Joanna Cosgrove01.28.10
Quercetin is a plant-derived flavonoid that has gained a reputation among athletes for its purported ability to help boost energy and endurance while eliminating fatigue. But researchers at the University of Georgia recently tested quercetin on behalf of The Coca-Cola Company to determine if its reputation translated into fact or fiction.
The study, “Dietary quercetin supplementation is not ergogenic in untrained men,” was published in the Journal of Applied Physiology (Vol. 107, October 2009). The double blind, placebo-controlled study tested the effects of short-duration quercetin supplementation on 30 active but not endurance-trained men. The men were given a sports hydration beverage prepared by The Coca-Cola Company four times a day for between nine and 16 days to maintain elevated blood levels of total quercetin throughout the day.
The beverage contained carbohydrates (sucrose and maltodextrins), NaCl, vitamins (niacin, B6, B12), citric acid, a gel-forming additive and quercetin (for a total of 1,000 mg per day). Those in the untreated placebo group ingested the same beverage without quercetin.
Participants abstained from caffeine, nonprescription drugs, vitamins, or other dietary supplements beginning three days prior to the pretreatment tests and continuing throughout the treatment, but maintained their normal diet and physical activity during the treatment period. Participants also refrained from exercise for 48 h before testing.
To evaluate the ergogenic—or energy boosting—effects of quercetin they consumed, the study participants were observed and neuromuscularly assessed during a 10-minute cycling test in which they performed “as much work as possible.” They were also assessed after one hour of moderate intensity cycling. Researchers used nuclear magnetic resonance spectroscopy to evaluate changes in oxidative capacity and VO2 peak was measured to assess any changes in whole body aerobic capacity.
At the end of the study, the researchers concluded that the quercetin supplementation “did not affect muscle oxidative capacity; measures of substrate utilization, cycling economy, or perception of effort during constant rate submaximal exercise; prolonged cycling performance; or strength loss following cycling in untrained men,” and did not support their initial hypothesis that quercetin has ergogenic effects.
“The null findings are important because they indicate that metabolic and physical performance consequences of quercetin supplementation observed in mice should not be generalized to humans,” they wrote.
“We were surprised not to find an ergogenic effect,” commented lead study author Kirk Cureton, PhD, professor in the University of Georgia’s Department of Kinesiology. “We thought there would be a positive effect in untrained men.”
He acknowledged a previous study which found a 37% increase in exercise performance in mice and inspired his team’s hypothesis for their human study. “They found increased growth of mitochondria and an increased aerobic muscle oxidative capacity, meaning the muscles in the mice could produce more ATP—more chemical energy,” Dr. Cureton told The Red and Black, an independent student newspaper serving the University of Georgia Community. “That apparently led to improved running performance, although we don’t know that that exactly was the reason.”
Given the sports nutrition consumers’ receptivity to any beverage that could deliver on a promise of increased performance, it’s no wonder why the hype surrounding quercetin caught Coke’s attention.
When asked about The Coca-Cola Company’s role in Dr. Cureton’s research, Crystal Warwell Walker, Coke’s director of communications replied, “We fund many different types of scientific studies at universities across the world. This is an example of some of the work we do to explore new ingredients.”
This is not the first functional beverage study funded by Coke that Dr. Cureton has undertaken. His research portfolio includes work with an experimental caffeinated sports drink, as well as testing how Gatorade and Powerade affect endurance performance.
“We aspire to help people lead active, healthy lifestyles. We do this through the beverages we produce, our marketing and packaging, the nutritional information we provide and our support of local physical activity programs in more than 100 countries,” Coke’s Ms. Walker said. “In a select number of products, we use well-researched functional ingredients to offer consumers more options.”
Dr. Cureton said that he has no additional studies with The Coca-Cola Company planned at this point.