"Vitamin D - why does it matter?" - defining vitamin D deficiency and its prevalence

Vitamin D deficiency is prevalent in about 50 % of adults and limited data support a similar prevalence in children. This is of concern, as vitamin D deficiency is a risk factor for falls and fractures and several double-blind RCTs provide evidence that supplementation reduces the risk of fall and fractures among the senior population. Further, large epidemiologic studies consistently report that vitamin D deficiency confers an increased risk of mortality, cardiovascular disease and cancer, especially colo-rectal cancer. However, as large clinical trials for non-musculoskeletal endpoints are missing today, public health recommendations are based primarily on bone health to argue vitamin D repletion in the population.