Gastric emptying of lactose and glucose-galactose in patients with low intestinal lactase activity.

To test the hypothesis that in subjects with low intestinal lactase activity (LLA) lactose solutions leaves the stomach at an abnormally fast rate, we have measured the gastric emptying rate of solutions of lactose and glucose-galactose in patients with LLA (n = 9) and in control subjects with high intestinal lactase levels (n = 7) as proved by the assay of disaccharidases in specimens of intestinal mucosa. The volume of the test meals was 300 ml. Lactose solutions contain 50 g of disaccharide and glucose-galactose solutions contain 25 g of each monosaccharide. The volumes remaining in the stomach at different times after the intragastric instillation of the test meals were estimated by the double sampling test meal. In the control group, minor differences between lactose and glucose-galactose gastric emptying rates was found. By contrast, in LLA patients, the lactose meal left the stomach at a significantly faster rate than the glucose-galactose test meal. These findings support previous evidence obtained in patients with putatively low intestinal lactase activity and are consistent with the view that duodenal osmoreceptors, whose excitation results in inhibition of gastric emptying, lie deeper than the disaccharidases in intestinal mucosa. Thus, incomplete hydrolysis of lactose results in a faster than normal gastric emptying rate of the sugar and this may contribute to the symptoms found in LLA patients after milk ingestion.