some surveys, and I think there was a ZOE survey that suggested that as many as 80% of them were dissatisfied with their sleep. So huge numbers. 

Jonathan Wolf: One of the things I'm struck by is a huge fraction of people who become ZOE members, talk about sleep as one of the things they want to improve. 

What is causing this today? Why is it that we're talking about sleep now that presumably we wouldn't have been talking about when we had the saber-tooth tigers next door?

Sophie Bostock: There's no doubt that if you look at sort of hunter-gatherer population, some of them don't have a word for insomnia. You know, their problems with sleep seem to be few and far between. 

So there is something about our modern lifestyles which is definitely causing our sleep to be under threat. 

It's very difficult to talk about sleep and lack of sleep without talking about technology and in particular without talking about smartphones, because the last sort of 20 or 30 years have seen this explosion in people having constant access to a device that gives them information. 

We as human beings are essentially always looking for information. Our brains are hungry for information, which is going to help us eat, help us socialize, help us feel safe.

And so we have given ourselves access to this machine, which will constantly update us and it gives us this little hit of dopamine, dopamine when we do that. 

So they're created to be very addictive and I think depending on the statistics that you look at, but at least perhaps one in four of us will suffer withdrawal symptoms if we are not close to or using our phone.

We are so used to instant access to things. We no longer wait, we no longer pause. So I would argue that in modern life we are always on. We are always stimulated .

A lot of the people that I meet with have poor sleep, even if they don't have a severe insomnia problem, they have a busyness all day. 

I think we are increasingly struggling to just be rather than do, and in order to sleep well, our brains need to be okay with just being, with just being able to relax. And that is hard. 

If we go onto Instagram and ways to relax, they will be: Well, you better do a cold plunge, you better do some meditation, you better do this, that. I'm going to go for a hike in the mountains. And of course, there are lots of wonderful things there.

But if we're constantly trying to cram as many things as we can into our days and take pictures about it and tell people about it, we're never really resting, and in order to rest well at night, I would argue that we need to be able to rest during the day. 

Jonathan Wolf: So for you, these phones are the biggest thing that is making sleep harder now than it was in the past.

Sophie Bostock: I think they have a lot to answer for.

What we've seen in research where people have turned the mobile internet access from their phones off, so they can still use them to call, and they end up with more time. What do they do with that time? Well they socialize in person and they go and exercise.

So certainly there are lifestyle factors, all of which relate to both mental health and sleep, which are often linked to phone and technology use. 

So we are a more sedentary population than we were 50, 60 years ago. We know that exercise is incredibly important for sleep, so we've got these very active brains and these perhaps less active bodies.

And then all the work that ZOE does around helping support people with healthy diets. Diet, of course, has a role to play with sleep as well, so we know that. 

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In general terms, ultra-processed processed foods tend to be linked to worse sleep, whereas plenty of fresh fruit and vegetables, high fiber diets, protein, all of those things are linked to better sleep.

Jonathan Wolf: We get so many questions from our listeners about sleep and very specific questions. So I would actually love to now run through the most popular questions that we get.

But I want to get your expert opinion, there were a whole bunch of these different questions: what is forest bathing and can it help you get more sleep?

Sophie Bostock: Oh, forest bathing. Lovely idea. I think the Japanese word for it is, and I will pronounce this wrong, but Shinrin Yoku or something, and the idea is that you are immersing yourself in nature. 

So in Japan, they have a lot of forests and so the research has mostly been done in forests. But actually, we know that we get these benefits in terms of reducing the stress response, lowering blood pressure, lowering breathing rates when we as human beings are exposed to natural environments.

So it might be a green space. It can also happen with a blue space. There has been research suggesting that the more time you spend in nature, not only is it good for your sleep, also for your general mental health, it goes back to that idea of doing versus being.

Very often, if we are in a natural environment like that, we get this sense of awe. It's that awe and sort of natural mindfulness of being in natural environments that you're like, Oh, look at that view, that very often will ease that stress response. 

