Effects of dietary fiber on mucosal growth and cell proliferation in the small intestine of the rat: a comparison of oat bran, pectin, and guar with total fiber deprivation.

The effects of dietary fiber on small intestinal mucosal mass, morphology, and cytokinetics were studied by feeding three qualitatively different forms of fiber to 40 rats for 4 wk. A fiber-free diet was fed to the control group and a similar diet with either a 20% oat bran, 10% pectin, or 10% guar supplement to the other three groups. All groups of rats exhibited similar caloric intakes and weight gains. Only the guar diet produced a significant increase in mucosal mass, as demonstrated by 19.1% increase in mucosal weight (p less than 0.05), a 16.7% increase in RNA (p less than 0.05) and an increase in DNA from 38.3 +/- 1.8 (SEM) to 44.6 +/- 2.3 micrograms/cm intestine/100 g body weight (p less than 0.05) when compared to the controls. The pectin-diet produced a decrease in villus height from 102.1 +/- 2.4 to 94.3 +/- 2.4 cells but an increase in crypt column length from 25.3 +/- 0.6 to 27.4 +/- 0.4 cells when compared to the controls (p less than 0.05). The shift in labeling index distribution curves for pectin and guar to the right and for oat bran to the left indicated an increase and decrease respectively in labeling index. The higher rate of epithelial cell migration in the pectin- and guar-fed groups shortened their estimated villus cell transit times to 36.4 +/- 0.7 and 37.0 +/- 1.4 h, respectively, when compared with 42.6 +/- 1.2 h in the oat bran and 41.1 +/- 1.0 h in the control (p less than 0.05). These results show that the modulation of small intestinal mucosal structure and growth by dietary fiber appears to be mediated through alterations in cell proliferation and that these changes depend not only on the quantity but also the quality of the fiber present in the diet.