A Survey of Melatonin in Dietary Supplement Products Sold in the United States

In the United States, melatonin products are widely available as dietary supplements. During the past few decades, melatonin products have gained popularity primarily as a sleep aid, with a variety of product forms available for different age groups of consumers. Recent reports have highlighted a rise in melatonin ingestion among children reported to poison control centers. The increased use of melatonin-containing products, the diversity in product forms, and reported label discrepancies has emphasized the need for additional research to better understand the marketplace. This work aims to measure melatonin content in products sold as dietary supplements and marketed for children, evaluate method performance across different product categories, and determine if product form has an impact on melatonin stability. One hundred ten (110) dietary supplement products labeled to contain melatonin and marketed towards children were purchased and analyzed using a targeted LC-MS/MS method validated for the qualitative determination of serotonin and quantification of melatonin, N¹-acetyl-N²-formyl-5-methoxykynuramine (AFMK), and N¹-acetyl-5-methoxykynuramine (AMK). Melatonin was identified in 108 of 110 products (98%) with a median concentration of 1.2 mg/g (range: 0.017-130 mg/g) or 1.7 mg/serving (range: 0.042-50 mg/serving). Further, in the tested products, melatonin content ranged from 0% to 667% of the label declaration. This study provides evidence to inform safety assessments and investigate potential factors that may influence reported concentrations, such as product stability and matrix influences.