For this study, researchers analyzed 30 melatonin supplements purchased from local grocery stores in Canada (one of the few countries, in addition to the U.S., where melatonin is available without a prescription). They tested to see how the amount of melatonin in the supplement matched up to the amount listed on the bottle.
“Melatonin content was found to be highly variable between samples and lots, with no pattern observed between brand, form of supplement, labeled value, or presence of other herbal extracts,” the study’s result section reads. The actual amount of melatonin ranged from -83% to +478% across the samples tested—meaning that some had levels that were 478% higher than what was listed on the bottle (while others contained less melatonin than what was promised on the Supplement Facts label).
“Additionally, lot-to-lot variability within a particular product varied by as much as 465%,” adds Ellen Wermter, FNP-BC, a family nurse practitioner and spokesperson for the Better Sleep Council.
“Even scarier,” Christina Graham, R.N., a registered nurse and Noom coach, says of the eye-opening study, “testing also found serotonin in 26% of the samples. Serotonin is more strictly controlled and the presence of unlabeled serotonin in significant quantities could lead to serious side effects.”