We investigated the plasma appearance of beta-carotene and canthaxanthin, an oxycarotenoid, in normolipidemic premenopausal women (n = 9) who ingested beta-carotene alone, canthaxanthin alone, and a combined dose. Blood samples were taken hourly for 12 h; additional blood samples were collected over 528 h. In a subset of the women (n = 5), plasma lipoproteins were separated into chylomicrons, very-low-density-lipoproteins (VLDL) subfractions, intermediate-density lipoproteins (IDLs), and low-density lipoproteins (LDLs). The appearance of beta-carotene in plasma was biphasic, with a minor peak at 5 h followed by a sustained peak at 24-48 h. The plasma appearance of canthaxanthin was monophasic, with a rapid increase to the final hourly measurement at 12 h and a steady decrease from the next measurement at 24 h. At 6 h, 23.4 +/- 2.9% of the increase in plasma canthaxanthin was associated with LDL, in contrast with 2.4 +/- 1.4% of the increase in plasma beta-carotene (P < 0.005). Ingestion of a combined dose of beta-carotene and canthaxanthin inhibited the appearance of canthaxanthin in plasma, chylomicrons, and each VLDL subfraction (P < 0.05), but did not significantly affect the rapid accumulation of canthaxanthin in LDL within 10 h. In contrast, ingestion of the combined dose did not significantly affect the appearance of beta-carotene in plasma or plasma lipoproteins. These findings suggest distinct mechanisms of incorporation into lipoproteins and specific interactions of beta-carotene and canthaxanthin during intestinal absorption in humans.

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