A circadian rhythm is a roughly 24-hour cycle, in the biochemical, physiological, or behavioural processes of most life on Earth, including humans. The term “circadian” comes from the Latin circa,  “day”, meaning literally “approximately one day”.


These circadian rhythms are controlled by a ‘master clock’ in our brain called the suprachiasmatic nucleus. It uses signals like light and darkness to know when to release certain hormones and neurotransmitters that tell us when to wake up and be active or to withdraw and go to sleep. From the beginning of time, people have awakened to morning light and fallen asleep in nighttime darkness. That’s how we’re genetically programmed to operate: We’re energized during the day and sleepy at night.


This is how it works:


In the morning, our body clock responds to the light by producing the hormones cortisol, adrenalin, and serotonin. Cortisol, produced by the adrenal glands, wakes us up and gets us going in the morning. Serotonin helps us regain consciousness, and adrenalin keeps us energized and active. As the morning wears on, the body clock signals cortisol levels to drop while continuing to increase levels of adrenalin and serotonin.


As the day goes on, our body temperature, which starts out low, begins to rise, and so does our metabolism. The body clock signals us to become hungry, and it signals the liver and digestive system to process nutrients. By midday, our metabolism is reaching its peak. That’s why midday is the right time to have your largest meal because midday is when your body is primed to deal with a lot of food.


Later in the afternoon, the body clock reduces its output of active, energetic hormones. Body temperature begins to fall, metabolism slows down, and we begin to wind down. Because of these slowdowns, we are poorly prepared to digest a large dinner when most North Americans have dinner, at around 6:00 to 9:00 PM, which is why smaller meals at dinner time are better suited to your inner rhythm. As the evening progresses and light fades, the body clock signals the pineal gland to convert serotonin into melatonin and we become tired. As melatonin and other sleep hormones increase, our temperature continues to drop, and we start thinking about withdrawing for the night; it becomes difficult to stay awake. This is the best time to fall asleep. Body temperature continues to drop as melatonin is released into the bloodstream.


Melatonin continues to be released until the body clock perceives a gradual increase of light. In the morning, the production of melatonin shuts down and the body clock begins the active cycle again, releasing cortisol. As sunlight increases, the body clock begins producing adrenalin and serotonin. And another day begins.


Melatonin production is controlled by light exposure. Your brain should secrete more in the evening, when it’s dark, to make you sleepy, and less during the day when it’s light and you want to stay awake and alert. However, many aspects of modern life can disrupt your body’s natural production of melatonin and with it your sleep-wake cycle.


Melatonin is a naturally occurring hormone controlled by light exposure that helps regulate your sleep-wake cycle.


It is very uncommon to have a melatonin deficiency which means it is very uncommon to actually need to take a melatonin supplement. If you value your sleep and you create a lifestyle that supports healthy sleep you should never need to take a supplement. Melatonin will be released as it should be, when it should be.


This can be difficult because we live in a society that encourages working late hours and spending more time than is healthy in front of screens. “Burning the midnight oil” is far too common and leads to sleep deprivation. Unhealthy foods too close to bedtime, drinking alcohol too late in the evening, and and not taking the time to prepare for bed are all things that will surely lead to struggles with sleep.


Spending long days in an office away from natural light, for example, can impact your daytime wakefulness and make your brain sleepy. Then bright lights at night—especially from hours spent in front of the TV or computer screen—can suppress your body’s production of melatonin and make it harder to sleep. However, there are ways for you to naturally regulate your sleep-wake cycle, boost your body’s production of melatonin, and keep your brain on a healthy schedule so you won’t need to be supplementing with hormones.


  • Turn off your television and computer. Many people use the television to fall asleep or relax at the end of the day, and this is a mistake. Not only does the light suppress melatonin production, but television can actually stimulate the mind, rather than relaxing it. Try listening to music or audiobooks instead, or practicing relaxation exercises. If your favorite TV show is on late at night, record it for viewing earlier in the day.


  • Don’t read from a backlit device at night (such as an iPad). If you use a portable electronic device to read, use an eReader that is not backlit, i.e. one that requires an additional light source such as a bedside lamp.
    Change your bright light bulbs. Avoid bright lights before bed, use low-wattage bulbs instead.


  • When it’s time to sleep, make sure the room is dark. The darker it is, the better you’ll sleep. Cover electrical displays, use heavy curtains or shades to block light from windows or try a sleep mask to cover your eyes.


  • Use minimal light if you go to the bathroom at night. If you wake up during the night to use the bathroom—as long as it’s safe to do so—keep the light to a minimum so it will be easier to go back to sleep.


  • Have a 30 minute bedtime routine. Our bodies need time to prepare for sleep so taking the time right before bed to wind down and relax will help you fall asleep quickly.


If you are practicing these healthy sleep tips and still struggling to sleep well you can contact sleepwise.ca for a free sleep evaluation.



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