Fix your body clock to improve long term health with Prof. Satchin Panda

0:00Welcome to ZOE Science & Nutrition, where world leading scientists explain how their research can improve your health.

0:14Today you'll hear from one of the world's foremost scientists on why living in harmony with your body clock is critical for your long-term health. Professor Sachin Panda is here to reveal why our body clots govern so much more than just how groggy we are when we wake up. Sachin is a highly cited professor at the renowned Salk Institute in California. and a best-selling author. He studies circadian rhythms, their regulation, and their impact on our health. Today, we hear how to harness these powerful invisible rhythms to increase our resilience to chronic disease.

0:54Satchin, we have a tradition here at Zoe where we always start with a quick-fire round of questions from our listeners, and we have some strict rules. You can give us a yes or a no, or if you absolutely have to, you can give us a one sentence answer. We know that's hard for professors, but they mainly manage it. Are you willing to give it a try? Sure. Wonderful. Does every part of our body follow a 24 hour cycle? Yes. Can eating breakfast at the wrong time wreak havoc on my circadian rhythm? I'm going to explain what is the wrong time because Because breakfast is not the morning meal. It's breaking the fast, which has to be consistent.

1:36If I live my life out of rhythm with my body clock, can I damage my health? Yes. If I adjust my lifestyle to match my circadian rhythms, can my health improve in just weeks? Yes. That wasn't so bad, was it? So now final question, and you can have a whole sentence. What's the biggest misconception that you hear about the body clock? that people have very different types of clock, which is not true. Everybody has the same 24-hour clock. So look, Sachin, I think most people listening to this podcast have heard of the body clock or circadian rhythms. And intuitively, they know that if that body clock is disrupted, you know, they don't feel great.

2:17I think any of us who have had, you know, children know what it's like to suddenly have your sleep broken or suddenly to be on weird cycles. I think many people like me have had experience of jet lag where you go and move to, you know, a country that's a long way west or east, and then it's very difficult for a few days. But I was always brought up to understand that it's just really mainly about sort of adjusting your sleep pattern after this transatlantic flight or making sure that, you know, the sort of thing I always say to my son, which bores him, which is he's a teenager. Oh, you should go to bed at a regular time or wake up at a regular time.

2:53That's the sort of thing that my mother used to say to me. But I think there's a lot more science that's been happening in recent years. And you're one of the leading researchers in the field. I'd actually love to start before we dig into how it impacts our health, just to understand a little bit about like, what are circadian rhythms and how do they work? Yeah, circadian rhythms literally mean 24 hours rhythms. So that means these are the internal timetables that are present in every organ, actually in every cell in our body that tells each of our hormones, brain chemicals, digestive juice, enzymes, or even every single gene to turn on and off at a specific time of the day or night.

3:39How do you know now that this exists and is in every cell? Is this something that we've known forever or is this relatively new? Almost 25 years ago, scientists figured this out. They developed new way to monitor circadian clock or 24-hour clock in individual cells. And what is interesting is if I take a chick swab or my skin cells and then put a magical gene that strums firefly into it, then the cell will glow and dim down in every 24 hours. and that's how scientists came to know that almost every cell in our body including our skin our fibroblast for example even hair follicles all of them have security and clock and does that mean because you might imagine that maybe the cells are in a 24-hour cycle but it doesn't really matter somehow for when they get turned into I don't know a particular like your your heart or your brain or whatever.

4:43Is it true that all the parts of our body are also on these 24-hour cycles? Or I mean, my heart is working after all, all the time, it doesn't switch off. So is it only is that on a 24-hour cycle? Yeah, actually, the heart beats 24 hours. But what is interesting is when we sleep, the heart actually slows down slightly. And then anticipating waking up, it begins to beat slightly faster. And you might say, well, this is a small change of heartbeat. Does it matter? And actually it does matter because there are many cases when your heart doesn't slow down at night, doesn't rest, because just like we, our brain needs rest, our heart also needs some rest.

