Melatonin supplements are increasingly popular, but the evidence is weak and mixed.

Will taking a melatonin supplement put you to sleep?
I don’t understand how Facebook’s algorithms work; but I wonder if they have gotten the false impression that I suffer from insomnia, since I have recently been bombarded with information about a multitude of natural sleep remedies. Most of them contain melatonin, sometimes combined with other natural ingredients. One product that is billed as “the No. 1 sleep supplement, with 1000s of happy customers” contains magnesium, valerian root, chamomile, L-theanine, and 5-HTP. They say it is clinically proven, but the product they sell has not been tested. I had heard that melatonin was useful for treating jet lag, but there are claims for its effectiveness in many other situations, and it has been studied for everything from cancer to heartburn. Its use is skyrocketing, with over 3 million Americans currently using it. I thought it would be useful to review the evidence.

Melatonin is indeed natural. It is a hormone produced in our pineal glands; more is produced at night than during daylight, and it plays an essential role in regulating our circadian rhythms.

Melatonin works in our bodies, but do melatonin supplements work?

A systematic review of published studies examined 35 randomized controlled trials; 83% were rated as high quality. They concluded:

The use of melatonin by healthy adults shows promise to prevent phase shifts from jet lag and improvements in insomnia, but to a limited extent. For the initiation of sleep and sleep efficacy, the data cannot yet confirm a positive benefit. No recommendation can be proposed for the use of melatonin in shift workers.

An information page from the National Center for Complementary and Integrative Health (NCCIH) recommends melatonin for jet lag, delayed sleep-wake phase disorder, some sleep disorders in children, and anxiety before and after surgery. But it doesn’t recommend it for cancer symptoms, shift workers, or insomnia. It reports side effects and safety concerns in children.

Clinical guidelines from the Journal of Clinical Sleep Medicine found “weak evidence against clinically significant efficacy in the treatment of sleep onset insomnia, with little systematic evidence regarding harms. However, mixed evidence suggests possible improvement in SL in an elderly population. Therefore, benefits were deemed to be approximately equal to harms.” The Sleep Foundation has published recommendations for good sleep hygiene and many experts recommend sleep hygiene over pills.

Side effects

Daytime drowsiness, headaches and dizziness are reported by a small percentage of users. Agitation and bedwetting have been reported in children. There is concern that it might delay puberty in children, but the research is inconclusive. There has not been enough research to evaluate its long-term safety or its use during pregnancy and breast-feeding. A number of drug interactions and interactions with medical conditions have been reported.

Choosing a supplement

The optimum dosage has not been established. In studies, the doses have ranged from 1 to 12 mg. Supplements typically contain 1-3 mg. Dosages between 1 and 10 mg can raise melatonin levels to 3-60 times the levels normally found in the body.

Caution is advisable, since quality control is a documented problem. 71% of products did not contain within 10% of the labelled amount of melatonin, with variations ranging from -83% to +478%, lot-to-lot variability was as high as 465%, and the discrepancies were not correlated to any manufacturer or product type. To make matters worse, 8 out of 31 products were contaminated with the neurotransmitter serotonin.

Conclusion: Strong claims, weak evidence

The evidence is mixed and weak. There is some positive evidence for melatonin, and side effects are mild. I wouldn’t discourage anyone who wants to give it a try, but I think good sleep hygiene measures would be a better first step for treating insomnia.

This article was originally published in the Science-Based Medicine Blog.

Dr. Hall is a contributing editor to both Skeptic magazine and the Skeptical Inquirer. She is a weekly contributor to the Science-Based Medicine Blog and is one of its editors. She has also contributed to Quackwatch and to a number of other respected journals and publications. She is the author of Women Aren’t Supposed to Fly: The Memoirs of a Female Flight Surgeon and co-author of the textbook, Consumer Health: A Guide to Intelligent Decisions.

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