Caffeine Disclosure in Weight Loss Teas and Its Public Health Implications: An Investigation Using High-Performance Liquid Chromatography

Weight loss supplements have become increasingly popular to help with weight management and health issues. A common ingredient found in these products is caffeine, a “generally recognized as safe” chemical, which can be harmful if taken at high doses or when ingested at the same time as certain medications. Under U.S. regulations, caffeine content must be reported on product labels only when it is added as an ingredient and not when it naturally occurs in herbs. Therefore, the threat posed by undeclared caffeine and the popularity of diet culture make it important to screen weight loss supplements and advise consumers about the risks associated with using such products. In this study, a real-world application laboratory activity for undergraduate students in general, analytical, and instrumental methods courses was developed. Students analyzed randomly selected weight loss teas to identify and quantify caffeine using high-performance liquid chromatography. Caffeine was identified by comparing the relative retention time of their samples to caffeine standards. Linear calibration curves, from an external standard or standard addition method, were used for quantification. Caffeine was detected in five teas where it was not declared on the package and in one where it was declared. For the tea bag where caffeine was disclosed, students quantified 30.7 ± 0.8 mg per bag, an amount that is statistically different than the reported concentration of 35 mg. Students discussed caffeine labeling regulations, considered their implications for public health, and applied chemistry concepts while raising awareness about weight loss supplements.