What is Circadian Rhythm and why is it important?

As we head into a new season and the skies become darker, it can really help us establish proper sleeping habits if we have a deeper understanding of our circadian rhythm.

The Cortisol Hormone

Our adrenal glands produce cortisol, which is our "fight or flight" hormone. We have two adrenal glands that sit on top of the kidneys. I like to say they are tiny but mighty. They secrete cortisol in response to any perceived stress. I highlight the word perceived. We are hardwired for a specific rhythm of cortisol, and this is very important because this means that we are also wired to have high cortisol levels in the morning and low cortisol in the evening. So as the sun rises in the morning and sets in the evening, so does cortisol. When we escape from this rhythm, it is significant.

Cortisol is an acute hormone. It saves our lives, but is time-limited, meaning it's there to stop the pain and then return to a baseline. We can compare this to running from a tiger in the jungle. Cortisol will come to save us. Today, we are not running from a tiger, but we have to survive each day, and cortisol helps us do that. Most of us will never have to run from a tiger, but we get stuck in traffic, eat the wrong foods, create long to-do lists that we worry about, and cortisol is there to help. It’s a (wear and tear) hormone helping us get through our day. By the end of the day, the cortisol, just like the sun, is low and allows us to sleep to recover, wake up and repeat our day to day activity.

The Circadian Rhythm

Unlike in the primitive days, we have changed cortisol from an acute hormone to a chronic hormone, and we have disconnected our natural living with the sun. We are catabolic by day and anabolic by night. When we go to sleep is when the growth and repair occurs.

This hormone balance is dictated by what we call circadian rhythm. Cortisol peaks at 6:00 a.m., and lowers throughout the day, and is at the lowest point at 10:00 p.m. This is when growth hormone, testosterone, and melatonin (the sleep hormone) take off. If your cortisol is high in the evening, you inhibit the output of these three essential hormones. The most crucial hours of sleep are between 10:00 p.m. and 2:00 a.m. when your pituitary gland puts out the most growth hormone.

It is important to understand that cortisol is secreted in response to any perceived stress, including eating the wrong foods, overthinking, emotional thoughts, and worry. When we perceive stress, we trigger a primitive part of our brain, above the midbrain's brainstem, an area called the reticular activating system (RAS). The RAS is where we initiate the signal for stress or cortisol release. The RAS sends an alert to the next part of the chain called the locus coeruleus, one of the smallest parts of the brain, but one of the most connected. That message is then released to the hypothalamus, saying it is time to release cortisol. The hypothalamus sends that signal to the pituitary that messages the adrenal glands. This hypothalamic-pituitary-adrenal influence is called the HPA axis.

Getting back to that rhythm of cortisol, when people have disrupted sleep, as in shift workers, they have disrupted that cortisol rhythm. There are people you may know who call themselves "night owls." They like to stay up late taking care of projects, catching up with their day, working in front of the computer, etc. They tend to get into bed after midnight, disrupting that precious sleep cycle. They say they feel fine and only need six hours of sleep. If they do that repeatedly, it will eventually catch up. You can adapt to that stress for a long time, decades perhaps, but at some point, the body says, "enough". These people put out cortisol when they should not be. Turning on electronics, even something as innocent as cruising social media appears harmless, yet these activities tell your brain that you are supposed to be awake—the response is an increase in cortisol. The body can only put up with this for a while, and then exhaustion takes over .

Sleep is affected, and your performance at work and school diminishes, followed by little to no exercise; later, joint pain and autoimmune disease. Humans can adapt to stressors for a while, and then the body begins to show wear and tear. The elevated cortisol at night blunts the anabolic output of hormones for growth and repair. If you cannot keep up with cortisol demands, you cannot put out as much cortisol over time. If you can't put out as much cortisol, you'll lose that cortisol reserve. The result? Our cells slow down, we become less efficient, and ageing accelerates.

How to optimize sleep in line with our cortisol release

Cooperating with the rhythm of cortisol means that you are in bed by 10:00. The hours before bed are not in front of a computer working on projects, but rather spent reading a book, listening to music, playing with pets or in nature. This will set the tone for a restful sleep. Keeping the bedroom cool with an open window and very dark is crucial. Added to that is placing your cell phone and other EMF items in another room. If you absolutely need an alarm, there are many options available that are called sunrise alarm where color mimics the sun rising that are more gentle and very effective. Getting up in the morning as close to the rising of the sun as possible will ensure that you are in the rhythm and have the ability to work with cortisol as it peaks.

Frances Michaelson

A pioneer in the fitness industry, Frances opened the first personal training center in the West Island of Montreal in 2001. In 2008 , Frances had the “gut feeling“ that there was more to learn about health and how our bodies function, which led to further her education in the field of Naturopathy and holistic nutrition. She has since authored two books. Her latest book, "Do you Have the Guts to be Healthy" was published in March 2021. As a trainer and naturopath, she truly loves seeing people transform themselves by trusting their bodies instead of getting caught up in the medical system. Practicing health is the only way to live the gift of life well!

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