Provitamin

Aprovitaminis a substance that may be converted within the body to avitamin.The termprevitaminis a synonym.

The term "provitamin" is used when it is desirable to label a substance with little or no vitamin activity, but which can be converted to an active form by normalmetabolicprocesses.

Example

Some provitamins are:

• "Provitamin A" is a name forβ-carotene,which has only about 1/6 thebiological activityofretinol(vitamin A); the body uses anenzymeto convert β-carotene to retinol. In other contexts, both β-carotene and retinol are simply considered to be different forms (vitamers) of vitamin A.
• "Provitamin B5" is a name forpanthenol,which may be converted in the body to vitamin B₅(pantothenic acid).
• Menadioneis a synthetic provitamin ofvitamin K.
• ProvitaminD₂isergosterol,and provitamin D₃is7-dehydrocholesterol.They are converted by UV light into vitamin D.The human body produces provitamin D₃naturally; deficiency is usually caused by a lack of sun exposure, not a lack of the provitamin.