The evidence that the xanthophylls, particularly lutein and zeaxanthin but also P-cryptoxanthin, naturally function in part as generic lipophylic antioxidants in humans is a sound hypothesis based upon epidemiological data and animal studies. There is a compelling amount of evidence that lutein and zeaxanthin are essential components of the human macula, and that they function to reduce photooxidation in sensitive tissues. They may also be involved directly as antioxidants in the pho-toreceptors. Supplementation with lutein and zeaxanthin is a potentially practical therapeutic means to ensure that adequate levels of macular pigmentation are maintained to protect the retina and slow the processes which contribute to AMD.
Astaxanthin is a powerful antioxidant and may have great potential in reducing human disease processes that involve free radical mechanisms. Because there is a paucity of knowledge about astaxanthin metabolism in humans, extensive work must be done to determine what benefit can be realized by the incorporation of this carotenoid in the human diet. Indeed, care is warranted in the consumption of these carotenoids at levels that far exceed normal intake, until solid data establishing the desirability of such practices are available. This is especially true for smokers, as suggested by the Finnish ATBC study and the CARET study (Albanes et al., 1996; Redlich et al., 1999).
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