“…In fact, megadoses of vitamins may even impair immune function in athletes (Prasad, 1980). Although the cellular antioxidant mechanism adapts efficiently to acute and chronic exercise (Mena et al, 1991), extreme physical exercise causes oxidative damage to athletes, which is reflected by increases in plasma levels of malondialdehyde (Marzatico et al, 1997), urine 8-hydroxideoxyguanosine (Radak et al, 2000) and erythrocyte catalase activity (Tauler et al, 1999), which could relate to exercise-induced immunodepression. Vitamin C supplementation augmented the increase in lymphocyte counts after exercise (Petersen et al, 2001;Peters et al, 2001b), attenuated the serum cortisol increase in ultramarathon runners (Peters et al, 2001a, b;Nieman et al, 2002b) and attenuated the increases in inflammatory cytokines (Nieman et al, 1997b(Nieman et al, , 2000bPeters et al, 2001a, b), when ingested in doses greater than or equal to 1000 mg/day, but not on 500 mg/day.…”