The ongoing scientific debate about the effects of resveratrol continues this month, as a Danish study has found that the polyphenol found in red wine “blunts [the] positive effects of exercise training.” But other scientists say the study raises more questions than it answers, and even the author says fitness buffs need not cut out red wine.
Researchers at the University of Copenhagen put 27 men—all around 65 years old, healthy but physically inactive—on a high-intensity Crossfit exercise regimen for eight weeks. Half the subjects took 250 milligrams of resveratrol each day; the rest took a placebo. The study found that exercise improved subjects’ cardiovascular health, measured mainly by their maximal oxygen uptake, but “the increase in performance was 50 percent less in the group receiving resveratrol than the group receiving placebo,” summarized Lasse Gliemann, an author of the study, published in the Journal of Physiology.
What could explain this apparently deleterious impact of resveratrol, an antioxidant that previous studies have found can trigger anti-aging benefits and mimic the effects of exercise and calorie restriction? One possibility, said Gliemann, is that “this amount of antioxidant decreases the presence of free radicals”—a harmful substance produced during workouts that also causes the body to adapt to exercise—which “might blunt the response to every exercise bout.”
However, another paper published this month contends that studies like Gliemann’s might be focusing on the wrong question. Dr. James Smoliga of High Point University claimed in the journal Aging that although resveratrol has been shown to mimic the effects of exercise training and calorie restriction in lab animals, it is unrealistic to expect a pill or wine to mimic these effects in humans. “There’s no doctor that would recommend drinking red wine instead of exercise or dieting,” Smoliga told Wine Spectator. “Seeing it as the equivalent of exercise is a little bit unfair to resveratrol.”
Furthermore, Smoliga argued that many resveratrol experiments targeting healthy populations “are often fundamentally flawed” by using paradigms appropriate for “populations with overt clinical disease.” If an antioxidant like resveratrol can reduce free radicals produced during exercise and consequently reduce the effects of exercise, Smoliga said, “it should also be able to counter the effects of free radicals in cancer or diabetes.” Healthy people may not experience obvious improvements due to resveratrol in the short term, but Smoliga believes that its protective benefits may become clear over longer periods of time.
Whether or not resveratrol is helpful for exercise training may depend on which measure of performance one accepts. The Danish study’s conclusion is based on evaluations of subjects’ maximal oxygen uptake, or the maximum amount of oxygen the body can use during exercise, a measurement that Smoliga finds ambiguous, since it represents “so many different things: blood, heart, blood vessels and muscles.” In fact, when it came to functional performance, Gliemann’s subjects in both the resveratrol and the placebo groups made significant and similar improvements in a step test and a 5-kilometer walk test. “Their aerobic performance improved equally to one another, essentially,” said Smoliga.
The body of knowledge on resveratrol’s effects is far from complete, but one thing is certain: Enophile athletes needn’t worry that a glass of wine will negate a trip to the gym. The amount of resveratrol administered daily to Gliemann’s subjects is roughly 100 times the amount found in one glass of Pinot Noir. “A newspaper has misquoted me [as] saying that red wine is bad for training adaptation,” Gliemann said, “and that’s definitely not the story here.”