LE Magazine May 2002
Page 2 of 2
Carotenoids and macular pigment
Scientific evidence is mounting to demonstrate the power of dietary antioxidants in maintaining eye health and warding off age-related macular degeneration. The most recent study to raid the headlines was the Age-Related Eye Disease Study (AREDS), which was carried out by the National Eye Institute. The large, multicenter study showed that a daily intake of 500 mg of vitamin C, 15 mg of beta carotene, 400 IU of vitamin E and 80 mg of zinc reduced the risk of developing advanced disease in those with intermediate damage by about 25%.
Other research has more specifically set its sights on examining the protective role of the carotenoids, lutein and zeaxanthin, against macular degeneration. Why? With several hundred carotenoids to be found, consider that only lutein and zeaxanthin are found in the retina.[22,23] Compared to other antioxidant concentrations found in the eye, German researchers found that lutein and zeaxanthin did not break down nearly as fast as lycopene and beta-carotene when exposed to free radical or UV light induced oxidative stress. The authors suggest that perhaps the slow degradation of lutein and zeaxanthin may explain the strong presence of these carotenoids in the retina. Also, the quick breakdown of lycopene and beta-carotene may suggest why these carotenoids are lacking in the same retinal tissues.
Researchers have also found that lutein and zeaxanthin are more highly concentrated in the center of the macula. There, the amounts of lutein and zeaxanthin are much greater than their concentrations in the peripheral region. At the Baylor College of Medicine, in Houston, scientific investigators demonstrated, using retinas from human donor eyes, that the concentration of lutein and zeaxanthin were 70% higher in rod outer segment (ROS) membranes where the concentration of long-chain polyunsaturated fatty acids, and susceptibility to oxidation is highest, than in residual membranes. The fact that lutein and zeaxanthin are particularly concentrated in these parts of the eye suggests that they may act as a shield or filter that helps to absorb harmful UVB light and dangerous free-radical molecules, both of which threaten the retinal tissue.[26,27]
Moreover, while macular pigment density decreases with age, and the risk of AMD increases-a coincidence that cannot be overlooked-researchers have also found that older folks with higher lutein and zeaxanthin concentrations in their macula tend not to develop the disease. Researchers at Arizona State University suggested that increasing macular pigment through dietary intake of lutein and zeaxanthin may retard age-related declines in visual function, and that high macular pigment density was associated with the retention of youthful visual sensitivity. After measuring the macular pigment density and visual sensitivity of 27 older subjects (aged 60 to 84 years) and 10 younger ones (aged 24 to 36 years), results showed that older subjects with high levels of lutein and zeaxanthin had visual sensitivity comparable to younger subjects. Conversely, older subjects with low lutein and zeaxanthin in their macula had lower visual sensitivity.
Weighing all the evidence to date, it stands to reason that increasing or maintaining levels of the carotenoids that make up the pigment, namely lutein and zeaxanthin, would support the protective role of macular pigment. While larger and longer trials will bear out what research now seems to suggest, increasing our lutein and zeaxanthin intake through diet seems to be a safe bet. However, nutritional scientists have not yet pinned down ideal amounts to recommend for lutein and zeaxanthin supplements. Bernstein explains that we currently hear much more about lutein, "since it is much more common in our diet, and commercial supplements of lutein have been available for a much longer time. Zeaxanthin supplements have been approved for human use only recently." For the time being, though, Bernstsein suggests consuming a diet high in fruits and vegetables. He adds that daily supplementation with at least 4 milligrams of lutein per day may be beneficial, but further studies are needed.
1. VandenLangenberg GM, et al. Associations between antioxidant and zinc intake and the 5-year incidence of early age-related maculopathy in the Beaver Dam Eye Study. Am J Epidemiol 1998;148:204-214.
2. Beatty S, et al. The role of oxidative stress in the pathogenesis of age-related macular degeneration. Surv Ophthalmol 2000 Sept-Oct;45(2):115-34.
3. Taylor A, et al. Protein oxidation and loss of protease activity may lead to cataract formation in the aged lens. Free Radic Biol Med 1987;3(6):371-377.
4. Landrum JT, et al. A one year study of the macular pigment: the effect of 140 days of a lutein supplement. Exp Eye Res 1997 Jul;65(1):57-62.