5:28Those people have a higher risk for heart disease in future. So it's pretty well documented for blood pressure also. So, for example, our blood pressure dips at night. And there are many individuals who have high blood pressure and their blood pressure doesn't dip at night. Versus there are some people who have high blood pressure, but their pressure actually dips slightly at night. And there are a lot of studies showing that non-dipping blood pressure actually has higher risk for heart disease in the future than dipping blood pressure. So you can have high blood pressure, but if your blood pressure still follows a circadian rhythm, then that reduces, that has a less risk for future heart attack.

6:13And so, Sajjan, both those examples you give are sort of things that are sort of slowing down or changing during nighttime. And it makes me think about, you know, we're all very familiar with sort of like the sleep mode on our phone or our computer, right? Where there's a sort of energy saving when it's not needed. Is this 24-hour cycle all about switching things off when I should be asleep? Or do we know why it's there? And is there like a simple answer across everything? Well, there are many things that go on in our cell, individual cells. For example, our cell has to take nutrition in, produce energy.

6:52And during energy production, there is some reactive oxygen species. So these are the byproducts of metabolism that are quite toxic to the cell. And similarly, there are many chemicals that are also produced during metabolism. You can say toxin or unwanted chemicals, they have to be cleaned up. And that cleaning up doesn't happen 24-7, just like your garbage truck doesn't come 24-7. It comes at a specific time of the morning. Similarly, when we sleep, that's the time when actually our body repairs itself, gets rid of the toxin. And it's not that the whole body is slowing down. Actually, the recycling, the rejuvenation, the repair process actually turned on during that time.

7:40Got it. So my analogy was a really poor analogy. It's not that it's going to sleep. It's more like saying, hey, we're switching over. I've heard Tim give this analogy. It's like the night crew is coming in and doing all of this cleaning and work. So actually lots of activity. But the point is they can't come in if like the daytime people are doing all their normal activity. So it's actually about shifting to a different set of processes inside us. Yeah. So that's why if the cleaning crew doesn't come in at nighttime and prepare all the damages, then next day you'll have a crappy day. You may not be as productive at work as you would be if the offices are clean and everything is nice for you to begin.

8:21So the same thing happens in our body. When our circadian rhythms are disrupted, then this repair and rejuvenation cycle is dampened or disrupted. And slowly the body accumulates a lot of these unwanted chemicals. And if it happens in the heart, then that can lead to increased risk of heart disease. If it happens in the gut or the digestive system, then that can lead to digestive issues or even in some cases, in extreme cases, cancer of the digestive tract, colon cancer, etc. I'm sort of curious with the overlap between the circadian rhythm and sleep, because, you know, we associate also obviously this cycle at nighttime with going to sleep.

9:05And you're describing it as also this period when all of this rest and repair happens. but sleep is obviously not something that's in every single cell. How should we think about these two fitting? Are they completely separate? Are they almost the same? Well, sleep is a very different state. During our sleep, a lot of things are happening. Our body temperature cools down, core body temperature cools down and actually peripheral skin temperature slightly goes up. Your digestive system also slows down, almost shuts down. Your breathing slows down. So sleep is not necessarily a function of the brain.

9:43It's actually a function of the entire body. Your muscle tone also goes down because you don't want to dream walk or sleep walk. And so Sachin, I'd love to transition to this topic about how all of this impacts our health as human beings. So I think you've explained the circadian rhythm is there in all of these individual cells. how is that impacting our health as a result? So let's start with a few things that usually happen in our normal lives. One is, just like when you have a watch, you can anticipate what's going to happen. So for example, if your office starts at 8 o 'clock, then in hour 7.30 or 7.15, you know that the traffic will be 30 minutes, whether you're taking a bus, train or driving, it will take 30 minutes.

