What is a Circadian rhythm?
Circadian rhythm refers to the 24-hour cycle that controls many biological processes. It is often said that if hormones are the symphony of our body, circadian rhythm is the conductor. This cycle helps the body regulate certain functions to specific times within 24-hours; for example, at night we sleep and repair, during the day, we eat, metabolize, and move. Due to the circadian rhythm, our body knows when to sleep, when to wake, and how to fluctuate release of hormones, blood pressure, temperature, insulin sensitivity, and many other functions. A regulated circadian rhythm is essential for health.
Why is it important?
Our circadian rhythm is controlled by the master clock of the brain, the suprachiasmatic nucleus of hypothalamus (1). This structure is connected to the retina of the eye, and is regulated by light exposure through the eye – or the absence of it. Exposure to light and dark influences the rhythm of the body, regulating the ebb and flow of hormone release. Cortisol and melatonin release is regulated by our circadian rhythm; both are hormones that influence our sleep-wake cycle (2). Cortisol promotes wakefulness while melatonin promotes sleepiness.
A German word meaning ‘time givers’ – refers to the external factors that influence our internal clock. Light is the most important factor, playing a huge role in regulating our circadian rhythm, but nutrients, nutrient timing, temperature, exercise, and social activity also play a role (3). Our ancestors lived in direct communion with the zeitgebers, and in turn had a healthy, well-regulated circadian rhythm. Nowadays, we are exposed to many factors that disrupt this cycle and we ignore the natural fluctuations of ’time givers’, leading to imbalances in our hormones, sleep issues, impaired immunity, and elevated stress hormones. Healing our circadian rhythm requires a return to the zeitgebers we once knew so well.
How to Heal Your Circadian Rhythm
1) Begin the Day with (sun)Light
The transition from darkness to the blue light present in early morning light exposure signals to the brain that it is morning, leading to a suppression of melatonin release and an increase in cortisol (4,5,6). Get at least 15 minutes of exposure, without sunglasses, to allow the photoreceptors in your eyes to register the blue light and send the signal to your brain, regulating your hormone cycling for the day. In a sunny climate, there is a high amount of blue light present; on a cloudier day, you may need more time outside. If it is a dark and cloudy day, or you are a shift-worker (and therefore not following the natural cycles of the sun) you can use a light box for 15-30 minutes first thing in the morning for a similar effect.
2) Remove blue light exposure at night
Since blue light signals to our brain that it is daytime, exposure to blue light at night is detrimental to our circadian rhythm. Unfortunately, many of us are consistently exposed to blue light via our phone, television, and computer in the evening. Blue light exposure inhibits the release of melatonin, the hormone that signals to our brain that it is time to sleep (7). Ideally, we would eliminate exposure to technology at night, since the blue light, as well as the onslaught of information, can be disruptive to sleep patterns. However, if you plan to work on your computer or use your phone in the evening, install f.lux or use the Night Shift feature (on Apple devices) and set the screen brightness to low. If you have to be in an environment where you will be continually exposed to blue light, or are a shift worker, you could benefit from amber-tinted glasses that block blue light from reaching the photoreceptors of our eyes. Whenever possible, dim the lights in the evening, or install red or yellow light bulbs into lighting fixtures you use at night.
3) Sleep in a cool, dark room
Lower temperature and darkness signal to your body that it is nighttime and time to sleep (3). Both factors play a huge role in regulating your circadian rhythm. Flashing or constant lights from alarm clocks, cell phones, baby monitors, house alarms, or other devices are stimulating and disruptive to our circadian rhythm. Cover lights, plug your phone in to charge outside the bedroom, and use a mechanical alarm (if you have a certain time you need to wake-up). Preferably, wake naturally with the increase in daylight in the morning; if this isn’t possible, you could invest in a light-based alarm.
4) Eat Well to Sleep Well
Certain building blocks are required to make melatonin, such as tryptophan. Halibut, tuna, crab, and turkey are all great sources of tryptophan. Tart cherries, walnuts, and almonds are natural sources of melatonin (8,9). Keeping blood sugar stable by limiting high glycemic foods and eating sufficient protein and fat throughout the day helps keep our hormones balanced. But be mindful of going too low-carbohydrate – research suggests it may interfere with sleep quality (10). Experimentation is helpful in determining what carbohydrate level is ideal for you. This is true of nighttime eating as well; for some, eating close to bedtime is disruptive to sleep, while others find that it stabilizes their blood sugar, leading to deep and undisturbed sleep.
5) Limit Alcohol
Although many people find it relaxing to finish their day with a ‘nightcap’ of beer or wine, studies show that this is not ideal for your circadian rhythm. While alcohol may help us fall asleep, it leads to an increase in disruption in the second half of sleep, as well as a decrease in REM sleep (11). This rebound effect can lead to waking in the early hours of the morning and being unable to fall back asleep. Additionally, since alcohol causes vasodilation, you may experience night sweats after drinking, an additional sleep disturbance (12). Alcohol also may increase your chance of experiencing sleep apnea (13).
6) Reduce Stress
Stress is linked to the release of cortisol, the stimulating hormone that we naturally release in the morning. Stress leads to elevated and dysregulated cortisol and disruption of our circadian rhythm (14). Healing our circadian rhythm must involve stress reduction. Whether it includes reducing your workload, asking for help, changing your appraisal of conflict, or decreasing the use of stimulants, stress reduction is key. Adding stress-reducing practices such as meditation, yin yoga, journaling, going for a walk, and tai-chi can also help to regulate our circadian rhythm and promote hormone balance.