Dhru Purohit Show
The Science Behind When To Eat and Other Top Lessons On Circadian Biology
Mon, 20 Jan 2025
This episode is brought to you by Pique Life and Birch Living. We used to think that the circadian rhythm only affected sleep. However, emerging science shows it’s deeply connected to metabolism, cognition, chronic disease risk, and many other critical aspects of health. Our biology is designed to function in harmony with the natural light-dark cycle, but modern society has significantly disrupted this balance. Today on The Dhru Purohit Show, we bring you a special compilation episode featuring Dhru's conversations with leading experts on the critical role circadian rhythms play in our health and well-being. Dr. Satchin Panda delves into his groundbreaking research on circadian biology, revealing how leveraging your circadian rhythm can significantly improve sleep, reduce the risk of chronic diseases, and enhance cognitive function. He also shares how time-restricted eating, exercise, and light exposure can help program your circadian rhythm, with a special focus on the importance of these tools for shift workers. Dr. Moore-Ede discusses the dangers of chronic blue light exposure and its profound impact on health, highlighting research that reveals how it disrupts circadian rhythms. He also examines the connection between light exposure and obesity and explains why these risks remain underrepresented in mainstream media. Dr. Satchin Panda, a professor at the Salk Institute and founder of the UC San Diego Center for Circadian Biology, is a leading researcher in circadian biology. Dr. Martin Moore-Ede, a former Harvard Medical School professor and expert in circadian rhythms, has conducted groundbreaking research on light's role in regulating sleep-wake cycles and overall health. In this episode, Dhru and his guests dive into: Why when we eat is more important than what we eat (01:38) Effects of chronic late-night eating (08:18) Adverse effect of disrupting our circadian rhythm (16:25) What is sleep debt (19:21) Paying attention to when you eat (30:16) Research on time-restricted eating (34:08) Why sleeping with the lights on is damaging to your health (39:01) Why sun exposure is critical for good health (41:55) Dr. Martin's recommended time for sun exposure (49:28) The link between blue light and obesity (51:42) Master clock of the circadian rhythm, cortisol, melatonin, and others (54:06) Why doctors aren't talking about the harmful effects of blue lights (59:03) Blue lights in hospitals and how they prevent healing (01:04:47) Also mentioned: Full episode with Dr. Satchin Panda Full episode with Dr. Martin Ede-Moore This episode is brought to you by Pique Life and Birch Living. Right now, Pique Life is offering 20% off the Radiant Skin Duo plus a free beaker and frother when you go to piquelife.com/dhru. To get 25% off your Birch Living mattress plus two free eco-rest pillows, head over to birchliving.com/dhru today. Learn more about your ad choices. Visit megaphone.fm/adchoices
Chapter 1: What is the importance of circadian rhythms?
Hi everyone, Drew Proat here. You know, when most of us hear the term circadian rhythm, we tend to immediately think about sleep. But the truth is that our circadian rhythm reaches far beyond sleep with significant, significant implications for all sorts of things like your immune health,
mental health, cognitive health, and your risk of all sorts of chronic diseases, including things like cancer. This is why it's so key to understand the role of our circadian rhythm and how adopting lifestyle practices to support it and staying away from the ones that don't support it will have a massive impact on your overall health.
In today's compilation episode, I'm talking with two experts on the topic of circadian rhythm. One of the first experts on the podcast is Dr. Sachin Panda. He's a professor at the Salk Institute of Biological Studies, a Pew Biomedical Scholar, and the founder of the UC San Diego Center for Circadian Biology. And he's also the recipient of the Julie Martin Mid-Career Award in Aging Research.
And in addition to Dr. Sachin Panda, we also have Dr. Martin Moore E. He's a highly respected expert in circadian rhythms and the impact that light has on our health. As a former professor at Harvard Medical School, he's conducted extensive research on the role of light in regulating our sleep-wake cycles and our overall well-being and our risk of chronic disease.
Okay, let's start off by jumping into my conversation with Dr. Sachin Panda on the importance of circadian rhythms, as well as why we want the timing of eating, sleeping, and other daily activities to align with the body's natural cycles. I want to jump right in.
Tell us about why when we eat, which is the timing of when we decide to eat, the window, might be just as important, if not more important, than what we eat.
