May 08, 2007

May 8, 2007 (Ft. Lauderdale) — People whose diet consists of foods that lead to a high dietary glycemic index have a substantially higher risk of progression of age-related macular degeneration (AMD), according to recent long-term results from the Age-Related Eye Disease Study (AREDS).

In fact, consumption of highly refined carbohydrates can lead to up to a 17% increased risk of AMD progression, according to a poster presented at the annual meeting of the Association for Vision and Research in Ophthalmology (ARVO).

This newest set of results from AREDS confirms findings from earlier years, but shows that the effect of diet on AMD is even stronger than previously thought. The longer-term results show a stronger effect, said Chung-Jung Chiu, PhD, assistant professor of ophthalmology at Tufts University, in an interview with Medscape.

The AMD arm of AREDS is a long-term clinical trial sponsored by the US National Eye Institute, and consists of more than 4757 people who have at least early-stage AMD. Enrollment for the study began in November 1992 and ended in January 1998; participants were followed for at least 5 years.

For this recent analysis, data were based on findings from 3977 participants, aged 55 to 80 years, who were at risk of progression of AMD. A total of 7232 eyes that did not have advanced AMD were placed into 1 of 3 AMD groups: group 1 consisted of 2697 eyes with no drusen; group 2 consisted of 1781 eyes with 1 or more intermediate drusen, extensive drusen, or pigment abnormalities associated with AMD; and group 3 consisted of 2754 people who had 1 or more large or intermediate drusen. Remaining eyes were found to have advanced AMD and were not included in this analysis.

At baseline, patients were administered a food-frequency questionnaire, from which researchers were able to extrapolate each participant’s overall dietary glycemic index.

Overall, 3541 eyes were from people whose overall dietary glycemic index was high; 3691 had a low dietary glycemic index. The study looked at risk of progression over 8 years; mean follow-up was 5.4 years.

When compared with people who had a low dietary glycemic index, those with a high glycemic index were, overall, 7.8% more likely to have their AMD progress. Those with a high dietary glycemic index in group 1 had a 5% higher probability of progression than their low glycemic counterparts; those in group 2 had an 8% higher probability of progression, and those in group 3 had a 17% higher probability of progression.

The findings are important because they show that keeping your glycemic low by dietary means can reduce the risk of AMD progression, Dr Chiu said. The researchers estimate that reducing the dietary glycemic index for the upper 50% of the older population might eliminate more than 100,000 new cases of advanced AMD in 5 years in the US alone.

According to Shweta Kaushik, a PhD candidate in the department of ophthalmology at the University of Sydney, in Australia, who was not part of the study but is working on a related research topic in the Blue Mountains Eye Study, this study is important because it highlights the role of diet in AMD. Ms. Kaushik recommended that doctors educate patients about the glycemic effect of specific foods.

In fact, the Blue Mountains study recently found that the consumption of high glycemic food in a large population predicted the development of early AMD. Because of this association, she was not surprised at the findings of the AREDS.

Educating patients about the glycemic effect of specific foods would be a worthwhile thing for doctors to do.

Foods that contribute to a lower dietary glycemic index include things such as legumes, rolled oats, basmati rice, whole bran, whole grains, and even pasta if it is cooked al dente (slightly hard). Foods that contribute to a higher glycemic index include things such asinstant oatmeal, overcooked pasta, white bread, and many types of potatoes, she said.

As a rule, foods that are more processed are more likely to increase blood sugar and foods that undergo less processing and are “whole” are thought to provide cardiovascular protection.

The AREDS study was funded by the NIH, Johnston & Johnston, and the American Health Assistant Foundation.

ARVO 2007 Annual Meeting: Abstract 2101-B710. Presented Monday May 7, 2007

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