Vitamin D supplementation reduces serum markers of bone resorption and muscle damage in female basketball players with vitamin D inadequacy.

This study aimed to investigate the effect of vitamin D supplementation at a dose of 4,000 IU/day for 6 weeks on serum levels of: 25-hydroxyvitamin D [25(OH)D], bone turnover [osteocalcin and carboxy-terminal telopeptides of crosslinks of type I collagen (CTx-I)], and muscle damage [lactate dehydrogenase (LDH) and creatine kinase (CK)] in middle adolescent (15-18 years) and late-adolescent to early adulthood (19-30 years) female basketball players with inadequate vitamin D status. Participants (N=24) were randomly assigned in a double-blind manner into a vitamin D or placebo group. Data were analyzed using separate 2×2x2 mixed ANOVAs with one within-subjects factor (time) and two between-subjects factors (condition and age). When a significant interaction was observed, the intra-group changes were assessed using paired t tests and Hedge's . Paired t-tests comparing intra-group changes in the vitamin D condition revealed a non-significant improvement in 25(OH)D ( = 0.06; g = 0.86), non-significant decreases in CTx-I ( = 0.13;  = -0.22) and CK ( = 0.07;  = -0.26), as well as a significant decrease in LDH ( = 0.004;  = -0.74). Paired t-tests comparing intra-group changes in the placebo condition revealed a significant decline in 25(OH)D ( <0.001;  = -0.77), as well as significant increases in CTx-I ( = 0.04;  = 0.47) and CK ( = 0.04;  = 0.36). Vitamin D supplementation at 4,000 IU/day could be effective in reducing bone resorption and muscle damage in female basketball players with inadequate baseline vitamin D, irrespective of age.