5. Wilson GA, et al. Smoke gets in your eyes: smoking and visual impairment in New Zealand. N Z Med J 2001 Oct 26;114(1142):471-4.
6 McCarty CA, et al. Risk factors for age-related maculopathy: the Visual Impairment Project. Arch Ophthalmol 2001 Oct;119(10):1455-62.
7. Smith W, et al. Risk factors for age-related macular degeneration: Pooled findings from three continents. Ophthalmology 2001 Apr;108(4):697-704.
8. Hiratsuka Y, Li G. Alcohol and eye diseases: a review of epidemiologic studies. J Stud Alcohol 2001 May;62(3):397-402.
9. Cruickshanks KJ, et al. Sunlight and age-related macular degeneration. The Beaver Dam Eye Study. Arch Ophthalmol 1993 Apr;111(4):514-8.
10. Taylor HR, et al. Visible light and risk of age-related macular degeneration. Trans Am Ophthalmol Soc 1990;88:163-73; discussion 173-8.
11. Snodderly DM. Evidence for protection against age-related macular degeneration by carotenoids and antioxidant vitamins. Am J Clin Nutr 1995 Dec;62(6 Suppl):1448S-1461S.
12. Hammond BR Jr, et al. Carotenoids in the retina and lens: possible acute and chronic effects on human visual performance. Arch Biochem Biophys 2001 Jan 1;385(1):41-6.
13. Hammond BR Jr, et al. Macular pigment density in monozygotic twins. Invest Ophthalmol Vis Sci 1995 Nov;36(12):2531-41.
14. Hammond BR Jr, et al. Sex differences in macular pigment optical density: relation to plasma carotenoid concentrations and dietary patterns. Vision Res 1996 Jul;36(13):2001-12.
15. Ciulla TA, et al. Macular pigment optical density in a midwestern sample. Ophthalmology 2001 Apr;108(4):730-7.
16. Richer S. ARMD-pilot (case series) environmental intervention data. J Am Optom Assoc 1999 Jan;70(1):24-36.
17. Berendschot TT, et al. Influence of lutein supplementation on macular pigment, assessed with two objective techniques. Invest Ophthalmol Vis Sci 2000 Oct;41(11):3322-6.
18. Seddon JM, et al. Dietary carotenoids, vitamins A, C, and E, and advanced age-related macular degeneration. Eye Disease Case-Control Study Group. JAMA 1994 Nov 9;272(18):1413-20.
19. Curran-Celentano J, Relation between dietary intake, serum concentrations, and retinal concentrations of lutein and zeaxanthin in adults in a Midwest population. Am J Clin Nutr 2001 Dec;74(6):796-802.
20. Bone RA, et al. Macular pigment in donor eyes with and without AMD: a case-control study. Invest Ophthalmol Vis Sci 2001 Jan;42(1):235-40.
21. Ferris, F et al. Age-Related Eye Disease Study. Arch Opthalmol 2001;119:1417-1436.
22. Schalch W. Carotenoids in the retina-a review of their possible role in preventing or limiting damage caused by light and oxygen. EXS 1992;62:280-298.
23. Yeum KJ, et al. Fat-soluble nutrient concentrations in different layers of human cataractous lens. Curr Eye Res 1999 Dec;19(6):502-5.
24. Siems WG, et al. Lycopene and beta-carotene decompose more rapidly than lutein and zeaxanthin upon exposure to various pro-oxidants in vitro. Biofactors 1999;10(2-3):105-13.
25. Rapp LM, et al. Lutein and zeaxanthin concentrations in rod outer segment membranes from perifoveal and peripheral human retina. Invest Ophthalmol Vis Sci 2000 Apr;41(5):1200-9.
26. Bernstein PS, et al. Identification and quantitation of carotenoids and their metabolites in the tissues of the human eye. Exp Eye Res 2001 Mar;72(3):215-23.
27. Moeller SM, et al. The potential role of dietary xanthophylls in cataract and age-related macular degeneration. J Am Coll Nutr 2000 Oct;19(5 Suppl):522S-527S.
28. Hammond BR Jr, et al. Preservation of visual sensitivity of older subjects: association with macular pigment density. Invest Ophthalmol Vis Sci 1998 Feb;39(2):397-406.
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