Fructose Malabsorption

In this article, fructose malabsorption, formerly known as Dietary Fructose Intolerance (DFI), which is a common cause of diarrhea, is described. Another, rare, Hereditary Fructose Intolerance (HFI), which causes impairment of liver, kidneys and small intestine is much more severe. Fructose malabsorption and HFI are NOT allergies.

In fructose malabsorption fructose can’t be efficiantly absorbed from unknown reason. Transport protein GLUT5, responsible for fructose absorption in the small intestine, may not be present or becomes inactive. People with fructose malabsorption have fructose absorption limit lower than 25 grams per serving, but this may differ a lot from person to person. Fructose, unabsorbed in the small intestine, reaches the colon, where bacteria ferment it and yield short chain fatty acids, carbon dioxide (CO2), hydrogen and methane, which cause symptoms. It is estimated that about 1/3 of people are fructose intolerant, and about half of them have symptoms. People with fructose malabsorption may be also sensitive to other non-digestable carbohydrates, such as sorbitol and xylitol, raffinose (beans) and inulin (polyfructose), (5).

Who Can Get Fructose Intolerant?

Anyone at any time can develop fructose malabsorption. Abnormality or lack of GLUT-5, a fructose transporting protein, may be inherited (5). Other causes, suggested so far:

• family predisposition; 
• overuse of High Fructose Corn Syrup (HFCS), or fruit juices in children (toddler’s diarrhea); 
• small intestinal bacterial overgrowth (SIBO);
• celiac disease; 
• chemotherapy or radiation;
• dumping syndrome (rapid stomach emptying).