Vitamins are often called micronutrients as we need only very tiny amounts of them. Currently, there are 13 recognized vitamins in humans: 4 fat-soluble (A, D, E, and K) and 9 water-soluble (8 B vitamins and vitamin C). They play many diverse roles in our body and thus are vital for proper functioning of the metabolism and the whole body. Humans need to intake vitamins (or their precursors) by diet, as we cannot synthesize most of them. Both deficient and excess intake (hypervitaminosis) of a vitamin can potentially cause clinically significant illness.