The effect of diets containing field beans of high or low polyphenolic content on the activity of digestive enzymes in the intestines of rats

Saline extracts of the intestinal contents of 36 rats, which had been randomly allocated into six dietary groups, were assayed for trypsin, α‐amylase and lipase. The activities of both trypsin and α‐amylase were significantly reduced in rats consuming diets containing testa from Dylan, a coloured flowered variety of field bean, whilst those receiving diets containing testa from the tannin‐free, white flowered variety Triple White had comparable activities with those on a control testa‐free diet. Polyvinyl‐pyrrolidone‐saline extracts of the gut contents, however, had similar trypsin activity for all diets and it was concluded that the original observed reduction in digestive enzyme activity was due to the presence of field bean polyphenolics, which are known to be present in the testa of all coloured flowered varieties. In contrast, lipase activity was increased in rats which received Dylan testa diets. It is suggested that the presence of field bean tannins stimulates an increased pancreatic secretion of all digestive enzymes; but in the gut, the affinity of tannin for lipase is less than for either dietary protein or the other digestive enzymes.