Changes

A '''vitamin''' is a [[chemical]] substance required, in very small amounts, to maintain an organism's health. They act as a catalyst in the body's chemical reaction, commonly as part of [[metabolism]]. It cannot be produced by the organism, and so must be obtained from dietary or other sources. In order for a substance to be classified as a vitamin, its deficiency must produce a specific [[disease]]. For example, ascorbic acid is a vitamin ([[Vitamin C]]) in humans because its absence produces [[scurvy]], a lack of Vitamin D will result in [[rickets]], and thymine is a vitamin (Vitamin B1) because its absence produces [[beriberi]]. There are exactly fourteen known human vitamins.

A '''vitamin''' is a [[chemical]] substance required, in very small amounts, to maintain an organism's health. They act as a catalyst in the body's chemical reaction, commonly as part of [[metabolism]]. It cannot be produced by the organism, and so must be obtained from dietary or other sources. In order for a substance to be classified as a vitamin, its deficiency must produce a specific [[disease]]. For example, ascorbic acid is a vitamin ([[Vitamin C]]) in humans because its absence produces [[scurvy]], a lack of Vitamin D will result in [[rickets]], and thiamin is a vitamin (Vitamin B1) because its absence produces [[beriberi]]. There are exactly thirteen essential vitamins for humans.

Some substances are vitamins in certain organisms, but not in others (for example, ascorbic acid can be produced by all [[mammal]]s except [[guinea pig]]s and [[human]]s, and so is a vitamin only in those two instances.  

Some substances are vitamins in certain organisms, but not in others (for example, ascorbic acid can be produced by all [[mammal]]s except [[guinea pig]]s and [[human]]s, and so is a vitamin only in those two instances.  

* [[Vitamin B6]]

* [[Vitamin B6]]

* [[Vitamin B9]]

* [[Vitamin B9]]

* [[Vitamin B12]]

* [[Vitamin B12]]

* [[Vitamin C]]

* [[Vitamin C]]