Picture of Vitamin D

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Picture of Vitamin D

Vitamins are substances that play an essential part in animal metabolic processes, but which the animals cannot synthesise. In their absence the animal develops certain deficiency diseases or other abnormal conditions. Vitamins are chemicals other than proteins, carbohydrates, fats and mineral salts that are essential constituents of the food of animals. Although certain animals can synthesise certain vitamins and all animals needing vitamin D can manufacture it from ergosterol in the presence of u.v. light, the precise mechanism of action of many vitamins is still poorly understood. Small amounts of vitamins are essential for the regulation of all bodily processes. With the exception of vitamin D, the human body cannot make its own vitamins, and some cannot be stored. Vitamins must therefore be obtained from a food on a daily basis. A person's diet must provide all the necessary vitamins.

Vitamin D is needed for the absorption of calcium and the regulation of calcium levels in the blood. Both vitamins, which have almost identical actions, are used for the prevention and cure of infantile rickets The absence of vitamin D in the food of young animals leads to the development of rickets unless the animal is exposed to sunlight or u.v. irradiation.; they are essential for the normal development of teeth, and are used for treating osteomalacia and dental caries. They are necessary for the absorption of Ca and P from the gut. Sunlight activates the metabolism of vitamin D in the body.

The first vitamin D to be discovered was a crude mixture called vitamin D1. Irradiation of erggoterol with u.v. light gives calciferol or vitamin D2. Irradiation of 7-dehydrocholesterol gives the natural vitamin D or vitamin D2, which differs in the structure only in the side chain.

Good sources of vitamin D are butter, margarine, cheese cream, yogurt, milk eggs and sunlight. It is soluble in fats, milk, butter and eggs. The richest sources of vitamin D are fish-liver oils, particularly those of the halibut and the cod.

Update by Karl Harrison
(Molecule of the Month for February 1997 )