Vitamins. Assorted multivitamin pills (red and orange) on plastic spoons. The red tablets (at right) contain an iron supplement. Vitamins are complex organic substances required in small amounts for the normal functioning of the body; as well as for healthy growth and development. Most cannot be made in the body and so are essential components of a healthy diet. There are 13 vitamins A,C,D,E,K and the eight B group vitamins. A lack of sufficient quantities of any of the vitamins in the diet can lead to specific vitamin deficiency diseases. Iron is an essential component in the transfer of oxygen in the body; a lack of iron in the diet can lead to anaemia.