What Happens to Fructose in the Gut?

Abstract

There is a separate transport system for fructose in the intestinal brush border. Fructose absorption takes place by facilitated diffusion, independently of the presence of energy supply or sodium. Until recently, the human fructose absorption capacity has been considerably overrated. It has been demonstrated with breath hydrogen tests that a dose of 50 g (2 g/kg body weight in children) is incompletely absorbed by most people; some actually absorb only 5g. Glucose, however, strongly facilitates fructose absorption. Diminished absorptive capacity for fructose may become of clinical relevance in case of consumption of apple juice, pear juice, or beverages sweetened with high-fructose corn syrups, and in case of concomitant consumption of, for instance, sorbitol. Fructose (and sorbitol) may have an aetiologic role in the irritable bowel syndrome in adults, and in recurrent abdominal pain and especially chronic nonspecific diarrhoea (toddler's diarrhoea) in children.