Age-related macular degeneration (AMD) is one of the leading causes of vision loss in older adults and a person's risk may partly depend upon diet.
When it comes to carbohydrates, quality rather than quantity may be more important, according to new research by Allen Taylor, PhD, director of the Laboratory for Nutrition and Vision Research at the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts University, and colleagues. Their findings were reported in the American Journal of Clinical Nutrition.
Taylor and colleagues analyzed data from a sub-group of participants in the Nurses' Health Study (NHS) who were enrolled in the Nutrition and Vision Program. The researchers looked at the total amount of carbohydrates consumed over 10 years and the dietary glycemic index, which is a measure of the quality of overall dietary carbohydrate.
"Women who consumed diets with a relatively high dietary glycemic index had greater risk of developing signs of early age-related macular degeneration when compared with women who consumed diets with a lower dietary glycemic index," says lead author Chung-Jung Chiu, DDS, PhD, scientist in the Laboratory for Nutrition and Vision Research at the HNRCA and an assistant professor at Tufts University School of Medicine. High total carbohydrate intake, however, did not significantly increase the risk factor for AMD.
"In other words, the types of carbohydrates being consumed were more important than the absolute amount," explains Taylor, senior author. A high-glycemic-index diet is one that is rich in high-glycemic-index foods, which are converted more rapidly to blood sugar in the body than are low-glycemic-index foods.
Chiu, Taylor, and colleagues examined the eyes of more than 500 women between 53 and 73 years of age, looking for changes indicative of early AMD. The researchers also analyzed the participants' diets, as reported in questionnaires that had been administered periodically over the course of 10 years preceding their eye exams.
"Dietary glycemic index may be an independent and modifiable risk factor for early AMD," concludes Taylor, who is also a nutrition, ophthalmology and biochemistry professor on the Tufts health sciences campus in Boston. "The likelihood of having abnormalities characteristic of AMD on eye exam more than doubled for women who consumed diets with the highest glycemic index, regardless of other factors already known or suspected to increase the risk of AMD, such as age, high blood pressure, cigarette smoking, and obesity."