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