Vitamins In the early 20th century the discovery of vitamins began. Today there is a chance that there are some vitamins that are still undiscovered. The definition of vitamin is: one of several substances necessary for animal nutrition, and occurring in minute quantities in natural foods; numerous types have been distinguished, and designated by the letters of the alphabet. Each and every living animal needs vitamins to grow and be healthy. Since the human body can t produce vitamins naturally or normally produce the amounts needed, food provides the body with them. There are different vitamins found in different foods. These vitamins give vital nutrients to an animal.