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The Connection Between Melatonin, Cortisol, Light and Your Sleep!

Many of us have heard of the term circadian rhythm, but are not really sure what it means. According to the Sleep Foundation, circadian rhythms are 24-hour cycles that are part of the body’s internal clock, running in the background to carry out essential functions and processes. One of the most important and well known circadian rhythms is the sleep-wake cycle.

When it comes to sleep we know it involves much more than just simply putting your head on the pillow, closing your eyes, turning off your brain, and opening your eyes in the morning. In fact, there is an internal ecosystem that is at work within your body that is closely connected with your environment to help produce hormones and neurotransmitters that are needed to help you fall asleep and wake up energized the next day.

The two hormones at play are melatonin and cortisol. Let’s take a closer look.


Melatonin is a hormone produced in response to darkness and is controlled by norepinephrine (another name is noradrenaline) - which is part of the parasympathetic nervous system - allowing us to “rest and digest” when secreted. Melatonin is derived from serotonin also known as the “feel good” hormone. Serotonin is derived from tryptophan, which many know is high in turkey! Have you ever wanted to take a nap after that Thanksgiving meal? You have tryptophan to thank for that! A few other tidbits about melatonin and its effects are:

  • Melatonin should be highest at night

  • Light exposure suppresses it production, therefore darkness increases its production

  • There is 400 times more melatonin in the gut than in the brain (it always goes back to the gut!)

  • It is a powerful antioxidant

  • Balances appetite hormones

  • Too much melatonin can negatively impact the circadian rhythm and sleep

  • Too little can also negatively impact the circadian rhythm and sleep


Many have heard of the hormone cortisol, it is often associated with stress and is produced by the adrenal glands. It is controlled by the sympathetic nervous system, also known as the autonomic nervous system, and directs the body's rapid involuntary response to danger or stressful situations AKA “fight or flight.” The opposite from melatonin. Cortisol is produced when our body perceives any stress. This stress can be acute (short term), such as giving a speech for work or school, getting into a heated argument, or being stuck in traffic, to name a few. Cortisol can also be released over a long period of time due to chronic stress. The body is good at handling acute bouts of stress. We are designed to recover from these short term stressors. But the body is not as good at handling chronic stress. And, to be clear, cortisol is not all bad, it is when cortisol is chronically elevated it can become an issue. A few more facts on cortisol:

  • It is your get up and go hormone

  • It should at its highest in the morning

  • Light exposure helps produce cortisol

  • It helps to regulate metabolism

  • It supports memory formation and learning

  • Chronic cortisol production can result in taxed adrenals, weight gain and fatigue

  • Low cortisol can cause fatigue, memory issues, hormonal issue, and trouble concentrating

So what does this have to do with your sleep?

The key to regulating your sleep cycle is light. How long and when you are exposed to light plays a significant role in your body’s production of melatonin and cortisol.

The circadian rhythms throughout the body are connected to an internal clock, called the circadian pacemaker. This master clock is located in your brain. When light enters your eye, it hits your retina, which is then transmitted to the suprachiasmatic nucleus (SCN) in your hypothalamus, and on to the pineal gland. This is where the body makes melatonin from serotonin. Therefore, when light is hitting your eye, melatonin is suppressed and cortisol is increased. If light is not hitting this area, melatonin is increased and cortisol is suppressed.

Since light exposure has such a profound effect on these two hormones, it makes sense to support our circadian rhythm and get morning light exposure and throughout the early day….which will boost our cortisol production in the morning and inhibit melatonin. The opposite is just as important to our circadian rhythm. At night, it is important to reduce our light exposure to help support these hormones…increase melatonin production and reduce cortisol, by limiting light.

Unfortunately, our internal clock does not recognize the difference between artificial blue light and sunlight. So even after the sun has set, and you are watching TV, working on your laptop, phone or tablet, or even in your room with LED lights, your body will send a signal that there is still light and melatonin will be suppressed…which is when you need to wind down. Your cortisol will still be up, which keeps you more alert and awake, and your melatonin is not being produced which we need to get into a relaxed state to sleep well.

If you are struggling with falling asleep or staying asleep, your production of these two hormones may be at play. Take the time to reinforce your circadian rhythm by incorporating these tips to your sleep routine:

Morning Routine:

  1. Try your best to get morning light either by sitting near a window or getting outside in the light. Before you even pick up your phone, watch TV or get on your computer. As the days are getting shorter this is getting harder to do. You may find you can’t get light before you do some of these things, but once that sun comes up make sure you make an effort to get real light in the morning.

  2. Also, taking a break from your morning routine by going for a morning walk or exercising outdoors is another way to get your morning light.

Afternoon Routine:

  1. If possible, eat lunch near a window or outside. In the winter eating outside may not be something many of us will want to do, but keep this in mind on those milder days or when the weather lends itself to this.

  2. Stop drinking coffee ideally before 2pm.

  3. Make sure you also avoid other foods and drinks that contain caffeine (chocolate, teas, and energy drinks). Here is study showing how caffeine resets your internal clock when we drink it too close to bedtime...And, I appreciate what Kenneth Wright, a sleep and circadian physiologist at the University of Colorado, Boulder has to say, who participated in the study. "The circadian clock goes way beyond “sleep and wake”, the circadian clock is present in cells throughout our entire body. It's in your fat cells, it's in your muscle cells. It's in your liver, for example, as well as in your brain. And irregularities in the circadian clock have been linked to everything from obesity to cancer.” We have to remember, all things matter.

Evening Routine:

  1. The timing of your dinner can affect your sleep cycle, it is best to eat before 7pm to maintain normal sleep patterns.

  2. You can dim your lights and turn off lights that you don’t need.

  3. Finally, please make sure you monitor your blue light from your devices.

    • Get blue light blocking glasses

    • Or add apps to your laptops, iphones, tablets that block the bluelight. Most already have this feature for this very reason, make sure you and your loved ones are using them!

I hope this explains the importance of your sleep-wake cycle, and helps to create some new routines for you and your family. It is important to pay attention to our body's internal clock and recognize the patterns when our hormones are off.

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