Outcomes of vitamin D3 supplementation on serum 25-hydroxy vitamin D in male runners: a randomized controlled trial

BACKGROUND: The role of vitamin D is well established in bone health and its deficiency could have an impact on athletic performance and injury. Several research reviews have suggested that vitamin D has a significant effect on muscle weakness, pain, balance, and fractures in the aging population; however, the athletic population is yet to be fully investigated.METHODS: We assessed serum 25-hydroxy vitamin D [25(OH)D] concentrations and the effect of short-term vitamin D-3 supplementation on long-distance runners. Thirty-four male athletes were double-blind randomly divided equally into vitamin D (25 mu g/day of vitamin D-3 intake) or placebo group.RESULTS: Both groups had normal meals with or without supplements. Before the intervention, serum 25(OH)D con-centration was 28.9 +/- 5.7 ng/mL, and 65% of subjects (n=22/34) had insufficiency of vitamin D. During the intervention, the mean amount of vitamin D intake was 40.0 +/- 5.5 mu g/day in the vitamin D group and 13.4 +/- 7.7 mu g/day in the placebo group, respectively. The serum 25(OH)D concentrations showed a significantly higher increase in the vitamin D group than that in the placebo group (P<0.001, P<0.01, respectively). After the intervention, the serum 25(OH)D concentration was significantly higher in the vitamin D group (P<0.001).CONCLUSIONS: Our study findings demonstrated that the serum 25(OH)D concentration during the postintervention was related to both the mean amount of vitamin D intake during the intervention period and preintervention serum 25(OH)D concentration.