The organic compounds other than carbohydrates, proteins and fats that are necessary to maintain normal health, growth and nutrition are called vitamins. It may be noted that vitamins are not used in building cells or as energy, source but they act as catalysts in biological processes, their deficiency causes serious diseases.
The vitamins are complex organic molecules, however, for the sake of simplicity, they are represented by letters such as A, B, C, D, E, K. More than 15 vitamins are known at present and each vitamin has its own specific function to perform in the body. Vitamins have different structures and in this respect they are quite unrelated to each other. Unlike other nutrients, vitamins are used in very small amounts, but there presence in the diet is very important. A balanced diet, therefore, must contain all these vitamins because deficiency of any of these vitamins may cause a disease. Vitamins are broadly classified into two types, water-soluble and oil soluble. Vitamins A, D, E and K are oil soluble whereas vitamins B and C are water-soluble.