Influence of the dietary carotenoids lutein and zeaxanthin on visual performance: application to baseball

Macular pigment (MP) is composed of the yellow, blue-absorbing carotenoids lutein and zeaxanthin. Although distributed throughout the visual system, MP is heavily concentrated in the central retinal area (eg, screening the foveal cones). Because light must pass through MP before reaching the receptors, it filters significant amounts of short-wave energy. Individual variation in peak absorbance is large and ranges from 0.0 to 1.6 optical density units depending largely on dietary intake. Several important functions of MP have been proposed. MP may serve to protect the retina from damage by absorbing actinic short-wave light (analogous to internal sunglasses) or by inactivating highly reactive free radicals and oxygen triplicates that are the by-product of light-driven cellular activity. MP may also serve, as proposed more than a century ago, to improve the retinal image through optical mechanisms. Recent data suggest that the MP carotenoids reduce glare discomfort and disability, shorten photostress recovery times, enhance chromatic contrast, and increase visual range (how far one can see in the distance). Lutein and zeaxanthin within the brain might also increase temporal processing speeds. This article reviews the influences of MP on visual function by exploring the implications of these visual improvements for baseball players.