Oxygen is 'vital to the working of the human body', but it isn't a 'vitamin'. --Fullmetajacket 22:36, 10 March 2007 (EST)
required, in very small amounts, to maintain an organism's health. They act
cannot be produced by the organism, and so
Some substances are vitamins in certain organisms, but not in others (for example, ascorbic acid can be produced by all mammals except guinea pigs and humans, and so is a vitamin only in those two instances.