Jonathan Wolf: Amazing. 

Another question, completely different, back to people with insomnia: can cognitive behavioral therapy, often called CBT, help? 

Sophie Bostock: Yes, it is the number one recommended treatment for insomnia. 

So cognitive behavioral therapy for insomnia is a toolkit of different techniques. It both includes the things that we typically think of as sleep tips. So sleep hygiene, that is one aspect of CBT for insomnia, but it goes much deeper. 

So it includes cognitive techniques to try and identify and address unhelpful thoughts about sleep. So we talked about the thought that I must fall asleep.

Perhaps the belief that I'm a bad sleeper, tomorrow's going to be a disaster if I don't sleep well, that sort of thing.

It also includes very often a technique called sleep restriction therapy where you actually go to bed later than normal. And what this does is it delays your bedtime, it increases sleep pressure.

So the more hours that you have been awake, the more pressure you build up to sleep. And by restricting your time in bed, you can help people to have less fragmented sleep. 

So that's one of the most powerful tools within CBT for insomnia. 

Jonathan Wolf: As part of this like intervention, you're actually making people go to bed later. 

Sophie Bostock: It sounds totally counterintuitive. 

Jonathan Wolf: It does sound slightly crazy.

Sophie Bostock: There's been research showing that just sleep restriction alone can help people with sleep quality. 

So you would usually start by keeping a sleep diary so you get an idea of what is normal for me. And what you'll typically find with people with insomnia is that they will go to bed perhaps quite early because they're quite worried about not getting enough sleep.

So let's say they go to bed at 9:00 PM and they set the alarm at 7:00 AM. Then they've got 10 hours where they could actually be in bed, but they'll say, Well, I only sleep for five of them. So they're actually only asleep for half of the time that they're in bed. 50% we would say is their sleep efficiency.

So where you've got someone who is sleeping for less than 80% of the time that they're in bed, this sleep restriction technique can be used to narrow their time in bed. So it makes them more tired and helps them to sleep through the night. 

Jonathan Wolf: It's really interesting. I feel like you've talked about insomnia a number of times and it's made me realize, I don't really know what insomnia is like.

You are describing something that is a long-term situation. How do you differentiate between insomnia and somebody who feels like I'm just going to bed too late and waking up too early? 

Sophie Bostock: So there's no doubt that there are insomnia symptoms, which a lot of people might have experienced. 

So a difficulty falling asleep, perhaps waking up during the night and not being able to fall back to sleep, or even just waking up in the morning and feeling totally exhausted. That can also be a sign of insomnia. 

But the clinical definition is a difficulty or dissatisfaction with sleep at least three nights a week for three months or more that has a negative impact on daytime functioning. 

So if you have poor sleep and actually you're coping really well during the day, it doesn't really impact you, that's not insomnia. 

The final part of it is that there has to have been adequate opportunity to sleep. So if you have a young mom of a baby, you know they probably haven't had the opportunity to sleep. That's not insomnia, that's just parenting. 

Jonathan Wolf: Alright, completely different question: Does alcohol help you fall asleep more quickly?

Sophie Bostock: Alcohol can help to sedate you, so it can help you relax and perhaps pass out or get into something which looks and feels like sleep. 

The problem is that when you get into sleep, the quality of that sleep can be very disrupted. So yes, it can make the time to fall asleep shorter. 

Once you are asleep, you tend to end up with very fragmented sleep. You have this REM suppression. So REM is rapid eye movement sleep often associated with dreaming, and it's really important for your emotional balance. 

What tends to happen with alcohol is that you get this delay till REM and then perhaps just before you wake up that you get these incredibly vivid dreams.

So you think you've dreamt more, but actually you've had a reduction in the amount of REM sleep. So you might end up feeling a bit sort of irritable and perhaps not quite have the same memory of the night before as you would've had if you'd had a good night's sleep. 

Jonathan Wolf: And Sophie, I have a question just for me now as I listen to this.

