If you have diabetes, you may be wondering, "What is the glycemic index, and should I use it to help control my blood glucose levels?" In this Health Alert, Johns Hopkins endocrinologist Dr. Christopher D. Saudek sheds light on this controversial topic.
A number of books and diet doctors advocate low-glycemic-index diets. Proponents of these diets claim that foods with a low glycemic index (such as whole grains and most fruits and vegetables) are more healthful than foods with a high index (such as white bread, candy, and soda) because they do not produce as rapid an increase in blood glucose levels when eaten.
Q. What is the glycemic index, and should it be used?
A. The glycemic index measures how much a given amount of a carbohydrate-containing food raises glucose levels within two hours in comparison to eating white bread, which is a reference point with a glycemic index of 100.
Foods with a glycemic index higher than 100, such as instant rice, cause a faster and greater surge in blood glucose. Kidney beans score low at 38, as glucose jumps much less after eating them.
The glycemic index can be complicated to use regularly since it is not listed on most food labels and the wide variability of numbers across websites makes it impossible to know what is correct. Foods are also rated as consumed individually, which is not how people usually eat -- it does not take into account, for instance, the fat in a meal. Finally, carrots, corn, and raisins score at the high end of the glycemic index, but these are clearly nutritious foods that don't need to be eliminated.
A useful, related concept is "glycemic load," which multiplies the glycemic index by the amount of carbohydrate in a typical serving, thus more accurately reflecting its effect on blood glucose.
Bottom line advice on the glycemic index: The most recent nutrition guidelines from the American Diabetes Association recommend monitoring carbohydrate intake as the key strategy for glycemic control, and that using the glycemic index and load may provide a modest, additional benefit. We agree.
