Is red wine a performance-enhancing drug?

Lance Armstrong’s doping revelation aside, a recent study added controversy to the question of whether quercetin, a red wine-derived substance, can boost athletic performance by boosting testosterone levels. Though it was a test-tube study not backed up by any human subject data, the researchers thought it significant enough to inform the World Anti-Doping Agency. Quercetin has been reported in reputable publications to enhance oxygen uptake and endurance, and since many of these have come out since my review in "Age Gets Better with Wine," so I thought it might be worth another look.

For starters, quercetin is an antioxidant bioflavanoid that can be found in foods other than wine (apples for instance.) It first caught researchers’ attention as a component of red wine, being a possible contributor (along with other compounds such as resveratrol) to the famous “French paradox.” Like other wine-derived compounds, quercetin seems to alter energy metabolism at a cellular level. But does this translate to measureable changes in athletes? The data is conflicting. One well-designed clinical trial examined the effects of a quercetin + vitamin C supplement on 60 male athletes. After 8 weeks of using the supplement, no changes in exercise endurance were found, but there were slightly reduced markers of post-exercise muscle damage and a reduction in body fat (compared to placebo.) Another study by the U.S. Army evaluated a high-dose quercetin supplement on aerobically demanding soldier performance. No measurable benefit was found, though this was a shorter trial (just over a week.) Still another trial on endurance runners found no benefit.

One way to troll for meaningful data from conflicting study results is what is called a meta-analysis, which combines the results of all properly designed published studies. The School of Applied Physiology at Georgia Institute of Technology in Atlanta conducted such a review, concluding that “On average, quercetin provides a statistically significant benefit in human endurance exercise capacity (VO2max and endurance exercise performance), but the effect is between trivial and small.” So whether red wine or quercetin supplements boost testosterone or not, the effect seems unlikely to be enough to affect the outcome of the Tour de France or explain the French paradox by itself. There are plenty enough healthy reasons to have a glass of wine anyway.