The Glycemic Index

Not the most effective nutrition therapy intervention

It is essential that clinicians be aware of expected outcomes from possible nutrition therapy interventions so that they can assist people with diabetes using the best approaches to achieve metabolic goals. Outcomes can be predicted from evidence-based technical reviews or from meta-analyses. Both are now available: the American Diabetes Association (ADA) 2002, Evidence-Based Nutrition Principles and Recommendations for the Treatment and Prevention of Diabetes and Related Complications, technical review (1) and position statement (2), and in this issue of Diabetes Care, Brand-Miller et al. (3) report on a performed meta-analysis of low–glycemic index (GI) diets.

The ADA technical review and position statement reviewed the role of the GI in medical nutrition therapy for diabetes. The reports acknowledge that differing food sources of carbohydrates have differing glycemic responses when the food is studied independently, in 50-g portions, and compared with 50 g of either glucose or bread (1). However, after reviewing the evidence, it was concluded that the total amount of available carbohydrate in meals or snacks is more important than the source (starch or sugar) or type (low or high GI) (A-level evidence), and although low-GI foods may reduce postprandial hyperglycemia, there was not sufficient evidence to recommend use of low-GI diets as a primary strategy in food/meal planning (B-level evidence) (2). These statements were based on a review of over 20 studies in which subjects with type 1 or type 2 diabetes ingested a variety of starches or sucrose, both acutely and for up to 6 weeks, with no significant differences in glycemic response if the amount of carbohydrate was similar. This recommendation was questioned in a letter to Diabetes Care by Irwin (4) with a reply to the letter by Franz and Bantle (5).

In the reply to Irwin, it was noted that in subjects with …