Circadian Rhythm 101: How To Support Your Body's Internal Clock Every Day

Physician By Eva Selhub, M.D.
Dr. Eva Selhub is a resiliency expert, physician, author, speaker, scientist, and consultant. She studied medicine at Boston University and is board certified in Internal Medicine.
woman outside in the sun

Your internal clock, also known as your circadian rhythm, enables your body to automatically know when to wake up and get out of bed and when it’s time to go to sleep, eat, and even ovulate. It also plays a major role in how productive and focused you are.

Here's a quick primer on how this fascinating system works, why it gets messed up, and how to optimize it so you can go through every day feeling energized (and sleep through every night feeling restored).

OK, so what's the circadian rhythm?

The circadian rhythm is the biological mechanism that controls the sleep-wake cycle, when hormones are released for ovulation and digestion, and when it is time for your body to sleep so that your muscles can rest, your memories can consolidate, and your immune system can get stronger.

Just like the ebb and flow and rhythm of nature, your body also needs this internal clock to operate with the natural rhythm of the earth to maintain good mental clarity and healthy moods, heart function, stress levels, and immunity.

These crucial processes for your health and well-being are largely tied to the the natural light that comes from the sun’s rays that is picked up by the suprachiasmatic nucleus (SCN) in your brain.

When sunlight comes in through the eyes, the SCN picks up the cue that it's daylight and time to get up and be active. As the light diminishes and then disappears, the clock signals the body that it is time to sleep.

Every 24 hours, the clock is reset as sunlight comes through. In addition, genes, or "clock genes" found in every cell of your body, also influence this rhythm, regulating physiological processes like energy metabolism, immunity, and memory formation.


Is our modern lifestyle messing with our biological clock?

In short: absolutely. It's pretty cool that we have a clock that is able to adjust our biological rhythm to our environment, but it's not so cool that our clocks are actually fairly screwed up because we don't abide by nature’s rhythms.

We mess up our clock by staying up late, working on our computers or smartphones, rarely getting outdoors or exercising, eating processed foods, and going on drinking or food binges in the early morning hours, and then drinking large volumes of caffeine to stay awake—just to name a few.

To say that our circadian rhythms have been disrupted is an understatement. Every system of the body needs to be in sync for the system to work well and efficiently. When the circadian rhythm is off, the body goes out of sync.

It's not surprising then that the drastic change in lifestyle and human social habits in the last 50 years has been linked to the rise in diseases like obesity, diabetes, sleep disorders, depression, and certain types of cancers, autism, and a variety of dementias, disorders that are likely associated with disturbances in the circadian rhythm.

5 ways to adopt a circadian-rhythm-friendly lifestyle.

While the circadian rhythm is susceptible to disturbances, the good news is that it can be brought back on track with simple lifestyle changes like these:

1. Enhance natural light exposure.

It's important that you expose yourself to natural light (versus the light coming from your computer screen or TV screen), especially in the morning and throughout the day. Once evening sets in, start dimming the lights inside your home and make sure your bedroom is completely dark (no TV or LED screens) by the time you go to sleep.

2. Get outdoors.

Though it is helpful to use a lamp when necessary, it's also important to expose yourself to natural light throughout the day. Spend more time outdoors where you can, and consider taking longer trips in nature for the sake of your health.

Research shows that taking two or three days to go camping where you have no access to electronics or even watches (allowing the sun to dictate when to rise and when to go to sleep) can greatly affect your sleep-wake cycle.


3. Practice good sleep hygiene.

The more regular your sleep, the better regulated your circadian rhythm will be. Here are a few ways to clean up your sleep hygiene routine:

  • Make sure your room is only for sleep and sex and is kept dark, quiet, and free of electronics.
  • Relax and do other stress-free activities—like journaling or reading—for an hour before sleeping.
  • Do not take naps longer than 20 to 30 minutes.
  • Limit caffeine use in general, and do not have any caffeine in the evening.
  • Keep a consistent schedule for going to sleep and awakening, only varying by one hour every now on then (like on the weekends).
  • Try a sleep promoting supplement, like magnesium.

4. Eat at set times.

Harvard scientists have discovered that we have a food-related clock that might supersede the light-based master clock. It was likely designed evolutionarily to avoid starvation.

Their studies suggest that fasting can help readjust sleep clocks in people with jet lag, so you can try a 16-hour fast by eating an early dinner around 4 p.m. and not eating again until 8 a.m. the following morning. Then, go back to a normal eating regimen, making sure you have 12 hours in between dinner and breakfast the next day.

Even if you're not fasting, swapping heavy foods like dairy and saturated fats from meats with vegetables and lean protein sources and eating your larger meals earlier in the day can support your circadian rhythm.


5. Manage stress.

Your "clock genes" and the regulation of all biological systems are intricately connected to the stress response. Higher stress levels offset your stress hormones and your melatonin levels, leading to more dysfunction of your internal clock.

Meditating daily, taking mindful walks in nature, exercising regularly, and limiting your intake of triggering news are all things that can help keep your stress levels in check.

The bottom line.

Your circadian rhythm is essentially your body's internal clock, and it plays a big role in your mood and energy levels. You can keep yours humming along smoothly by avoiding artificial light at night, getting outside more during the day, and paying attention to your stress levels at all times.


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