Athens, Ga. The antioxidant quercetin is increasingly being marketed as a supplement that boosts athletic performance, but a new University of Georgia study finds that it is no better than a placebo.
Professor Kirk Cureton, head of the department of kinesiology in the UGA College of Education, and his colleagues tested quercetin in a double-blind, placebo-controlled study that assessed a variety of measures, including the ability of muscles to synthesize energy, cycling performance, perceived exertion and strength loss following exercise. The researchers, whose results appear in the early online edition of the Journal of Applied Physiology, found that quercetin did not improve athletic performance in any of the measures they examined.
"We did not see any performance enhancing effect of quercetin," Cureton said. "To a certain extent that was disappointing because our hypothesis, based on previous studies in mice, was that we would see positive effects. But our findings are important because they suggest that results from the animal studies shouldn't be generalized to humans."
Quercetin is a naturally occurring antioxidant found in the skins of fruits, leafy vegetables, and berries, as well as in black tea, red wine and various fruit juices. It is sold as a supplement in nutrition stores and is an ingredient in sports drinks such as FRS Energy, which is promoted by cyclist Lance Armstrong.
In mice, quercetin has been shown to stimulate the production of mitochondria, which are the energy producing components of muscle cells and other tissue. One study found that mice supplemented with quercetin increased their running endurance by up to 37 percent.
In humans, however, the results have been mixed. An early and widely-cited study reported improvements in performance during a cycling time trial, but Cureton notes that data from the experimental group was not compared to the control group, making the statistical si
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University of Georgia