Effects of dietary fiber on intestinal glucose absorption and glucose tolerance in rats.

The effects of acute and chronic dietary fiber (cellulose and pectin) supplementation on both intestinal glucose absorption and oral glucose tolerance were studied in rats. The effect of intraluminal fiber on intestinal glucose absorption was evaluated in perfused jejunal loops as was the effect of a single cellulose or pectin-supplemented meal on serum glucose responses to a carbohydrate load. Neither pectin nor cellulose impaired jejunal glucose absorption, but pectin did decrease serum glucose responses to an oral carbohydrate load. Chronic fiber supplementation significantly decreased intestinal glucose absorption in rats who had received for 5 wk a fiber-free diet supplemented with either cellulose (10%) or pectin (5%). Chronic supplementation with cellulose or pectin impaired intestinal glucose absorption and decreased serum glucose responses. These results suggest that differences in glucose homeostasis observed after ingestion of single high-fiber meals may be caused by viscosity-related delays in the rate of gastric emptying, whereas differences noted after chronic supplementation of dietary fiber are related to adaptive changes in the intestine.