Influence of vitamin C diet supplementation on endogenous antioxidant defences during exhaustive exercise

We determined the effects of dietary vitamin C supplementation on erythrocyte antioxidant enzymes and on plasma antioxidants during athletic competition and short-term recovery. Blood samples were taken from 16 volunteer endurance athletes, participating in a duathlon competition, under basal conditions and both immediately and 1 h after the competition. The results were analysed taking into account the individual vitamin C intake and the plasma levels. Athletes were assigned to either the vitamin C-supplemented or control groups (n=8 each). The control group had normal plasma ascorbate levels, the supplemented group high levels as a result of the higher vitamin C intake. Uric acid and lactate dehydrogenase increased after the competition only in the control group. Plasma ascorbate decreased after short-term recovery in the supplemented group. Erythrocyte catalase activity increased after the competition in the supplemented group. Glutathione peroxidase activity (determined with cumene hydroperoxide as substrate) increased only in the control group after short-term recovery. This pattern may suggest an important role for plasma ascorbate, and dietary vitamin C supplementation, in the defence against oxidative stress induced by exercise and in avoiding negative effects on erythrocyte integrity.