Effects of Vitamin D Supplementation on Muscle Strength in Athletes A Systematic Review

The purpose of this systematic review of the literature was to investigate the effects of vitamin D supplementation on muscle strength in athletes. A computerized literature search of three databases (PubMed, Medline, and Scopus) was performed. Included in the review were randomized controlled trials, published in English, which measured serum vitamin D concentrations and muscle strength in healthy, athletic participants ages 18-45 years old. Quality was assessed using the PEDro scale.Five randomized controlled trials and one controlled trial were identified, and quality assessment showed five trials were of ʼexcellent qualityʼ and one was of ʼgood quality.ʼ Trials lasted from 4 weeks to 6 months and dosages ranged from 600 IU to 5000 IU per day.Vitamin D2 was found to be ineffective at impacting muscle strength in both studies wherein it was administered. In contrast, vitamin D3 was shown to have a positive impact on muscle strength. In two studies, strength outcome measures were significantly improved following supplementation (p < 0.05). In the other two studies administering vitamin D3, there were trends for improved muscle strength. Specifically, improvements in strength ranged from 1.37% to 18.75%. Additional studies are needed to confirm these associations.