[Update on recent progress in vitamin D research. Vitamin D and metabolic disease.]

Numerous epidemiological studies and meta-analyses have indicated that there is a link between Vitamin D insufficiency/deficiency and metabolic disorders such as type 1 and type 2 diabetes mellitus as well as metabolic syndrome. However, vitamin D supplementation has not demonstrated improvement effects in obesity, disorders of glucose and lipid metabolism in any of these illnesses;therefore, the details of the causal relationship remain unclear. Improvement in glucose metabolism was observed in a study in which only vitamin D deficient patients with 25-hydroxyvitamin D[25(OH)D]levels of less than 20 ng/mL were given native vitamin D supplementation. Further studies are needed to determine the 25(OH)D level at which intervention is needed along with the required amount and duration of such supplementation.