So I feel that now at age 50, if I even drink a small amount, it has a terrible impact on my sleep. But I'm sure that in my twenties, I could drink and sleep fine. Is that true? 

Sophie Bostock: It probably is true. I mean, there's lots of things going on there. You may well have developed some sort of tolerance in your twenties.

Many students, I feel, probably build up some sort of tolerance to alcohol and we’re less likely to experience hangovers in our twenties and thirties. 

Generally speaking, our physiology is more adaptable, more flexible. Certainly as we get older, typically our sleep becomes more fragmented, lighter, we have less deep sleep. We also get a little bit less REM sleep. 

That is an age-related change. It doesn't mean that we can't protect good quality sleep and with good sleep habits. You often find really good sleepers in their sixties and seventies, but they're more vulnerable to sleep disruption. 

So a sleep saboteur like alcohol can become more powerful as we get older.

Jonathan Wolf: And so as we're getting older and if we are trying to have great longevity, maximize health years and just sort of enjoy all those years. So show up good through this. 

What is your perspective on alcohol? 

Sophie Bostock: It comes back to what we were talking about earlier, that if you are too strict with anything in life, if you are removing perhaps social occasions with family where everyone, I'm thinking about my dad's 80th birthday, and everyone drinking champagne and really enjoying that social scene.

Do you need alcohol to enjoy that? Probably not. But if you had a glass of champagne, I don't think you should feel guilty about it either. 

Generally speaking, from a sleep perspective, if you are going to drink alcohol, drink it earlier in the day. We don't want to be drinking alcohol close to going to bed.

I've certainly found personally that I've reduced the amount that I drink because I feel better without it. But I know that there are some benefits to polyphenols, for example. Listen to Tim Spector talk about some benefits of red wine. 

So everything in life is a balance and for me, alcohol is a sleep saboteur.

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Jonathan Wolf: If someone was saying to you, I'm drinking a glass of wine every night and I want to improve my sleep quality, what would you say to them? 

Sophie Bostock: I would say, let's do an experiment. I'm all about self-experimentation, and if that one glass of wine is had earlier in the evening with a meal, it might not be disrupting sleep. But we don't know that until you try it. 

And actually, I would say that one of the most useful things about wearable devices, tracking devices for sleep is, I've worked with a number of people who have seen the impact of alcohol on both their sleep quality and their recovery the following day, and they've been like, Alcohol really has an impact on me.

It is that objective data that has actually helped them to reduce their alcohol consumption.

Jonathan Wolf: Alright, let's move on past alcohol. What about sleeping pills? Are they a good solution if you need to sleep better? 

Sophie Bostock: There are certain times in people's lives where sleep can become so difficult that I think, going to see your doctor and being prescribed a sleeping pill can give people some short-term relief.

So I'd very much see sleeping pills as something for severe sleeping problems. You've kind of tried everything, you don't seem to be able to get a handle on your sleep. 

Under the guise of a medical professional, you take these pills, which for a few weeks hopefully are going to help you to get to sleep. 

The quality of sleep that you get from sleeping pill-induced sleep is not the same as natural sleep. You very often end up with this sort of hangover, groggy effects the next day. 

The quality of the sleep will be not quite as restorative as it would've been without a sleeping pill. 

We know that in the long term, it can be quite difficult to come off some sleeping pills. Some of them are quite addictive, and there's both a physiological aspect to that, but also a psychological aspect. 

Because you've got this solution that you believe is going to help you sleep well. I actually often talk about the importance of the placebo effect.

So we know that roughly two-thirds of the effectiveness of sleeping pills on average is actually down to a placebo effect. This is why sleep beliefs are so important. That I could give you a little sugar pill and I could say, Jonathan, this is going to help you sleep better. And on average, you will fall asleep about 10 minutes faster, which is not dissimilar from taking a sleeping pill.

Usually, I will try everything else other than sleeping pills, mostly because behavioral and psychological interventions are more effective in the long term. We were talking earlier about CBT for insomnia and how that's the number one recommended approach for insomnia. 

