|2004Q-0180 - Qualified Health Claim (QHC): Lutein and Eye Disease|
|FDA Comment Number :||EC8|
|Submitter :||Mr. Greg Williams||Date & Time:||06/29/2004 06:06:16|
| Alcon Laboratories Inc, the world's leading eye care company, sells a dietary supplement which incorporates, with other antioxidant vitamins and minerals, lutein and zeaxanthin, the carotenoids found in the macula. The ocular macula is the region of the eye providing both color vision and greatest resolution. While the explicit function of these xanthophylls is not fully understood, their properties are well-known. These forty- carbon, highly conjugated, and somewhat surface active compounds are known to be localized in membranes, to be esterified with organic acid moieties (organic fatty acids or proteins), and to function as antioxidants and quenchers of free radicals. Because of their high conjugation, they also absorb light at the blue end of the visible and near UV spectrum. These biomolecules thereby protect those at risk to oxidative damage, notably the elderly. Consequently, it would appear highly desirable to increase the awareness of the benefits of these compounds that are available in supplements for individuals either at greater risk of oxidative stress and the diseases known to be their sequellae or of xanthophyll deficiency in their diet.
Because of extensive research on carotenoids in photosynthesis, the function of carotenoids in this setting has been well established, from assisting in harvesting photons of light to protecting fragile photocenters from oxidation, from an atmosphere rich in oxygen. It is presumed the function of the carotenoids in the retina, another location of high metabolism and high oxygen tension, parallels that in the plant kingdom. Carotenoids are found ubiquitously in the plant kingdom, from green leaves to the coloration of fruits and vegetables, with functions from dissemination of seeds to protection of fruit from oxidation / spoiling. Carotenoid biosynthesis does not occur in man, and so must be obtained from the diet.
Epidemiologic evidence has demonstrated strong correlations of carotenoids in the diet with diminished incidence of AMD. The epidemiologic evidence for regular consumption of spinach, a source of lutein as the free alcohol, is exceptionally noteworthy. Corn is a good source of zeaxanthin esters. Both lutein and zeaxanthin are essential fats, produced in the plant kingdom, but not in animals, not in man, and so must be obtained through the diet, or through supplementation. The form of these xanthophylls in the eye, and transported in the serum, is known to be the free alcohol, at least in part bound to and localized by proteins through esterification. Dietary sources of free alcohol or ester forms have been demonstrated to be equally bioavailable, hardly surprising given the abundance of lipases and esterases in the digestive tract. Clear evidence for specificity (and significance) of these carotenoids in the macula, is provided by the inversion of the ratio of lutein:zeaxanthin in its center, the foveal pit, crucial for all high-definition vision, from reading and watching movies to cutting wood or knitting a sweater.
In conclusion, the body of information currently available provides ample justification for a health claim for these essential biomolecules. However, based upon the extensive body of information available, ocular health claims should not be limited to the ester form of lutein. Alcon strongly recommends in the interest of public health that the Agency grant an ocular health claim for supplementation of both forms (free alcohol or ester) of both ocular xanthophyll carotenoids, lutein and zeaxanthin.