title: Absorption of all-trans and 9-cis beta-carotene in human ileostomy volunteers.
abstract: 1. Mass balance studies were carried out in fasted ileostomy subjects (n = 5) given an oral physiological dose (10 mg) of beta-carotene [all-trans: 9-cis, 84:16 (w/w)] dispersed in vegetable oil. Blood and ileal effluent samples were collected and analysed for beta-carotene. 2. Results showed that 90% (range 97.0-74.3%) of the total beta-carotene was absorbed without measurable perturbation of plasma total beta-carotene concentration, or change in the all-trans: 9-cis beta-carotene ratio. Peak loss of beta-carotene in ileal effluent occurred at 4.9 h (range 2.9-8.4 h) postingestion, and no further loss was detected after 5.4-12.4 h, depending upon the individual. Comparison of the ratio of all trans-beta-carotene to 9 cis-beta-carotene in the test meal and effluent indicated that isomerization did not occur during passage through the gastrointestinal tract and that both isomers were similarly absorbed. However, the all-trans: 9-cis beta-carotene ratio of the plasma did not change. Reasoned assumptions allowed the construction of a mathematical model of plasma beta-carotene disposal. 3. It is concluded that physiological doses of isolated all-trans and 9-cis beta-carotene are well absorbed without necessarily causing detectable excursions in plasma beta-carotene concentrations, or altering the ratio of all-trans to 9-cis beta-carotene. Isomerization of beta-carotene does not occur during passage through the gastrointestinal tract. Absorbed beta-carotene is rapidly cleared from the plasma to an unobservable pool at a rate similar to that of chylomicron triacylglycerol.
authors.affiliation: Institute of Food Research, Colney, U.K.
authors.forename: R M
authors.initials: RM
authors.lastname: Faulks
authors.forename: D J
authors.initials: DJ
authors.lastname: Hart
authors.forename: P D
authors.initials: PD
authors.lastname: Wilson
authors.forename: K J
authors.initials: KJ
authors.lastname: Scott
authors.forename: S
authors.initials: S
authors.lastname: Southon
mesh_terms: D003093:Colitis, Ulcerative / Q000601:surgery; D005260:Female; D006801:Humans; D007081:Ileostomy; D007082:Ileum / Q000378:metabolism*; D007408:Intestinal Absorption; D008297:Male; D008875:Middle Aged; D013237:Stereoisomerism; D019207:beta Carotene / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*
chemical_list: D019207:beta Carotene