ARS is the U.S. Department of Agriculture's chief scientific research agency.

The study was led by Chung-Jung Chiu with Allen Taylor, both at the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) in Boston, Mass. Taylor is director of the Laboratory for Nutrition and Vision Research at the HNRCA.

The researchers analyzed dietary intake and other data from more than 4,000 men and women aged 55 to 80 participating in the Age-Related Eye Disease Study, or AREDS.

Diets high in carbohydrates that are quickly digested and absorbed, resulting in a rapid rise in blood sugar levels, are considered high-glycemic-index diets. Examples of such "fast carb" foods are white bread, rice, potatoes and pasta, and also sugars and corn syrups. Carbohydrates leading to a more gradual rise and fall in blood sugar levels comprise low-glycemic-index diets. Such "slow carb" foods include whole-grain versions of bread, rice and pasta.

Central vision loss is one of the first signs of age-related macular degeneration (AMD), a disease that is one of the leading causes of blindness among the elderly.

Consuming a diet high in fast carbs is also suspected of being involved in the vision loss that sometimes occurs in people with diabetes. The researchers theorize that the type of damage to eye tissue produced by fast carbs could be similar in both AMD and diabetic eye disease.

At this time, there is no effective cure for AMD, so finding modifiable risk factors is important. While it's too soon to recommend dietary slow carbs as a preventive strategy for AMD, replacing fast carbs with whole grains may soon prove to be an early dietary intervention to slow its progression.