Define Absorption, Storage and Elimination of Vitamin D?

As we have already mentioned earlier, all fat-soluble vitamins share a common metabolic fate. Vitamin D is absorbed along with fats from the duodenum and jejunum. Bile too is essential for the effective absorption of fats and therefore of vitamin D.

Conditions unfavourable to fat absorption such as lack of bile, disorders such as sprue and celiac disease results in poor absorption of vitamin D. Once absorption is complete, vitamin D enters the blood as n part of the chylonmicrons. Vitamin U formed in the skin by the direct irradiation of the provitamin present in the skin is directly absorbed into the blood stream. The vitamin is stored in concentrated quantities in the liver and to a lesser extent in the skin, spleen, lungs,. brain and kidney. The main pathway of excretion of vitamin D is through the bile into the small intestine and consequent faecal excretion. Only less than four per cent of the intake of the vitamin is excreted by the urinary pathway.