Detecting adverse events in dietary supplement research: Lessons from ephedra alkaloids

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In some countries, dietary supplements can be marketed with claims of efficacy or safety without any clinical trial support. As such, there is public concern whether these products are safe for use by the general population. Guidelines established by the United States Food and Drug Administration and the international pharmaceutical industry can be used to provide safety information within the umbrella term of dietary supplements. A dietary supplement would be clinically useful if the therapeutic benefits outweighed the side effects. Unfortunately, the side effects or adverse events associated with dietary supplement use are not well documented. Lack of statistical power and proper study design are the main reasons studies are unable to detect and determine the frequency of the adverse events associated with supplements. However, when adverse events are detected, the causality between the adverse events and the supplement can be diluted by factors such as underlying disease, the irregularity of product purity and uncertainty of how the subjects' exposure to the supplement is related to potential adverse events. As such, studies intending to detect adverse events need to carefully select the study population, document concomitant disease and medications, test product purity and determine the subjects' exposure to the supplement via blood sampling.

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