What is the role of Melatonin on sleep?

At the heart of the sleep-wake cycle lies an internal 24-hour clock. This is the first element in this cycle. This clock diligently dictates whether we feel tired or wide awake at regular intervals. Think of it as your body’s timekeeper, engaging in a constant conversation with every organ, ensuring they all play in harmony. This clock, intriguingly, operates on a 24-hour schedule, ensuring that it syncs up with our planet’s 24-hour day.

The second element in this sleep/wake cycle is a chemical substance that builds in your brain called Sleep Pressure. Simply said, it is the (good) fatigue that slowly accumulates in your system throughout the day.

These two elements create a balance between energy and sleepiness, allowing one to feel energy throughout the day and enough fatigue later in the day to be able to sleep during the night.

The hormone of darkness.

Now, let’s introduce our star of the show – melatonin, affectionately known as the “vampire hormone” or the “hormone of darkness.”

Melatonin is not a sleeping aid in and of itself (at least not for healthy individuals), it has little influence on the generation or the quality of sleep. Its main role is to regulate the timing of when sleep occurs, hence, it is the host of sleep. Melatonin is a messenger used by the 24-hour internal clock in the brain to communicate with the rest of your brain and body about the sleep-wake cycle.

The process for melatonin to be released is as follows. The 24-hour clock in your brain, when receiving the change in light frequency at the end of the day and perceiving dusk, instructs the pineal gland (deep in the back of the brain), that it is dark, and melatonin can be released. Melatonin goes into the bloodstream with a loudspeaker shouting out a clear message to your body “It’s dark, it’s dark”.

The race for sleep.

Using a metaphor shared by Dr. Matt Walker, imagine sleep as a 100-meter race, with melatonin as the voice of the official starter, shouting “Runners, on your marks…”, and firing the starting pistol.

Here’s the catch: melatonin is an official, not a racer. The true participants in this race are the brain regions and processes that actively generate sleep. Melatonin’s role is to round up the “runners” (the brain regions and processes) and guide them to the starting line of bedtime. In essence, melatonin provides the official instruction to commence the sleep event (being the timing official) but doesn’t take part in the race itself (the runners do).

Once asleep, melatonin decreases across the night into the morning hours. In the early morning, as sunlight enters the brain through the eyes (even with closed eyelids), a brake pedal is applied in the brain, shutting off the release of melatonin. The absence of circulating melatonin now informs the brain and body that the “finish line” of sleep has been reached. The race of sleep is over.

So, to recap, melatonin is a hormone, that gets released in the brain as soon as it detects darkness, as a messenger shouting out loud to the body that it is soon time to sleep, yet it does not generate sleep itself.

Do not light up the night.

So, what happens when we use artificial light (lamps, light bulbs, devices, TV, etc.) after sunset?

From an evolutionary perspective, it is only recently that humans have changed the day/night cycle by using more and more artificial light at night pushing towards a later bedtime. Artificial evening light, even that of modest strength can trick our internal clock into believing the sun has not set yet. The brake on melatonin, which should have been released with sunset, remains applied, and melatonin is not released.

In a study comparing healthy individuals reading a printed book versus an iPad or tablet at night before bedtime, it was found that the electronic device suppresses melatonin release by over 50% at night. Indeed, tablet reading delayed the rise of melatonin up to three hours, relative to the natural rise in the same individuals when reading a printed book. When reading a tablet, the melatonin peak, and thus the instruction or gunshot to start the sleep race (using the same analogy as before) did not occur until the early morning hours, instead of before midnight.

These individuals also took a longer time to fall asleep than when reading a paper book, on average delaying sleep for 90 minutes per night. One night may seem insignificant, but by the end of the week, that is almost 11 hours of sleep deprivation, making us, humans, the only species that voluntarily deprives ourselves of sleep.

Melatonin supplements.

We cannot close on the topic of melatonin without referring to OTC supplements:

OTC melatonin is not carefully regulated by the FDA. Scientific evaluations have found (supported by a study of The University of Guelph) that melatonin supplements vary from 83% less than the label suggests to almost 500% more than the label suggests, making it a very unreliable supplement.

But still, OTC melatonin consumption has quintupled in North America in the last 20 years. An answer may lie in the use of modern light and electronic devices. Based on a survey conducted by the Sleep Foundation, “U.S. adults spend 3.5 hours on social media before bed each day” and 74.7% of social media use occurs before bed.

We just said that melatonin is a hormone naturally produced by your body and regulated by light exposure and darkness. We, and not the rotation of the planet, now decide when it is “night” and when it is “day” creating an unbalance of the natural 24-hour predictable pattern given by nature.

Boost your melatonin.

Other than a call to action on this topic, we aim to share with you information on melatonin, how the human body works and the reasons why a supplement may not be the first answer to solve sleep issues (unless your physician has prescribed it).

Understanding how this “100 mt race called sleep” works and the role of melatonin in your sleep performance is key for you to make educated changes in your daily routine or teach others (kids for example) the habits that will allow for a better, deeper, and restorative sleep.

The best five practices you can include in your day to regulate melatonin are:

Expose yourself to morning light 30 minutes after waking up (if you live in the hemispheres, then turn on the lights upon waking and enjoy a bit of sunlight as soon as the sun rises). Do not use sunglasses, but please do not look at the sun.
Go for a short walk (5-10 minutes suffice) at dusk. Let your brain know the sun has set and darkness is here.
Dim the light at night.
Stay away from electronics (including TV) one hour before bedtime.
Keep your bedroom dark during the night.

Sleep tight and don’t let the lights bite (your melatonin),

Rosana