Xanthophylls are a group of oxidised carotenoids that may play a role in human health. Xanthophylls are found in wide variety of plant foods such as green leafy vegetables, and can also be found in the tissues of animals that feed on xanthophyll containing plants. Xanthophylls are dietary antioxidants and play a role in providing antioxidant protection to cell membranes. A number of studies have reviewed the benefits of carotenoids including xanthophylls and the closely related carotenes, and found that they do confer health benefits of the consumer. Two xanthophylls, lutein and zeaxanthin are particularly interesting xanthophylls with regard to eye health, as they appear to accumulate in the macula of the eye and confer protection against age-related deteriorations in vision. In particular, both lutein and zeaxanthin may protect from the formation of cataracts and other opacities of the eye, through their ability to inhibit free radical damage to the eye from ultraviolet light and oxygen.
The evidence that lutein and zeaxanthin have a protective role against the formation of cataracts is reasonably consistent. Many studies have for example shown that increased intake of lutein and zeaxanthin are able to reduce the risk of developing cataracts. A lower prevalence of cataracts have been shown for both men and women, and the reduction in risk of cataract operations for those consuming the most xanthophylls may be as high as 20 to 50 %. Egg yolks are yellow because of their high concentration of lutein and zeaxanthin and therefore can be a good source of dietary xanthophylls.
The macula of the eye is actually yellow in colour due to the presence of lutein and zeaxanthin. Another related xanthophyll, meso-zeaxanthin is also present, and may be synthesised in the eye from either lutein or zeaxanthin. In the macula, the zeathanthin tends to be present in the central fovea region, with lutein concentrated more to the periphery. The presence of the xanthophylls in the eye protect the macula from blue light, and this is thought to occur through an inactivation or inhibition of free radicals, and this limits the damage caused to the underlying photoreceptors. It is well reported that the amount of pigment in the macula of the eye is inversely related to the risk of developing age-related macular degeneration, which can lead to vision loss and blindness. Both supplementation with lutein or zeaxanthin and the consumption of foods containing lutein and zeaxanthin, such as green leafy vegetables, can significantly increase the xanthophyll concentrations in the macula and this may provide significant protection against tissue damage.
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