Clinical Controversies in Vitamin D: 25(OH)D Measurement, Target Concentration, and Supplementation

Despite a plethora of recent research and systematic reviews of available data, controversy continues to surround the definition of optimal vitamin D. status, the daily intake needed, and the potential adverse health consequences of "insufficiency." Efforts to standardize vitamin D measurement and improve understanding of the physiologic consequences of other vitamin D metabolites such as 3-epi and 24,25(OH)(2)D (and potentially other vitamin D compounds) are needed. Currently, measurement of circulating 25(OH)D is accepted as the approach to define an individual's vitamin D status. However, existing 25(OH)D assays may include other vitamin D metabolites such as the 3-epimer of 25(OH)D and 24,25(OH)(2)D. It seems unlikely that the controversy will soon be resolved.