Fructose malabsorption is in fact quite different from hereditary fructose intolerance!
Hereditary fructose intolerance (HFI) is a genetic condition, caused by a congenital lack of the enzyme Fructose 1-Phosphate Aldolase. It appears with a frequency of 1:20.000-1:130.000 (depending on research source) and leads to liver damage, kidney damage and hypoglykemia. In this case, fructose is transported without a problem via the transport system (GLUT-5) through the intestine into the body, but it cannot be broken down properly by the liver.
Fructose malabsorption (= dietary fructose intolerance (DFI) ) is, however, an acquired condition caused by a defective transport system (GLUT-5) in the small intestine. This means that the fructose cannot be absorbed into the body at a sufficient rate. But if it has been successfully transported then it can be broken down without a problem. Every third European suffers from fructose malabsorption!
The term "fructose intolerance" is often used by the public to describe fructose malabsorption or dietary fructose intolerance. On the Food Intolerance Network website we will use the term "fructose intolerance". We never talk about hereditary fructose intolerance (HFI) unless this is referred to specifically!
How does fructose malabsorption work?
Sugars are absorbed via the intestines with the help of GLUT transporters. The GLUT-5 transporter is responsible for fructose. It takes the fructose from the intestinal lumen into the enterocyte. However, this transporter also reacts to other substances. Some sugar alcohols like sorbite block it, and glucose stimulates its activity. Every molecule of glucose makes it possible to absorb a molecule of fructose. That is why people with fructose malabsorption should stay away from sorbitol, mannitol, isomalt etc and add glucose when they have to eat a larger amount of fructose (after the restriction diet). The level of transporters that are still functioning is different from person to person, which is why the "glucose-trick" does not work for everyone! This needs to be established individually!
Why some people develop fructose intolerance is not clear as of yet! But it has been observed that over the past few years carbohydrate absorption malfunctions have been on the rise.
(1)Rainer Klinke, Hans-Christian Pape, Stefan Silbernagl (Hrsg.): "Lehrbuch der Physiologie", 5. Auflage. Thieme, Stuttgart 2005
(2)Ledochowski M, Widner B, Fuchs D. "Fruktosemalabsorption". J Ernährungsmed 2000; 2: 10-14
(3)Born Peter, World J Gastroenterol 2007 November 21;13(43): 5687-5691 "Carbohydrate malabsorption in patients with non-specific abdominal complaints"
(4)Manir Ali, Peter Rellos, Timothy M Cox, ItMed Genet 1998;35:353-365, "Hereditary fructose intolerance"
Last Updated on Tuesday, 22 February 2011 09:22