Resveratrol, 3,5,4′-trihydroxy-trans-stilbene, is a natural polyphenol found in red grapes and other plants. It is believed to improve cardiovascular functions and lower blood lipids, owing to its antioxidant properties.

Lasse Gliemann, University of Copenhagen, Denmark, and colleagues investigated whether resveratrol supplements could enhance training-induced improvements of the cardiovascular functions of older men. In contrast to expectations, however, resveratrol did not potentiate the positive effects of physical training, but rather counteracted most of them. Administration of resveratrol, in fact, suppressed the improvement in oxygen uptake as well as the reduction in blood pressure and blood lipids normally observed upon training.
Resveratrol supplements are thus disadvantageous when performing physical exercise.

• Resveratrol Blunts the Positive Effects of Exercise Training on Cardiovascular Health in Aged Men,
  L. Gliemann, J. F. Schmidt, J. Olesen, R. S. Bienso, S. L. Peronard, S. U. Grandjean, S. P. Mortensen, M. Nyberg, J. Bangsbo, H. Pilegaard, Y. Hellsten,
  J. Physiol. 2013.
  DOI: 10.1113/jphysiol.2013.258061