Two natural-food mixed meals composed in accordance with the present dietary recommendations were given to 10 diabetic patients on two occasions. The meals were planned to achieve large differences in glycemic index (GI) by altering the food structure but maintaining an identical nutrient composition. In the first study, two meals were compared that contained either pasta or bread made from durum wheat flour. In the second experiment a meal with parboiled rice, red kidney beans, and bread made from whole-wheat grains was compared with a meal of sticky rice, ground red kidney beans, and bread made from ground wheat. All of the other ingredients in these meals were identical. The area under the curve for blood glucose (BG) and plasma insulin (PI) was significantly lower after the meal with pasta (BG: -35%, P < 0.05; PI: -39%, P < 0.05) and the meal with parboiled rice (BG: -42%, P < 0.001; PI: -39%, P < 0.01), respectively, compared with the corresponding high-GI meals. The results shows the importance of preserved structure in common foods and support the applicability of the GI concept to mixed meals.