Intragastric vs intraintestinal viscous polymers and glucose tolerance after liquid meals of glucose.

To determine whether viscous fibers improve glucose tolerance by slowing gastric emptying or impeding intestinal uptake of glucose, 800 mL of 0.2 mol glucose/L were instilled into the stomachs of the dogs and allowed to empty from the stomach out the proximal limb of a duodenal fistula while simultaneously fresh solution was instilled into the distal duodenum at the same rate. This technique allowed us to study 33 g pectin/L, isoviscous 400 g PEG 20,000/L, or 11 g guar/L when present with glucose in the stomach only, the intestine only, or in both stomach and intestine. Rates of gastric emptying and plasma glucose were lower when viscous polymer was present at both sites than at either site separately. Slowing of gastric emptying was an interactive outcome of viscosity at both loci, probably from slowed intestinal absorption of glucose with its exposure to more intestinal sensors. Reductions in postcibal glucose concentrations depended on slowing of both gastric emptying and intestinal absorption.