Lipid peroxidation in vivo is induced by exercise on a bicycle ergometer in athletes

There is a widely held belief that exercise leads to lipid peroxidation. Plasma hydroxy fatty acids originate from the diet and possibly from lipid peroxidation in vivo. We examined whether acute exercise (1 h at ∼76% of predicted maximal aerobic capacity) leads to an increase in plasma hydroxy fatty acids without the confounding influence of the diet in 7 male athletes. In addition, using a random-sequence cross-over design, we examined whether vitamin C supplementation of 1 g per day for 10 days prior to exercise could prevent exercise-induced lipid peroxidation. Supplementation doubled the plasma vitamin C from 56.9 ? 3.4 to 112.7 ? 14.6 μM (P< 0.001) and lowered pre-exercise plasma hydroxy fatty acids from 1.30 ? 0.18 to 1.03 ? 0.14 μM (P< 0.05). Plasma hydroxy fatty acid levels rose up to 3-fold during exercise in some athletes on placebo and peak levels were reached after 20 min. The rise in plasma hydroxy fatty acid levels was delayed and remained lower after supplementation with vitamin C compared to placebo: 0.01 ? 0.07 vs. 0.63 ? 0.16 μM (P< 0.05). Vitamin C supplementation reduced pre-exercise creatine kinase levels (193 ? 52 vs. 277 ? 68 U/L; P< 0.05) but its effect on exercise-induced changes in creatine kinase did not reach statistical significance. In conclusion, large supplements of vitamin C reduced exercise-induced lipid peroxidation in athletes. This small, but carefully controlled study illustrates the usefulness of plasma hydroxy fatty acid levels to monitor lipid peroxidation in vivo in acute studies.