So we talked about some of the ingredients: we talked about sleep hygiene, we talked about cognitive strategies, we talked about sleep restriction. There's also a very specific approach called stimulus control, which sounds a bit more complicated than it is really. 

It's just the idea that you use your bed for sleep and perhaps for sex, but nothing else, just the good stuff. So you only get into bed when you are sleepy. And if you're really not, even if it's two or three o'clock in the morning, you get out of bed. 

And this is to break any sort of negative connection that people build up between their bed and not being able to sleep. 

So if you wake up regularly at 2, 3, 4 o'clock in the morning, your brain sort of learns Oh yeah, your bed is the place where you worry about stuff. To try and break that cycle, take yourself out of bed. 

Then the final ingredient for CBT for insomnia is relaxation strategies. And these come in many different forms and I would probably include some mindfulness-based strategies here, but whatever works for you in terms of relaxation.

So I've skipped there and to CBT for insomnia simply because I know we were talking about sleeping pills, but I would be starting with CBT for insomnia if I possibly could, or even doing that alongside taking sleeping pills. And you'll find that the more lasting effects come from CBT-i.

Jonathan Wolf: Fascinating. The next question I had actually ties into that, which is, can exercise help you get better sleep? 

Sophie Bostock: Oh yes, a hundred percent. I say a hundred percent, you can take it too far. So for most people, exercise is wonderful. It impacts on the three main systems that I would say influence your sleep quality. 

So first of all, you've got your circadian rhythms, which I know have been talked a lot about on the podcast, but this is your 24-hour intrinsic rhythms. 

We are designed to be active and alert during daylight hours and to rest and recover at night, and the more consistent we can be with our sleep timing, the better quality sleep will get.

Exercise is one of those things, we call them zeitgebers, that helps to moderate our circadian rhythm. So long as we're doing our exercise during the day, that helps to send an alerting signal to the brain, and that is going to increase the likelihood that the brain is ready for sleep at night. So that's one positive of exercise.

The second is the increased sleep pressure that I've mentioned already. And this is just the buildup of a chemical called adenosine that helps us feel drowsy. 

So when we expend energy, we break down a molecule called ATP, we release adenosine as a side effect, and that builds up gradually over the day and helps us feel tired. So more exercise, more adenosine will be sleepy. 

Then the third and final sleep system is the stress system that I've talked about already. And we know that exercise has a brilliant sort of moderating effect on the stress response system. 

So although in the short term exercise is a stimulus, it's a stressor, it gets the body going. It's that recovery afterwards that helps to decrease the activation of the stress response, helps us to relax. 

So the reason I said a hundred percent for exercise and then changed my mind is that if you exercise too intensively, too close to bedtime, it can be a problem. 

There was a recent study, from wearers of the WHOOP wearable actually, that came up with intense exercise, even four hours before bed could still interfere with the quality of sleep.

But that would have to be pretty full-on exercise, I think, to have that effect. 

Jonathan Wolf: You need enough time to start feeling tired from the exercise you did.

Sophie Bostock: Yeah and for your body temperature to cool, I think that's a big thing. 

I think about it as a runway towards sleep and a bit like a race car. You know, the faster you've been going during the day, the more length you need to give yourself in terms of time to slow down. 

Jonathan Wolf: Is scrolling on my phone a way to unwind at the end of the day?

Sophie Bostock: Some people will say yes, but actually, you've still got a mental stimulus there, so it might be a step on your wind-down.

But this is where I'm really keen that people set a timer for how long they scroll for. It's not necessarily a bad thing. It's a bad thing when you're scrolling for an hour and a half and you're meant to be scrolling for five minutes.

Jonathan Wolf: Oh, I've got one here. Can eating turkey help you get to sleep? 

Sophie Bostock: Okay, so the theory here is that I think it's the tryptophan content in the turkey, which supposedly is going to help you sleep. 

I believe I read some research that suggests that the amount of tryptophan in turkey that we get would not really be enough to influence your sleep. You'd have to consume 50 turkeys or something to really influence that. 

