Postprandial hyperglycemia and hyperinsulinemia are determinants of the metabolic risk imposed by sedentary and overfeeding lifestyle. The consumption of Leguminosae may modulate glucose metabolism with positive effects on diabetes and heart disease prevention. Phaseolus vulgaris contains alpha-amylase inhibitors potentially capable to modulate the metabolic and endocrine responses to the meal. We investigated the effect on postprandial glucose response of acute administration of a standardized bean isolate protein (BEANBLOCK?, Indena S.p.A., Milano, Italy) supplement to a mixed Mediterranean meal.

Twelve healthy subjects (BMI: 21.4±1.4 kg/m2, 22.5±2.0 yrs) received in two different occasions, in a randomized cross-over and double-blind design, a standardized meal (40% of their energy expenditure, 999±143Kcal) consisting of a sandwich (white bread, ham, tomato, olive oil) with either 100 mg bean isolate protein or placebo.. Serum glucose, insulin and C-peptide concentrations were sampled at baseline and every 10 minutes in the first hour after the meal consumption and every 15 minutes thereafter up to 3h.

Compared to placebo, bean isolate protein reduced the glycemic response to the meal (97 ?4 vs 109? 7 mg/dl at 30 minutes, p= 0.04). Interestingly, this effect was obtained with smaller insulin (p= 0.04) and c-peptide increments (p=0.03) in the first 90 min of the study.

Bean isolate protein caused a slower glucose release during bread starch digestion, which in turn required a smaller stimulation of insulin secretion to control postprandial hyperglycemia. This mechanism may prove useful in insulin resistant subjects and warrant further investigation in groups at cardiometabolic risk.