ABSORPTION OF ALL-TRANS AND 9-CIS BETA-CAROTENE IN HUMAN ILEOSTOMY VOLUNTEERS

1, Mass balance studies were carried out in fasted ileostomy subjects (n=5) given an oral physiological dose (10 mg) of beta-carotene [ah-tr ans: 9-cis, 84:16 (w/w)] dispersed in vegetable oil, Blood and ileal e ffluent samples were collected and analysed for beta-carotene. 2, Resu lts 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 efflue nt indicated that isomerization did not occur during passage through t he gastrointestinal tract and that both isomers were similarly absorbe d, However, the all-trans:9-cis beta-carotene ratio of the plasma did not change, Reasoned assumptions allowed the construction of a mathema tical model of plasma beta-carotene disposal, 3, It is concluded that physiological doses od isolated all-trans and 9-cis beta-carotene are well absorbed without necessarily causing detectable excursions in pla sma beta-carotene concentrations, or altering the ratio of all-trans t o 9-cis beta-carotene. Isomerization of beta-carotene does not occur d uring passage through the gastrointestinal tract, Absorbed beta-carote ne is rapidly cleared from the plasma to an unobservable pool at a rat e similar to that of chylomicron triacylglycerol.