Circadian rhythm essentially relates to almost a daily timetable of things that has to happen in our body, whether it is fighting infection, metabolic balance, brain health, or even repair and rejuvenation for injuries. And when we think about circadian rhythm, then since it's a big new concept, it's also a little bit difficult to understand. But just imagine that in our life, daily life,
we organize our life around time we think of the whole day what time I have to get up what time I have to go to school or send kids to school and then what time I go to work what we do and then in the evening what time I have to meet friends or get back to home what time we sleep so similarly every single cell in our body has its own 24 hours timetable
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Chapter 2: How does timing of eating affect health?
that means the cell has to decide okay this is the time i have to make energy this is the time when i have to recycle this is the time to divide and rejuvenate so this is a very new concept of in science and this has the potential to impact our daily habits and it has the potential to increase efficacy of medications that we take or supplements that we take on a daily basis
And also what we're seeing now, there are also new drugs that are based on circadian rhythm to essentially based on the idea that as we get older or in many diseases, our circadian clocks are disrupted. And the question is, if we can fix our clock with a new drug, can we also fix a disease? So these are the three big principles that are coming into play.
And you mentioned time-restricted eating, intermittent fasting. that's kind of one aspect of this circadian rhythm biology but this is actually one way to get into the science because once we understand why we should be eating in less than 12 hours and why that has to be consistent what is the science behind it then we can dissect a little more into the interrelated parts of fasting sleep
what time we should be exposed to light, when we should exercise. And that will give strong production of these enzymes and increased acidity to break down food. And then there is a weird thing that happens around sleep time or late at night. Our stomach is more sensitive. So that means even a little amount of food can hyper, it's almost like
The stomach is sleeping and all of a sudden somebody comes and knocks on the door and not only you wake up, you actually wake up with increased vigilance. You may pick up a stick or something thinking that somebody is invading. So stomach actually hyper reacts by producing too much acid.
And now, too much acid is actually not that bad, but what happens is too much acid can go up our esophagus and can cause acid reflux. And I told you that how at nighttime, Our mouth actually reduces saliva production. The reason is in our sleep we should not be drowning in our saliva. So saliva neutralizes a lot of acid.
So then we have increased acid production at night and less saliva to neutralize it.
and that's one reason why people eat too late at night not all some might actually experience more acid reflux than other right so now in the next step in digestion is after this stomach is digesting food it goes to the intestine and the intestine kind of has a peristaltic motion so that means it beats and sends that food slowly while the intestine is also absorbing nutrient
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Chapter 3: What are the dangers of late-night eating?
And that process almost shuts down during our sleep or late at night. So that means even if you have eaten food, it actually doesn't get digested, the nutrient doesn't get absorbed late at night. So this is a clear example how even very basic step of digestion has a strong circadian rhythm, and that helps to make sure that our food is digested the right way.
And the reason why everything shuts down in the digestion at night is during the daytime or when we eat, just imagine, it takes a lot of energy, a lot of acid to break down food. Imagine kind of digesting that piece of sushi that you ate. So if your stomach is digesting that piece of sushi, At the same time, it must be damaging some stomach lining, and that actually happens.
So that stomach lining has to be repaired at night. So there is a different circadian rhythm starting from the brain that produces growth hormone in the first couple of hours of our sleep. And although we are not growing after reaching adulthood,
Chapter 4: What is sleep debt and how does it accumulate?
in size or height but actually we are replacing many of our stomach lining and many other cells throughout the body and that happens only at night time so again there is another clock that kind of works with the digestion clock to make sure that during daytime we digest and at night time we repair so these are just
There is few examples, but if we drill down, almost every single cell has its own clock and it has implications for how we should live, how we should organize our day around these clocks.
Yeah, it's really fascinating. When you really get a chance to zoom out, we see that the world and the way that nature was set up, including the 24-hour cycle of the sun and how it interacts depending on where you live in the body, the sun rising and setting, that was the foundation of what our biology evolved around.
And now, through modern living, we're able to eat later, we're able to microwave foods later, we're able to get processed foods later,
and a lot of these foods are way more addictive than they ever were hyper palatable i guess is the right word so we're in a situation where we can see now through your example that just by regularly eating late or late at night or right before bed or midnight snacking as many people do we can now see that things like acid reflux in your example why they could be so prevalent among society, right?
What would be another example that's tied to late night eating? Common things that you see that people are struggling with in their body that they may not understand has to do with circadian biology. So one is acid reflux. Another one could be waking up and not feeling rested, right? Is there anything else that you'd want to mention?
Yeah, so acid reflux and indigestion, another thing that we talked about. And again, going back to the same digestion process, one more thing is when we eat something, most of our food does have some carbohydrate, unless you are just eating ketogenic diet, which is very difficult to do for long term. But for every regular person, we consume some carbohydrate.
