Melatonin content did not meet within a 10% margin of dietary supplement label claims in more than 71% of supplements, with the actual content ranging from 83% less to 478% more than the concentration declared on the label, according to a study published in the Journal of Clinical Sleep Medicine.
“We found that some products have much more melatonin than is indicated on the label,” study co-author Praveen K. Saxena, PhD, professor in the department of plant agriculture and the Gosling Research Institute for Plant Preservation at the University of Guelph in Ontario, Canada said in a press release about the findings. “Our findings reveal that further research is needed to clearly establish the stability and appropriate storage conditions to ensure safety, efficacy, and quality of melatonin products.”
Saxena and lead author Lauren A.E. Erland analyzed 31 supplements by ultraperformance liquid chromatography with electrochemical detection. All products were purchased from local grocery stores and pharmacies in Guelph, Ontario. Supplements spanned 16 different brands and included a representative sample of formulations, including liquids, capsules and chewable tablets.
Further analysis with mass spectrometry also found serotonin, a much more strictly controlled substance, in 26% of the tested supplements. According to the authors, the presence of unlabeled but significant quantities of serotonin could lead to serious side effects.
A new clinical practice guideline suggests that clinicians not use melatonin as a treatment for sleep onset or sleep maintenance insomnia because the overall evidence available was weakly against melatonin’s efficacy.
Because melatonin is classified as a dietary supplement, it is not subject to the same scrutiny as medications that are approved by the US Food and Drug Administration. When comparing supplement labels, US consumers should look for the “USP Verified” mark, which indicates that the formulation meets the requirements of the US Pharmacopeial Convention.
Erland LAE, Saxena PK. Melatonin natural health products and supplements: presence of serotonin and significant variability of melatonin content. J Clin Sleep Med. 2017;13(2):275–281.