The effects of an antioxidant-supplemented beverage on exercise-induced oxidative stress:: results from a placebo-controlled double-blind study in cyclists

The objective of this study was to test the effects of an antioxidant-supplemented beverage on exercise-induced oxidative stress in moderately trained cyclists. A double-blind study was conducted in moderately trained cyclists. They were randomly allocated to receive either an antioxidant ( 13 subjects) or a placebo ( 13 subjects) 15 min pre-exercise ( 30 ml. kg(-1)) and during a 90 min constant-load test ( 30 ml. kg(-1). 15 min(-1)) on a bicycle ergometer at 70% VO2max: The supplemented beverage contained black grape ( 81 g/l), raspberry ( 93 g/l) and red currant ( 39 g/l) concentrates, and its total antioxidant capacity, measured by the ABTS(.+) technique, was 0.41 mM Trolox. No significant difference from basal to post-exercise period was detected for plasma TBARS in either the placebo group or the group receiving the antioxidant supplemented beverage. Post-exercise carbonyls decreased by 29% in the group receiving antioxidants, and the pattern of change was significantly different between antioxidant and placebo conditions. The urinary excretion of 8-OHdG increased significantly by 21% in the placebo group. Again differences in the pre- to post-exercise change were significant between both conditions These results suggest that in moderately trained cyclists, antioxidant supplementation counters oxidative stress induced by a 90 min exercise at 70% VO2max: