FRUCTOSE ABSORPTION

Fructose found in modern diets as a constituent of the disaccharide sucrose is absorbed by a well-characterized absorptive system integrating enzymatic hydrolysis of the disaccharide and transfer of the resulting two monosaccharides through the apical membrane of the epithelial cell. The increasing use of high-fructose syrups and crystalline fructose prompted new studies aimed at the determination of the absorptive capacity for free fructose in the human gut. Results indicate that the capacity for fructose absorption is small compared with that for sucrose and glucose and is much less than previously estimated. The unexpected finding that the simultaneous ingestion of glucose can prevent fructose malabsorption suggests that the pair of monosaccharides might be absorbed by the disaccharidase-related transport system as if they were the product of the enzymatic hydrolysis of sucrose. This absorptive mechanism might not be able to transport fructose when ingested without glucose.