A differentiation is made between types of fructose intolerance.
Hereditary fructose intolerance, a hereditary disorder of the fructose metabolism, is a rare enzyme disorder affecting fructose reduction in the liver. It is caused by a lack of enzyme Aldolase B. The consequence is slight to intense hypoglycaemia.
Intestinal fructose intolerance, usually called fructose malabsorption, is much more common. About 30-40% of people are affected. Here there is a deficiency in transport protein GLUT-5. This normally transports the fructose through the small intestine mucosa. In the case of fructose malabsorption, this does not happen and instead the fructose enters the large intestine where it causes discomfort such as bloating, stomach cramps and diarrhoea. Fructose malabsorption therapy consists of a diet low in fructose. The tolerance threshold for fructose differs greatly from person to person. Also, nutritive sweeteners Sorbit, Mannit and Xylit must be avoided because they additionally hamper fructose absorption. According to reports, food products that have a higher proportional glucose content than fructose are tolerated better. Lists of permitted food products exist for this purpose.
There is a possibility of a link between the two gastrointestinal illnesses, celiac disease and hereditary fructose intolerance. Research has shown that celiac disease occurs more frequently (>10%) in people who suffer from hereditary fructose intolerance than in the general population.