Low vitamin C values are linked with decreased physical performance and increased oxidative stress: reversal by vitamin C supplementation
Reviewer: Dr. Alan Gaby, MD
Author: Paschalis V, et al.
Reference: Low vitamin C values are linked with decreased physical performance and increased oxidative stress: reversal by vitamin C supplementation. Eur J Nutr 2016;55:45-53.
Design: Randomized, double-blind, placebo-controlled crossover trial.
Participants: One hundred healthy males (mean age, 22 years).
Study Medication and Dosage: Vitamin C at a dose of 1,000 mg per day or placebo for 30 days. After a 60-day washout period, each person received the alternate treatment for an additional 30 days.
Primary Outcome Measure: Maximal oxygen uptake (VO2 max) during the performance of aerobic exercise to exhaustion. VO2 max is a measure of aerobic capacity.
Key Findings: Prior to vitamin C supplementation, compared with the 10 subjects with the lowest plasma vitamin C levels (Group A), those with the highest plasma vitamin C levels (Group B) had a significantly higher mean VO2 max. Mean daily vitamin C intake was 33 mg in Group A and 166 mg in Group B. In Group A, compared with placebo, vitamin C supplementation increased VO2 max (p < 0.08), whereas vitamin C had no effect on VO2 max relative to placebo in Group B. The improvement in VO2 max in the subjects in group A who received vitamin C brought the VO2 max to a level similar to that of subjects in Group B.
Practice Implications: In this study, a substantial number of healthy young males consumed less than the Recommended Dietary Allowance (RDA) for vitamin C of 90 mg per day. Low vitamin C intake was associated with decreased aerobic capacity, which was corrected by vitamin C supplementation. In contrast, vitamin C supplementation did not improve aerobic capacity in people whose diet contained abundant amounts of the vitamin.