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We've talked a little bit earlier about generally speaking, a healthy unprocessed diet, which might include protein, some lean meat is probably going to be good news for sleep. 

I have not seen any research specifically on turkey that shows that it improves your sleep. What may be happening around Thanksgiving, you have, you know, lots of excitement, lots of food as you are relaxing afterwards. You've had a very social occasion. There's all sorts of things that will reduce your stress response in that environment, perhaps lead to some good sleep. Might not be the turkey. 

Jonathan Wolf: So one of the things that has really surprised me at ZOE, if I look at what we see now and what I would've imagined eight years ago when I knew nothing about nutrition or the rest of it, is that people following the ZOE advice from their app and when we did this randomized controlled trial, seeing really big impact on sleep.

I never would've thought that food had anything to do with sleep. Are you surprised to hear that? And do we have any understanding of why this shift in diet that's really optimized about health might be affecting sleep really quite fast?

Sophie Bostock: I think this is a fascinating area for research. I think we'd need to do more research on it. We've got suggestions of why this might be the case. 

So I think one of the first studies to look at food and mental health, I think it was called the Smiles Trial. And they compared just a kind of Mediterranean-style diet, I think with some sort of social connection intervention. 

So both of them were helpful for mental health, but actually amongst people who had an unhealthy diet, this Mediterranean-style diet really significantly improved mental health.

Now, mental health and sleep, as we've already talked about, have an incredibly close relationship. So if you can do anything which is going to improve emotional health, it is very likely that your sleep will improve as well, because the two are just so intertwined. 

In terms of the mechanisms, what role does the gut microbiome have to play? It's certainly going to have a role. 

There's a good sort of indication that more fibrous diets, which are going to be good for your gut microbiome, are also good for sleep. I don't think we know enough yet to say exactly what is going on here. 

Also, we don't want too much inflammation. We know that if your body is in a state of high inflammation, you are likely to have poor sleep. Sleep itself lowers inflammation, so it is again, a two-way relationship. 

But ultra-processed foods have been linked to insomnia, for example, so we've got lots of indications which suggests that improving your diet should improve your sleep.

But I think it's great that you've got some emerging data from ZOE that suggests that, you know, there is a very much a causal, a driving relationship.

Jonathan Wolf: So, the final one of these questions, and I think it's right in this area: cheese, because I grew up, everyone told me if you eat cheese before you go to bed, you get nightmares. 

Sophie Bostock: So there was a paper that was published I think just a month or two ago on this, and it was actually a survey. So this was a Canadian study and over a thousand students who got credit for taking part in the survey.

They asked them about the foods they ate and whether the people thought they influenced their sleep and their dreams. And out of a thousand people, I think only 1% suggested that dairy influenced their dreams. 

The study suggested that that population were more likely to be lactose intolerant. So of course, if you are eating something that really doesn't agree with you, it may well disrupt your sleep.

Jonathan Wolf: What about supplements? The two supplements that particularly came up in these questions were melatonin and magnesium. 

Sophie Bostock: Okay, so both quite big topics. Let's tackle magnesium because in a way it's a bit less controversial. I think of magnesium as a Swiss army knife of supplements. 

Really, it sort of seems to do a bit of everything. It's involved in hundreds of enzymatic reactions in the body. There's no question that we need it. 

There's also no question that if we have a generally pretty healthy diet with lots of fresh fruit and vegetables, we will probably get enough magnesium in our diet. 

What we don't know from the research is whether magnesium has any impact on your sleep if you are not magnesium-deficient. 

There was a study in December last year that looked at magnesium L-threonate, and that seemed to suggest that, yeah, help people fall asleep, perhaps 10, 20 minutes faster, improve sleep quality. 

So anecdotally, I know a lot of people who take magnesium and say it improves their sleep.

I think the effects are probably not that strong. But if it works for you, try it. It's pretty inexpensive. It's pretty difficult to overdose on magnesium. We're just going to excrete it out again. 

