Sleep is a really important part of life. Sure, you might not be conscious while it’s happening, but take it away and you won’t be feeling all too well. Our body needs sleep to repair and function properly. But to get to sleep, it’s necessary that our body knows that it’s nighttime. That’s what the circadian rhythm is for.
In this post, I’m going to give you a bit of an explanation what the circadian rhythm really is, why you should even care, and finally, some ways to improve it.
WHAT’S THE CIRCADIAN RHYTHM AND WHAT DOES IT DO?
Your circadian rhythm is the 24-hour rhythm in which your hormones regulate each of your body’s functions. It’s your body’s daily to-do list. For instance, in the morning, your body should wake up and get ready for the day. At night your body should start producing hormones to put you to sleep.
All this is regulated by your body’s internal clock, which is attuned to a normal day. The circadian rhythm works in a 24-hour loop, which means it does al these things about every 24 hours. This helps our body adapt to the Earth’s 24-hour day cycle.
The main clock is situated in your brain, in a part called the suprachiasmatic nucleus (but let’s just call it the SCN for now). Besides the main clock, there are many different clocks situated in different parts of our body. There’s even a separate circadian clock in each of our different cells.
These are peripheral circadian clocks that tell the time for each of the different organs. For example, the peripheral clocks in the digestive system respond to the intake of food and tell you when to be hungry.
It’s the job of the central clock, the SCN, to synchronize all these other clocks. Imagine for example if you worked together in a team, and each of your team members had their own watch. Suppose that you have a job that you have to do together at 2 PM, but each of your watches is set on a different time.
To make sure everybody starts at the same time, you synchronize your watches. To do this, it’s the SCN that says: “this is 2PM, everybody synchronize their watch to mine” If everybody operates on a different time schedule, your entire plan would fall apart. That’s why the SCN makes sure all clocks are synchronized. If your circadian clocks were the A-Team, your SCN would be Hannibal.
In a normal, healthy human with a good circadian rhythm, all these clocks are finely attuned to each other, and this allows your body and even all your individual cells to perform whatever task needs done in perfect harmony.
However, it’s possible that your clocks are off balance, or that all the different clocks are set at a different time. This isn’t a good thing and leads to a lot of chaos going on in your body.
Imagine if you’re a businessman and you’ve got a meeting today with an important client. The problem is, your watch is a few hours off and you get to the meeting at 5 PM while the meeting was actually at 3 PM. That would be bad for business, right?
Or imagine you have a date with a new love interest. You were supposed to meet for coffee at noon, but your watch is one hour off. Well, congratulations, you stood up your date and blew your chance with what could have been the love of your life.
The best analogy you can make is music. If an orchestra doesn’t play in harmony, the music doesn’t sound very good either.
The same goes for the hormonal rhythms in your body. When the circadian clocks aren’t synchronized, your cells aren’t working together in harmony and important stuff doesn’t get done properly.
If we’re talking about sleep, for instance, it might be nighttime and it’s dark outside but you’re not sleepy because your clock is 6 hours overtime, so you’re not producing melatonin at that time. Since you don’t produce melatonin, you don’t become sleepy.
But the circadian clock does so much more than just sleep. The circadian rhythm regulates the time of day when you have the most strength, when you’re most alert and even the time you’re supposed to get horny.
When your circadian clocks are finely attuned, you will have good sleep and good health. When your circadian rhythm is messed up, your health will suffer greatly. Poor circadian rhythm is linked with increased risk of heart disease, diabetes, cancer and a whole range of other debilitating diseases.
And if that weren’t enough, it also makes you fat.
This basically means that a disrupted circadian rhythm will wreck your health in every conceivable way.
So trust me, it’s really in your best interest that you take good care of your internal clock.
WELL THEN, HOW DO I MAKE SURE MY CLOCK IS SET RIGHT?
First of all: the circadian clock doesn’t regulate itself. It doesn’t automatically follow the right pattern no matter what you do. Even if it’s 10 PM on your watch, that doesn’t mean your brain knows it’s that late, because your cells on their own don’t know how to read a watch by themselves.
So there must be something else, right? Some other way our body tells time?
There is. To tell time, your body uses cues from your environment. Those cues are called zeitgebers, a German word for ‘time givers’.
One of those, and probably the most important one, is light. Exposure to light is the primary cue that our body uses to tell time. That actually makes sense, doesn’t it? Because what’s the big difference between day and night? When it’s day, the sun is up and there’s a lot of light outside. At nighttime, it’s supposed to be dark.
When light from any kind of source, enters your eyes, it activates your SCN, signaling to your central clock that it’s daytime.
Remember that we used to live in a world without electronic lighting. In this world of days gone by, most light we had to go on was the light of the sun.
Sure, we could make fires in the evening. But we never came even close to the constant bombardment of electric lighting and computer screens that we expose ourselves to in the present day.
When it was nighttime, it was pretty much completely dark, and your body could tell that it was either night or day.
It’s the kind of light that makes all the difference too. Light has different wavelengths that each have its distinct colour. Light consists of various wavelengths such as blue light, red light, infrared light or ultraviolet light (as well as some others).
