7. Optimize Your Circadian Rhythm; Sleep Like a Champ

TL;DR: Get up with the sun, eat during the day, make sure to avoid artificial light before bed and keep your room cool and dark while you sleep in order to optimize your circadian rhythm.

What Is The Circadian Rhythm?

“If you want to find the secrets of the universe, think in terms of energy, frequency and vibration.” -Nikola Tesla [1]

The circadian rhythm is an internal biological cycle that regulates when an organism sleeps and when it is awake. The timing of the circadian rhythm is governed by a circadian clock in each cell, which has been found in not only humans, but plants, animals, fungi, and certain bacteria. The term circadian comes from latin circa (“about”), and dian (“a day”).

The circadian rhythm governs many vital functions in the body, and is controlled primarily by light levels in the environment, which is why our sleep cycles are usually in sync with the sun. Our modern environment, however, often confuses our circadian clock mainly due to artificial lighting, as well as eating too late, and sleeping in a room that is too hot.

For a little more theory on sleeping, see our article on why do we sleep?

Why Is the Circadian Rhythm Important?

Most of us know that awful feeling when it comes time to go to sleep, but our minds race on keeping us awake. On the opposite side of the spectrum, we all have those early mornings before work that test our strength as we struggle to pull ourselves awake. See our article for what to do on those days when you need a little energy boost here.

Why is it that sometimes when we want to be awake we aren’t fully, and when we want to go to sleep we struggle? What controls these underlying processes?

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The circadian rhythm.

The circadian rhythm came about long ago in our evolutionary history and has deep ties to many processes in our body. It is thought that the rhythm evolved in response to the light levels in the organism’s environment – which is correlated with availability of food [3]. Organisms that could “tell” when it was day time, which is when food is more available usually, could gather more food and reproduce more successfully. Food and other predictable daily repeating events grow faster than those that don’t, which has even been scientifically shown in cyanobacteria [4].

Just like in our ancient single-celled ancestors, we too have a rhythm embedded into our biology that dictates many activities in our body.

The following bodily activities vary according to the circadian rhythm:

Body temperature
Pulse rate and blood pressure
Reaction time and performance
The production of melatonin, serotonin and cortisol
Intestinal activity [5]
Neurotransmitter levels [6]

During waking hours, we are more catabolic – breaking tissues down – and during sleep we are more anabolic – building things up. This means that we can be more active during the day and use up nutrients and other resources, but at night we need to recover and build again. If we disrupt this process, key hormones like testosterone, growth hormone, and melatonin aren’t produced enough and our recovery suffers. [7]

See the image below for other physiological changes that happen to our bodies due to our circadian rhythm.

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Keeping this rhythm consistent and aligned with the sun will ensure that our bodies are properly synced to the day/night cycle, and will ensure that our bodies are running efficiently for the task at hand. The main factors that cause our circadian rhythm to become disrupted are being exposed to light when it’s dark out, going to bed too late or early compared to the sun, and eating too close to bedtime or during the night.

Sleep deprivation is very linked to circadian rhythm disruption, and sleep deprivation causes serious impairment. 63% of Americans self-reported that they do not sleep enough according to a 2011 study by The National Sleep Foundation. Sleep deprivation raises systolic blood pressure, leads to insulin resistance even in young people, and it is a predictor of the following: weight gain, traffic accidents, type 2 diabetes diagnosis, mental illnesses, developing the seasonal flu, and cardiovascular diseases [5].

People who have to work night shifts have a circadian rhythm that is misaligned with the sun, and it may be why one study found a 15% increased risk of coronary artery disease amongst nurses who worked rotating night shifts for 10 years or more [9]. Many other studies have found links between shift work and chronic disease, though it may not be conclusive.

How Does The Circadian Rhythm Work?

