Small intestinal transit and digestibility of lactitol in Wistar rats

The study was conducted to evaluate if the recovery of lactitol and its cleavage products varied when different doses of this disaccharide sugar alcohol (150 and 1,200 mg/kg body weight, respectively) were given by gastric gavage to unadapted male rats. Phenol red added to the test solution as marker dye served to determine the intestinal transit and distribution areas. Marker transit revealed that the test substance did not reach the cecum in all series. Gastric emptying was more retarded after the high dose. Administration of low doses did not alter intestinal transit and luminal volume as compared to control animals. But a much larger luminal volume was found in the third intestinal quarter after the high doses, although the marker transit through this segment was equal under all experimental conditions. The total gastrointestinal recovery of lactitol at 63.2 (+/- 3.9) and 75.5 (+/- 4.5)% was significantly different (p < 0.001) 1 hour after administration of 150 mg and 1200 mg/kg body weight, respectively. Only free sorbitol was detected in the gastrointestinal contents in both dosage groups. Based on these results and correcting the values for marker recovery (85% in both groups), it is reasonable to assume that the maximum amount of lactitol that can be hydrolyzed and absorbed by the small intestine is 11.2 and 25.2%, respectively, and not zero. In conclusion, the caloric availability of lactitol is dose-dependent and should be determined under normal conditions in which the laxative threshold is not exceeded.