Consequences of vitamin C supplementation in competitive athletes during incremental exercise

Abstract

Twenty-one male basketball player (22-33 yr.) volunteered to participate in the experiment and gave their written consent. Subjects were randomly assigned to a control (control group-C) (n=10) or vitamin C (VC) (n=11) – supplemented group. The mean values (X) and standard deviation (±SD) of age and body height were 27,1±4,0 yr and 194,0±8,8 cm, while VO2max 44,7±4,2 ml/min/kg for the supplemented group and 23,3±1,3 yr, 190.0±3,3 cm, and VO2max 46,7±7,8 for the control group. During the experiment both groups were on a mixed, isocaloric diet (25% proteins, 55% carbohydrates, 20% fat). The average daily caloric and vitamin C intake from the diet of the C group equalled 3578±186 kcal and 75.6±7.7 mg. Respective values for the C group were 3715±127 kcal and 81.3±6.9 mg. All of the tested subjects performed similar, high intensity basketball training, six times per week, ranging from 90 to 120 min daily. Eleven subjects supplemented their diet with 240 mg of vitamin C (Acerola C – Nutrilite USA) taken as eight capsules three times daily (3 in the morning - 2 at midday and 3 capsules in the evening) for 2 weeks. Remaining subjects did not ingest any supplements (control group-C). No differences were observed in oxygen uptake during the progressive endurance exercise test between the supplemented and control groups during initial testing and after 14 days of the experiment. Vitamin C supplementation did not significantly effect resting creatine kinase (CK) activity as well as the level of malondialdehyde (MDA) and uric acid (UA). On the other hand the progressive endurance exercise protocol caused a significant rise (p<0,05) in CK activity which remained at that level after 30 min of recovery. The level of UA and MDA after exercise rose insignificantly. After 30 min of recovery statistically significant differences were registered only in case of UA. Vitamin C supplementation did not affect the amount of leukocytes and reticulocytes in peripheral blood (Tab. 2 and 3). On the other hand after exercise and during the 30th min of recovery in the group supplemented with vitamin C a tendency for lower leukocyte count was observed in comparison to the control group. Similar tendencies were registered in case of reticulocytes (Tab. 2 and 3). The endurance exercise protocol caused a significant increase (p<0,01) in the leukocytes and reticulocytes count, both after 12 min of exercise and after its cessation (Tab. 2 and 3). After 30 min of recovery a decrease of leukocytes and reticulocytes count in blood was observed which were slightly higher than at rest. It seems that dietary vitamin C content of the tested subjects was sufficient and an additional intake through supplementation did not cause significant metabolic changes and did not effect VO2max values during the endurance exercise protocol.