1. Conventional (CV) rats were given a single oral dose of 1 or 2 g maltitol. Urine and faeces were collected during the following 24 h and their contents of maltitol and sorbitol were measured.
2. Very little of either substance appeared in the faeces but appreciable amounts of sorbitol found in the urine indicated that the maltitol had been hydrolysed.
3. Excretion of maltitol and sorbitol was compared in germ-free and CV rats given an oral dose of 2 g maltitol. Significantly less of both substances was recovered in the faeces of CV rats, but urinary excretion was similar in both environments.
4. Maltitol injected intravenously gave rise to only traces of sorbitol in the excreta. A dose of 250 mg was cleared almost completely from the circulation within 1 h.
5. It is concluded that maltitol is hydrolysed by animal tissues, either in the gut lumen before absorption or in the gut wall during absorption. Maltitol and sorbitol are also degraded by gut bacteria, mostly in sites distal to the main absorptive area. The contribution to the host's nutrition would depend on the extent to which the end-products of fermentation are absorbed from the colon.