Why has Nature Chosen Lutein and Zeaxanthin to Protect the Retina?
To protect the retina against oxidative damage, nature has used xanthophylls as an effective protector that can absorb damaging blue light, neutralize photosensitizers and reactive oxygen species, and scavenge free radicals. Co-localization of protective and protected molecules should significantly enhance the effectiveness of protectors, especially when the local concentration of xanthophylls in the membrane is not very high.
Analysis of zeaxanthin distribution within individual human retinas
Retina contains two isomeric xanthophylls—lutein arid zeaxanthin—with the greatest concentration at the center of the macula and diminishing with eccentricity. The results and observations support the hypothesis that lutein and/or zeaxanthin undergoes oxidation in the retina followed by nonstereospecific reduction to regenerate the observed suite of stereoisomers. The presence and distribution of these stereoisomers appear to be consistent with, and support, a hypothesis of antioxidant function for the macular carotenoids.
The Pharmacological Effects of Lutein and Zeaxanthin on Visual Disorders and Cognition Diseases
The relationship between L, a dietary xanthophyll carotenoid, and visual and cognitive health is particularly compelling because L is taken up selectively into eye and brain tissue [10,123,124]. In part, the beneficial effects of L are thought to be attributable to its antioxidant and anti-inflammatory properties. Given that the eye is an extension of the neural system, L is increasingly recognized as having a role in cognitive function . In pediatric brains, the relative contribution of L to the total carotenoids is twice that found in adults, accounting for more than half the concentration of total carotenoids. The greater proportion of L in the pediatric brain suggests a need for L during neural development as well .
Lutein and Zeaxanthin Isomers in Eye Health and Disease
Current evidence suggests lutein and its isomers play important roles in ocular development in utero and throughout the life span, in vision performance in young and later adulthood, and in lowering risk for the development of common age-related eye diseases in older age.
Nutritional factors and visual function in premature infants
There is current interest in the macular pigment in relation to age-related macular degeneration, but these pigments may also have a protective role in the retinal pigment epithelium of the newborn infant. Little information is available on blood lutein and zeaxanthin levels in neonates. Levels of lutein in human milk are two to three times higher than those of beta-carotene, whereas their concentrations in the mothers’ blood are approximately the same. Human milk is the main dietary source of lutein and zeaxanthin for infants until weaning occurs. The biochemical mechanisms which mediate the transport of the macular carotenoids into the eye are not known, but tubulin has been identified as the major carotenoid-binding protein, and may play a role in the physiology of the macula.
Possible influences of lutein and zeaxanthin on the developing retina
LZ may help reduce the retina damage caused by lipofuscin in the RPE. As much as half of the lifetime accumulation of lipofuscin in RPE may occur in the first five years of life (Wing et al 1978; Feeney-Burns et al 1984). Increasing MP earlier in life could theoretically slow the accumulation of lipofuscin as well as reduce the free radical oxidants that it produces. Given the low risk and clear potential benefit, it would be prudent to increase lutein consumption earlier in life while further evidence of its benefits emerge.
The material was prepared by World Medicine