Effects of vitamin C on oxidative stress, inflammation, muscle soreness, and strength following acute exercise: meta-analyses of randomized clinical trials

Background Vitamin C (ascorbic acid) seems to attenuate the overproduction of reactive species during and after exercises. Yet, no meta-analysis has summarized the magnitude of this effect. The objective of this study was to systematically review the effects of vitamin C supplementation on oxidative stress, inflammatory markers, damage, soreness, and the musculoskeletal functionality after a single bout of exercise. Methods Major electronic databases were searched, from inception to September 2019, for placebo-controlled randomized clinical trials (RCTs) that evaluated the effects of vitamin C supplementation on oxidative stress parameters, inflammation markers, muscle damage, muscle soreness, and muscle functionality after a single bout of exercise in healthy volunteers. Random effects modelling was used to compare mean changes from pre- to postexercise in participants that were supplemented with vitamin C versus placebo. Data were reported as standard mean difference (SMD) and 95% confidence interval (CI). Results A total of 18 RCTs, accounting for 313 participants (62% males, median age = 24"years) were included. Vitamin C supplementation reduced lipid peroxidation immediately (SMD = − 0.488; 95% CI = − 0.888 to − 0.088), 1"h (SMD = − 0.521; 95% CI = − 0.911 to − 0.131) and between 1 and 2"h (SMD = − 0.449; 95% CI = − 0.772 to − 0.126) following exercise. Exercise induced interleukin-6 (IL-6) response was attenuated 2"h (SMD = − 0.764; 95% CI = − 1.279 to − 0.248) and between 1 and 2"h (SMD = − 0.447; 95% CI = − 0.828 to − 0.065) after exercise. No effects of vitamin C supplementation were found on creatine kinase (CK), C-reactive protein (CRP), cortisol levels, muscle soreness, and muscle strength. Conclusion Vitamin C supplementation attenuates the oxidative stress (lipid peroxidation) and inflammatory response (IL-6) to a single bout of exercise.