Persistent Effect of Vitamin D Supplementation on Musculoskeletal Parameters in Adolescents One Year After Trial Completion

We showed a beneficial effect of vitamin D supplementation on musculoskeletal parameters in adolescent girls in a 1-year, randomized, double-blinded placebo-controlled trial (RCT). Our objective for this study was to investigate the residual effect of vitamin D supplementation on bone mineral content (BMC), bone mineral density (BMD), at the lumbar spine and hip, lean mass, and height, 1 year after trial completion. We performed post hoc analyses in 167 adolescents, 86 girls and 81 boys, age 13.9 ± 2 years, who received vitamin D or placebo during the trial, and continued into the follow-up trial. Musculoskeletal parameters were measured at baseline, 12 months (intervention), and 24 months (follow-up). ANOVA and t tests were used to compare results between the placebo group and the merged vitamin D arms (200 or 2000 IU/day), by gender. Baseline characteristics were comparable between treatment groups at entry into the extension. Girls who had received vitamin D during the trial, had significantly larger hip BMC increments compared to those assigned to placebo, at 24 months compared to study entry, but not 24 compared to 12 months, which persisted in adjusted analyses. There were no significant differences in bone mass changes between treatment groups in boys, at 24 months compared to 12 months or to baseline. The beneficial effect of vitamin D supplementation on hip bone mass, achieved in girls during the trial, persisted 1 year after trial completion. These net cumulative increments, 1 year after discontinuation of supplementation, may have important implications on optimizing peak bone mass accretion in adolescent girls.