Assessment of lutein bioavailability from meals and a supplement using simulated digestion and caco-2 human intestinal cells.

Lutein and zeaxanthin are selectively accumulated in the lens and macular region of the retina. It was suggested that these xanthophylls protect ocular tissues from free-radical damage that can cause cataracts and age-related macular degeneration. Insights regarding the absorption of dietary xanthophylls for delivery to ocular tissues are limited. Our primary objective was to examine factors affecting the transfer of lutein from foods to absorptive intestinal epithelial cells during digestion. Lutein and other carotenoids present in spinach purée and lutein from a commercial supplement were relatively stable during in vitro digestion. Micellarization of lutein and zeaxanthin during the small intestinal phase of digestion exceeded that of beta-carotene and was greater for xanthophylls in oil-based supplements than in spinach. Apical uptake of lutein from micelles by Caco-2 human intestinal cells was linear for at least 8 h, and accumulation from synthetic micelles exceeded that from micelles generated during simulated digestion. Stimulation of chylomicron synthesis resulted in the secretion of 7.6 +/- 0.1% of cellular lutein into the triglyceride-rich fraction in the basolateral chamber. These data support the use of simulated digestion and the Caco-2 cell model as effective tools for identifying factors affecting absorption of dietary carotenoids.