Glycemic Index and Load Foods and Diabetes
The glycemic index (GI) measures how different carbohydrate-containing foods affect blood glucose. The carbohydrate-containing foods are ranked based on how each food’s effect on blood glucose compares to that of a standard reference food (pure glucose). A food with a high GI will raise blood glucose levels more than lower-GI foods.
Foods with a GI of 70 or above are considered high-GI foods, while anything with a GI of 55 or under is considered a low-GI food. Medium-GI foods have a GI between 56 and 69. Some examples of relatively low-GI foods include beans, peas, and lentils, many fruits and nonstarchy vegetables, and sweet potatoes, yams, and corn.
The glycemic index represents the type of carbohydrate in foods, not the amount. The serving sizes and how many grams of carbohydrate are in the foods you’re eating are still important. Watch your portions!
Glycemic load (GL) measures the impact that both the type and amount of carbohydrate in a certain food will have on blood glucose levels. It’s calculated by multiplying a food’s glycemic index by the amount of carbohydrate in the food/serving. As with the glycemic index, foods with a high GL have a greater impact on blood glucose than lower-GL foods do. Glycemic load may not be a practical tool for everyday meal planning; the glycemic index is more widely used and predictable than glycemic load. (For more information about GI and GL, check out Glycemic Index Diet For Dummies by Meri Reffetto [Wiley].)
Both the type and amount of carbohydrate in a food affect blood glucose levels, but studies show that the quantity of carbohydrate in a food generally has a stronger effect on blood glucose than the quality (the GI). This means that the first step toward blood glucose management for most people with diabetes, at least in terms of meal planning, will be some sort of carbohydrate counting/control rather than using the glycemic index. However, the glycemic index (and possibly glycemic load) may be useful tools when used in conjunction with carbohydrate control, for people who are looking to fine-tune their diabetes management efforts.