Fructans of chicory: intestinal transport and fermentation of different chain lengths and relation to fructose and sorbitol malabsorption

Fructans (fructooligosaccharide a and inulin) are of increasing interest to clinical nutritionists as functional food additives. The chemically closely related food carbohydrates fructose and sorbitol are implicated in functional bowel disease. Intestinal handling of these carbohydrates is incompletely understood. Intestinal absorption, transit, and fermentation (breath hydrogen and methane, venous acetate, blood glucose, and urine fructans) after ingestion of 10-30 g short- and long-chain fructans from chicory were studied by single-blind, crossover randomization in 10 healthy adults. Responses were compared with responses after ingestion of lactulose, fructose, and sorbitol. Breath hydrogen and venous acetate production increased in proportion to increasing fructan dose and were similar to responses to lactulose. The transit times of long-chain fructans were longer than those of short-chain fructans (75 compared with 30 min, P<0.001). Semiquantitative estimates of unabsorbed carbohydrate were not significantly different with either short-chain fructans or lactulose as nonabsorbable standards. Venous acetate curves were less precise estimates of the magnitude of carbohydrate malabsorption than were breath-hydrogen curves (P<0.01). All subjects showed malabsorption of 50 g fructose, resulting in significantly more symptoms than 20 g fructose (P<0.05). Ingestion of sorbitol with equimolar amounts of glucose did not reduce malabsorption or abdominal distress. Abdominal symptoms after fructans increased with increasing dose and decreasing chain length. The overall gastrointestinal effects of short-chain fructans seem similar to those of lactulose. Fructans with different chain lengths may have different physiologic properties and further studies of fructans in disease states are warranted.