Someone has said that melatonin damages the heart. The reality, according to science, is that we can be calm

Melatonin is a hormone that now is on many people’s lips being a key element in the regulation of our biological clock, and above all being well known for its relationships with sleep induction. It is precisely for this last reason that in recent years people have been supplementing with melatonin pills to be able to sleep better or regulate their sleep schedules more, but now the alarms have gone off about the possible side effects it may have.

The alarm voice. There are many benefits that melatonin has with its continued use as a supplement beyond those related to sleep, such as anti aging thanks to its antioxidant capabilities. But beyond the benefits, a study has raised the alarm: it can cause heart failure. However, there is much to qualify in this statement.

Obviously, something like this can generate great unrest in society, precisely because it is a widely used supplement in different countries because it can be purchased without any type of medical prescription (except for the highest doses). And this attraction has been used to create pills, gummies or even infusions that have melatonin inside.

But the reality is that nothing we ingest can be harmless to our body, especially if very specific safety guidelines are not followed. Although in the case of melatonin everything indicated that it was completely safe and that everything behind it was something positive. Until now.

What the study says. The focus of the controversy centers on a preliminary study (and this is important) that is going to be presented at the American Heart Association Scientific Sessions 2025. This work analyzed the medical records of more than 130,000 adults with insomnia, comparing 65,414 people who had used melatonin for a year with another group who had not used it.

The results of this study they pointed in this case because users who used melatonin chronically were twice as likely to be diagnosed with heart failure. But they went further by showing that there was a 3.5 times greater risk of hospitalization for heart failure.

But saying ‘double’, the truth is that it does not provide much information (beyond fear), but what is important here would be to talk about the absolute increase in risk, as the Secretary of State for Health points out in his X account.

Tranquillity. But the reality in this case is that there is no need to sound the alarm immediately because of the ‘fault’ of a study that has not yet been reviewed (since it is not even published in a journal). Right now there is a large amount of scientific evidence that proves how safe melatonin isand a single study does not put in check all the scientific literature behind it, although it does open a door to be able to investigate in a more in-depth way. melatonin side effects.

For example, in 2022 a systematic review was published on high doses of melatonin in adults found minor adverse events such as drowsiness, headache or dizziness, but no increase in serious adverse events. The same thing happened with the StatPearls article of 2024 which indicated there was no evidence of toxic effects.

Specifically in chronic use we have a 2023 study by Givler which confirms that the administration of between 5-6 mg of melatonin per day does not generate serious long-term risks. Although logically it is important to use it above all as an ‘help’ to have more adequate sleep hygiene with the aim of not depending on exogenous melatonin to be able to sleep.

And it is necessary to carry out studies that are appropriate to look for this correlation. The study that has highlighted melatonin is not the most appropriate as it is observational and not a randomized clinical trial. This means that it has not been possible to verify exactly whether these differences are due to chance and, above all, there has been no control over the patient groups, since it has been done with their clinical histories.

The correct thing to do in these situations is to propose a study with two groups: one where patients take melatonin and another where they do not. But until we reach this point, it is important to calculate the number of patients needed, how they are selected and the baseline characteristics they must have so that there are interchangeable patients in both groups and many other factors. Everything necessary so that the conclusion of the study has great external validity for the entire population.

Investigation remains. Logically, any type of supplement, and especially if it is hormonal, can lead to different side effects. The issue in this case is that research is needed to look for side effects and ask ourselves if it is necessary for doctors to start prescribing it in all doses. And, as we have said before, a prescription is only needed for the highest doses, but the lowest doses can even be found in a supermarket.

Although whenever you have doubts about the safety of the medication, the important thing is always to consult with your primary care doctor so that the dose can be adjusted based on the particular history of each patient.

Images | Isabella Fischer Robina Weermeijer

In Xataka | Of course melatonin has side effects. There is nothing special or alarming about it