Xanthophylls and the eye

Lutein (L) and zeaxanthin (Z) are the only carotenoids found within the retina, and although they are not essential micronutrients, they have antioxidant and photoprotective functions that are thought to be useful in the prevention of onset or progression of age-related macular degeneration (AMD). This condition is the leading cause of visual loss in the developed world, and the number of people affected by it is predicted to increase dramatically as the proportion of the population aged over 65 years increases. Epidemiological studies suggest that people who consume high levels of L and Z are at lower risk of AMD than those who consume low levels. Intervention studies have shown that increasing dietary intake of foods that contain L and Z or consuming L and Z supplements can increase serum and retinal levels of L and Z. L and Z supplementation is thought to increase macular pigment optical density (MPOD, the amount of L and Z within the macular region of the retina), although clinical methods for MPOD assessment can be unreliable. Small randomized controlled trials have demonstrated improvements in visual function in people who have age-related macular disease and have taken nutritional supplements that contain more than 10 mg L. The results of a large multicenter trial, AREDS 2, are due in December 2012. These results will inform clinical practice with regard to the recommendations that are made about L and Z supplementation for the prevention of progression of AMD.