We conducted a systematic review and meta-analysis of randomized controlled trials examining the effect of vitamin C and/or E on exercise-induced training adaptations. Medline, Embase and SPORTDiscus databases were searched for articles from inception until June 2019. Inclusion criteria was studies in adult humans where vitamin C and/or E had to be consumed alongside a supervised exercise training program of ≥4 weeks. Nine trials were included in the analysis of aerobic exercise adaptations and nine for resistance training (RT) adaptations. Vitamin C and/or E did not attenuate aerobic exercise induced improvements in maximal aerobic capacity (O2max) (SMD -0.14, 95% CI: -0.43 to 0.15, P = 0.35) or endurance performance (SMD -0.01, 95% CI: -0.38 to 0.36, P = 0.97). There were also no effects of these supplements on lean mass and muscle strength following RT (SMD -0.07, 95% CI: -0.36 to 0.23, P = 0.67) and (SMD -0.15, 95% CI: -0.16 to 0.46, P = 0.35), respectively. There was also no influence of age on any of these outcomes (P > 0.05). These findings suggest that vitamin C and/or E does not inhibit exercise-induced changes in physiological function. Studies with larger sample sizes and adequate power are still required.
Keywords: Antioxidant; endurance performance; resistance training; skeletal muscle; vitamin.