Effects of Various Commercial Whole-Grain Breads on Postprandial Blood Glucose Response and Glycemic Index in Healthy Subjects

Postprandial hyperglycemia is a serious risk factor for cardiovascular disease and type 2 diabetes mellitus (T2DM). As diet is a cornerstone of both T2DM prevention and therapy, we investigated the effects of various commercially available breads on postprandial glucose response and glycemic index. Furthermore, the impact of oilseed- and protein-enriched breads was evaluated, as well as the influence of different wheat flour coarseness settings. Three experiments were conducted to study the effects of various breads on the postprandial glucose levels of randomly selected subjects (42 in total). First, putative differences of seven types of commercially available whole-grain breads were studied. Second, the influence of oilseed- and protein-enriched breads was investigated and third, the influence of different wheat flour coarseness settings was characterized. The total area under curve (AUC), postprandial glucose response, peak glucose level and glycemic index were calculated for each condition. Consumption of various types of whole-grain breads resulted in large variations in postprandial glucose response and significant differences in calculated glycemic indices. Furthermore, postprandial glucose levels and glycemic indices appeared significantly lower for protein-rich bread than compared to oil-seed-rich bread. Interestingly, no significant differences in postprandial glucose levels or glycemic indices were detected for fine, medium or coarse wheat flour breads. Based on the correlation study, breads with low total carbohydrates and high amounts of protein are advisable for the prevention of high glucose loads and should be considered by people suffering from T2DM. Trial registration: O2413 (Ethics Commissions of Upper Austria)