Effects of vitamin D on muscle mass and function in high school athletes.

Nutrition and exercise have effects on the body. The aim of the present study was to assess vitamin D status (serum 25-hydroxyvitamin D [25(OH)D] levels) and investigate its associations with muscle mass and function, as well as the effects of vitamin D supplementation on muscle function in high school athletes. Twenty-one high-school athlete students (6 males and 15 females) participated in this study. The serum 25(OH)D levels of 15 athletes (71.4%) with vitamin D insufficiency (VDI)/vitamin D deficiency (VDD) were and those of six athletes (28.6%) with vitamin D sufficiency (VDS) were 24.2 (22.3-27.0) ng/mL and 35.8 (33.0-38.9) ng/mL, respectively. Serum 25(OH)D concentration was significantly associated with total power in the male, female, and total athlete groups. Daily 1,000 IU vitamin D supplementation for 6 months increased serum vitamin D levels from 27.0 (22.9-32.1) ng/mL to 37.9 (28.9-40.9) ng/mL and improved muscle function in the total athlete group. Our findings suggest that daily 1,000 IU vitamin D supplementation should be recommended to optimize maximal aerobic power in high school athletes. J. Med. Invest. 72 : 167-171, February, 2025.