Regulacje i polityka gospodarcza · 8.10.2009

ODS Nutrient Biomarkers Analytical Methodology: Vitamin D Workshop; Notice

Vitamin D is a fat-soluble vitamin that is naturally present in very few foods, added to others, and available as a dietary supplement. It is also produced endogenously when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis. Vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first occurs in the liver and converts vitamin D to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol. The second occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH) 2 D], also known as calcitriol. Serum concentration of 25(OH)D is the best indicator of exposure to vitamin D from all sources. It reflects vitamin D produced cutaneously and that obtained from food and supplements. There is considerable discussion of the serum concentrations of 25(OH)D associated with deficiency (e.g., rickets), adequacy for bone health, and optimal overall health. In fact, different assay methods are used to assess 25(OH)D. The methods themselves vary and there are considerable differences among laboratory results even when they use the same method.