Vitamin C status and physical working capacity in adolescents

The effect of ascorbic acid supplementation on physical working capacity was studied in young adolescent boys in which the concomitant biochemical riboflavin and pyridoxin deficiencies were corrected by medicamentous prophylaxis. After daily administration for two months of 70 mg ascorbic acid, the mean plasma vitamin C in the experimental group (n = 49) rose from 0.33 to 1.49 mg/dl (p less than 0.001) and the prevalence of deficient plasma vitamin C values (less than 0.20 mg/dl) decreased from 52.3 percent to zero. The improvement in vitamin C biochemical status was also accompanied by a statistically significant increase in VO2 max. (p less than 0.01). There were no significant changes neither in the mean plasma vitamin C values nor in the mean VO2 max. in the control group subjects (n = 42). The increase in VO2 max. in the experimental group was primarily the result of an increase of VO2 max. in subjects with initially lower values. When data from both experimental and control groups were pooled together, a positive and significant association was found between VO2 max. and the increase of plasma vitamin C values below 1.0 mg/dl. No further increase in VO2 max. was observed when vitamin C plasma values reached 1.0 mg/dl or more. The two regression lines crossed at X = 0.86 mg/dl. This cut off point of plasma vitamin C level corresponds to a dietary intake of about 80 mg of ascorbic acid per day. The results of this study are in agreement with the suggested optimal ascorbic acid daily intake obtained by kinetic studies with (1-14C) ascorbic acid.