Physiological effects of retrograded, alpha-amylase-resistant cornstarch in rats

Retrograded amylose was prepared by gelatinization of high amylose cornstarch, followed by storage at 1 degrees C for 48 h. The insoluble residue, which resisted hydrolysis with porcine amylase, was dried and fed to male Wistar rats for 14 d in powdered semisynthetic diet. Control rats received a similar diet containing sucrose in place of resistant starch. Fecal collections were performed throughout the feeding period. After 14 d the animals were killed. The small intestine and cecum were removed for morphological examination, measurement of small intestinal crypt cell production rate (CCPR) and analysis of luminal carbohydrate content. Blood samples were collected for analysis of cholesterol, glucagon, and enteroglucagon. In the starch-fed rats, fecal bulk and excretion of starch were higher than in the controls, but they declined markedly over the feeding period. Cecal size and contents were also greater in the starch-fed rats, and cecal pH was significantly lower. The CCPR was 66% higher in the ileum of the starch-fed rats (P less than 0.001), but there was no difference in the jejunum. There were no differences in serum cholesterol or enteroglucagon levels. We conclude that retrograded amylose is partially degraded in the alimentary tract of rats, but it contributes significantly to fecal bulk.