So it's one of those where I'm like, Well, you may as well experiment with it, particularly if you are in a population that has experienced quite a lot of chronic stress. Because we know that that decreases your storage of magnesium. 

So any chronic stressor, and that might mean a lot of exercise or going through menopause. There are certain populations who will be at more risk of magnesium deficiency. 

Jonathan Wolf: Thank you. What about melatonin? 

Sophie Bostock: Melatonin in this country here in the U.K. is only available on prescription from your doctor. I know a lot of people listening will be in the U.S. and other parts of the world where they may well be able to buy it as a supplement over the counter. 

So the reason that it is only available on prescription here is it's a natural hormone. It's got very few side effects, actually, relative to other sleeping pills, but it does have physiological effects.

So, melatonin we all naturally secrete from the pineal gland in the brain. And if you have regular sleep patterns, regular circadian rhythms, you'll typically release it about an hour and a half to two hours before your normal bedtime. 

It is often called the hormone of darkness. So if you're in very bright light as we are recording in the studio, that would really interfere with your melatonin levels, and that could either delay the secretion of melatonin or reduce the amount that you get, which would make it a bit harder to fall asleep.

As we get older, we produce less melatonin. So in this country, it can be prescribed for insomnia for adults over the age of 55. But the reason it's not really prescribed for adults below that age is because there's not really much evidence that it helps them not for insomnia. 

So what melatonin is good at is changing the timing of sleep. So if you've got someone who has a circadian rhythm disorder where they are going to bed very, very late at night, their body clock is delayed by four or five hours relative to most of the rest of us, then melatonin is that tool that can be used to bring the body clock forward. 

So I would say that it's probably not going to help you very much if you have insomnia. I think a lot of melatonin is purchased in the U.S. by people who have that belief. 

The stuff that you buy over the counter is notoriously unreliable. When they've done analysis of how much there is in particularly gummies, which often people buy for their kids, we know that the amount of melatonin in those is anything from 74% to 374% of what is actually advertised. 

To get melatonin to actually work, you need to get the right dose at the right time. So. If you do think melatonin might be helpful for you, and it might be a circadian rhythm issue, it may be that particularly for children with autism, ADHD, sometimes they have circadian rhythm issues as well, go and speak to your doctor. 

I would always prefer that a medical professional is managing the dose, the timing, and also the quality of that melatonin that you are taking. 

Jonathan Wolf: Amazing, Sophie. Well, you have answered a lot of listener questions. I'd love to pull this together now into sort of quite straightforward, actionable advice.

And maybe we could start with this sleep hygiene. Because you've used that word many times through this fascinating conversation. Could you maybe describe to me if you were trying to say, Jonathan, this is the sleep hygiene that you or a standard person should have. What is that? 

Sophie Bostock: Let's keep it simple.

Start first thing in the morning. Wake up at the same time as often as you can. So set your alarm for the same time each day. When you start to do that for a week or two, you'll find that you don't need the alarm anymore. But try and aim for a consistent wake-up time. 

Aim to get some natural light, ideally within the first hour after waking, that's going to kickstart your circadian rhythm for the day, tell the clock that it's wake-up time. 

The advantage of doing that is that if you get this bright light in the morning, it's going to banish the melatonin. So you're going to feel more alert, but automatically 15 or 16 hours later, you are going to start to feel sleepy. 

Move your body during the day, whichever way makes you feel happy, but get physical, be active. There was some recent research actually suggested that yoga was one of the best forms of exercise for sleep. So it doesn't need to be super intensive, it just needs to feel good for you. 

Take some time out to relax during the day, particularly if you're a busy person that goes from A to B at 300 miles an hour. Just take 15 minutes for yourself, a moment to be and not do.

Then, as we come towards bedtime, try and have a consistent wind-down time. I'm not bothered about whether you get into bed at exactly the right time, but try and have a consistent time where you start to switch off. 

