Can Diet and Supplements Preserve Vision? Story Cover Cover
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Can diet and supplements preserve vision? Story Cover Cover Devon Schuyler zeaxanthin had a 35 per cent lower risk of developing neovascular AMD than those with the lowest intake. (Archives BEYOND the age-old admonition to ‘eat your carrots’, diet of Ophthalmology, September 2007; 125:1225-1232.) and nutrition has not been exploited as a tool to prolong eye Another nutrient that may play a role in AMD is omega-3 health – until recently. Recent years have seen an explosion of fatty acids, which are found in cold-water fish.The Blue research on possible ways to preserve vision through Mountains Eye Study of more than 2,000 Australian adults supplement use and diet. found that those whose diets were high in omega-3 fatty This line of research has “gotten a lot of traction” since the acids, especially from fish, were less likely to develop early and eighties, said Emily Chew MD, director of epidemiology and late AMD. (Archives of Ophthalmology, July 2006, 124(7):981-6.) clinical research at the National Eye Institute (NEI).“People A recent case-control study of more than 4,000 AREDS are very interested in it.” participants found that those who ate a diet rich in omega-3 The most exciting results came from the NEI’s own Age- fatty acids were less likely to develop neovascular AMD Related Eye Disease Study (AREDS), a randomised trial that (Archives of Ophthalmology, May 2007, 125:671-679). found that supplemental antioxidants and zinc could benefit An analysis of the NHANES (National Health and people with intermediate-stage macular degeneration or Nutrition Examination Survey) linked blood levels of vitamin advanced disease in one eye.AREDS was especially important D to a reduced risk of early AMD, although there was no because it represents one of the only times nutritional relationship to advanced AMD. Like omega-3 fatty acids, supplements have been shown to be beneficial in the vitamin D may reduce inflammation and reduce the growth of treatment of disease, notwithstanding the claims of your new blood cells in the retina. (Archives of Ophthalmology, May neighbourhood health food store. 2007;125:661-669.) Indeed, a 2006 review by the National Institutes of Health Finally, two studies of nearly 4,000 AREDS participants in Annals of Internal Medicine named just one other instance found a link between a high intake of refined carbohydrates in which supplements have been proven to prevent disease: and an increased risk of onset and progress of AMD. calcium and vitamin D for reduction of fractures in (American Journal of Clinical Nutrition, October 2007;86:1210- postmenopausal women.The review didn’t address pregnant 1218; Chiu, C-J., Milton, R.C., Klein, R., Gensler, G., and Taylor,A., women, children, or those with vitamin or mineral Association between dietary glycaemic index is related to deficiencies. progression of age-related macular degeneration:A prospective Even though few definitive studies exist, scientists have Foods rich in lutein and zeaxanthin include kale, spinach, study from the Age-Related Eye Diseases Study.Am. J. Clin. Nut. found many other intriguing links between diet and collard greens, and other yellow and dark green leafy (2007) 86, 1210-8.) One hypothesis is that diets high in supplement use and healthier eyes.Antioxidants (including vegetables. refined carbohydrates boost the level of glucose in the cells, carotenoids such as beta-carotene, lutein and zeaxanthin), Inflammation is another factor that appears to play a role in increasing protein damage due to modifications by sugars or omega-3 fatty acids, and other nutrients may play a beneficial multiple diseases, including heart disease, macular their break-down products, and oxidative stress. role in conditions ranging from macular degeneration to degeneration, and dry eye. Omega-3 fatty acids, which are Although these observational studies have found some dry eye. found in cold-water fish, may help the eyes by reducing this intriguing links between specific nutrients and a reduced risk Dr Chew cautioned that most studies on diet, supplements inflammation and promoting proper blood vessel formation. of AMD, it’s impossible to know whether the relationship is and vision are observational, which makes it impossible to From antioxidants to zinc, here’s an overview of what’s truly cause-and-effect. Fortunately, a randomised trial called draw firm conclusions about what to eat or what pills to known about diet, supplement use, and vision: AREDS-2 is investigating whether supplemental lutein, take. zeaxanthin, and omega-3 fatty acids might be able to “These studies tell us that there might be something there, Age-related macular degeneration postpone the development of AMD. Enrolment has already but we still need to do well-conducted randomised Age-related macular degeneration is the leading