The circadian rhythm is governed by circadian clocks. Each cell has its own clock. In one celled organisms, there is only one clock, but in larger organisms like humans, each cell’s clock has to be synced with others in the body. Each cell can talk to each other by taking an input from other cells, using this input to regulate its clock, and output information to communicate to other cells.

All of these clocks sync together within a tissue and form a cohesive timing, so each organ has its own clock and all of the clocks are arranged in a hierarchy. The liver and brain are highest in the hierarchy and have the most central role in regulating timing. The master clock is located in a part of the brain called the suprachiasmatic nucleus (SCN) [3].

There are three main factors that control the circadian clocks:

Light – the dominant factor
Food
Activity

Sound, temperature and movements also play a role.

Light enters the retina in the eyes, and a signal is sent to the neurons in the SCN, which holds the master clock.

Ancient Egyptian Sun Gazing [10]

Light Levels

The amount of light required to impact and change the timing of the circadian rhythm is at least 1000 lux. An average sunny day exposes you to between 32,000 and 130,000 lux, but the typical office is between 300 and 500 lux. This means that the average office worker’s body doesn’t know that it is day time during work, which results in an unnatural circadian rhythm [5].

How Long is a cycle?

It has been found that in a lab setting at constant light, humans naturally settle into a 24.2 hour cycle. [14][15]

How Do I Optimize My Circadian Rhythm?

First, there is a lot for most people to improve on when it comes to circadian rhythm. Take each step one at a time and slowly chip away at your habits. The first step is to go to sleep and wake up at the same time every day. Next, control the timing of your: light intake, food intake, and exercise in that order.

Light – The Master Clock

Light is the primary regulator of circadian rhythm. Ideally, we would use the sun to time our rhythm, but advancement in lighting technology has greatly modified our environment – and impacts our circadian rhythm. Blue and green light (380 – 565 nanometers) have the strongest effect on circadian rhythm. When we have incandescent lights in our environment late at night – see below, it tricks our body into thinking it is day time.

Colors of light released from different types of lighting [6]

Light In The Morning

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To achieve a healthy rhythm, we should get blue light – ideally from the sun – as soon as we can in the morning and during the day. Ideally within half an hour of waking, and for at least 10 minutes, but more is ideal. The earlier our blue light exposure in the morning, the earlier our melatonin starts secreting at night – leading to better sleep quality [17]. Interestingly, early morning light exposure has even been linked to leaner body composition. [6].

In one study, 34 overweight women were exposed to white light for 45 minutes between 6 and 9 am, and on average they lost significantly more fat than the placebo group – 0.35 kg, and lowered their body fat % and appetite. [18]. There are also studies that show relief of seasonal affective disorder with morning light exposure.

Sunlight is ideal for setting the circadian rhythm, but if that is not practical, you can still use a bright light when you wake up. See more in our article on sleep products.

Light at Night

On the flip side, make sure that you limit blue and green light exposure at night. The main sources of light at night are indoor lighting, and computer and phone screens. Both of these sources can be controlled by avoiding them, modifying them with software, or wearing blue light blocking glasses – see our article on sleep products. Ideally, reduce blue light exposure at least an hour or two before bed.

It is especially important to keep your bedroom as dark as possible during sleep. In one study, regular room light levels reduced how long melatonin stays in people’s system during sleep by 90 minutes, AND in 85% of people, it reduced total melatonin secretion by more than 50% [19]. Even small amounts of light in the bedroom have been linked to 65% increased risk of depression in one study [20].

Don’t use your phone or tablet close to bed unless you have modified the screen’s light output to reduce blue and green light, which can easily be done with an app. Research from the Lighting Research Center at the Rensselaer Polytechnic Institute in New York observed that using an iPad at midnight reduced melatonin by 8% and using it at 1am reduced melatonin by 23% [21].

While blue light at night may be bad for your sleep, the good news is that red or near infrared light one to two hours before bed may help secrete more melatonin [22]. See more on red light therapy.

