Green Tea Research Today is a free monthly online journal that collates and summarizes the latest research about Green Tea, including details on benefits, antioxidants, weight loss, diet, side effects. | ||||||||
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The caffeine contents of dietary supplements commonly purchased in the US: analysis of 53 products with caffeine-containing ingredients.Andrews KW, Schweitzer A, Zhao C, Holden JM, Roseland JM, Brandt M, Dwyer JT, Picciano MF, Saldanha LG, Fisher KD, Yetley E, Betz JM, Douglass L Nutrient Data Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, US Department of Agriculture, Beltsville, MD, USA. karen.andrews@ars.usda.gov 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%. Published 23 August 2007 in Anal Bioanal Chem, 389(1): 231-9.
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