Effects of dietary fiber constituents on intestinal morphology and nutrient transport.

Adult male rats were fed for 4 wk on diets containing no addition, 10% fiber (methoxylated pectin or cellulose), or 2% cholestyramine. Weight gain and food intake in the fiber-fed groups were significantly greater than in control or cholestyramine-fed rats. The small intestine was examined for changes in jejunal villus structure and for in vitro transport characteristics by estimation of unidirectional influxes of 3-O-methylglucose (3-O-MG), alpha-aminoisobutyric acid (AIB), and sodium (Na). Feeding of either fiber component resulted in increases in intestinal villus length and width and in a marked increase in the influxes of 3-O-MG and AIB. Influx of Na also increased but less dramatically than the organic solutes. Cholestyramine feeding resulted in shortened villi and increased separation between villi in the jejunum. With this feeding regimen, influxes of 3-O-MG and AIB were increased, but Na influx was not changed. The results show that certain dietary fiber components may modify intestinal architecture and indicate that these structural changes may be correlated with altered functional characteristics.