The Glycemic Index: Flogging a Dead Horse?

Abstract

The glycemic index (GI) is a classification of foods based on their blood glucose-raising potential. The American Diabetes Association (ADA) has questioned the clinical utility of the GI and recommends that priority should be given to the amount rather than the source of carbohydrate. Some have interpreted this to mean that all carbohydrates have a nearly equal impact on blood sugar, and some feel that the GI is now a dead issue. Nevertheless, the reasons for questioning the clinical utility of the GI are unfounded because of the following: 1) they are based on studies of single test meals, which provide insufficient evidence on which to base dietary recommendations; 2) they are based on a faulty interpretation of the studies actually cited as evidence; 3) they take no account of better designed studies showing that the GI does apply in mixed meals; and 4) they take no account of studies showing that a low-GI diet improves overall blood glucose control in persons with diabetes. The GI is a valid and potentially useful concept, but is also deceptively complex. There are a number of unresolved problems and unanswered questions, and the appropriate place for the GI in patient education is not known. However, progress cannot be made without balance and objectivity.