Provitamin
A provitamin is a substance that may be converted within the body to a vitamin.[1] The term previtamin is occasionally used as a synonym,[2][3] though it has its own distinct usage for Vitamin D.
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 normal metabolic processes.
Example
Some provitamins are:
- "Provitamin A" is a name for β-carotene,[1] which has only about 1/6 the biological activity of retinol (vitamin A); the body uses an enzyme to 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 for panthenol, which may be converted in the body to vitamin B5 (pantothenic acid).
- Menadione is a synthetic provitamin of vitamin K.
- Provitamin D2 is ergosterol, and provitamin D3 is 7-dehydrocholesterol. They are converted by UV light to previtamin D2 and previtamin D3, which in turn spontaneously convert to vitamin D2 and vitamin D3.[4][5]
The human body produces provitamin D3 naturally; deficiency is usually caused by a lack of sun exposure, not a lack of the provitamin.[6]
References
- ^ a b "provitamin" – via The Free Dictionary.
- ^ Cammack, Richard; Atwood, Teresa; Campbell, Peter; Parish, Howard; Smith, Anthony; Vella, Frank; Stirling, John, eds. (1 January 2006). Oxford Dictionary of Biochemistry and Molecular Biology. Oxford University Press. doi:10.1093/acref/9780198529170.001.0001. ISBN 978-0-19-852917-0.
- ^ "previtamin - definition of previtamin in the Medical dictionary". The Free Dictionary. Archived from the original on 22 September 2011. Retrieved 22 September 2011.
- ^ Carey, Francis A.; Sundberg, Richard J. (1990). Advanced Organic Chemistry. Part A: Structure and Mechanisms (3rd ed.). New York: Plenum Press. p. 616. ISBN 0-306-43440-7.
- ^ Björn, Lars Olof (6 December 2012). Photobiology: The Science of Light and Life. Springer Science & Business Media. pp. 265–266. ISBN 978-94-010-0581-4. Retrieved 27 February 2026.
Ultraviolet-B radiation can photoisomerize the provitamins to the corresponding previtamins ... The previtamins are slowly converted by a non-enzymatic and non-photochemical reaction to the vitamins.
- ^ "Office of Dietary Supplements - Vitamin D". ods.od.nih.gov. Retrieved 31 October 2020.