Utilization and excretion of a new sweetener, fructooligosaccharide (Neosugar), in rats

In order to study the digestibility of the fructooligosaccharide "Neosugar," [U-14C]Neosugar or [U-14C]sucrose was orally administered to germfree, conventional and antibiotic-treated rats and the radioactivities of expired 14CO2, urine and feces were determined 24 h later. More than 50% of the Neosugar was expired as CO2 in conventional rats. This was the same as for sucrose, but the time course was delayed by about 2 h. In germfree rats, no 14CO2 was released for the first 8 h, and 14CO2 released after 8 h probably reflected bacterial colonization of the gut. The radioactivity of the urine was about 3-4% in all groups, but that of the feces from germfree rats was about eight times higher than the level in conventional rats. When [U-14C]Neosugar was anaerobically incubated with the cecal contents of conventional rats, more than 10% of the added Neosugar was metabolized to CO2, about 66% to volatile fatty acids and about 7% to microbes. More than 58% of 1-14C-volatile fatty acids such as acetic acid, propionic acid or butyric acid injected directly into the cecum of conventional rats was excreted as CO2 within 24 h. These results indicate that Neosugar given orally to rats is metabolized mainly to volatile fatty acids and CO2 by intestinal microorganisms, and the volatile fatty acids produced are absorbed and further converted to CO2 in the body. Thus, the data indicate that Neosugar is partially utilized as an energy source.