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Weight-loss supplements containing ephedra and guarana may result in significant changes in cardiovascular state and metabolism, according to investigators at the University of California, San Francisco. Although the FDA banned ephedra as a weight-loss supplement, it is still available under the name ma huang, a traditional Chinese medicine, and in a synthetic version. Guarana is an herb containing caffeine.
Researchers tested the supplement Xenadrine RFA?which contains 25.4 mg of ephedra alkaloids and 185 mg of caffeine?and guarana?which contains 167 mg of caffeine?against a placebo in 16 healthy patients. The results showed that repeated doses of ephedra and guarana elevated ephedrine blood concentrations, increased the heart rate and blood pressure, and adversely affected glucose and potassium homeostasis. If obese people began taking these supplements, they could worsen conditions related to obesity, such as insulin resistance and metabolic syndrome. The investigators concluded that these dietary supplements could have poor effects on the cardiovascular system, particularly among people with high blood pressure, glucose intolerance, and atherosclerosis.
Ms. Farley is a freelance medical writer based in Wakefield, RI.