Effect of Eight Weeks of Vitamin D Supplementation on Body Composition, Speed and Fatigue Time in Military Force

Background and Aim: Clinical studies show the effect of vitamin D on muscle strength in athletes. In addition, vitamin D deficiency is more common in people with higher physical activity than in others. Therefore, it seems vitamin D supplementation in the military can improve their health and physical performance. Methods: This study is a double-blind clinical trial was done in Isfahan, Iran in 2019. According to the inclusion and exclusion criteria, 100 militaries were randomly assigned to two groups of supplement and placebo groups (n=50). Demographic data and physical activity of militaries were collected by questionnaires. For all of the participants, measurements of height, weight, waist circumference, fat and muscle mass of the body were conducted. Sport tests of speed and time of fatigue were done. Data analysis was performed by SPSS software, version 18.0. Results: The two groups of intervention and placebo were matched in terms of age, serum vitamin D level and level of physical activity. The mean of serum vitamin D level in the intervention group at the end of the study was higher than the placebo group (p <0.05). There were no differences in anthropometric indices (weight, waist circumference and BMI) as well as body composition between the two groups receiving vitamin D and placebo at the end of the study (p <0.05). Fatigue time more increased in the vitamin D supplement group than in the control group (p <0.05) but no difference was seen in the 10 m speed test (p <0.05).  Conclusion: The findings of this study show that vitamin D supplementation can increase fatigue time in military force, but it does not influence body composition and speed.