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Zeaxanthin Essential to Eye Health Zeaxanthin, one of only two dietary carotenoids that the human retina accumulates, is essential for protecting the retina from the damaging effects of light. This finding is the result of a study conducted by researchers at the Schepens Eye Research Institute and associates at the Columbia University School of Medicine; the University Eye Clinic, Leipzig, Germany; and the University of British Columbia, Vancouver, Canada. The results follow those of the Age Related Eye Disease Study (AREDS). AREDS, which was sponsored by the National Eye Institute, showed that consuming high doses of dietary antioxidants daily helps slow the progression of age-related macular degeneration (AMD). (Zeaxanthin and lutein were not commercially available when the AREDS began and were not included in the study.) In the Schepens study, investigators tested the hypothesis that retinal zeaxanthin prevents light-induced photoreceptor cell death. Researchers assessed retinal damage in Japanese quail, since the retina of the animal is like the human macula in that it contains more cone photoreceptors than rods. The Japanese quail retina is also highly selective in accumulating dietary zeaxanthin and lutein, like the human retina. The quail were fed a carotenoid-deficient (C-) diet for 6 months. Groups of 16 birds (8 male, 8 female) were fed a C- diet supplemented with 35 mg 3R,3'R-zeaxanthin for 1, 3 or 7 days. One group was continued on C- diets. Half of each group was exposed to intermittent 3200-lux white light (ten 1-hour intervals separated by 2 hours in dark). After 14 additional hours in the dark, investigators collected one retina of each quail for high performance liquid chromatography analysis, and embedded the contralateral retina in paraffin for counts of apoptotic nuclei. After 7 days’ supplementation, concentrations of zeaxanthin in quail serum, liver and fat had increased by factors of 50.8, 43.2, and 6.5, respectively. In contrast, retinal zeaxanthin fluctuated significantly upward on day 3, but investigators saw no net change on day 7. The number of apoptotic rods and cones in light-damaged eyes correlated significantly and inversely with zeaxanthin concentration in the contralateral retina (r = -0.61 and r = -0.54), but not with serum zeaxanthin. Researchers observed similar correlations with retinal lutein, which correlated strongly with retinal zeaxanthin (r = 0.95). SOURCE:
Thomson LR, Toyoda Y, Langner A, Delori FC, et al. Elevated retinal
zeaxanthin and prevention of light-induced photoreceptor cell death
in quail. Invest Ophthalmol Vis Sci 2002;43:3538-49.
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