Background:
There has been no report of the vitamin D status of the professional athletes from Iran to date. This study was performed to evaluate the efficacy of weekly vitamin D supplementation on athletic performance in Iranian athletes expedited to Asian competition in Taipei, China, 2015.
Methods:
This study was a randomized controlled clinical trial. Seventy subjects were enrolled in the study. The athletes were randomly divided into two groups: vitamin D supplement (D; received 50,000 IU of vitamin D supplement weekly) and control (P, received a placebo weekly). Duration of the study was 8 weeks. Anthropometric, dietary, athletic performance, and biochemical evaluations were performed for all subjects in the beginning and in the end of the intervention period.
Results:
A significant rise in circulating 25(OH)D concentration was observed in D group (17.3 ± 16.9 ng/mL,
P
< 0.001), whereas in
P
group, there was a statistically significant decrement (−3.1 ± 8.4 ng/mL,
P
= 0.040). There were no either within- or between-group significant differences in Ergo jump, vertical jump, and agility tests. In strength leg press tests, both groups showed a significant improvement. However, comparisons of changes revealed that the improvement in D group was significantly higher than in
P
group (
P
= 0.034). Moreover, in sprint test (one repetition-Max, 1RM), only D group had a significant within-group improvement (
P
= 0.030).
Conclusions:
Weekly supplementation with 50,000 IU vitamin D resulted in nearly 17 ng/mL increment in circulating calcidiol. This increase was associated with significant improvement of power leg press and sprint tests in D-supplemented group.