With no evidence of insomnia, melatonin is over-the-counter in pharmacies


With sale released in pharmacies from December, melatonin supplements promise to turn fever among those who want to sleep better, but doctors warn that the replacement of this hormone should only be done by people who have a deficiency of it in the body. According to them, these products are not effective in treating insomnia.

On social networks, melatonin capsules are also advertised as an ally in weight loss, but there is no scientific evidence about this effect either.

Melatonin was already marketed in compounding pharmacies requiring a prescription, but a decision by Anvisa (National Health Surveillance Agency) last October placed it in the category of food supplements, which does not require a prescription.

In countries like the United States and several in Europe, the product is also sold as a supplement in higher doses (0.3 mg to 5 mg) than approved by Anvisa (0.21 mg per day).

In approving the use, Anvisa says that the supplement is intended for people over 19 years and should not be used by children, pregnant women and nursing mothers. It reinforces that claims of benefits associated with the consumption of melatonin have not been approved.

Produced by the pineal gland, located in the central region of the brain, the hormone melatonin has the function of regulating people’s biological clock.

According to endocrinologist Bruno Halpern, head of the weight control center at Hospital Nove de Julho, it sends information to the brain that night has arrived and this can have a sedative effect on the body. “At night, we do many other things besides being sleepy. The liver reduces the production of glucose, the pancreas reduces the production of insulin”, he says.

He says that, like other hormones, melatonin supplements should only be used by people who have reduced melatonin in the body and need replacement. “Those who have thyroid disease, hypothyroidism, benefit from thyroid hormone. If you don’t have it, you won’t. The idea is the same.”

Neurologist and sleep doctor, Lucio Huebra, member of the Brazilian Academy of Neurology, states that there is no evidence that melatonin replacement is effective against insomnia. “In the guidelines [diretrizes] for insomnia, melatonin is not a treatment guideline, it is not a good option. They bring the evidence is weak, there are other more effective options where the benefit outweighs the risk.”

Huebra says there are specific situations in which melatonin supplementation can be helpful, such as when the brain is exposed to different times than when the hormone is naturally produced by the body.

For example, people dealing with time zone issues, so-called jet lag. “Our body is used to producing and releasing melatonin at a certain time. If we change time zones, one way to readjust is to take melatonin, so that the brain is exposed to it and sets a new time to sleep.”

According to Halpern, there is some positive evidence for the use of supplemental melatonin in older people with sleep disorders, who, in general, are deficient in the hormone. “Over 60 years, the production of melatonin drops a lot, up to a quarter of the production of a young adult.”

Another advantage for this audience, says the doctor, is that melatonin supplements do not alter sleep architecture, as most hypnotics do. “In that sense, it’s an option, but it’s less efficient.” People with some types of blindness can also benefit from supplementation.

The endocrinologist also says that many younger people, as they live in brighter environments and are exposed to cell phone and computer screens, may also have a melatonin deficit and, in theory, could benefit from supplementation. “The body may think that night is no longer night, that it is day. This influences not only sleep but also other metabolic regulations.”

Another concern of physicians is the fact that melatonin supplements, like other products in this category, are not subjected to the well-controlled studies required for medications.

“We don’t know what their pharmacodynamics and pharmacokinetics are. You take melatonin and it won’t work as if it were the body itself making it. You can take it and have an early peak or a very high dose”, says Halpern .

Huebra reinforces this with the example of a Canadian study that showed that melatonin supplements sold without a prescription, on pharmacy shelves, often had doses different from those described on the label, had varying doses depending on the lot and each capsule, or were still marketed with other stimulant substances such as serotonin, caffeine and taurine.

According to the neurologist, the substance is relatively safe and there are no reports of serious side effects with its use. “These are more general effects, such as headache, nausea, dizziness, irritability. In more sensitive patients, you can feel drowsy the next day.”

Inadvertent and prolonged use of melatonin can also theoretically affect the body’s natural production of the hormone. This is called negative feedback, which all hormone-producing glands have. The more hormone you take, the more the body stops producing because it interprets it as if there was enough.

For Huebra, another risk of trivializing the use of melatonin supplements is the person not seeking a diagnosis for insomnia and an effective treatment. “There are several sleep disorders. In the layman’s view it’s just ‘I sleep poorly’, but actually there are several causes for this and different treatments.”

In the opinion of general practitioner and family doctor Gustavo Gusso, a professor at USP, more important than using melatonin supplements to sleep better is that the person strives to have good sleep hygiene, which involves a change in lifestyle .

He says this is a difficult point to convince. “People already come to the office asking Rivotril to sleep. We family doctors live a daily battle to convince people to avoid medication, encourage sleep hygiene, physical activity, meditation, therapy.”

Gusso claims to try to convince people by explaining that sleep, like other functions, is an exercise that requires training. “If you delegate sleep to a medication, you lose the ability, the function to sleep.”

According to him, it is normal for people to go through phases of difficulty sleeping, but it is healthy for them to understand what is happening in order to correct the cause.


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