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ARS Home » Northeast Area » Boston, Massachusetts » Jean Mayer Human Nutrition Research Center On Aging » Research » Publications at this Location » Publication #37596
Title: DISCRIMINATION IN ABSORPTION OR TRANSPORT OF BETA-CAROTENE ISOMERS FOLLOWING ORAL SUPPLEMENTATION WITH EITHER ALL-TRANS OR 9-CIS BETA-CAROTENE

Author
item GAZIANO MICHAEL - HARVARD MED SCH
item JOHNSON ELIZABET - TUFTS-HNRCA
item KRINSKY NORMAN I - TUFTS UNIVERSITY
item RUSSELL ROBERT M - TUFTS-HNRCA
item MANSON JOANN E - HARVARD MED SCH
item STAMPFER MEIR - HARVARD SCH PUB HEALTH
item RIDKER PAUL M - HARVARD MED SCH
item FREI BALZ - HARVARD SCH PUB HEALTH
item HENNEKENS CHARLE - HARVARD MED SCH

Submitted to: The American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: For six days, twenty-four human subjects were given beta-carotene (BC) supplements in one of two forms: man-made BC (all-trans) or a mixture of all-trans BC and BC derived from a type of algae (9-cis). The six-day sup- plementation period was followed by supplementation with varied doses and types of BC on alternating days for a total of 23 days of supplementation. During this second phase of the study, the 24 subjects were divided into three groups which received the all-trans BC or two different dose sizes of the BC mixture. The first phase resulted in large increases in blood levels of both forms of BC, with the all-trans BC supplemented group showing large increases in blood levels of both all-trans and 9-cis BC. The group given the mixture of BC also showed increases in blood levels of all- trans and 9-cis BC. The amount of the increase did not rely on the dose size. However, even with the mixture, the 9-cis BC levels were only a small lamount of the total blood BC. Results after the 23 days of supplementatio every other day were not different from those for the six days of supplementation. These results indicate a difference between these two forms of BC, but where the difference occurs is not yet known.

Technical Abstract: Human subjects (n = 24) were supplemented for 6 days with 100 mg/d beta-carotene (BC), either as synthetic all-trans BC or a natural BC preparation derived from the alga, Dunaliella salina, that consisted of a 50:50 mixture of all-trans- and 9-cis-BC. This loading dose was followed by a 23-day dose consisting of alternate day supplementation with 50 mg all-trans BC or either 66 mg or 100 mg of the natural 50:50 isomeric mixture. The loading dose resulted in significant increases in plasma levels of both isomers, with the all-trans BC-supplemented group showing a 7.2-fold and 5.0-fold increase in the all-trans and 9-cis levels in plasma, respectively. The group receiving the 50:50 mixture showed a 4.0-fold and 3.7-fold increase in all-trans and 9-cis levels in plasma, respectively, without any dose-dependency. Even with the 50:50 mixture, the 9-cis levels remained as only a small fraction of the total plasma BC. Results after an additional 23 day period of alternate day supplementation were not dif- ferent from those described above for the 6 day supplementation. Increases in LDL levels of total BC correlated strongly with the increases seen in plasma levels. Plasma vitamin E and ubiquinol showed no effect of the BC supplementation; however, the level of lycopene in the LDL decreased significantly. Thus, a strong discrimination between these two geometrical isomers of BC has been demonstrated, although the site of discrimination, i.e., absorption in the intestine, tissue uptake, or secretion from the liver, has not been determined.