Also, a vitamin is a substance that is made in the body either not all or in sufficient quantities to meet human needs.
The vitamins are essential for growth and health. An absence or deficiency of vitamin creates specific disorders.
Several vitamins function as enzyme cofactors (vitamin A, K and C, thiamin, niacin, riboflavin, vitamin B6, biotin, pantothenic acid, folate and vitamin B12) and not all enzyme cofactors are vitamins.
Some vitamins functions as biological antioxidants (vitamin E, and C) and several function as cofactors in metabolic oxidation-reduction reactions (vitamin E, K and C, niacin, riboflavin and pantothenic acid).
There are nine water-soluble and four fat soluble vitamins. Water soluble vitamins generally have limited storage ability in the body, with the exception of vitamin B12.
On the other hand, fat soluble vitamins are very dependent upon the processes of normal lipid digestion and absorption, such as the presence of bile and the construction of chylomicrons in the cells lining human small intestine. The four fat-soluble vitamins are:
*Vitamin A (retinol)
*Vitamin D (cholecalciferol)
*Vitamin E (tocopherol)
*Vitamin K (menadione)
Vitamin in general