So in that hour of wind down, you know, get done what needs to be done for tomorrow. Some form of relaxation, something to look forward to, whether it's a warm bath or reading a book, or doing some breath work, listening to music, some intimacy with your partner, with your family. Social connection is often neglected in terms of its role in improving sleep. 

Then, during sleep, you want darkness using eye mask or blackout blinds. Try and sort of banish light from your sleep environment and just let it come. Don't try too hard to sleep. 

Jonathan Wolf: That sounds brilliant. 

The one thing I haven't heard you mention, I'm curious about is use of that smartphone. Because you said right at the beginning that like that's the number one thing that's really changed everything and made this worse.

Sophie Bostock: In my book, that wind-down time, that's when I'd be switching off the phone. 

Ideally, the phone does not come with you into the bedroom. Buy a cheap alarm clock that has no smart functions. And this is something that actually, it can be really good for families.

So parents will often say, you know, how do I separate my teenager from their phone? Well, if it's something that everybody does, it's just a norm. 

The phones don't go into the bedroom. That's not where they live. That just is a rule that you can make for yourselves. 

Jonathan Wolf: If I do all of these things, if I'm not in the insomnia [group], but I'm in that 50 to 60% of people are not getting their best sleep, can it really transform my sleeping?

Sophie Bostock: All of those things might help a bit. I don't want to overdo the sleep hygiene piece because I also know there are some great sleepers out there who have pretty poor sort of sleep habits. 

They're all part of this picture of positive sleep health. I think if there was anything to add to that, it's just that I would love people to believe that sleep is important, but also to believe that they are good sleepers.

A lot of what I do is help people build confidence. So if you do those habits, what happens is that you build confidence that you are going to sleep well. So that helps to ease the anxiety. 

If you're someone who has been anxious about sleep in the past, the danger of this advice is that it's too rigid, and that if you haven't had 15 minutes of daylight within an hour of waking up, you start to get anxious.

If your phone has accidentally gone into the bedroom, then you might have a terrible night's sleep. So these are guidelines. They are recommendations. They are not strict rules. 

Jonathan Wolf: What about wearables that track sleep? They're obviously very popular. Can they help? 

Sophie Bostock: I'd say they absolutely can help. It depends what you are using them for.

So I believe they can be a brilliant accountability buddy. So if you set yourself a goal around improving sleep consistency, for example, and you are tracking that, that is a behavior that's actually very easy to change over time, that is going to be linked to better quality sleep. 

I think where they can become a little unhelpful is where people become fixated on the numbers, and there is a very real condition called orthosomnia, which is an obsession with the perfect night of sleep.

Ultimately, the most important thing is how you feel during the day, and although wearables can give you some useful indicators, it's really about how you feel is the most important metric that we have. 

Jonathan Wolf: I was going to ask about your own sort of sleep habit. What are the critical things that you try and make sure you do?

Sophie Bostock: For me, it is about doing exercise in the morning, definitely getting some bright natural light and as much natural light, actually during the day as possible. 

I recently broke my collarbone. And so for at least a week or so, I wasn't getting outdoors as much as I normally would, and I really noticed it.

Obviously, I was in pain as well and that wasn't very helpful for my sleep, but I noticed that as soon as I started reintroducing just walking, not even intense exercise, my mood improved, my sleep improved. So for me that's an absolute must.

But also I would say just taking that scientist approach to my own sleep testing, trying new things.

We talked about magnesium earlier, do an experiment with that. I'm currently trying a sauna blanket to see whether that improves my sleep. 

I think taking that curiosity, what can I do? Does it make a difference for me because we're all different? 

Jonathan Wolf: Final question. If you were going to say one thing that a listener could start doing today, what would you say?

Sophie Bostock: I'm going to give you something a little bit different here. So there's a technique to help you fall back to sleep called cognitive shuffling. 

I've talked to a few people recently and they've found it really useful. So this comes from research that compared what happens when good sleepers fall asleep versus poor sleepers.