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Food – Peripheral Clocks

So far we’ve covered the master clock governed mostly by light. The clocks in the other organs and parts of the body are called the peripheral clocks. Each clock has its own rhythm, but it is important that all of the peripheral clocks and the master clock are in sync. In addition to light, food also impacts the circadian rhythm, especially the peripheral clocks. As stated in one study, “food intake can uncouple peripheral clocks from control by the SCN”. This means that to sync them up and have a properly timed body, we need to control the time period in which we eat.

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Eating during the day time is the most important factor here; ie try your best to only eat while the sun is up. Also, try to eat the majority of your calories earlier in the day if possible, as well as your fats. Save most of your carb-rich foods for dinner. Along the same vein, don’t eat within 3 to 4 hours of bed, ideally.

Next, work on maintaining a consistent eating window of between 6 and 12 hours. If you only eat while the sun is up, you’re already likely doing this. Eating all day is very bad for your circadian rhythm, even though most people do it – see the graph below. It is very easy and beneficial to shorten this window. A popular example is the noon to 8pm eating schedule for men, and 8am to 8pm for women. Some people go as far as to eat one meal a day (OMAD), but that may be extreme.

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Next, eat at the same time every day so that you establish a rhythm. Just as a regular bed time will impact circadian rhythm, so will regular eating times. Some studies have observed a correlation between irregular eating patterns and metabolic syndrome and obesity, and one controlled cross-over study found that irregular eating decreased the thermic effect of food, increased appetite, and impaired blood sugar control [23].

Mental and Physical Exercise

Both physical and mental exercise should be performed during daylight hours when possible because being active is an ‘awake’ signal to the body. Along the same line, remain active during the day, and use as much energy as you can mentally and physically so that you feel more tired by bedtime.

Temperature

Colder temperatures in the night stimulate sleepiness, and warmer temperatures in the morning make you more awake. If you can, program your thermostat for a few degrees in either direction if possible, or use a cooling pad at night – see sleep products. One tip is to go into a sauna or steam room and have enough time to cool down before bed because this temperature change is what seems to trigger sleepiness.

Interestingly, insomniacs usually have a higher core body temperature right before bed than regular sleepers. It appears that higher temperatures cause the brain to be more active and have a harder time slowing down to enter sleep. Higher brain activity, or not being able to stop thinking, actually raises the temperature of a person’s brain keeping their body stuck in day time mode. Research has even shown that wearing a water cooled helmet that cools insomniacs’ heads before sleep helped them sleep almost as easily as regular sleepers, and the colder the better.

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Sounds

Sounds seem to keep us awake, which may be obvious. Keep your bedtimes as quiet as possible – even people’s voices may stimulate our brains into a waking state. One interesting tip for mornings is to have birds singing, or even to sing yourself to stimulate wakefulness. The theory is that for millions of years we heard the sounds of birds when waking up and we have associated this with morning time biologically.

Another kind of noise that may actually help us sleep better is using pink or white noise machines to drown out other noises. If you find noises keep you up at night, try a pink or white noise machine – or good old fashioned ear plugs. See more in sleep products.

“But I’m A Night Owl”

Many people think they are night owls, but most often it is the case that their environment over the years has pushed their circadian rhythm later. At the end of the day, do what feels best and experiment a bit. Try to go to bed closer to the sunset and wake up closer to the sunrise for a week consistently and see if you feel any better. If you want an outside perspective on your natural circadian timing, try an MEQ test, which helps you to determine your chronotype – see more on the 4 chronotypes in our article here.

Summary

There is a lot of information in this article. If there’s one thing you do, keep your circadian rhythm in sync with the sun. Sleep at a consistent time. During the beginning and middle of the day before the sun sets, be active, get outside, and eat most of your food for the day, then relax and stop eating as it gets dark out. Make sure that your room is very dark when you are sleeping or it will impact your sleep quality. When you’re awake, be fully awake, when you’re resting, be fully at rest and get the best of both worlds.