New Concepts in Vitamin D Requirements for Children and Adolescents: A Controversy Revisited.

North American and European authorities have identified thresholds up to 50 nmol/L serum 25-hydroxyvitamin D (25[OH]D) as optimal for pediatric vitamin D status. These recommendations are relative to skeletal endpoints, as vitamin D plays a pivotal role in bone mineral content (BMC) accretion. Suboptimal vitamin D consumption during youth may therefore hinder BMC acquisition, and contribute to an increased fracture risk. Though vitamin D requirements range between 400 and 800 IU/day, not all children achieve this. To encourage adequate vitamin D consumption, strategies such as supplementation, food labeling, and fortification, are currently being investigated. There is moderate support for the role of vitamin D supplementation on adolescent BMC accrual; however, factors such as age, maturation, population ancestry, and latitude, are not consistently accounted for across studies. Vitamin D is also linked with extraskeletal endpoints (e.g., muscle mass/function, adiposity, and metabolic health) in children, but the cross-sectional data do not necessarily align with results from experimental trials. Based on the evidence currently available, there is no need for a revision of the pediatric vitamin D recommendations at this time. Additional trials are required, however, to build upon the hypothesis-generating observational data, and to provide evidence for future vitamin D requirements across the globe.