Sun X, Tanisawa K, Zhang Y, et al. - By performing this study on 95 participants, researchers ascertained if body composition and physical fitness in healthy adults can be directly affected by 1 year of vitamin D₃ supplementation. They randomized the participants to receive either 420 IU vitamin D₃ per day (n = 48) or placebo (n = 47) in a double-blind manner for 1 year. Following 1 year of vitamin D₃ supplementation, they detected a significant rise by almost 11.2 ± 9.2 ng/mL and 7.0 ± 7.8 pg/mL in the levels of serum 25(OH)D and (1,25[OH]₂D), respectively. The vitamin D group exhibited a significant rise in lean body mass from 43.8 ± 9.6 to 44.3 ± 9.8 kg, while there was no change in placebo group following 1 year intervention. Overall, findings revealed the effectiveness of 1 year of vitamin D₃ supplementation in improving lean body mass, but not muscle strength and cardiorespiratory fitness in healthy adults.