Lutein is an oxygenated carotenoid (xanthophyll) found in dark green leafy vegetables. High intakes of lutein may lower the risk of age related macular degeneration and possibly cardiovascular disease and cancer. Our objective is to provide a quantitative understanding human lutein metabolism as it might occur in vivo. Therefore, we dosed a normal adult (fasting) with 14C-lutein (125 nmol, 36 nCi 14C), dissolved in olive oil (0.5g/kg body weight) and mixed into a banana shake. Blood, feces, and urine were collected just before (baseline) and at several time intervals after dosing. Plasma was isolated, and its lipoprotein fractions were separated by ultracentrifugation. The parent compound (lutein) and its metabolite (3'-epilutein) were identified in these fractions using HPLC. The HPLC effluent was collected in twenty seconds intervals and its 14C content was measured by accelerator mass spectrometry. The 14C in plasma peaked at 0.005 amol 14C/L plasma/dose at 5 h post dose and reached its maximum of 0.0208 amol at 14 h post dose. This plasma 14C-labeling pattern differed from that obtained from 14C-beta-carotene. Forty five percent of the dose was absorbed and 10% of the dose was eliminated in urine during the first two weeks after dosing. We concluded that lutein is well absorbed and that the mechanism of absorption and distribution for lutein may differ from those of beta-carotene. Supported by NIH NCRR P41 RR 13461, and NIDDK DK48307.
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