['We have investigated the influence of vitamin C diet supplementation on the antioxidant response and nitrite levels in lymphocytes and erythrocytes during diving apnea.', 'Seven male professional apnea divers participated in a double blind crossover study. Divers were randomly assigned to either vitamin C supplemented or placebo groups. The subjects did not take any other supplements than the ones provided for this study.', 'One group was supplemented with vitamin C capsules (1 g per day) for 7 days while the other group took a placebo composed of lactose. The usual dietary habits of participants were assessed using a self-reported 7-days 24-h recall before the day of the study. Blood samples were taken under basal conditions, immediately after diving apnea for 4 h and after 1 h of recovery.', 'Catalase activity increased in erythrocytes (23%) and superoxide dismutase increased in lymphocytes (35%) during the recovery only in the placebo group. Lymphocyte ascorbate levels increased in the supplemented group after diving (85%) and maintained high at recovery. Plasma nitrite levels increased about twofold in both groups during the recovery. Erythrocyte nitrite levels increased after diving (50%) and about twofold during the recovery in the supplemented group. Nitrite levels and iNOS levels in lymphocytes were higher in the placebo group than in the supplemented during the recovery. Erythrocyte carbonyl derivates were unchanged in all situations.'] Does vitamin C supplementation influence the antioxidant response and nitric oxide handling of erythrocytes and lymphocytes to diving apnea?