BACKGROUND: We studied the effects of supplementation of vitamin C and carbohydrate on acute exercise-induced lipid peroxidation. METHODS: Experimental design: two randomized controlled trials. PARTICIPANTS: 17 endurance athletes. Interventions: in study I, nine athletes repeated twice a 10.5-km maximal run and ingested in a randomized single-blind order either 2.0 g vitamin C or placebo. In study II, eight athletes repeated twice a 27-km maximal run and ingested in randomly either 105 g carbohydrate or placebo. Venous blood samples were taken before the exercise, immediately after the exercise, and after a recovery period of 90 min (study I) or 120 min (study II). Measure: serum diene conjugation, lipid peroxidation. RESULTS: In study I, there was no difference in serum diene conjugation between the trials during exercise (pre- vs post-exercise). However, during the recovery period (post-exercise vs recovery sample) serum diene conjugation concentration decreased by 11% in the vitamin C trial but not in placebo (p = 0.028). In study II, there was no difference between the carbohydrate and placebo trials. CONCLUSIONS: Vitamin C and carbohydrate do not prevent exercise-induced increase in oxidative stress, but vitamin C, being a potent aqueous antioxidant, seems to decrease the levels of diene conjugation during recovery after exercise. The clinical significance of this phenomenon needs further evaluation.
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