The Vitamin D Function: Bone Metabolism and Other Novel Functions

Abstract

Vitamin D plays an important role in the regulation of calcium homeostasis and bone metabolism. Among the vitamin D metabolites, serum 25-hydroxyvitamin D (25-D) concentration is the best indicator of vitamin D status. Vitamin D insufficiency is known to cause secondary hyperparathyroidism, which adversely affects bone metabolism. In addition, vitamin D insufficiency has been associated with other health outcomes including not only osteoporotic fractures but also cardiovascular disease, fall, skeletal muscle function, cancers, respiratory diseases, and all-cause mortality. However, substantial debate about the optimal vitamin D status to prevent those diseases has been continued. Present paper would review the recent knowledge of vitamin D function, meta-analyses of randomized trials of vitamin D supplementation and the requirement of vitamin D.