On the basis of their solubility in water or fat, vitamins are classified into two groups:
1. Fat - soluble vitamins: Vitamins that are soluble in fat and oils, but not in water, belong to their group.
For example: Vitamins A, D, E and K.
2. Water - soluble vitamins: Vitamins that are soluble in water belong to their group. For example: B group vitamins (B1, B2, B6, B12, etc) and vitamin C. However, biotin or vitamin H is neither soluble in water nor in fat. Vitamin K is responsible for the coagulation of blood.
