Vitamin D metabolism, functions and needs: from science to health claims

Vitamin D is a nutrient long considered as essential for skeletal health but is now attracting interest from medical and nutritional communities as knowledge emerges of its biological function and its association with decreased risk of many chronic diseases. A question emerges: How much more vitamin D do we need for these new functions of vitamin D? This review discusses vitamin D physiology and hypovitaminosis D and presents two vitamin D dietary policies: that according to regulatory authorities and that of nutrition scientists. Scientific evidence suggests that 25(OH)D serum levels should be over 75 nmol/L; otherwise, there is no beneficial effect of vitamin D on long-latency diseases. Current regulatory authority recommendations are insufficient to reach this level of adequacy. Observational and some prospective data show that vitamin D has a role in the prevention of cancer as well as immunity, diabetes and cardiovascular and muscle disorders, which supports the actions of 1 alpha,25(OH)2D at cellular and molecular levels. The recent assessments done by the European Food Safety Authority should lead to new health claims. Vitamin D, through food fortification and supplementation, is a promising new health strategy and thus provides opportunities for food industry and nutrition researchers to work together towards determining how to achieve this potential health benefit.