Provitamin
Provitamins are precursors to vitamins and have yet to be converted into them in order to be of benefit to the body.
Examples
- The provitamin A (α-, β- and γ- carotene and β-cryptoxanthin ) as a precursor of vitamin A ( retinol ). This is true of most mammals . The cat is not able to do this. It also needs retinol, but cannot convert β-carotene into retinol (β-carotene is not a provitamin for cats) and must therefore obtain vitamin A from the liver.
- Dexpanthenol can be converted to pantothenic acid (vitamin B 5 ).
- The provitamin D 2 ( ergosterol ) is a precursor of the vitamin D 2 ( ergocalciferol ).
- Provitamin D 3 is produced from 7-dehydrocholesterol in the skin through UVB radiation . The provitamin D 3 is thermally unstable and is converted into vitamin D 3 ( cholecalciferol ) by thermal isomerization .
literature
- George FM Ball: Vitamins In Foods: Analysis, Bioavailability, and Stability. CRC Press 2005. ISBN 9781420026979 .
Individual evidence
- ^ S. Ebel and HJ Roth (editors): Lexikon der Pharmazie , Georg Thieme Verlag, 1987, p. 542, ISBN 3-13-672201-9 .
- ^ Brockhaus ABC Chemie , VEB FA Brockhaus Verlag Leipzig 1965, p. ###.
- ↑ JA Olson: Provitamin A function of carotenoids: the conversion of beta-carotene into vitamin A. In: The Journal of nutrition. Volume 119, Number 1, January 1989, pp. 105-108, ISSN 0022-3166 . PMID 2643691
- ↑ James G. Morris: Idiosyncratic nutrient requirements of cats appear to be diet-induced evolutionary adaptations . In: Nutrition Research Reviews 15, 2002, pp. 153-168.