Less Insulin is Needed for Regulation of Postprandial Glucose in Healthy Subjects after Wholekernel Rye Bread and Dark Durum Wheat Pasta than after Wheat Bread

Decreased glucose and insulin responses to carbohydrates are considered beneficial for health. Dietary fiber, structure of food, baking and processing influence these responses. Twenty subjects (10 men and 10 women, aged 28±1 y, BMI 22.9±0.7 kg/m 2 ) with normal glucose tolerance were recruited. The test products were wholekernel rye bread (60% of whole kernels) containing lactic acid (Rye 1), wholemeal rye bread containing oat (β-glucan concentrate (Rye 2), dark durum wheat pasta and white wheat bread. The test portions contained 12.8, 17.0, 5.6 and 3.2 g of dietary fiber, respectively. Each subject received five breakfasts (wheat bread twice) in random order during a period of 3 months. The breakfast contained the test product with 50 g available carbohydrates, 3 dl non-caloric orange drink and 40 g cucumber with breads or 19 g tomato sauce with pasta. A fasting and 8 postprandial blood samples were collected at intervals of 15-30 minutes during 3 hours. Glucose and insulin areas under the curve (AUC) were calculated. No significant differences in glucose AUC between the products were found, but insulin AUC of Rye 1 (P=0.001) and pasta (P=0.001) were significantly smaller than that of wheat bread. Maximal glucose response was lower to pasta than to wheat bread (P=0.006). Maximal insulin responses to Rye 1, Rye 2 and pasta were decreased compared to wheat bread (P=0.001, P=0.009, P=0.001, respectively). In conclusion, less insulin is required for the regulation of postprandial glucose after the wholekernel rye bread and dark durum wheat pasta than after the wheat bread. The way of processing and the structure of food may be more essential for the regulation of glucose and insulin metabolism than the amount of dietary fiber.