The glycaemic index connection

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

Compared with people with diets that measured lowest on the glycaemic index, people eating the highest glycaemic index foods were almost 1 1/2 times as likely to have features of macular degeneration. The higher the dietary glycaemic index, the more severe the disease. Further, people with a higher than average glycaemic 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 glycaemic index values below the median,” the study’s authors concluded.

Tips to reduce your risk

• Choose foods with lower glycaemic indexes—These are foods that have not undergone processing to remove the fibre-rich portions of the plant. Good options are whole wheat flour, brown rice, and pulses (beans, lentils, and peas).
• Limit foods with higher glycaemic indexes—Examples of these foods include white bread, sugar, white rice, and potatoes. High-glycaemic-index diets are implicated in many chronic diseases such as diabetes, heart disease, and cancer.
• Try whole grain versions of your favourite 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 glycaemic 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)