Q: I hear watching the glycemic index of foods can help lower blood glucose. What do glycemic index and glycemic load mean?
A: The glycemic index (GI) measures the increase in blood glucose levels during the two hours after eating a particular kind of food. Some foods that contain carbohydrate create a quick and more dramatic rise in blood glucose, such as white rice and dry cereal. Others cause a slower and less dramatic rise, such as legumes (beans) and pasta. Glucose is the standard for the glycemic index, and it is assigned an arbitrary number of 100. Several GI food lists have been developed, assigning foods GI numbers relative to the glucose standard of 100. GI numbers are available only for several hundred commonly eaten foods, such as carrots, watermelon, and potatoes, but not for mixed foods, like casseroles and vegetable soup.
GI does not consider the portion of food, but glycemic load (GL) does. The GL takes the glycemic index of a food and considers its common serving sizes to give a more practical indicator of the effect of that food on blood glucose.
Many of the foods with a low glycemic index are healthy foods. Consider eating more whole grain breads and cereals, legumes, and fruits and vegetables. Include these foods in your eating plan, but don't omit foods with a higher GI if they are healthy and you enjoy them.
Hope Warshaw, R.D., CDE, is a contributing editor to Diabetic Living and author of Diabetes Meal Planning Made Easy, fourth edition (American Diabetes Association, 2010).
Answer reviewed July 2010