10:34So at 7.15, you are getting ready. Just imagine, if you didn't have a clock, then you'd wait till 8 o 'clock, close to 8 o 'clock. Seeing other people driving to work or moving towards work, then you'll start. And then you'll be late to your office. And when you're late, then it doesn't do well on your performance. So one function of circadian clock is actually prepares us for what is going to happen next. So for example, early in the morning, as I mentioned, one or two hours before we wake up, our sleep hormone, belotonin, is already on decline. So it's making sure that we don't feel sleepy when we are ready to wake up.

11:21We breathe slightly more and then our body temperature begins to rise. All of these preparations are happening anticipating you wake up which is very different from the way that you feel isn't it because the way it feels particularly when your alarm clock goes off is like oh i was in such deep sleep i've got to drag myself out but it's interesting and i've seen this similarly when you wear a um like a blood sugar sensor interestingly you see this also i've seen this myself in my blood sugar that like i feel like i'm dragged out of bed but actually interestingly you know i've seen that my blood sugar has tended to go up maybe for like an hour or two, I think, beforehand.

11:58So what you're saying is my body knows a lot that my brain doesn't. So my brain is complaining, but somehow my body already sort of knew where I was going to be. Actually, what happens is when you have to wake up to alarm clock, that is a sign that you haven't slept enough. You are waking up one or two hours before you're supposed to, your body is supposed to wake up. By the time your body is not prepared, you're trying to drag yourself out of bed. Then the question is, so what harm is there? And actually, for most of us, just imagine if you have a new car, even if you do bad driving, it's not going to affect your performance.

12:40But if you have a really old, cranky car and you are doing bad driving, it's going to show up. The engine might give up. This is exactly what happens and we have seen this experiment done over the last hundred years all over the world. When there's a daylight saving time or twice a year, the time changes. And at least in fall, when the time actually falls back, so that means you have to wake up an hour earlier than the previous night. That morning, a lot of people, millions of people are waking up when their body is not ready yet. It's just one hour change. And that's the time when we see there is a spike in heart attack in the morning.

13:27There's a spike in heart attacks on the day of daylight saving. That's amazing and terrifying. And also that happens to the older individuals, but then those who have a weaker heart. There's also the day when there's a spike in road accident in the morning. Because even young adults and middle-aged adults who are driving, their brain is not ready enough to do that very complicated calculations. Because when you're driving, your brain is doing a lot of calculations. At what speed you're going, you're guessing what's the speed of the car in front of you or the side when you're changing length. And you really see that in the total statistics in the States, there are more road accidents the following day than across all the other days.

14:11Yeah. And also, if you just look at heart attack incidences that are reported to emergency room, this is again data from the last 30, 40 years, showing that even on a daily basis, there is a spike in heart attack only in the morning, because that's when the heart has to start pumping slightly faster than in the nighttime. And this is when there is a higher incidence of heart attack. So you're just giving that as an example where if your body had time to prepare, then it's less likely. But because suddenly it's like, I'm getting up, I need to walk around. And presumably these are people whose hearts are not in very good shape.

14:49It's like too big a shock. And you're saying there was a heart attack. Whereas if this body clock had been able to prepare you, then you would have been okay. Yeah. So this is an example of anticipation. Your body, your circadian clock is anticipating waking up and preparing you. So the other thing is to do two different things at two different separate time of the day because you cannot do those two things together. Just like you mentioned, like the custodial staff or the cleaning crew comes late at night or very early in the morning and cleans up the office. And you cannot have the cleaning crew coming in when you're in the middle of a meeting during the daytime.

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17:36So almost in every cell, there are many chemical reactions that are going on. One type of chemical reaction, what we call oxidative process. So that is, this is a process where oxygen is used to typically break down things. For example, when you are breaking down fat and making ketone bodies, these are the small, tiny fat-like molecules which have a lot of benefits. That's one kind of process. But then the flip side of that process is making fat when we eat a small part of our nutrient that we eat is actually used to make fat and this breaking fat and making fat cannot occur at the same time and they are temporarily or timely they are separated to two different times of the day.

