Vitamins are organic compounds that an organism needs for various vital functions (but not as an energy source), but which cannot be synthesized in sufficient quantities by the metabolism. They belong to the so-called essential substances and must be obtained through the diet. Some vitamins are supplied to the body in the form of precursors (so-called pro-vitamins), which the body then converts into the active form.
There are fat-soluble (lipophilic) and water-soluble (hydrophilic) vitamins. Chemically, vitamins do not form a uniform substance group. Since they are quite complex organic molecules, they do not occur in inanimate nature. They must first be formed by plants, bacteria or animals. Plants do not need vitamins because they can synthesize all the necessary organic substances themselves.