Digestion, excretion, and energy value of fructooligosaccharides in healthy humans.

The fate of fructooligosaccharides (FOS) in the human gastrointestinal tract was evaluated in six healthy volunteers over an 11-d period. After an equilibration phase, 20.1 g FOS/d was given in three identical postprandial doses. Distal ileal output of FOS and their constituent components were determined by intestinal aspiration after a single meal, and the amounts of FOS excreted in stools and urine were also measured. Most of ingested FOS, 89 +/- 8.3% (mean +/- SEM), was not absorbed in the small intestine, and none was excreted in stools, indicating that the portion reaching the colon was completely fermented by colonic flora. A small fraction of ingested FOS was recovered in urine. The mean estimated energy value of FOS was 9.5 kJ/g. We conclude that in healthy humans, FOS are only slightly digested in the small intestine and then fermented in the colon, resulting in reduced energy production.