The good sleepers will describe seeing very visual things which are not rational, not related to each other. Whereas a poor sleeper will often describe planning thoughts, anxious thoughts, thinking about, I've got to do this then.

So to try and promote the mind state of a good sleeper, this cognitive shuffling technique involves thinking of a random word. Any word. 

So last night my word was leprechaun, and then with each letter of that word, thinking of another random word. So my L might have been lemons. Every time I think of that word, I try and visualize it. So I go from lemons. To elephants. I wasn't actually quite sure how to spell leprechaun, but I was asleep before I got to the end of the word, so it didn't really matter.

But that technique might be useful. 

Jonathan Wolf: Sophie. That sounds amazing. I've never heard of cognitive shuffling before, so I think what you're saying is I come up with a word like elephant and then I take the first letter of it and I try to come up with a random word that begins with E, like eagle, and I think of a picture of it.

Sophie Bostock: Yep. 

Jonathan Wolf: Then I go to the next one, like L and I think of lemon. 

Sophie Bostock: It's a simple sort of word association, image association game for your mind. There's no pressure here. It's just for fun. 

Jonathan Wolf: I'm definitely going to try that. Excellent. And see how that works. I'm going to try and summarize and we covered so many different things.

The first thing that springs to mind is, I need to go away and do an experiment on drinking alcohol. That self-experimentation on these things is really important and to see what happens in fact, when I drink it or not.

You pointed out potentially it's just a component with quite a lot of other things and we tend to overemphasize maybe one element of the sleep. So maybe the story I'm telling is that it's so bad for my sleep, but actually [could just] be part of what makes it that way. 

The other thing that I have really taken away that I hadn't understood before is that there's a large number of us who are not sleeping really well. You said like 50%-60%, but then there's 10 to 20% who really have this insomnia.

You've talked quite a lot about very specific ways to deal with this if you have insomnia, starting with this CBT and how powerful it is.

And that really made it a bit different from this huge chunk of us who are struggling with sleep and that the big reason why this is so much more of an issue today than 25 years ago is phones.

Because we've had lights and things like this for a long time, but the phone is a really big difference.

The thing I've understood about this is you're saying as human beings, our brains are wired to seek information and these phones are constantly giving us this new information and giving us this sort of dopamine hit. 

So it means that we just don't want to put it away. So we have to recognize that and think more about sleep than otherwise. 

Not sleeping is really bad for us and it can cause heart attacks and all these sorts of things, but actually, just in the short term, it makes us really irritable. 

You described this thing about sleeping next to a nest of saber-tooth tigers. You wouldn't sleep very well and you would want to be anxious the next day because there were saber-tooth tigers.

But actually, now we are messing up with our sleep without that reason. But it means that our perception of threat is higher, and this is part of why we're so irritable with our partners when we don't sleep well. 

One of the things that you sort of came round to over and over again is how much our attitude therefore matters. How are your own assumptions about your sleep causing problems? And can you be more relaxed about all of this? And maybe already I will sleep much better.

But you were pretty clear, in fact, there's quite a few things that I could be doing about my sleep to make it better. And interestingly, they start at the very beginning of the day.

So you said the first thing on sleep hygiene is actually to wake up at the same time every day. Whereas I tend to think immediately about the night. And I think, like many people, I wake up at a completely different time at the weekend than during the week.

Natural light; as soon as possible in the first hour, try and do some exercise. Try and take 15 minutes at some point during the day to relax. 

And only then did you talk about the bedtime routine, which I thought was really interesting. And there again, consistency was the first thing you said. 

So a consistent wind downtime, an hour, which is immensely longer than I go from stopping thinking about work to going down. Try and disconnect from the phone at that point and do something else that is going to help you relax.

Darkness during sleep. The bedroom: the bed is not for your phone, it's for sleep. Maybe sex. 

And if none of this is working, you gave us a lovely little tip at the end: cognitive shuffling. Think about that word, think about the images, and hopefully you'll be asleep before you get to the end of the word.

Sophie Bostock: Fantastic. It's an amazing summary.