Vitamins are essential organic substances needed by the body in small amounts to perform specific metabolic functions. There are 13 legitimate vitamins that exist as either fat-soluble (A, D, E, K) or water-soluble (C, B-complex). Fat-soluble vitamins are stored in tissues while water-soluble vitamins are not stored and require consistent dietary intake. Deficiencies of vitamins can result in diseases like rickets, osteomalacia, beriberi, and pellagra depending on the specific vitamin lacking in the diet.