For circadian rhythm, it’s mostly blue light that matters because it’s this wavelength that our brain associates with day. Exposure to red light isn’t likely to mess with your circadian clock. Electric lights emit a high amount of blue light (although relatively weak), whereas a fire would emit mostly red and infrared wavelengths. That means a candle has a different effect on your circadian rhythm than a lightbulb.
AN HOUR OF SUN A DAY KEEPS THE INSOMNIA AWAY
To set your circadian clock, it’s important that you expose yourself to a lot of intense light during the day, so your brain can actually tell that it’s daytime. It’s not enough that your indoor lighting is on all the time. No, you actually have to get outside in daylight for this. That’s because the intensity of the light is very important too.
We measure the intensity of light in lux, like we measure our weight in pounds or kilograms, or temperature in degrees. The higher the amount of lux, the stronger the light and the more powerful of a daytime signal that light gives.
For instance, if we sit in front of a computer screen, we expose ourselves to 50 lux worth of light, maybe a bit more. Compare that to a sunny summer day. On a day like that, we can expose ourselves to light in the range of 100.000 lux. As you can see, there’s no competition for sunlight.
Ideally, you spend the entire day outside in the sunlight, so your circadian clock perfectly attunes to the natural day/night cycle. This makes it easier for you to become sleepy at nighttime. That’s the ideal scenario.
Unfortunately, in this modern world of ours, it is a very unrealistic one. We have jobs to go to, we have to sit inside our little cubicle and stare at our computer screen. Society does not make it easy for us to live according to our evolutionary blueprint.
Getting enough light exposure doesn’t need to be a black or white scenario, of course. It’s not like you either get sun all day long or no sunlight at all. There is definitely some wiggle space for you to work with. Even an hour or two more sun exposure can make all the difference between good sleep and poor sleep.
To get more sunlight exposure, you have a couple of different options. For example, you can ride to work on your bike every morning to expose yourself to morning sunlight, instead of driving a car. At lunchtime, you can go outside for half an hour to have your meal. Small things like those can already produce a noticeable effect on your circadian rhythm.
Alternatively, you could buy a special lightbox that emits very powerful blue light. These light boxes mimic the intensity of sunlight and emit a high amount of lux, and while they’re not even close to the real thing, they’re still a good alternative if you are usually inside most of the day.
THERE’S A DIFFERENT SIDE TO THIS AS WELL
As sure as you need lots of light during the day to tell your brain that it’s daytime, you need to completely avoid light during the evening to make sure it knows that night is coming.
Watching TV or sitting in front of a computer screen in the evening is one of the worst things you can do to wreck your circadian rhythm.
Now, I know, most of the time we can only watch TV or sit behind our computer in the evening because we’ve got jobs or school to go to.
So it sounds like I’m saying: don’t have any fun at all in the evening, just live in darkness and go to bed.
Again, that would be a little extreme, and there are workarounds to this. For example, there’s a computer program called f.lux you can install on your computer that filters out blue light. It doesn’t filter out all of the blue light, but it still gets rid of a fair amount of it.
If you want to completely block out blue light and still don’t want to give up your TV, you can always get some blue blocking glasses. They’re quite cheap, and they work really well in filtering out blue light coming into your eyes.
All of this doesn’t really matter that much if you got enough sunlight during the day. If you spend all day outside, exposed to intense sunlight all day, looking at a TV in the evening isn’t going to disrupt your circadian rhythm all that much.
However, it’s different if you only get outside for two hours a day. In that case, blue light emitting screens are definitely going to have a noticeable impact on your ability to sleep.
It definitely matters how the rest of your day was.
RECAP – FOR GOOD SLEEP, DO THIS:
– In the beginning of your day, right after you wake up, get outside and expose your eyes to daylight. If it’s still dark outside, use a lightbox (I use this one) that emits high intensity blue light. This is CRITICAL!
– During the day, get outside as much as possible. Go for a stroll at lunch break. Instead of driving somewhere in your car, go on foot or use your bike. The more daylight exposure you get during the day, the stronger the effect on your circadian rhythm will be.
– After the sun has gone down, make sure you avoid any more blue light exposure, be it from computer screens, your TV or your cell phone. Dim the lights as much as possible, preferably wear blue blocking glasses. Reading on e-ink devices like your Amazon Kindle is still okay, as long as there’s no backlight. Of course, a regular book is the gold standard.
Remember, the most important thing is that the body can tell the difference between day and night. The larger the difference is between the amount of light in the day versus the night, the better your body will be able to tell when it’s actually day and when it’s actually night.
If your circadian rhythm is strong, you can just chuck out your melatonin pills. Your body is perfectly capable of producing melatonin on its own when your biological clock is functioning properly.
If you follow these instructions, you will have markedly improved sleep. And remember, light is just ONE of the different environmental cues that your body uses to tell time. Nevertheless, proper light exposure is the most important one, and it’s the one you should try to optimize first.
I also want to make the point that just fixing light exposure by itself might not fix your sleep problems and get rid of your insomnia in one blow. Sometimes you have to resolve other metabolic and hormonal issues as well. However, proper circadian rhythm isn’t just a nice thing to have, it’s the basis of good sleep.
And it’s a must have for good health in general.