Journal Title (Medline/Pubmed accepted abbreviation): J. Appl. Phyiol.
Page Numbers: 990-1000
Background: The increased cellular metabolism associated with exercise increases production of free radicals. Because of the damaging effects of free radicals on cells, increased free radical production has historically been viewed as a negative consequence of exercise. However, it is now recognized that free radicals and other reactive species play important signaling roles in the cellular response and adaptation to exercise. The immune system is one such system that is responsive to this type of signaling. The authors wanted to know if antioxidant supplementation, which would theoretically reduce free radicals/oxidative stress in cells, could actually have a negative impact on the adaptation to exercise training.
Hypothesis: Supplementation with vitamins C and E will reduce the rate at which the body adapts to routine exercise. Therefore, without supplementation, exercise-induced IL-6 production will decrease after a 16 week exercise program whereas with supplementation, there will be less of a decrease.
Subjects: 21 healthy males that exercise between 2-4 times per week, age about 25-35 y.
Experimental Design: randomized, placebo-controlled, double-blinded
Vitamins- tablets that contain 500 mg ascorbic acid (vitamin C) and 400 IU RRR-α-tocopheryl succinate (vitamin E)
Placebo- tablets made of starch, cellulose, and calcium hydrogen anhydrous (no vitamins)
Protocol: The participants were first evaluated for VO2max (maximum consumption of oxygen) and Pmax (maximum power) and randomized to one of the two groups. Subsequently, vitamin (or placebo) supplementation commenced, lasting 16 wks. Four weeks into the supplementation period, all participants performed an acute exercise trial where they cycled at 65% Pmax on a stationary bicycle for 1 hr. Blood samples and muscle biopsies were collected before and after training as well as 3 hrs after training. Then, participants engaged in a cycling exercise protocol 5 times per week for the remaining 12 wks. Training intensity was based on the individuals’ Pmax that was determined at the start of every week. Training was different on different days of the week and included both interval training and less intense, longer rides of “cardio” training. Training length or intensity was increased every week. Another acute exercise trial was completed within 3-4 days of the last training session. Blood was analyzed for vitamin C and E concentrations, IL-6, IL-1ra, cortisol, and protein carbonyls (used to assess oxidative injury). Biopsies were analyzed for mRNA concentration for specific genes, the concentration of various proteins, and malondialdehyde (MDA; an indicator of oxidative stress).
Key practice applications: This study provides evidence that supplementation with vitamins C and E may attenuate the immune response to exercise. However, there were only very small differences between the vitamin group and the placebo group in regard to markers assessing the adaptive response to exercise. The authors concluded that there were no beneficial effects of vitamins C and E supplementation in their study.
Limitations It would have been interesting if the study design included a performance measurement to assess whether the 12 wk exercise training allowed the placebo group to improve more than the vitamin group (or not).
- There is a chance that some of the athletes in the supplement group were vitamin deficient before supplementation. Therefore, supplementation would lead to gains in performance and body functionality, where it may have a different effect in vitamin-replete athletes.
Key search terms for this article (5-7 terms): antioxidants, vitamin C, vitamin E, ascorbic acid, tocopherol, oxidative stress, adaptation