Effect of diet on intestinal xylose absorption in dogs.

The absorption of xylose at different levels of the intestine was compared in five dogs receiving diets containing either wheat bran, polyethylene particles (PE), or horse-bean hulls. The absorption was determined by serial collection of the interstitial fluid (ISF) in different parts of the small intestine and colon, and blood concentration after the administration of D-xylose as a solution (0.5 g/kg body weight) into the duodenal bulb. Xylose was mostly absorbed from the duodenum, and its concentration in the duodenal ISF and in plasma was reduced on a diet containing fiber, irrespective of the nature of fiber. In contrast, a negative linear relation between the mean retention time of digesta in the small intestine and the amount of xylose absorbed by duodenum was evidenced (r = -0.843). The results indicate that changes in transit linked to the presence of fiber in a diet are a major operative factor in the rate of carbohydrate absorption. They suggest that the absorption can be affected by a relatively minor change in the intestinal transit of digesta.