Bones and beyond: an update on the role of vitamin D in child and adolescent health in Canada.

Knowledge regarding the physiological role and dietary requirements of vitamin D has dramatically expanded over the past several decades. The "new" vitamin D is not only a mediator of calcium homeostasis, but also has important immunomodulatory, anti-microbial, and anti-proliferative actions. Amidst the growing interest in vitamin D as a mediator of many chronic diseases of adulthood such as cancer and type II diabetes, less attention has focused on the implications of the new understanding of vitamin D for child and adolescent health. This article reviews the definition of vitamin D insufficiency (VDI) as it applies to children and adolescents, the current vitamin D status of Canadian children and adolescents, pediatric conditions that may be related to VDI, and the evidence base for current dietary recommendations for vitamin D intake. Pharmacokinetic studies and epidemiologic research that incorporates clinical and functional outcomes are needed to clarify the role of vitamin D in growth and development and the specific dietary vitamin D requirements among Canadian children and adolescents.