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. | 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. |