ABSTRACT
Vitamins are low-molecular-weight organic substances required in small amounts in the diets of higher animals for normal growth, maintenance of health, and reproduction. All animals need vitamins, but not every vitamin is required by all animals; e.g., vitamin C is needed only by humans, guinea pigs, monkeys, some birds, and some fish that lack the enzyme gulonolactone oxidase, which is required to make 1-ascorbic acid from glucose via D-glucuronic acid. Plants and microorganisms can synthesize all vitamins.
