High Antioxidant Diet May Delay Age-Related Macular Degeneration

A diet high in antioxidants including vitamins C and E may forestall age-related macular degeneration, according to researchers here. Older individuals who consumed above-median amounts of beta carotene, zinc, and vitamins C and E in their diet were 35% less likely to be diagnosed with the disease, reported Redmer van Leeuwen, M.D., Ph.D., of the Erasmus Medical Center and colleagues.

The study, published in the Dec. 28 issue of the Journal of the American Medical Association, added to the growing yet often conflicting evidence about the effect of dietary antioxidants on age-related macular degeneration, a disease linked to oxidative stress. There is evidence that antioxidant supplements can be beneficial. The randomized, placebo-controlled Age-Related Eye Disease Study (AREDS) showed that supplement intake of five to 13 times the recommended daily allowance (RDA) of beta carotene, vitamins C and E, and zinc, given to participants from retinal clinics with early or monocular late age-related macular degeneration, resulted in a 25% reduction in the five-year progression to late age-related macular degeneration, the authors noted.

The current prospective cohort study, which focused on dietary sources, included more than 4,000 participants, ages 55 or older. They were in the Rotterdam study, which was designed to examine the frequency of and risks factors for a variety of common diseases. All participants underwent an ophthalmologic exam and completed a food frequency questionnaire at baseline (from 1990 to 1993). Participants underwent three additional follow-up eye exams at yearly intervals until 2004. Average follow-up was eight years. During the study period, 560 individuals (about 13%) were diagnosed with age-related macular degeneration.

 After adjusting for potential confounders, a 1-standard deviation increase in dietary vitamin E intake was associated with a reduced disease risk of 8% (hazard ratio=0.92; 95% confidence interval=0.84-1.00). The same increase in dietary zinc was linked to a 9% risk reduction (HR=0.91; 95% CI=0.83-0.98). Above-median intake of all of four key nutrients-beta carotene, zinc, and vitamins C and E-was associated with 35% reduced risk (HR=0.65; 95% CI=0.46-0.92), compared with below-median intake.

 Excluding the 559 participants who took antioxidant supplements from the analysis did not substantially change the results, although the researchers noted that the number of supplement-takers was relatively small and that there was no data on what dosages they took or how long they took supplements. "Although in need of confirmation, our observational data suggest that a high intake of specific antioxidants from a regular diet may delay the development of age-related macular degeneration," the authors concluded.

A higher intake of vitamin E can be achieved by eating whole grains, vegetable oil, eggs, and nuts. High concentrations of zinc can be found in meat, poultry, fish, whole grains, and dairy products, the researchers advised. Carrots, kale, and spinach are the main suppliers of beta carotene, while vitamin C is found in citrus fruits and juices, green peppers, broccoli, and potatoes. "Based on this study, foods high in these nutrients appear to be more important than nutritional supplements," they said.

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