SERUM RESPONSE OF ALL-TRANS AND 9-CIS ISOMERS OF BETA-CAROTENE IN HUMANS

Objective: Little work has been performed on the serum response of var ious carotene isomers. The present study was carried out to examine th e serum response of all-trans and 9-cis isomers of beta-carotene (BC) using frequent blood sample collections at early time points. Methods: Serum responses of all-trans BC and a mixture of BC isomers containin g 80% 9-cis BC were studied in 15 men by measuring the serum concentra tions of BC at 1, 3, 5, 7, 9, 12, and 24 hours after a single large or al dose of all-trans BC or 9-cis BC. Results: The serum response to an oral dose of all-trans BC (120 mg) significantly increased from basel ine at 24 hr (p < 0.004). After an oral dose of a mixture of BC isomer s (120 mg, 80% 9-cis BC), the peak concentration of 9-cis BC was signi ficantly greater that baseline values (p < 0.016). Conclusions: Increa ses in serum all-trans BC levels, in part, may be due to greater intes tinal absorption, whereas the inability to measure a significant incre ase in the concentration of 9-cis BC may indicate poor absorption, iso merization to all-trans BC, or a very rapid tissue uptake.