The glycemic index connection

Macular degeneration attacks the part of the eye responsible for central vision. In its early stages, the disease may make straight lines appear wavy or make objects look fuzzy. As it progresses, reading, driving, and other activities that require sharp vision become more difficult.

In the study, over 4,000 people between ages 55 and 80 had their diets categorized by glycemic index—a measure of food’s blood sugar—raising effects. A high-glycemic-index diet raises blood sugar levels after a meal more than a low-glycemic-index diet does.

Compared with people with diets that measured lowest on the glycemic index, people eating the highest glycemic index foods were almost 1 1/2 times as likely to have features of macular degeneration. The higher the dietary glycemic index, the more severe the disease. Further, people with a higher than average glycemic index diet had a 49% increased risk of advanced macular degeneration.

“We estimate that 20% of cases of advanced macular degeneration would be eliminated if people consumed diets that have dietary glycemic index values below the median,” the study’s authors concluded.

Tips to reduce your risk

• Choose foods with lower glycemic indexes—These are foods that have not undergone processing to remove the fiber-rich portions of the plant. Good options are whole wheat flour, brown rice, and legumes (beans, lentils, and peas).
• Limit foods with higher glycemic indexes—Examples of these foods include white bread, sugar, white rice, and potatoes. High-glycemic-index diets are implicated in many chronic diseases such as diabetes, heart disease, and cancer.
• Try whole grain versions of your favorite carbs—Look for whole wheat pasta, brown rice, and multigrain breads.
• Switch your sweetener— If you’re looking for a healthier way to sweeten your coffee or tea, stevia is a natural sweetener that has a value of zero on the glycemic index.

Choosing unprocessed, whole foods appears to be a wise choice for eye health. The researchers noted, “Our results also suggest that the quality, not the quantity, of dietary carbohydrates influences the risk of macular degeneration.”

(Am J Clin Nutr 2007;86:180–8)