Effects of vitamin D3 supplementation for 12 weeks on serum levels of anabolic hormones, anaerobic power, and aerobic performance in active male subjects: A randomized, double-blind, placebo-controlled trial

Maintenance of the serum 25-hydroxyvitamin D (25-OH-D) concentration at recommended levels is essential due to its role in the regulation of anabolic hormones and athletic performance. However, the results of the clinical experiments in athletes are controversial. The present study aimed to investigate the effect of vitamin D3 supplement on serum levels of anabolic hormones, cortisol, anaerobic and aerobic performance in active males. In this double-blind, randomized controlled trial, 46 active males randomly assigned to vitamin D3 supplement (VDS; 2000 IU/day) or placebo for 12 weeks. The Wingate test, VO(2)max, and serum levels of 25-OH-D, Parathyroid hormone (PTH), total testosterone, growth hormone (GH), Insulin-like growth factor-1 (IGF-1), and cortisol were assessed. Subjects in the VDS group had a higher serum level of 25-OH-D (p = 0.004), VO(2)max (p = 0.016), and average power (p = 0.044) compared to the placebo at the end of the study. Also, lower levels of PTH (p = 0.004) and fatigue index (p < 0.001) were observed in VDS group at the end of the study. The serum cortisol levels were reduced significantly only in subjects with vitamin D deficiency in VDS group (p = 0.042). There was a significant reduction in serum testosterone levels in VDS group (p = 0.013). No change was indicated in serum levels of GH and IGF-1 in VDS group compared to the placebo (p > 0.05). The present study showed an improvement in aerobic capacity, anaerobic performance, and vitamin D status following vitamin D3 supplementation. However, more studies are required for the effect of vitamin D3 on serum concentration of anabolic hormones.