AUGUST 2009

To safeguard your vision, eat plenty of citrus fruits, leafy greens and cold-water fatty fish like salmon, but cut down on high-glycemic index foods such as sweetened drinks and desserts, candy, potatoes and white bread. That’s the takeaway from the first-ever composite scoring system to rate foods according to their effects on the risk of age-related macular degeneration (AMD), the leading cause of vision loss among older Americans. Other foods that scored positively included vegetable oils, nuts and whole grains.

Chung-Jung Chiu, DDS, PhD, of the Laboratory for Nutrition and Vision Research at Tufts’ Jean Mayer USDA Human Nutrition Research Cen ter on Aging, and colleagues published their findings in the journal Ophthalmology. They looked at links between overall dietary patterns and risk of AMD among 4,003 participants in the Age- Related Eye Disease Study (AREDS).

Previous Tufts research had established an association between the glycemic index (GI) and AMD risk. High-GI foods trigger a rapid rise and fall in blood sugar; low-GI foods, such as lentils, soybeans and many wholegrain products, change blood sugar more gradually. (See the March 2009 Special Report.) That rush from high- GI foods may eventually damage the macula, the part of the retina responsible for detailed central vision, by causing protein or membrane damage and cell toxicity. Allen Taylor, PhD, director of Tufts’ vision lab, likens the effect to the damage caused to an apple when it browns from exposure to air.

On the other hand, certain nutrients have been suggested to have a protective effect against AMD. The new study added to the evidence for omega-3 fatty acids, found in cold-water fatty fish. Interestingly, part of the protective effects of omega-3 fatty acids may be through modulating the unfavorable blood lipids after a high-GI meal.

Participants who ate foods rich in antioxidants— vitamin C, vitamin E, zinc, lutein and zeaxanthin— were also at lower risk of AMD. Lutein and zeaxanthin are plant pigments found in broccoli, spinach and other leafy greens; lutein is also found in egg yolks. These antioxidants can help reduce the oxidation stress caused by high-GI foods.

Beta-carotene, another nutrient previously thought to protect against AMD, did not affect risk in this new analysis.

Chiu and colleagues cautioned that further research is needed to confirm the relationship between AMD and the factors in the new scoring system.

Fats That Fight AMD Two other new studies, both published in Archives of Ophthal - mology, add to the evidence that your diet affects your risk for AMD. In one, researchers found that eating one serving of fish per week reduced AMD by 31%, while snacking on one or two servings of nuts cut the risk by 35%. Researchers, who followed 2,454 participants for 10 years, noted that both fish and nuts are sources of omega-3 fatty acids. Jennifer S.I. Tan, MBBS, BE, of West moreland Hos pital, University of Sydney, and colleagues suggested, “These fatty acids may protect the eyes by preventing the buildup of plaque in the arteries or reducing inflammation, blood-vessel formation and oxygenrelated cell damage in the retina.”

Eating more than one serving of fish per week didn’t increase the protection, however, suggesting a threshold effect. And greater intake of linoleic acid countered the benefit from eating fish; an unsaturated omega-6 fatty acid, linoleic acid is found primarily in vegetable oils.

In the second study, Elaine W.T. Chong, MD, PhD, of the Centre for Eye Research Australia, and colleagues analyzed data on 6,734 individuals, ages 58 to 69. Those who consumed higher levels of trans fats—found in baked goods and processed foods— were more likely to have late AMD. Higher intake of olive oil, however, was associated with decreased prevalence of late AMD. Dr. Chong and colleagues concluded, “Our findings suggest that people who follow a diet low in processed foods high in [trans fats] and rich in omega-3 fatty acids and olive oil might enjoy some protection from developing AMD.”

TO LEARN MORE: Ophthalmology, May 2009; abstract at dx.doi.org/10.1016/j.ophtha.2008.12.025. Laboratory for Nutrition and Vision Research www.tufts.edu/~ataylo01. Archives of Ophthal - mology, May 2009; abstracts at archopht.ama-assn. org/cgi/content/short/127/5/656 and archopht. ama-assn.org/cgi/content/abstract/127/5/674.