Daily intake of high dietary fiber slows accelerated colonic transit induced by restrain stress in rats.

Background: Stress and central corticotropin releasing factor (CRF) are contributing factors to the pathogenesis of irritable bowel syndrome (IBS). It has been shown that restraint stress and central CRF stimulate colonic motility in rats. Short-chain fatty acids (SCFAs) are produced by bacterial fermentation from dietary fibers. It is controversial whether daily intake of dietary fiber is beneficial for patients with diarrhea-predominant IBS. We studied whether dietary fiber intake affects colonic transit and motility stimulated by restraint stress and central CRF in rats.

Methods: Corn starch is digested almost completely in the small intestine, while potato starch shows substantial resistance to alpha-amylase and its consumption leads to stimulation of large-bowel fermentation. Four weeks after a corn starch, potato starch, or usual diet (rat chow), colonic transit and motility stimulated by restraint stress and intracisternal (ic) injection of CRF were studied. Fecal concentration of SCFAs in the cecum was measured by high-performance liquid chromatography (HPLC).

Results: Four-week treatment with potato starch diet significantly increased cecal concentrations of SCFAs, compared to treatment with corn starch diet. Accelerated colonic transit induced by stress and ic injection of CRF (1 microg) were significantly attenuated in rats receiving potato starch diet compared to rats receiving corn starch diet. The incidence of unformed stool (diarrhea) induced by stress and CRF was also reduced in rats receiving potato starch diet compared to rats receiving corn starch diet and usual diet.

Conclusion: It is suggested that daily intake of a high-fiber diet may prevent stress- and CRF-induced acceleration of colonic transit and diarrhea. This study may contribute to treatment for the patients of diarrhea-predominant IBS.