Antioxidant may boost exercise endurance

updated 5:19 p.m. ET June 29, 2009

NEW YORK - Eating a variety of fruits and vegetables rich in the antioxidant quercetin may boost endurance, according to a small study with healthy college students.

The 12 fit college students, who were not regular exercisers, were given quercetin supplements for 7 days, which appeared to boost exercise endurance compared with a similar 7-day period without supplements, researchers report in the International Journal of Sports Nutrition and Exercise Metabolism.

Quercetin, a compound abundant in red apples, red onions, berries, cabbages and broccoli, and green and black teas, is believed to have multiple antioxidant and anti-inflammatory, and cell-energy activation properties that benefit health.

However, most previous research involved animals, report Dr. J. Mark Davis, at University of South Carolina in Columbia, and colleagues.

To test whether quercetin supplements benefit energy production in humans, Davis' group enlisted 7 men and 5 women, an average of 23 years old, to participate in a crossover study. At the beginning of the study, investigators measured students' maximum oxygen uptake and the number of minutes they could ride a stationary bike.

For 7 days, the participants followed their regular routines and diet, but drank Tang plus placebo, twice daily. For another 7-day period, the participants drank Tang containing 500 milligrams quercetin. The investigators again measured the volunteers' maximum oxygen uptake and exercise endurance. This process was repeated after another 7-day period when volunteers drank similar tasting and colored Tang without quercetin.

Compared with days of no supplementation, the quercetin supplement periods were associated with a modest — nearly 4 percent — increase in maximum oxygen uptake. Quercetin was also associated with a 13 percent increase in "ride time" before the volunteers were too fatigued to continue.

These findings suggest quercetin "may be important in relieving fatigue that keeps (people) sedentary," Davis commented in a university press release.

If confirmed in further investigations, quercetin supplementation may become a beneficial endurance booster for regular exercisers and athletes alike, Davis and colleagues surmise.

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