The findings of a new study suggest that many popular melatonin supplements, which are commonly available over-the-counter and used for sleeping problems, often have different amounts of certain ingredients than is actually listed on the label.
In addition to inaccurate amounts of melatonin, researchers also discovered that many of the popular sleep aid supplements contain unlabeled amounts of serotonin, which can be harmful to consumers. The findings were published in the Journal of Clinical Sleep Medicine.
Canadian researchers tested 31 commercial supplements of melatonin, including 16 different brands and different forms of the supplement, including liquids, capsules and chewable tablets. They also tested the supplements for the presence of serotonin.
The study concluded the melatonin content of the supplements ranged from -83% to +478% of the labeled content.
Researchers said the difference in content from one lot of the supplement to another lot of the same brand also varied, by as much as 465%. There was no correlation between varying content and manufacturer or product type.
In the majority of the products, 71% overall, the melatonin content did not meet the 10% margin claimed on the label.
Melatonin is a natural hormone that mediates circadian rhythm and the sleep cycle. It is popular and widely available as an over-the-counter supplement to treat and prevent sleep problems, including insomnia and jet lag. In recent years, consumers have increasingly used the supplement to help with sleep problems.
Data from the National Center for Health Statistics of the National Institutes of Health indicates the use of melatonin supplements has more than doubled in the U.S. since 2007. Some doctors have begun prescribing the supplement to children, causing many researchers to warn against the practice, due to its potent effects.
The new study also identified the presence of serotonin in 26% of the products.
The presence of serotonin 5-hydroxytryptamine was identified in eight of the supplements at levels of 1 to 75 micrograms. Serotonin 5-hydroxytryptamine is a related indoleamine and a controlled substance. It is used to treat certain neurological disorders.
Researchers said manufacturers should use increased controls during processing to ensure the supplements meet their label claim. They should ensure products are free from contaminants such as serotonin, which is more strictly controlled than melatonin and can have negative side effects.
Inconsistent levels of ingredients in dietary supplements have been a recent and ongoing concern. In 2016, testing indicated that nearly 80% of the herbal supplements sold by GNC, Wal-Mart, Walgreens and Target did not contain the primary ingredient listed.
GNC announced new testing guidelines for its herbal supplements in March 2016, after an investigation concluded many of their supplements were fake and did not contain ingredients advertised.
Dietary supplements are responsible for tens of thousands of emergency room visits each year in the U.S. It is important that supplements contain the ingredients, and in the amounts indicated, listed on the label. However, the FDA is not allowed to regulate dietary supplements and does not approve them or their claims before they hit the market. The agency only becomes involved if a specific supplement is linked to a health problem.