Controlled vitamin C restriction and physical performance in volunteers.

A double-blind study on the effects of vitamin C restriction on physical performance was executed with 12 healthy men. During seven weeks of low vitamin C intake six subjects were on a daily diet of regular food products, providing 20% of the Dutch Recommended Dietary Allowances (RDA) for vitamin C (Dutch RDA is 50 mg/day). Other vitamins were supplemented at twice the RDA level. After three weeks of low vitamin intake an additional vitamin C dose of 15 mg/day was provided, resulting in a total intake of 25 mg/day (50% of the Dutch RDA). Six control subjects consumed the same diet supplemented with twice the RDA for all vitamins. In the restriction group blood vitamin C levels decreased significantly (p less than 0.01). Vitamin C restriction had no harmful effects on health, aerobic power (VO2-max), and onset of blood lactate accumulation (OBLA). However, an increased heart rate at OBLA level was observed during the period of low vitamin C intake (p less than 0.05), possibly by interference with either catecholamine or carnitine metabolism. These results suggest that short-term marginal vitamin C deficiency does not affect physical performance in single bouts of intensive exercise.