A natural antioxidant compound found in red grapes and other plants, called resveratrol, blocks many of the cardiovascular benefits of exercise, according to research from the University of Copenhagen.

Resveratrol has received widespread attention as a possible anti-ageing compound and is now widely available as a dietary supplement. Much has been made of its role in explaining the cardiovascular health benefits of red wine and other foods. But the new research, published 22 July 2013 in the Journal of Physiology, suggests that eating a diet rich in antioxidants may actually counteract many of the health benefits of exercise, including reduced blood pressure and cholesterol.

In contrast to earlier studies in animals in which resveratrol improved the cardiovascular benefits of exercise, this study in humans provided surprising and “strong” evidence that in older men, resveratrol has the opposite effect.

According to the study’s authors, a new view is emerging that antioxidants are “not a fix for everything”, and that some degree of oxidant stress may be necessary for the body to work correctly. The Copenhagen study suggests that reactive oxygen species, generally thought of as causing ageing and disease, may be a necessary signal that causes healthy adaptations in response to stress like exercise.

Study method

The authors of the study examined 27 healthy, physically inactive men around 65 years old for 8 weeks. During the 8 weeks, all of the men performed high-intensity exercise training and half of the group received 250mg of resveratrol daily. The other group received a placebo pill. The study was double-blinded so that neither the subjects nor the investigators knew which participant had received resveratrol and which had taken a placebo.

“We found that exercise training was highly effective in improving cardiovascular health parameters,” said Lasse Gliemann, a PhD student who worked on the study. “But resveratrol supplementation attenuated the positive effects of training on several parameters including blood pressure, plasma lipid concentrations and maximal oxygen uptake,” he said.

Findings surprising

Researchers said they were surprised to find that resveratrol supplementation in aged men decreased the positive effects of exercise training on cardiovascular health, in part because their results contradicted findings in animal studies.

“It should be noted that the quantities of resveratrol given in our research study are much higher than what could be obtained by intake of natural foods,” said Ylva Hellsten, the leader of the project.

Research adds to evidence questioning antioxidant supplementation

Researchers said this study added to the growing body of evidence questioning the positive effects of antioxidant supplementation in humans.

US-based medical not-for-profit organisation the Mayo Clinic said the study had wider implications for research.

“In addition to the surprising findings on exercise and resveratrol, this study shows the continuing need for mechanistic studies in humans,” said Michael Joyner, from the Mayo Clinic. “Too often human studies focus on large scale outcomes and clinical trials and not on understand the basic biology of how we adapt,” he said.

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