Dear Miyuki,
I am not an expert in this area.
If you have not already done so, try a Google search on “9-cis-beta carotene vitamin A activity” (omit the quotes). It seems to return quite a lot, also scientific literature on the topic.
Try also Google Scholar.
Hope this helps a little.
All the best,
Anders
Anders Møller
Danish Food Informatics
Borgediget 12
DK-4000 Roskilde, Denmark
From: Food Composition Discussion Group [mailto:[log in to unmask]] On Behalf Of Miyuki Shimizu
Sent: 04 November 2014 11:09
To: [log in to unmask]
Subject: Inquiry about vitamin A activity in cis-beta carotene
Dear, all,
I’m an intern working at the nutrition division at FAO. I’m currently working on the food biodiversity database for cassava crop. In the following paper, the retinol equivalents are calculated based on the total values of all-trans-beta carotene and cis-beta carotene.
(Reference: http://pubs.acs.org/doi/abs/10.1021/jf5018302)
I’m trying to figure out the metabolism of cis isomer of beta carotene, whether it has vitamin A equivalent activity. All-trans-beta carotene is the most suitable precursor for vitamin A, but several studies have provided the evidence that 9-cis-beta carotene is a precursor of 9-cis retinal or retinoic acid. As far as I know, there is little evidence that 9-cis-beta carotene is found in human plasma since cis-beta carotene is isomerized to all-trans beta carotene after its oral administration.
I would highly appreciate if someone can share their information/data/experience regarding the vitamin A activity of cis-beta carotene:
- For VITA in retinol activity (RE) should 9-cis-beta carotene have: 1/6 or 1/12 or 0 vitamin activity?
- For VITA_RAE should 9-cis-beta carotene have: 1/12 or 1/24 or 0 vitamin activity?
Could you also then provide your source of evidence?
Thank you in advance for your attention to this matter.
Reference:
Beta-Carotene: The Controversy Continues.
http://www.altmedrev.com/publications/5/6/530.pdf
Evidence of cis-trans isomerization of 9-cis-beta-carotene during absorption in humans.
http://ajcn.nutrition.org/content/64/2/177.short
Best regards,
Miyuki Shimizu, MS, RD
Nutrition Intern
Food and Agriculture Organization of the United Nations (FAO)
Nutrition Education and Consumer Awareness Group (ESNE)
Nutrition Division (ESN)
Viale delle Terme di Caracalla, 00153
Rome, Italy
Room : B246
Tel.: +39 06570 55899
Website : http://www.fao.org/food/en/
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