Majority of melatonin supplements do not meet labelled claims for melatonin content

A new study from the University of Guelph raises significant concerns over the actual melatonin content in melatonin products marketed in Canada. Melatonin, a neurohormone that mediates circadian rhythms and the sleep cycle, is a popular and widely available supplement used for the management of insomnia and jetlag.The study examined the melatonin content of 30 melatonin products purchased from local grocery stores and pharmacies in Guelph, Ontario. All products were labelled with a Health Canada Natural Product Number (NPN). Sixteen different brands, with a representative sample of various dosage forms (e.g., liquid, capsule, tablet, sublingual tablet, chewable tablet), were tested using ultraperformance liquid chromatography.Overall, 71% per cent of the melatonin products did not meet the label claims for melatonin content within the accepted 10% margin. The highest variation was seen in one chewable tablet product that showed a 478% higher melatonin content than the label claim, containing about 8.7 mg of melatonin rather than the 1.5 mg stated on the label. In addition, this brand showed considerable (465%) variably in melatonin content between different lots.The supplement that showed the greatest reduction in melatonin content compared to the labelled amount was a capsule that also contained lavender, chamomile and lemon balm; it showed an 83% lower melatonin content than labelled.The products with the least variability in melatonin content were those with the simplest mix of ingredients, generally tablets or sublingual tablets containing only melatonin and a filler (e.g., cellulose derivatives, silica).Overall, lot-to-lot variability in melatonin content among melatonin products ranged from 0.37% up to 466%. Tablets and sublingual tablets generally showed the least variation. Liquid supplements also showed fairly low lot-to-lot variability.Serotonin was found as a contaminant in eight of the 30 samples tested. Most of these were supplements that contained other herbal products or extracts (e.g., passionflower, hops, valerian root). Serotonin content ranged from 1.21–74.27 μg. In products found to contain serotonin, lot-to-lot variability in serotonin content ranged from 1.25%–133%.The authors postulate that the excessive melatonin content in some products might be explained by the intentional addition of excess melatonin to ensure that products meet the minimum label claim. Although these higher than labelled amounts are unlikely to present a significant health risk, higher doses could lead to unpleasant or unexpected side effects in some patients (e.g., those more sensitive to exogenous melatonin, those taking medications that may interact with melatonin, pregnant women).Serotonin, a biosynthetic precursor of melatonin and a potent neurotransmitter, cannot be purchased in supplement form. In most situations, it would be considered an undesirable contaminant, because serotonin overdose can occur with relatively low amounts. Serotonin syndrome, which can have very mild to fatal outcome, can be exacerbated by interactions with other medications, such as selective serotonin reuptake inhibitors and the analgesic tramadol. The source of contaminant serotonin in these melatonin products was not readily apparent and requires further research.The high variability in melatonin content found in this study—ranging from −83% to +478% of the labelled concentration—as well as the presence of serotonin as a contaminant in many melatonin supplements, shows that best practices for producing melatonin supplements requires greater scrutiny to ensure product consistency and safety.ReferencesErland LA, Saxena PK. Melatonin natural health products and supplements: presence of serotonin and significant variability of melatonin content. J Clin Sleep Med 2017;13:275-81.University of Guelph. U of G study finds instability, serotonin in melatonin supplements. http://news.uoguelph.ca/2017/02/u-g-study-finds-instability-serotonin-melatonin-supplements/ (accessed February 18, 2017).

Majority of melatonin supplements do not meet labelled claims for melatonin content

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