[Vitamin D: vitamin from the past and hormone of the future]

In the last decade there has been a rising recognition of potential clinical significance of the vitamin D. Vitamin D regulates about 3% of the human genome. Thus, vitamin D deficiency is common and high in various populations across the world including Croatia. In this paper vitamin D metabolism and up to date knowledge of vitamin D function in calcium metabolism, muscular function and in prevention of infection, malignancy, autoimmune and cardiovascular diseases is presented. Reasons for pandemic vitamin D deficiency and guidelines for vitamin D supplementation are given.