Vitamin D is a fat soluble vitamin and has been called the sunshine vitamin. The role of this vitamin has been known for several decades. It promotes the formation of bone. This is achieved by promoting the intestinal absorption of calcium. It is available from several sources, but the fish liver oils are the best sources. There is another source for which one does not have to pay. This source is sunlight which is free. Of course, sunlight does not contain vitamin D. The UV radiations which are part of the sunlight are able to act on a precursor of vitamin D present in the skin. This precursor molecule is called 7-dehydrocholeserol.

Vitamin D is actually a prohormone. Enzymes present in the liver and kidney convert vitamin D to its active form. This active form is called 1, 25-dihydroxycholecalciferol. Since this active form of vitamin D contains three hydroxyl groups, this compound is known as calcitriol. Calcitriol is able to act as a hormone and is released from the kidneys. It is calcitriol which promotes the absorption of calcium into the bloodstream.

Deficiency of vitamin D has been associated with increased blood cholesterol levels which in turn would make an individual susceptible to coronary heart disease. When vitamin D is not available in sufficient quantities fro food, the body tends to synthesize more cholesterol so that more vitamin D precursor is available in the skin. It is this response which leads to increased blood cholesterol levels. When vitamin D is deficient, there is increased calcification of the arteries, a phenomenon which promotes plaque formaton.

  • Vitamin D is probably the best antibiotic produced in nature. It has the ability to boost the functioning of the immune system. The T-cells of the immune system are normally in a dormant or, inactive state. When they are activated, they turn into killer cells. Vitamin D is involved in this activation. When T cells are exposed to the invading pathogens, they extend some ‘antennae’ which are actually vitamin D receptors. When vitamin D binds to these receptors, T cells are activated. If sufficient numbers of vitamin D molecules are not available for binding, the activation of T cells is stopped.
  • Vitamin D is also capable of inhibiting the development of some autoimmune disease. Multiple sclerosis and inflammatory bowel disease are classical examples. Vitamin D also enhances the phagocytic activity of the macrophages.
  • Vitamin D also promotes the synthesis of an anti microbial peptide called cathelicidin within the macrophages.

When vitamin D is deficient, glucose tolerance is reduced. This implies that low availability of vitamin D in the body can predispose to the development of diabetes. It has also been shown that nearly 77% of all cancers can be prevented by vitamin D.