Effects of vitamin D supplementation on muscle function and recovery after exercise-induced muscle damage: A systematic review

Background Vitamin D is essential for the optimal health of the skeletal system. However, this vitamin is also involved in other functions of the human body, such as muscle, immune and inflammatory ones. Some studies suggest that adequate levels of vitamin D support muscular function during exercise and accelerate recovery because they reduce specific pro-inflammatory cytokine levels, but those results have not always been observed. Therefore, this review aims to evaluate the effects of vitamin D supplementation on inflammation, oxidative stress and recovery after exercise. Methods This systematic review was conducted using the Preferred Reporting of Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A literature search of SPORTDiscuss, PubMed, Web of Science and Scopus was performed from inception through February 2022. The articles' methodological quality was assessed with the PEDro scale. Results After the application of the inclusion and exclusion criteria, 11 eligible articles were included. All the studies were considered of moderate methodological quality. Ten studies involved regular vitamin D supplementation for more than 7 days, and one study performed acute vitamin D supplementation 24 h before exercise. Conclusions The existing evidence suggests that vitamin D supplementation for periods of more than 1 week with a minimum dose of 2000 IU/day appears to be an efficacious strategy for attenuating muscle damage and inflammation after exercise. The potential positive effects on muscle function, muscle pain and oxidative stress need to be confirmed with new investigations. Further research is also required to determine the adequate vitamin D dosage to obtain positive effects without adverse effects.