As with other hormones, using Melatonin properly requires some basic knowledge of what and how it does in your body. Hormones are VERY powerful molecules, and are VERY precisely controlled to do good, not harm.
Where does melatonin come from and how does it work?
Melatonin is synthesized by a tiny pea-size gland right in the middle of your brain, the pineal gland. The pineal does not store melatonin. Once it is made, it is instantly released in tiny quantities into the circulation.
Thus, presence of melatonin in your blood depends on WHEN melatonin is synthesized.
"It is Night!" or why Light matters
Melatonin informs all the cells that it is Night. Moreover, it tells them that the Night is "normal", meaning it is really Darkness around you. This is accomplished by an elegant way melatonin production is regulated through a combination of the Clock and Light signals.
The Clock restricts the timing of melatonin production to what it believes to be Night. If the Clock believes it is Day, melatonin will not be secreted, no matter whether you are in bright light or in a pitch-dark room.
Still, Light has special powers over Melatonin. If light interrupts nighttime darkness, melatonin synthesis is halted instantly. Whichever melatonin is still in your blood is then quickly destroyed by the liver.
It takes a while to turn melatonin synthesis back on after lights are turned off. Practical advice - keep the lights real dim if you wake up at night, just enough not to trip over.
Nature rule: Light and Melatonin are not meant to be together! Tiny melatonin quantities circulate in your body only if your Clock thinks it is Night and only if there is no Light around.
Take-home message: Melatonin is produced only when your Clocks permit, and this is only when the Clocks think it is Night. Light exposure interrupts Melatonin production at night.
Why is it important for cells to know whether it is Night or Day?
Would it be easy for you to plan things for the next few hours if you would not even know whether it is Day or Night right now? Presumably not. Our cells are no different. They have a lot to accomplish every day to stay alive and healthy.
Their complex molecular work has to be done in a very specific order, similar to an assembly line. Thus, cells have to coordinate their work with each other real well and keep the same pace or Period.
Imagine that your brain cells are on schedule, ready to think and memorize right after you wake up, only to find out that other cells missed their schedule of delivering nutrients or oxygen on time. Being smart would have to be postponed.
Your cells are highly specialized, and so is the timing of when they do certain things. Thus, when melatonin reaches a cell and tells "It is Night!", what that cell will do depends on its specialization. Some will start housekeeping, other produce hormones, or build neuronal networks.
Take-home message: Melatonin is an important message of Night for your cells. It coordinates their specialized nighttime activities.
What if your Clock is mistaken, and it is not Night outside your window?
This can happen for several reasons, Jet Lag being the most obvious one. You fly a jet across several time zones very fast. This takes your Circadian Clock by surprise. While your Clock still believes it is Night, based on your regular New York time, you are enjoying a sunny view of Rome.
What will happen to melatonin in such case? Melatonin production will occur only at the times when your Clock permits, i.e., during your Clock's "subjective Night" according to New York time, and only if there is no Light around to suppress melatonin synthesis.
During the real "objective Night" in Rome you will lack melatonin, since your Clocks would think it is Day and would not permit melatonin production. This, in part, interferes with your sleep, since Melatonin promotes sleep in humans.
The only good news is that the Nature Rule that Light and Melatonin should not co-exist, will remain in effect. Why is this a good news? Because having two signals that tell your body the exactly opposite is very confusing and can cause damage.
For example, think of your eyes and its main photosensory part, the retina. Retina values melatonin so much that, in parallel with the pineal gland, it makes its own melatonin at night, just not to get short of it. Melatonin helps retina to repair itself after a long and tough daytime work. It also makes retina more sensitive to Light, in case the night vision is needed. If melatonin is present in the eyes at the same time when Light bombards it with photons, retina is damaged.
Take-home message: During Jet Lag, melatonin will not be produced throughout the entire Night, until your Clocks synchronize with local time.
What happens if you take melatonin as a drug or supplement?
There are a few issues to consider, if you want to treat yourself the right way. Those include the dose, preparation, time of administration and their optimal combination.
After you take a pill containing melatonin, the Clock & Light control over melatonin levels in your body takes backstage. Now, you are the one who is in charge of doing it right. When you are in a cockpit, better know a few rules to fly safe.
Drug or Supplement?
In some countries, Melatonin is sold as a drug and requires doctor's prescription. In other countries, it is freely available and labeled as food or dietary supplement. Without getting into what, how and why is defined as a food supplement, let us just clarify the relationship between Food and Melatonin.
First, your body never relies on food when it comes to Melatonin. All the Melatonin your cells are normally exposed to is made by your pineal gland at night. Other sites of Melatonin production, such as your eyes, are making very little quantities and for their own local use.
Second, whatever we eat has negligible amount of Melatonin, if any. Even those food products that are reported to contain more of it, still have only nanograms per pound or kilogram. To give you a perspective, an equivalent of the lowest dose of melatonin we recommend (0.1 mg=100,000 nanograms) is contained in 82 lb (37kg) of walnuts, 60L of cherry juice concentrate or 5500 bananas.
Is there a way for our diet to reduce our melatonin levels? Yes, there are.
Protein malnutrition can affect Melatonin, since it is produced in the pineal gland from an essential amino acid Tryptophan, which we can acquire only through food. Thus, if your diet is extremely low in proteins, your circulating melatonin levels may suffer. Tryptophan deficiency is extremely low in developed countries and related to problems with its absorption, not ingestion. The effects of other dietary products on melatonin synthesis by the pineal gland are not well studied, though caffeine and alcohol were reported to suppress melatonin levels.
Take-home message: Melatonin is a hormone that our body produces in small amounts and only at night. Melatonin does not come to us through food and its use should be treated as any hormone therapy, with knowledge and care.
After you take a small oral dose of Melatonin (0.1-0.3 mg), your blood melatonin levels will quickly rise close to what you normally have at night (~50-150 pg/ml in blood). Depending on the dose taken, what else you consumed in parallel, and how fast your liver metabolizes melatonin, increase in blood melatonin levels will occur within 15-30 min and will last for 3-6 hours.
If you will take a higher dose of Melatonin, you will increase its circulating levels way above those that your cells are normally exposed to.
This excessive Melatonin will be keeping your liver busy, since it has to metabolize it. This may take your liver away from other 500 tasks it is supposed to do to keep you in good health. This can also change the way other drugs used in parallel are metabolized, changing their blood concentration.
Your fat cells will be also picking up excessive Melatonin, since it easily dissolves in fats. Later, these fat cells will be slowly releasing Melatonin back into your blood throughout the day, the time when melatonin signal should not be present.
All these are bad news for different reasons, even though Melatonin does not seem to have an acute toxic effect when even high doses are consumed.
Importantly, unless you block the Light exposure after taking Melatonin, the Nature Rule is broken. Your entire body and especially the Circadian Clock will be confused by Light and Melatonin coinciding in time. This is because Melatonin will be telling it is Night, while Light will indicating that it is Day. Even your eyes would not know whether to adapt to light or darkness, and this can hurt your retina.
Take-home message: Use low-dose melatonin (0.1-0.3mg). Make sure that either the lights are off or you are blocking the light with a sleep mask, or dark sunglasses for around 5h after taking a pill.