As part of a study initiating the development of an analytically validated Dietary Supplement Ingredient Database (DSID) in the United States (US), a selection of dietary supplement products were analyzed for their caffeine content. Products sold as tablets, caplets, or capsules and listing at least one caffeine-containing ingredient (including botanicals such as guarana, yerba mate, kola nut, and green tea extract) on the label were selected for analysis based on market share information. Two or three lots of each product were purchased and analyzed using high-pressure liquid chromatography (HPLC). Each analytical run included one or two National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs) and two products in duplicate. Caffeine intake per serving and per day was calculated using the maximum recommendations on each product label. Laboratory analysis for 53 products showed product means ranging from 1 to 829 mg caffeine/day. For products with a label amount for comparison (n = 28), 89% (n = 25) of the products had analytically based caffeine levels/day of between -16% and +16% of the claimed levels. Lot-to-lot variability (n = 2 or 3) for caffeine in most products (72%) was less than 10%.
This article illustrates the importance of having analytical data on the vitamin and mineral contents of dietary supplements in nutrition studies, and describes efforts to develop an analytically validated dietary supplement ingredient database (DSID) by a consortium of federal agencies in the USA. Preliminary studies of multivitamin mineral supplements marketed in the USA that were analyzed as candidates for the DSID are summarized. Challenges are summarized, possible future directions are outlined, and some related programs at the Office of Dietary Supplements, National Institutes of Health are described. The DSID should be helpful to researchers in assessing relationships between intakes of vitamins and minerals and health outcomes.
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