Cereal fructans: in vitro and in vivo studies on availability in rats and humans

The bioavailability of cereal fructans (fructooligosaccharides) was investigated both in vitro and in vivo. In vitro studies indicated very slow hydrolysis by human gastric juice and by homogenate of the intestinal mucosa (rat). After intubation of fructans into the stomachs of rats, the recovery of fructans in the small intestine and colon was approximately the same as that of an unabsorbed marker (polyethylene glycol), indicating no or very low disappearance of fructans in the small intestine. In vivo studies of the small intestine in rats showed that the rate of disappearance of fructans was lower than that of mannose, which is known to be absorbed through passive diffusion. In addition the cariogenic effect of cereal fructans was compared to that of glucose. Acid formation from low molecular-weight fructans was found in human dental plaque in vitro. A mouth rinse with unfractionated fructans, containing some quantities of sucrose, fructose and glucose, resulted in relatively low pH values in human plaque in vivo, even if the decrease in pH was somewhat less pronounced when compared with a mouth rinse with glucose.