Vitamin D insufficiency and musculoskeletal health in children and adolescents

A large body of data demonstrates a high prevalence worldwide of hypovitaminosis D in children and adolescents, at a critical time of bone mass accrual. Increasing evidence supports a deleterious effect of vitamin D insufficiency on musculoskeletal health in this age group based on cross-sectional studies, studies relating vitamin D to biochemical variables in the homeostatic pathway for vitamin D physiology (PTH, calcitriol, bone remodeling). Two recent randomized interventional trials show that vitamin D supplementation increases accrual of bone mass in girls, and this is partly explained by enhanced calcium absorption and bone mineralization. However, recent data also suggest beneficial effects on lean mass and bone geometry. It remains uncertain whether the beneficial effects of vitamin D in girls are reflected in the peak bone mass they eventually attain. A desirable 25(OH) D level to optimize musculoskeletal health in girls seems to be between 30 and 40 ng/ml (70–100 nmol/L). Future investigations are needed to shed light on mechanisms for the beneficial effect of vitamin D on musculoskeletal health, on optimal timing and dosing for vitamin D supplementation, on the biological basis for sexual dimorphism in the response to vitamin D supplementation in the young, and on the key clinical outcomes, such as lifetime reduction in fracture risk.