STARCHES OF VARIED DIGESTIBILITIES DIFFERENTIALLY MODIFY INTESTINAL FUNCTION IN RATS

Starches of different digestibilities may enter the colon to different extents and alter colonic function. Male Fischer 344 rats were fed di ets containing 25% cooked potato starch, arrowroot starch, high amylos e cornstarch or raw potato starch for 6 wk. Fecal weight, transit time , colonic thymidine kinase activity (a marker for cell proliferation), and weight, starch content and pH of the cecum and proximal and dista l colon were measured. Raw potato starch was much less completely dige sted than high amylose cornstarch, resulting in a 32-fold greater amou nt of undigested starch entering the cecum in the raw potato starch gr oup. Both the high amylose cornstarch and raw potato starch diets sign ificantly enhanced fecal weight and produced large intestinal hypertro phy, effects that were greatest in the raw potato starch group. Raw po tato starch feeding was associated with the highest level of thymidine kinase activity, although the differences in thymidine kinase activit y among the four groups were not significant. This diet also produced a 50% longer transit time. Entry of a large amount of raw potato starc h into the colon resulted in greater luminal acidity, greater luminal bulk and slower transit. A much smaller amount of starch entered the c olon in the high amylose cornstarch group and resulted in fecal bulkin g but no alteration in transit.