Nondigestibility of a new sweetener, "Neosugar," in the rat

The digestion of Neosugar, a mixture of 1F-(1-beta-fructofuranosyl)n-1 sucrose [n = 2, 1-kestose (GF2); n = 3, nystose (GF3); n = 4, 1F-beta-fructofuranosyl nystose (GF4)] was investigated in vitro and in vivo by using the rat. The results obtained were as follows. GF2 and GF3 were not hydrolyzed by a pancreatic homogenate. The GF2- and GF3-hydrolyzing activities of the enzymes in the intestinal mucosa homogenate were negligible compared with the activities of maltase and sucrase. GF2 and GF3 added to the incubation mixture did not affect the activities of sucrase and maltase in the intestinal mucosa. Long-term ingestion of Neosugar did not cause induction or suppression of GF2- and GF3-hydrolyzing enzymes in the small intestine. [U-14C]Neosugar injected intravenously was rapidly excreted in the urine without having undergone any degradation. These results indicate that Neosugar, which consists of GF2, GF3 and GF4, is scarcely hydrolyzed by the digestive enzymes of the gastrointestinal tract and internal organs, and that suggests to us that Neosugar is not utilized as an energy source in the body.