Journal of the American College of Nutrition, Vol 15, Issue 6 620-624, Copyright © 1996 by American College of Nutrition

JOURNAL ARTICLE

Serum response of all-trans and 9-cis isomers of beta-carotene in humans

E. J. Johnson, N. I. Krinsky and R. M. Russell
Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA.

OBJECTIVE: Little work has been performed on the serum response of various carotene isomers. The present study was carried out to examine the 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 containing 80% 9-cis BC were studied in 15 men by measuring the serum concentrations of BC at 1, 3, 5, 7, 9, 12, and 24 hours after a single large oral 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 baseline at 24 hr (p < 0.004). After an oral dose of a mixture of BC isomers (120 mg, 80% 9-cis BC), the peak concentration of 9-cis BC was significantly greater that baseline values (p < 0.016). CONCLUSIONS: Increases in serum all-trans BC levels, in part, may be due to greater intestinal absorption, whereas the inability to measure a significant increase in the concentration of 9-cis BC may indicate poor absorption, isomerization to all-trans BC, or a very rapid tissue uptake.

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