18:25Similarly there are also many other examples where the body is programming our cells or the circadian clock is programming our cells to do certain things that are safer to do at night. And one example is, when should our cells divide? Our skin actually repairs itself or recycles itself roughly in every 15 to 30 days. So that means we have new skin every 15 to 30 days. Similarly, our gut lining also changes in 15 to 20 days. Obviously, we talk about gut and gut health quite a lot on this show. There's no sunlight inside. so what's happening to the why is the gut cells on some sort of 24-hour cycle well there are a lot of things that we eat those are not actually nutritious there are very toxins and they also damage our gut lining and just like you cannot repair a highway when the traffic is still flowing you cannot repair the gut lining when it's still digesting food so that's why the gut lining also repairs itself at nighttime and at nighttime the movement of food through the gut that also slows down so all of this helps to repair the gut so now imagine if someone is a shift worker or if you have a jet lag you flew from London to California and you thought this is sunny day let me go lie on the beach but actually your skin cells are dividing because they're still in London time.

19:55Unless you have enough sunscreen, you are actually at a high risk for certain damage to your skin. So this is another example where circadian clock not only times things to keep us safe within our body, it also times our activities in a way that it's safe from damaging effect of UV light from the sun. And then the third one is pretty obvious that the compatible processes, things that should happen, that can happen together, actually happen together. So, for example, we are more active during daytime and we are more likely to have access to food. So it's very obvious that most people feel hungry in four to five hours during daytime and they can eat.

20:38And the pancreas is also trying to produce more insulin during our wakeful time than in our sleep time. Our digestion is also programmed to be more optimum during our wakeful time. So these are the compatible processes that are aligned together. A lot of people listening and saying, yeah, that sounds really good. I'm not sure that my lifestyle is actually that in line with my circadian rhythm. You know, I know that every morning during the week, I wake up much earlier than I really want to. And I know that, you know, I'm a great example of this. I sort of know I'm not supposed to snack after dinner.

21:16But I can tell you last night I was watching Netflix at about 10 p.m. I'm thinking about this show as I ate my dark chocolate because I'm really addicted to it, thinking that you were going to tell me today that I was naughty. So like we're many of us in our modern life, right? Because of electric lights, all these things, you know, we're not living sort of just in line with this cycle. How significant can the impact on our health be? There are three or four different lines of studies to figure out what happens if we don't pay attention to circadian rhythms. The first one I would say is epidemiological study or looking at what happens to people who do evening shift or night shift work.

21:57Are they at a higher risk for certain disease than people of the same age and gender who are not doing night shift work or evening shift work? Nearly one-fifth of the population in many industrialized countries work in shift. and nearly one fourth to one third of the population in many developing countries work in shift. So there are a lot of people. And how big is that impact on your health if you're doing these night shifts? It's very clear that shift workers are at a high risk for metabolic disease, whether it's obesity, diabetes, heart disease, or vascular disease, kidney disease, all of these diseases.

22:36they're also at a high risk for many types of cancer to the extent that world health organization categorized night shift work as a potential carcinogen it's similar to chemicals that are known to cause cancer and satchin is it only shift workers who need to worry about this or for the rest of us who are lucky enough that you know then they're not having to work in the middle of the night, but they're still probably not following a real cycle. I could tell you that I am definitely not going to bed when it goes dark outside. Is there any real risks or not? Yeah, we don't have to go to bed right after sunset.

23:18I mean, there are researchers who have gone to populations which don't have access to electricity or very minimum amount of electricity, and they find that these populations still stay awake in the evening. They have a candlelight or firelight and they go to sleep between 9.30 and 10.30 p.m. and then wake up around, say, 6 a.m. or around dawn. So it's not that we have to fall asleep as soon as it becomes dark. But the other point is, well, if you're not a shift worker, should you worry about it? And the answer is, well, you may not be a card-carrying shift worker, but are you living the lifestyle of a shift worker?

