A vitamin is an organic molecule (or a set of molecules next door to connected chemically, i.e. vitamers) that is an vital micronutrient which an organism needs in small quantities for the proper committed of its metabolism. vital nutrients cannot be synthesized in the organism, either at all or not in acceptable quantities, and therefore must be obtained through the diet. Vitamin C can be synthesized by some species but not by others; it is not a vitamin in the first instance but is in the second. The term vitamin does not add up the three further groups of vital nutrients: minerals, vital fatty acids, and necessary amino acids. Most vitamins are not single molecules, but groups of partnered molecules called vitamers. For example, there are eight vitamers of vitamin E: four tocopherols and four tocotrienols. Some sources list fourteen vitamins, by including choline, but major health organizations list thirteen: vitamin A (as all-trans-retinol, all-trans-retinyl-esters, as competently ...