Gut: The Inside Story of Our Body’s Most Underrated Organ

by Giulia Enders

The mechanism behind fructose intolerance is different once again from that involved in the digestion of gluten or lactose. The cells of people with hereditary fructose intolerance contain fewer fructose-processing enzymes. That means fructose may gather in their cells, where it can interfere with other processes. Fructose intolerance that appears later in life is thought to be caused by a reduced ability of the gut to absorb fruit sugars. Such patients often have fewer transporters (called GLUT5 transporters) in their gut wall. When they ingest even a small amount of fruit sugar—for example, by eating a pear—their limited transporters are overwhelmed and, as with lactose intolerance, the sugar from the pear ends up feeding the flora of the large intestine.