Here is the full transcript of researcher Emily Manoogian’s talk titled “Pay Attention To Your Body’s Master Clock” at TEDxSanDiegoSalon conference.
Listen to the audio version here:
TRANSCRIPT:
For the past ten years, I’ve been studying chronobiology, the timing of biology. I’ve got to explore the field through endocrinology and neuroscience, and all my experiments have been in the lab. But to design my latest experiment, I found myself on a rooftop at 3 a.m. watching an elevator rescue, and then 20 minutes later, speeding down the middle of the street in a fire truck.
And those were two of eight calls that we went on between 10 p.m. and 6 a.m., all so I could understand the demands of a 24-hour shift schedule on firefighters. At the end of that ride-along, I went home and I went to sleep. And at the same time, a lot of firefighters on call that night were just starting their next 24-hour shift.
As a researcher here at Salk, I’m now applying my knowledge of chronobiology to help a wide variety of individuals, including firefighters, to help prevent and treat disease. I’ve been in the field of chronobiology for a while, and I’m still blown away by the importance of timing in biology and the beautifully intricate system that regulates it. And it still astonishes me that, as a society, we’re largely unaware of and thus ignore our biological clocks.
Circadian Rhythms
Circadian is Latin for “about a day,” and we use the term “circadian rhythms” because in almost every living organism, we see clear 24-hour patterns at every level of biology, including behavior, physiology, and even individual cell function. In humans, when we think of behavioral rhythms, the first thing that comes to mind is sleep and wake cycles. But we also have rhythms in our mood, cognition, and learning.
We even have daily patterns in the language that we use, our concerns, and our emotions. At the physiological level, pretty much anything that you would get tested at the doctor’s office has a circadian rhythm. For instance, your heart rate and blood pressure naturally rise in the afternoon and are lowest while you sleep, and you have a peak of triglycerides in the morning.
Due to these daily changes, it’s a pretty good idea to schedule your doctor’s visits for the same time of day every time. And all these changes in physiology and behavior all stem from rhythms in individual cells. And if you look at it collectively, mentally and physically, you’re a different person at different times of day.
Now, all of these rhythms come from within you. So if I stuck you in a constant environment, those rhythms would still persist. But that’s not the world that we live in.
Master Clock
So our body also looks for cues, like light and food, to coordinate with the world around us. And it’s this combination of your body’s internal rhythms with external cues from the environment that determine our rhythms and physiology and behavior. So how do we do this?
Almost every cell in your body has a molecular clock that keeps about a 24-hour rhythm. Now, I say “about” because each one keeps a slightly different time, so you need something to coordinate them. To do this, we have a master clock in our brain called the suprachiasmatic nucleus, or SCN for short, which is a complicated name for where it’s located.
Now, what you’re watching is a video of the SCN from a mouse brain with a fluorescent tag attached to a piece of the molecular clock. So every time that piece of the clock is made, it lights up. Now, this video is taken over many days, but one full wave is about 24 hours.
Now, not only does the SCN coordinate all these clocks throughout your body, but it also incorporates external cues from the environment. And it’s this coordination that allows our body to prepare for the day ahead. It helps us be alert when we wake up.
Circadian Disruption
It has our digestive system ready to process food when we eat, and it helps our organs rest and repair while we sleep. Now, the two biggest cues you can give your body to tell at the time of day is light and food. And evolutionarily, those were very reliable cues to know the time of day.
Fortunately, in modern society, light and food are available and taken advantage of around the clock. This can lead to circadian disruption. Circadian disruption occurs when those internal circadian clocks are challenged by conflicting external cues. The most common examples are shift work and jet lag. Over 20% of the U.S. population does shift work. Each schedule is a little different, but they all face abnormal patterns in sleep, eating, and activity.
They’re the crux of our society. They keep everything going. Our newscasters, cleaning crews, chefs, construction workers, journalists, and the heroes of our society, the firefighters, police officers, doctors, EMTs, nurses, and military, they take the hardest schedules, mentally and physically challenging, just to support our community.
Jet Lag and Social Jet Lag
Yet, unfortunately, shift work is linked to a wide variety of diseases. In fact, the World Health Organization actually lists shift work as a carcinogen. Yet, there’s still no way to stop these risks from increasing and keep doing harm.
Now, you may not do shift work, but I’m guessing that everyone here has been jet lagged. And I’m not just talking about that first day of sleep deprivation. I’m talking about those following days of muscle weakness, nausea, moodiness, fuzzy thinking, and exhaustion at seemingly random times of day. That’s a feeling of circadian disruption. And this is because our bodies were not meant for airplane travel. For every hour that you make your body shift, it takes about a full day to catch up.
So, if you fly from San Diego to Paris, a nine-hour phase shift, it’s going to take your body about eight to ten days to get there.
So, on that first day when you’re having breakfast, your body thinks it’s time to go to bed. And on that last day when you’re about to fly home and you’re finally feeling good again, you’re going to make your body shift all over again.
Now, unfortunately, circadian disruption is not limited to shift work and jet lag. Our society has become exceptional at ignoring and disrupting our body’s natural rhythms. It can start with something really simple. Say it’s a Friday night and you’ve had a really long week and all you want to do is come home, relax, and just, you know, let it ease off. So, you do, you eat, and then, you know, it’s time to binge watch your favorite TV show. And then you’ll need a drink or a snack to go with it.
