Using the Intelligence of Circadian Rhythms to Optimize Your Sleep
When we talk about wellness, emphasis is often put on what we do for our health. But as biologist Dr. Satchin Panda tells us, when you do these things may be just as important: Our internal clock, or circadian rhythms, control many of our body’s daily processes, like digestion and the sleep-wake cycle. Panda, whose research has greatly contributed to science’s understanding of circadian rhythms, explains how we can best optimize our internal clocks for better sleep and overall health.
A Q&A with Satchin Panda, PhD
Circadian rhythms are the different things that happen in our body on a daily basis according to our internal clock. Our brain has a clock that is internally programmed1 and tells us when to sleep and when to wake up. Almost every organ in our body has a clock, too. The clock in our stomach controls when digestion happens and when it turns off and rests. Even our skin has its own clock that determines when skin repairs itself.
These rhythms keep us healthy. If you break the natural cycle of these clocks by eating late or sleeping less, you slowly become predisposed to a variety of diseases, including diabetes and obesity.
The circadian rhythms in our brain are connected to the outside world via light that enters our eyes. Our brain’s circadian clock releases melatonin at night and tells us it’s time for sleep after the sun goes down, and when the sun rises, melatonin decreases, waking us up. For a long time, we’ve known that there are many people who are blind and cannot see the outside world but still can sense light that can regulate the timely rise and fall of melatonin. Almost twenty years ago, we discovered that there’s a special protein called melanopsin in the eye that senses blue light and tells the body that it’s morning or night. Melanopsin senses blue light specifically because sunlight is rich in it. And many blind people also have this melanopsin protein, which explains how our eyes can sense light and synchronize our brain clock to the day-night cycle.
“Managing blue light—increasing your exposure to it during the day and reducing your exposure to it at night—can help keep your circadian rhythms functioning optimally.”
As we’ve begun to research blue light more, we’ve discovered that exposure to blue light through indoor light, tablets, and phones can increase our alertness and may be related to adverse health effects, such as depression. We were not designed to see the amount of blue light that we do these days. For the past 250,000 years, humans were exposed to candlelight or firelight at night, which don’t have that much blue light. Only in the last 150 years have we had electrical lighting. Today, if you went to a grocery store, the light there would be thousands of times brighter than simple candlelight and also would contain much more blue light, which confuses our brain about whether it’s day or night. This keeps us awake and leads to poor-quality sleep. It also suppresses the production of melatonin and disrupts our sleep cycle when viewed at night. Managing blue light—increasing your exposure to it during the day and reducing your exposure to it at night—can help keep your circadian rhythms functioning optimally.
A cup of coffee in the morning resets our internal clock to the same extent that bright light does. We can use coffee to our advantage during the first half of the day to help us wake up and feel more alert. Coffee first thing in the morning along with a bit of physical activity and having your first calories of the day will help synchronize the brain clock and the body clock.
However, in the late afternoon or evening, coffee begins to work against your clock. It signals that it’s morning and has an alerting effect on the brain, which can negatively affect sleep.
The amount of natural melatonin a person has is very individual. As we get older, we produce less and less of it. Supplementing with melatonin or a melatonin precursor, such as adenosine, may be helpful as you age. Timing is important, because melatonin doesn’t just make our brain sleep; it makes our entire body sleep by slowing down how our body processes carbohydrates and sugar. Wait at least one hour after eating your last meal to take melatonin so that it does not interfere with your blood sugar control and can help you sleep better.
Genetic studies have found that some people may have rare mutations in certain genes that allow them to get away with less sleep. Conversely, there are also other genes that make certain people need more sleep. The caveat to this is that you may function better if you get more sleep, regardless of your genetics. If you habitually sleep for six hours, try to get one or two more hours of rest and see if you feel any different the next day.
If you can, try not to set an alarm on some days. When we don’t set the alarm to wake up, we get the sleep our brain needs.
The brain remembers how much sleep we lost from one night. The next day, we need to recoup those hours of sleep lost with extra sleep or we’ll feel cranky, which is called sleep rebound. If a person stays awake for an extra three or four hours one night, their circadian rhythm is affected for two to three days as it tries to reset back to normal. This can knock out half your week as your clock tries to catch back up. This is especially relevant for shift workers, and studies have shown that shift work may increase the risk of cancer. But if you’re someone who stays up late sometimes on the weekends, it would be too extreme to be overly worried about cancer risk. However, research does suggest that it may still increase your risk of diabetes and obesity.
“If a person stays awake for an extra three or four hours one night, their circadian rhythm is affected for two to three days as it tries to reset back to normal.”
Sleep rebound is very obvious with high school kids and young adults. But as we get older, our brain doesn’t remember how much sleep we had the previous day and we wake up not feeling that tired, even if we didn’t get much rest. That doesn’t mean that we haven’t done some damage to our health; it’s just that our brain doesn’t remember that we have to catch up. That’s why some people think they need only six hours of sleep per night, while really their bodies would do better with more.
If you can get more sleep to recover from a restless night, that is always better. Any sleep debt you pay off is better than not paying it off. If you can’t make up the sleep for some reason, I recommend doing a little bit more physical activity or eating less the next day, which can counter some of these negative health effects.
When we eat affects our sleep. In some of the studies we’ve done with the app called myCircadianClock, we ask people to record when they eat, and we have found that nearly 50 percent of adults eat for fifteen hours or longer during the day. That means from their first meal or first cup of coffee at 6 a.m., they are having their last meal or sip of wine late into the night. We now know that these long periods of eating are not good for our health—they disrupt the circadian rhythm and affect our sleep. On the other hand, time-restricted eating for ten hours of the day gives our body time to rest.
As far as exercise, just as our brain needs to sleep at night and is more active midday, our muscles are much better prepared for exercise in the late afternoon. Between 5 and 8 at night is the best time to exercise because our muscles may be more flexible, our joints may have less chance of injury, and we may recover much better from exercise. And there’s new research showing that exercising at the right time can also boost the circadian rhythms because on days we exercise, we tend to sleep better. We’re just beginning to study the relationship between circadian rhythms and exercise, which could have exciting implications for athletes. For example, performance could be enhanced by having them practice at certain times of day.
1. Try to be in bed for eight hours so that you can get between six and seven hours of sleep.
2. After waking up, wait for at least one hour but ideally two hours before you have your first calorie from either food or a drink.
3. After eating your first meal, eat all of your calories from food and drinks within ten hours.
4. During the daytime, step outside for at least half an hour to get enough bright light. You don’t have to look at the sun; even under shade there should be enough light to synchronize your biological clock and get the mood-boosting benefits. Plus, it’s totally free.
5. Two to three hours before your bedtime, don’t eat or expose yourself to bright blue light.
Satchin Panda, PhD, is a professor at the Salk Institute for Biological Studies and a founding executive member of the Center for Circadian Biology at the University of California San Diego. He is a leading expert in circadian rhythm research and has published a book called The Circadian Code, detailing his research findings.
This article is for informational purposes only. It is not, nor is it intended to be, a substitute for
professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice. To the extent that this article features the advice of physicians or medical practitioners, the views expressed are the views of the cited expert and do not necessarily represent the views of goop.
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