Effect Of Vitamin D3 Supplementation On Serum 1,25(OH) 2 D Status Of Athletes: Systematic Review And Meta-analysis

Abstract

Vitamin D is an essential fat-soluble vitamin, which plays an important role in the maintaining of good health. Without sufficient vitamin D, people cannot absorb enough calcium, which is a primary component of the bone. In the past century, vitamin D deficiency is heavily studied and lots of scientists report that vitamin D deficiency is related to several health problems, such as osteoporosis, muscle aches and weakness. Vitamin D supplements and vitamin D fortified foods always have claims of bringing people health benefits including bone health and muscle function. PURPOSE: This study is designed to investigate the effects of vitamin D3 supplementation on serum 1,25(OH)2D among athletes. METHODS: Literature search of PubMed, Embase and Cochrane Library databases from inception to Sept. 2019 was accomplished. Duplicates were removed at the stage of title and abstract assessment with assistant from Mendeley tools and by notes from Cochrane library. RESULTS: 6 RCTs with 205 athletes (vitamin D3 = 107, placebo = 98) finally met inclusion criteria. 20 athletes were lost to follow-up and 185 athletes (vitamin D3 = 100, placebo = 85) were documented with complete result. The intervention of vitamin D3 significantly improved the level of serum 1,25(OH)2D (SMD 3.77, 95% CI: 1.88 to 5.66, P < 0.01). Among athletes with insufficient baseline serum 1,25(OH)2D, vitamin D3 daily dosage at 5000 IU for over 4 weeks led to serum 1,25(OH)2D concentration of 31.7 ng/ml. Athletes with sufficient serum 1,25(OH)2D level at baseline were recruited in only one study, and the participants were assigned to either vitamin D3 at a daily dosage of 3570 IU or placebo for 12 weeks, their serum 1,25(OH)2D sufficiency (VD: 37.2 ± 7.6 vs 45.6 ± 7.6; PL 38 ± 6.8 vs 32 ± 8.4) was well maintained above the cut-off boundary with improved serum 1,25(OH)2D status in supplementation group. CONCLUSIONS: Serum 1,25(OH)2D concentration was improved after supplementation in this meta-analysis. Additional well-designed RCTs with large number of participants from a variety of sports that examined the effect of vitamin D3 supplementation on serum 1,25(OH)2D concentrations are needed.