Circadian Rhythms are 24-hour cycles that control physiological function in all living beings. They are commonly referred to as “sleep-wake cycles” but they control much more than just that.
Have you ever wondered how your body knows when to go to sleep and wake up, why you get hungry at the same times every day, or why your doctor tells you to take a blood test at a certain time of day? These can all be explained by your circadian rhythm.
There are 2 “clocks” that help the body keep track of time: central and peripheral clocks. These let your cells know what to do at the right time.
The main one is your central clock. The central clock is located in the Suprachiasmatic Nucleus (SCN) of the brain and it is the master regulator of biological activity. You can think of it as the pacemaker that controls the rhythms and timing of all of your physiological functions. Activity, rest, appetite, hormone secretion, body temperature; it controls everything.
The way it does this is through communicating with clock genes in peripheral cells. Each gene has a clock gene in front of it that controls its genetic expression. The relatively recent science of epigenetics has taught us that it’s not the actual genes that matter so much as the genetic expression.
Circadian rhythms have a MASSIVE impact on gene expression. Circadian rhythms also control the function of your mitochondria and microbiome.. yes even the bacteria in your gut have a circadian rhythm and are performing different functions based on the time of day.
Put simply, your circadian rhythm is arguably the most important foundation of health as it controls nearly every system in the body. When we disconnect from our natural rhythms, disease ensues.
It is also important to note that in addition to daily rhythms we have other natural biorhythms longer in duration than 24 hours known as infradian rhythms. The most common example of this would be the female menstrual cycle approximately every 28 days. Another example would be seasonal variations in biological functions.
Peripheral clocks are located in your peripheral tissues. These are in part controlled by the central clock but also have some independent functions.
What Controls Circadian Rhythms?
Circadian rhythms exist in the absence of any external inputs but are strongly impacted by our environment. Environmental or external cues that help to synchronize our rhythms are known as Zeitgebers (meaning time-givers).
Major Zeitgebers (plus there are several other inputs)
- Light
- Food
- Exercise
- Temperature
Light is by far the MOST important input to synchronize our circadian rhythm. Before the invention of electric lighting in the 1800’s, there was no such thing as artificial light. Since the beginning of life on Earth the only sources of light were the sun, the moon, the stars, and fire. Humans have evolved with these as their only sources of light up until very recently. We are all familiar with the concept that we can produce Vitamin D from sunlight (UV-B) which is extremely important for our health, but beyond that there is very little mention of light’s impact on our biology.
The sun provides a variety of different spectra throughout the day that serve different functions in regulating our circadian rhythm. For example, the morning sunrise provides a small spike of blue light which releases cortisol and activates our body for the upcoming day. On the opposite end of the day, the absence of light stimulates the release of melatonin to shift our body into sleep mode. As a society that spends 90+% of it’s time indoors, it’s evident that our circadian rhythms are seriously out of whack!
Tips:
- Spend as much time as you can outside at different times of the day (without getting burnt)
- If there’s only one time you get outside, make sure it’s during the sunrise!
- Avoid artificial light at night (check out our blog on the effects of blue light at night) after the sun has set
- Use NaturoBlocks blue blocking glasses to protect yourself from artificial blue light
Food
Timing of food is another major Zeitgeber. Time-restricted eating is a powerful practice to ensure you are keeping your circadian rhythm intact. To learn more, be sure to check out our recent blog on Time Restricted Eating!
Eating late at night is one of the worst things you can do for your health because it signals your body that it’s still daytime which severely impacts sleep quality. Your digestive system (like all other systems) is regulated by your circadian rhythm and functions best during the day. For example your insulin sensitivity and digestive enzyme release are both highest during the morning/mid-day. This is consistent with traditional systems of medicine that almost uniformly recommend eating the majority of your food at this time.
Tips:
- Eat when the sun is up
- Stop eating minimum 3 hours before bed
- Minimize your eating window to 12 hours or less
Exercise and Temperature
These are less relevant but still important. Exercise is obviously a day-time function thus you should not do any type of strenuous exercise late at night. Your peak coordination, reaction time, muscle strength, and cardiovascular function are all during the afternoon.
Body temperature fluctuates throughout the day and the most important takeaway is that a decrease in body temperature improves sleep function. Always sleep in a cool environment and avoid elevating your core temperature before bed.
SummaryIf your circadian rhythm is not functioning properly you will see little results with many other lifestyle changes or supplements. It is the foundation of physiological function, therefore we MUST respect our natural rhythms and cycles. The absolute best way to reset your clock is to go camping for a week. You will be forced to rise with the sun, eat and exercise during the day, and rest at night free of artificial light in a cool environment. This is how we are designed to live and I can almost guarantee if you fix your circadian rhythm you will achieve a new level of energy and vitality!