cause of begun, and results will be available in about five years. controlled trials,” she said. vision loss in people aged 65 and older.That’s why it was so That’s because people who use supplements may be more groundbreaking when the AREDS trial found that a Diet and cataract risk educated, have more resources, less obesity, and have a combination of vitamin C (500mg), vitamin E (400 IU), beta- healthier lifestyle than those who don’t take them – all of Observational studies have linked specific dietary patterns carotene (15mg), and zinc (80mg) with cupric oxide (2mg) and supplements to a reduced risk of cataract. For example, which might explain why they tend to have fewer eye was able to reduce the risk of disease progression for those problems. Moeller et al showed eating according to the USDA Food with intermediate AMD or advanced AMD in one eye.The Guide Pyramid reduced risk for cataract (Moeller, S.M.,Taylor, It’s also difficult to determine exactly what components of trial, which enrolled more than 4,000 adults aged 55-80, found foods might have beneficial effects. Fruits and vegetables A.,Tucker, K.L., McCullough, M.L., Chylack, L.T., Hankinson, S.E., that people with intermediate AMD who took the Willett,W.C., Jacques, P.F. Overall Adherence to the Dietary contain numerous nutrients, so components like beta- supplement had a 25 per cent reduction in the risk of carotene may be only part of the story – or may act as Guidelines for Americans is Associated with Reduced Prevalence of progression to advanced AMD over a five-year period. Early Age-Related Nuclear Lens Opacities in Women J Nutr. markers for other nutrients. Based on the results of AREDS, ophthalmologists now Although it’s too early to make specific supplement (2004)134,1812 9) and the Blue Mountains Eye Study found recommend the AREDS supplement.The combination that people who took daily multivitamins and B vitamin recommendations for most people concerned with their supplement is sold commercially and they include OcuVite vision (the major exception being certain people with AMD), supplements, especially folic acid and vitamin B12, were less PreserVision, Bausch and Lomb; ICaps,Alcon Laboratories; likely to develop cataracts (Am J Ophthalmol. 2001 what’s good for preventing cancer or cardiovascular disease Ocular Formula #2,VisiVite; and others.The supplement is may well be good for preventing vision loss.That’s because Jul;132(1):19-26). Folic acid and vitamin B12 may work by recommended to people with intermediate AMD, but not to reducing blood levels of homocysteine. the same oxidative damage that contributes to heart disease patients with early AMD. and other age-related illnesses also appears to affect the eye. A recent analysis of data from about 35,000 women in the Eating a diet rich in fruits and vegetables may also help Women’s Health Study revealed that those with the highest “When junk proteins accumulate, they create oxidative ward off AMD. In the Dietary Ancillary Study of the Eye stress and become toxic to the lens and retina,” said Allen intake of lutein and zeaxanthin from food, and vitamin E from Disease Case-Control Study, people with the highest intake of food and supplements were at decreased risk for cataracts Taylor MD, director of nutrition and vision research at Tufts lutein and zeaxanthin from foods had a reduced risk of AMD University. (Arch Ophthalmol. 2008 Jan;126(1):102-9). (JAMA, November 1994, 272:1413). In the Rotterdam study, More recently, CAREDS (Carotenoids in the Age-Related Researchers hope that ingesting antioxidants, which are people with the highest dietary intake of beta-carotene, found in fruits, vegetables, nuts and grains, might slow the Eye Disease Study) found that women with high dietary levels vitamin C and E, and zinc were at reduced risk of developing of lutein and zeaxanthin had a 23 per cent lower prevalence damage. Of particular interest are lutein and zeaxanthin, plant AMD. (JAMA. 2005 Dec 28;294(24):3101-7). More recently, a pigments that have the ability to filter damaging rays of blue of nuclear cataract than those who had low levels. (Archives of case-control study of more than 4000 AREDS participants Ophthalmology, March 2008, 126:354-364.) light and also appear to act as scavengers of free radicals. found that those with the highest dietary intake of lutein and 10 Story Emily Chew Jeffrey Gilbard Eric Donnenfeld Allen Taylor Cover Cover Conflicting conclusions from studies Biloba extract, and 100mg of resveratrol. Eric Donnenfeld MD, of Ophthalmic carotene is “not a suitable substitute” in Despite these promising links from Although no randomised, prospective Consultants of Long Island, said that he the treatment of retinitis pigmentosa observational studies, randomised clinical trials have shown that these recommends fish and flaxseed oil not only because it’s “not predictably converted controlled trials have told a different story.