Patients who curtail their intake of foods with a high dietary glycemic index may reduce their chances of developing age-related macular degeneration (AMD).

Researchers at Tufts University in Boston studied 4,099 nondiabetic adults ages 55-80. Using food-frequency questionnaires, investigators analyzed participants’ diets, paying particular attention to the amount and type of carbohydrates consumed.

Foods with a high glycemic index include those containing simple carbohydrates, such as cookies, cake, candy, and pizza. Relatively low-glycemic index foods include brown rice, barley, and many vegetables and fruits.

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The participants’ eyes were also checked for evidence of AMD. The investigators graded the severity of macular degeneration on a scale of 1-5, with 1 being normal and 5 indicating advanced disease.

After controlling for a range of factors, including BMI, age, sex, alcohol consumption, sun exposure, and education level, investigators found that people with a glycemic index higher than the median for their sex had a 49% increased risk of advanced AMD.

Researchers say this study “supports and strengthens” their hypothesis that diets with a higher glycemic index increase the risk of AMD, and they estimate that 20% of prevalent cases of advanced disease would be eliminated if patients consumed diets that have glycemic index values below the median.

Although the exact cause of AMD is not yet known, the researchers believe that dietary glycemic index may increase AMD risk “through several common etiologic factors of diabetes and cardiovascular disease, including…increases in oxidative stress, inflammation, and hyperlipidemia” (Am J Clin Nutr. 2007;86:180-188).