A partially purified white bean amylase inhibitor was found to reduce starch digestion and inactivate intraduodenal amylase in humans by 94 to 99.9%.16 The authors of this study reported that perfusion of the partially purified inhibitor (2.0, 3.5 or 5 mg/ml at the rate of 5 ml/min) into the duodenum of humans rapidly inhibited alpha-amylase activity in a dose-dependent manner. The inhibitor also inactivated intralieal and salivary amylase in vitro studies. Additionally, the specific activity of the inhibitor was not affected by exposure to gastric juice and was only minimally affected by exposure to duodenal juice.

In studies in normal subjects and in patients with diabetes mellitus, a purified amylase inhibitor from beans was found to exert a “starch blockade” effect. In comparison with the placebo, ingestion of this inhibitor with 50 g starch substantially reduced post-prandial increases in plasma concentrations of glucose and insulin in both normal subjects and those with diabetes.