Brooke Hannah, Simonette Mallard and Bernard Venn
Objective: Strategies to prevent and control diabetes are important with an increasing number of people at risk. Recommendations to consume whole grain foods or basing food choices on Glycemic Index (GI) may be useful in this regard. Methods: We undertook a randomized crossover study in which 120 healthy young adults consumed white bread and whole grain bread sandwiches. The commercially produced breads were chosen to have similar available carbohydrate contents per sandwich (26 and 27 g, respectively) but published GIs that represented high (75) and low (49) GI products. Participants were randomly assigned a filling of jam (n=42), cheese (n=36), or nut-based spread (n=42). The amounts of carbohydrate in the fillings were 12g (jam), 1g (cheese), and 11g (nut-based spread). On different days, each participant consumed a white or whole grain sandwich containing their assigned filling. Blood glucose responses were measured at intervals over two hours. Results: The glycemic responses between white and whole grain sandwiches, represented by incremental area-under-the-blood-glucose-curve (iAUC) were not different. For white and whole grain sandwiches, respectively, the iAUCs (mmol/L*min) were: jam 125 vs 109, P=0.26; cheese 71 vs 53, P=0.06; and nut-based spread 94 vs 72, P=0.12. The lack of postprandial glycemic difference between sandwiches was in contrast to the GI difference between bread types (P=0.03). In regression analysis, the choice of filling had a greater influence over the postprandial response than the type of bread. Conclusions: The data are consistent with American Diabetes Association advice to monitor the amount of carbohydrate intake. Nevertheless, there are attributes other than glycemia to recommend whole grains.
