Apart from the macronutrients e.g. proteins, carbohydrates and lipids, which form major building blocks of the body, there are other components which are required for proper functioning of the body. One such micronutrients are vitamins.
1What is vitamin D?
Vitamin D belongs to the class of fat-soluble vitamins. It goes by the name ‘Calciferol’ in the scientific linguistics, and by the term ‘sunshine vitamin’ colloquially. It is both a nutrient that we can acquire, and also a hormone produced endogenously in the body.
Synthesis of vitamin D
Opposed to water-soluble vitamins, vitamin D is readily soluble in fats or lipids. This class also contains vitamins A, E, and K.
Endogenously, vitamin D is synthesized in the skin on exposure to the ultraviolet rays in sunshine. This form of vitamin D which is formed in the upper layers of the dermis is called previtamin D. This is later converted to vitamin D3. From the skin, it can either be stored in fat cells called adipocytes or be sent to the liver for further activation. This transport is also fat-dependent. Under the effect of liver enzymes, this form of vitamin D 3 is hydroxylated at the 25 position of the side-chain, which is further converted in a similar reaction at 1 position by the enzymes in the kidney. Finally, the activated form of vitamin D, the 1, 25 hydroxylated vitamin is formed. This activated form, also called calcitriol, is responsible for carrying out various homeostatic functions and calcium regulation in the body.