Ileorectostomy or cecectomy but not colectomy abolishes the plasma cholesterol-lowering effect of dietary beet fiber in rats.

Adult male rats were fed a cholesterol-free diet with no added fiber (fiber-free) or with 10% cellulose or beet fiber. After 7 d of feeding, plasma total cholesterol concentrations were significantly lower in rats fed beet fiber than in those fed fiber-free or cellulose diets. This difference was due mainly to lower HDL cholesterol concentrations and remained significant for 28 d. The hypocholesterolemic effect of beet fiber relative to fiber-free disappeared when the cecum and colon were concurrently resected (ileorectostomy). Plasma cholesterol concentrations were the same in colectomized rats as in sham-operated rats fed the same diet and significantly lower in animals fed the beet fiber diet than in those fed the fiber-free diet. In cecectomized rats fed beet fiber, plasma cholesterol concentrations were intermediate between sham-operated rats fed the beet fiber diet and cecectomized or sham-operated rats fed the fiber-free diet. Fecal bile acid excretion was higher in rats fed the beet fiber diet than in those fed the fiber-free diet but did not correlate with plasma total cholesterol concentration. In rats with intact ceca, cecal total and individual short-chain fatty acids correlated negatively with plasma total cholesterol concentration. Dietary beet fiber lowers plasma cholesterol concentrations in rats, and the lower digestive tract, especially the cecum, seems to be necessary for this effect.