Melatonin: What is it? What is it for? Function, Side Effects, Contraindications and How to Take it

It is a neurohormone produced by the pineal gland, and it is believed that its primary function is to regulate sleep.

This hormone is produced from the moment you close your eyes. At the moment that there is light, nevertheless, a neuro-endocrine message generates a blockage in its formation. Therefore, the secretion of this substance is determined almost exclusively by the photosensitive structures, and significantly it is activated at night.

Melatonin is a substance classified as indoleamine and its precursor to serotonin, an important neurotransmitter. It is speculated that the photoreceptive structures of the retina and pineal gland produce Melatonin, the modification of the serotonin synthesis pathway through an enzyme, serotonin N-acetyltransferase.

The circulating Melatonin acts in different organ systems and prepares to induce sleep. This production apparatus is present in invertebrates in general.

It is also believed that maternal Melatonin could help control the infant’s sleep cycle. Surveys have shown that the babies showed synchronicity with the mother. Since Melatonin is present in breast milk and its concentration is higher at night, babies sleep more when they have been breastfed at night.

The pineal gland must secrete this substance correctly to achieve restful sleep. In addition, it is assumed that other functions are carried out by Melatonin, such as the body’s thermal regulation and changes in sexual behavior.

Production and Action

As with serotonin, Melatonin is also produced from an amino acid called tryptophan, which is usually ingested in a balanced diet. The concentration of serotonin in the pineal gland increases during the day while there is light, the reverse of what happens with Melatonin.


As we have seen, the production of this chemical substance is directly related to the presence of light. When light strikes the retina of the optic nerve, other neuronal connections lead to the pineal gland, through which there is inhibition of melatonin production.

The increase in production occurs during the night between 02: 00-03 a.m., in a normal life rhythm, and this increase in sleep helps in production yields.

During normal sleep, it is where much of the energy and organic balance is restored, and the proper production of Melatonin with other concomitant phenomena produce:

  • Significant decrease in the production of cortisol and adrenaline.
  • Restoration of damaged DNA molecules
  • Blocking of calcium channels

It has its peak production at three years of age and decreases significantly between 60 and 70 years; this makes the elderly usually get poor quality sleep. At the age of 60, you have half the average amount.

Melatonin can also be secreted, causing drowsiness and relaxation when a meal is made too high in carbohydrates, taking a hot bath, or prolonged exposure to the sun.

In addition to inducing sleep, it is a powerful antioxidant that, like other antioxidants, can slow down the aging process. As an antioxidant, it possibly reduces the level of the catabolic hormone cortisol. There is also evidence that it stimulates the production of growth hormones.

Consequences of the decrease in Melatonin

A person under stress usually produces more adrenaline and cortisol. Four molecules of free radicals are made for each molecule formed of adrenaline, and therefore, the probability of injury to cells increases.

In addition to epinephrine and cortisol, stress induces the formation of an enzyme “tryptophan prolapse,” capable of destroying tryptophan before it reaches the pineal gland. There is no manufacturing of Melatonin or serotonin (which can lead to excess carbohydrates, with a tendency to weight gain and depression).

Melatonin is an anti-radical substance. It can cross the blood-brain barrier (the membrane that protects the brain), thus performing functions at the neuronal level. This action is critical in protecting neurons against the damage of free radicals.

Our brain tissue is much more susceptible to the action of free radicals than any other part of the body. To the extent that the levels of this neurohormone are falling, there may be a concomitant decrease in brain function.

Sleep disorders can also be a decrease in the effects of the neurohormone. With aging, the pineal gland works less, causing a drop in melatonin production.

This ends up causing some elderly patients a poor quality of sleep or insomnia. However, they can fall asleep quickly when they should not, during the day, watching television, etc.

As we age, our immune system loses performance by lowering its defenses which allows our body to become more vulnerable to the constant aggression of external agents.

Current research has suggested an essential relationship between some hormones (estrogen, testosterone, DHEA, Melatonin, pregnenolone, and growth hormone) and the immune system.

At this point, Melatonin has become an agent of maintenance of the harmony and functioning of the immune system.

It seems to be able to increase the mobility and activity of immune cells, strengthen the formation of antibodies, facilitate the defense against viruses, moderate overproduction of corticosteroids generated by prolonged or repeated stress, and balance thyroid function, which acts directly on the production of essential defense cells, the lymphocytes.

Although there is little data on the indirect long-term effects of Melatonin on the body, people should know what the best individual dose is, starting with about 3 mg per day. Melatonin has to be taken at night, preferably a couple of hours before bed.

The optimal dose can vary a lot between different people, apparently due to changes in the hepatic metabolism of the substance. The speed of metabolism is essential for increasing amounts over time.

Side effects and contraindications

Daytime sleepiness, nightmares, vivid dreams, sleepwalking. The daytime sleepiness affects the ability to operate machinery or drive a vehicle safely. It produces headaches and dizziness, nausea, and abdominal cramps. Occasionally depression and irritability may be present, in addition to the loss of sexual desire. It decreases the metabolic rate and decreases the appetite. It can aggravate hypertension, liver disease, and seizures.

  • Melatonin can interfere with the effectiveness of oral contraceptives.
  • It should not be taken if you are prescribed anticoagulants, such as warfarin.
  • It can interfere with the patient’s medication.
  • It can interact with immunosuppressants.
  • It can interfere with antipsychotic and antidepressant drugs.
  • It should not be taken if you are already taking sleeping pills or sedatives.
  • It should not be taken for more than two months. There are no available scientific studies on the long-term use of synthetic melatonin supplements.
  • Women should not take it during pregnancy or breastfeeding.
  • Children must not take it under 12 years of age.
  • Melatonin supplements are available in two forms. One is synthetic and is considered safe for use. The other is derived from animals, and pineal tissue has a high risk of contamination and infection. Do not forget that you should go to your doctor before you start taking any medication.

How to take Melatonin

It is recommended to take Melatonin at night, in a dose of 1 to 2 mg per day, but always under medical supervision. The lowest amount of 800 micrograms seems to have no effect, and the 5 mg dose should be used with caution.

Although there are studies that support the properties of Melatonin for the treatment of cardiovascular problems, its use in people suffering from this type of pathology is not currently recommended; until the investigations are confirmed. Especially in patients with glaucoma, people with depression, and patients with diabetes.