Vitamin D: extent of deficiency, effect on muscle function, bone health, performance, and injury prevention

Vitamin D deficiencyis increasingly being identified in children, adolescents, and adults. Primary production of the active form of vitamin D occurs via a photolytic reaction induced by ultraviolet radiation B. Vitamin D has important effects on bone and muscle as well as on the immune system. Isolation ofa vitamin D receptor on muscle cells has been accompanied by studies showing receptor polymorphisms and age-related functional changeswhich have an effect on muscle performance. Insufficient levels havebeen associated with increased risk of stress fractures, decreased muscle performance, and increased sick days. Although there is still debate about the appropriate levels of vitamin D, studies have suggested a minimal level of 32 ng/ml. Supplementation serves as an inexpensive option associated with reduction in both morbidity and financial costs.