That means that's broken down and that increases blood sugar level and the pancreas has to adjust that sugar by producing insulin. And pancreas does have a circadian clock. So that means it actually doesn't produce enough insulin late at night. So that's one. And then the second thing is the sleep hormone melatonin that goes up at night.
And that's why people who have sleep problems, they think that they can sleep well by taking extra melatonin. And I'll get to that. But the melatonin actually has another break on insulin production.
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Chapter 5: How can time-restricted eating improve health?
The third thing that happens is when- And just to make sure I understood that correctly, and kind of recapping for our audience, so that regular, we're not talking about occasionally people eating, and the tendency is that at late night, people want highly palatable, salty, sugary type things. They want chips, which again,
are types of foods that again that are not you know the ketogenic route right yeah they're they contain a lot of starches starches are broken down as sugars inside your body and not only are you inhibiting your melatonin production which is going to throw off your sleep you're also keeping your blood glucose yeah around higher longer yeah which has all sorts of downstream effects
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Chapter 6: What are the health risks of blue light exposure?
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Chapter 7: Why is sun exposure critical for well-being?
Yeah, and also since it's the time when insulin production, it's not that insulin production has shut down. It's actually there is a trickle of insulin that comes out and it continues for a long time because it has to work hard to get the glucose absorbed. So then your insulin level remains high in the blood for a long time.
And that has a lot of other effects because insulin also promotes fat making. So our cells actually make more fat also in response to insulin. So that's another reason why late night eating can cause weight gain. Chronic late night eating. Chronic late night eating.
Even if the calories are the same, chronic late night eating could be or is, is it could or is contributing to weight gain?
Yeah, so this is something that has to come from clinical studies, but at least in mice or in laboratory animals, where we can accurately control what time they're eating, how much they're eating, what quality of food they're eating. There we can see that when they eat,
randomly or eat when they're supposed to sleep then they gain excess body weight yeah it's so fascinating because then it also helps many people understand how they feel like they're caught in a vicious cycle yeah because when you eat late at night and your glucose stays up and your insulin stays up again chronically we're not talking about the one or two times that people do that occasionally just to live your normal life that you're doing
you end up in a place where so many things are disrupted in your metabolic health, but then also that leaves you in the morning because your sleep is disruptive that you're more likely to have cravings for sugary, hyperpalatable foods the next day in addition to just feeling not 100%.
No, that's true. I mean, a lot of people, we think that we can get away with occasional late night eating. And this is where the circadian rhythm, again, some of the concepts of circadian rhythm kicks in. When we think about what are the adverse effects of disrupting our rhythm, we always think of people who do night shift work, evening shift work, or morning shift work.
And there is a rich literature from over the last 100 years. People have gathered a lot of literature saying that many people who work late at night or night shift workers, they are actually at a very high risk for metabolic disease. cardiovascular disease, heart disease, etc.
cancer, cancer, I think I read somewhere that demand mark now will, like will provide extra compensation for shift workers who are diagnosed with cancer. Yeah, because there's so much literature that's there with the association of shift work and cancer.
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Chapter 8: How do circadian rhythms impact chronic disease risk?
Engaged in some sort of work.
Some sort of work. You're not just lying in bed with your eyes open. Of course, if your eyes are open and you're watching TV, that's also... Sure.
Watching TV or if you're on your mobile phone. Yeah. That's also work as far as your body's...
Because your body is not resting. And if you do that, on an average, once or twice a week, that is shift work. Because your habitual sleep time, suppose, say, is 11 o'clock every night. And once or twice, you are staying awake either till one o'clock in the morning, or you're waking up at three or four o'clock in the morning to get to work or do something.
And now if we think about it, almost 70, 80% of us are shift worker, or we are living the life of a shift worker.
So if you look at the average person who's listening a day, because they're disrupted at least a couple times a week, they're looking at their phone, they're up for a couple hours, they can't go back to sleep, essentially they're a shift worker. They are a shift worker.
Talk to us about sleep debt, how it accumulates, and if people are listening today and they have sleep debt after you describe it, what can we begin to do? Is it again doubling down and making sleep a priority? So let's chat about it big picture. What is sleep debt?
Well, sleep debt is, our body needs, for example, seven hours of sleep because a lot of studies around the world, when they look at what is the average number of hours people sleep and what are the comorbidities or diseases or even longevity, what they find is six and a half to seven and a half hours in adults, older adults.
We're not talking about college students or high school students, older adults. That seems to be the sweet spot. People who sleep less, they have more comorbidities. And people who also sleep more, maybe they have underlying conditions. That's why they're sleeping more. They also have other comorbidities. Right.
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