23:59And that brings up the question of, okay, so what is the lifestyle of a shift worker or what is typically defined as shift work. There is no internationally recognized rule about what is defined as shift work, but there are many European countries who roughly define shift work as staying awake for two or more hours between 10 p.m. and 5 a.m. and engaged in some physical activity or mental activity. It's not that you are lying in the dark room and you cannot sleep for three to four hours. That's not sleep work. But you have to be awake and be active and engaged in some kind of work. So now just imagine how many people stay awake for two or more hours between 10 p.m.

24:50and 5 p.m. A lot of people. What it really means is, are you reducing your sleep by roughly two hours for 50 days in a year? So that is once a week. So it's pretty easy to achieve is basically the message you're describing. Like, you know, just the weekend decided to stay up late or staying up one night during the week late or any of these things, you know, can have that impact very fast. I think you've painted the picture about like why this is really important and that there's real health risks if you're if you're not there. I guess I'd love to talk about, OK, the practical tips for somebody listening to this about ways that they can adjust their lifestyle.

25:33And I'm particularly interested in in the in food and sleep that our listeners could actually take. And I think I'd love to start with time restricted eating. and that is in part because I have to admit I was very skeptical about this just a couple of years ago and when I first heard about it it sounded pretty crazy it was like oh you know it's another one of these fads that somebody's come up with and just like you know drinking cauliflower soup it's like it doesn't make any any sense but actually Zoe did a huge study last year which was called the the big if study with around 37 ,000 people because it's something Tim and and Sarah were really interested in because I think of research like your own and what was really striking was, you know, on this very large sample of people, there was a real impact on energy and hunger after just a few weeks of making this adjustment, which was, I was really surprised by.

26:26So I've had to accept there's definitely something, there's something around this. So could you tell us about, you know, based on your own research and the other researchers out there, what does all this circadian rhythm tell us about when we should eat? So there are two fundamental discoveries about what resets or synchronizes our circadian rhythms. One is light, the daylight or light that is rich in blue light that goes through our eyes and resets our brain clock and resets when we sleep, when we wake up. So that's light is one cue. But the other cue is when we eat. If we eat at the wrong time, like one night, if you're eating very late into the night, then that night, your body clock gets confused, thinking, huh, was it a delayed dinner or was it an early breakfast?

27:21And for the next few days, it gets confused. So all the body clock, the clocks in the liver, gut, heart, kidney, all of those clocks get disrupted, so they can't work pretty well. So just a late night can like mess up all, and it's not even just my gut. It can even mess up my liver or my heart. That doesn't sound good as someone who has a tendency to maybe have that little snack before bedtime. Yeah, because your body is thinking, well, was it evening? Was it a long, was it a late dinner? So after we learned this, then the question was, well, we know that having a strong circadian clock is good for health.

28:00In modern life, it's very hard to control light exposure because from morning to night and also late into the night, until we close our eyes, we're always exposed to light. It's very difficult to control that. But can we control when we eat? And just by when we eat, can we change health? So, you know, what is now popular as time-restricted eating or intermittent, very popular form of intermittent fasting, it was not there 12 years ago. So my lab was the first one to do this experiment in mice, just like all basic scientists do, because we can control the experiment pretty well and we can also do molecular analysis.

28:44So we took a few groups of young mice and they were identical in genes. They were born from the same parents, grew up in the same room. they had the same microbiome they ate the same number of calories from the same food the food we gave them was relatively high in fat and carbohydrate which would be equivalent to eating say fish and chips every day or a burger every day you know all the bad food you can think of not the healthiest diet for a mouse or or a human being we knew that when mice are given this kind of food and they're allowed to eat whatever they want to eat. They become very obese, diabetic, they have high risk of cardiovascular disease and also the increased risk of liver disease and cancer.