The body needs vitamins just as it requires other food constituents such as proteins, fats, carbohydrates, minerals, and water.
Vitamins serve as coenzymes or cofactors in enzymatic reactions.
They are required only in trace quantities because they are not consumed in the reactions. The major vitamins are designated by the letters A, C, D, E, and K, and the term B complex. The B vitamins and vitamin C are water-soluble. The rest are fat soluble and are not absorbed unless the body's digestion and absorption of fats is normal. Deficiencies of the fat-soluble vitamins can be produced by various malabsorption syndromes.