Lectins, trypsin and α-amylase inhibitors in dietary supplements containing Phaseolus vulgaris

Some dietary supplements used to control overweight are based on protein concentrates from Phaseolus vulgaris, or kidney bean, known to contain high levels of alpha-amylase inhibitor, which may reduce the adsorption and prevent the digestion of carbohydrates. These concentrates of kidney bean also contain significant levels of antinutritional factors such as lectins and trypsin inhibitors. In recent years the concentrates of kidney bean have been processed to inactivate lectins and trypsin-inhibitor activity while preserving substantial alpha-amylase inhibitor activity. The aim of this study was to investigate and to compare the activity of the alpha-amylase inhibitor in some commercial supplements, and to determine the levels of residual lectins and trypsin inhibitors. The results show that the technological treatment used to reduce the levels of lectins and trypsin inhibitors partially decreases the activity of the amylase inhibitor. This study suggests the need for better standardization of the technological treatment of protein concentrates to ensure both the efficacy and safety of these dietary supplements.