And the show is very good. And so, you’ll need another drink. And before you know it, it’s one or two in the morning before you finally put that last drink or snack down. And that sounds like a great Friday night. Unfortunately, Monday rolls around and you’re back on your regular schedule. You might be waking up two or three hours earlier than you did on the weekend.
It’s a very common story. It’s a very common way in which we naturally disrupt our body’s rhythms. In fact, it’s so common that there’s actually a term for this. These really large shifts between our weekdays and weekends or free days and work days is actually referred to as “social jet lag.” Your body may be in the exact same city, but it feels like it’s traveling back and forth between two or three time zones every weekend, like San Diego to New York or Mumbai to Tokyo. Chronic circadian disruption has wide impacts on your health. The circadian system is linked to every level of physiology.
Health Impact of Circadian Disruption
So, disrupting those rhythms can lead to an increased risk for a wide variety of diseases, including reproductive disorders, metabolic disorders such as diabetes, cardiovascular disease, cancer, neurodegenerative disorders, and mental health issues such as bipolar and depressive disorders. In fact, our lab came up with the list of over a hundred diseases that are linked to circadian disruption. So, what are we going to do about this?
As I said, light and food are the two biggest external cues you can give to your body to tell it the time of day. Light talks directly to that master clock in your brain, the SCN, and food talks directly to all the other clocks in your body. Research is ongoing, but this is what we know so far.
You need to keep your body on its schedule so it can prepare itself for what it needs to do. This means using those external cues to support your biological clocks. Tell it when it’s morning and when it should be awake, and decrease stimulation at night so it can get a proper rest.
Timing of Light and Food
First, let’s talk about light. We’ve all probably heard of the role of light in sleep. In the morning, you need to get lots of bright light. I’m not talking about office light. I’m talking about natural sunlight. You can easily do this by taking a 10-minute walk outside, or if the only light that you’re going to get is on your commute to work and the sun isn’t hitting you directly in the eyes, try not wearing sunglasses.
And at night, to tell your body it’s time to rest, dim or turn off lights that you’re not using, and if you’re going to be looking at a computer, phone, tablet, try using a blue light filter. Well, what I’m really excited to talk to you about today, and what all of my research is pretty much currently focused on, is the timing of food. Now, don’t get me wrong, what and how much you eat is extremely important for your health, but recent studies have found that when you eat is just as important.
Your body needs at least, at least 12 hours of fasting every day to function properly. Our lab uses a smartphone app called My Circadian Clock to understand when people eat. In one of our recent studies, we found individuals have an average eating interval of 15 hours a day. That’s nine hours of not eating. That means if your eyes are open, your mouth is open.
Recent studies have found that time-restricted eating, which only changes when you eat, not what you eat, can improve glucose tolerance and insulin sensitivity, can lead to about a 5% weight loss, improves endurance, and decreases blood pressure.
So, how does only changing when you eat have such a big effect? First, your body has a natural rhythm and glucose regulation, so it interprets food differently at different times of day. A bowl of ice cream at noon is going to be much easier for you to digest than it is at midnight.
Secondly, as I said, you need 12 hours of fasting so your body can properly rest and repair. When you’re continuously taking in new calories, you break up that rest, and you never get to break down the energy stores that you already have, meaning you never burn fat. Over time, this can lead to weight gain and eventually to diseases like diabetes and cardiovascular disorders.
And finally, food is a wake-up cue to the brain. So, you’ll fall asleep after that late-night drink or a snack or a heavy meal, but the quality of sleep that you’re going to get is going to be greatly decreased. Time-restricted eating is a simple lifestyle change. Eat within the same 10-hour window every day. That’s it. So, if the first thing that you have is at 8 a.m., the last thing should be at 6 p.m.
Now, the exact time of day is going to depend on your schedule and your preferences. The only restriction is that you leave at least three hours before you go to bed of only water so your body can get that proper rest. Now, I realize that a lot of you just did some mental math, and I’m probably not your favorite person right now, because you may have just interpreted what I said as, if you want to be healthy, you can no longer have a social life or go get drinks or you’re only going to have to day drink all the time, and that’s not completely true.
Conclusion
What I’m saying is timing matters, and when you eat is just as important as what and how much. The same way that you should eat a healthy meal every day, you should also eat it when your body expects it and give it at least that 12-hour rest. Of course, there are going to be cheat days. That is completely fine. Same way you eat cake, you might end up eating it at night, and it’s okay. Awareness is really the issue.
Acting like the timing that you eat doesn’t matter is like thinking French fries are just as healthy as broccoli. I went on that 24-hour ride-along because I’m designing an experiment to help test the benefits of time-restricted eating on firefighters on a 24-hour schedule. They can’t change when they get a call or when they get a chance to sleep, but by changing something as simple as when they eat, they have long-term benefits on their health and make those 24-hour shifts a lot easier.
The circadian system is a pillar of health that, for far too long, has been ignored or misunderstood, and we now know that with simple, non-invasive lifestyle changes, we can support our biological clocks to optimize performance, delay the onset of age-related illnesses, and prevent and treat disease. Thank you.