What kinds of fructose indigestibilies are there?
Basically there are two kinds of fructose indigestibilty: Fructose malabsorption, often erroneously called fructose intolerance, and hereditary fructose intolerance.
Fructose Malabsorption
Fructose malabsorption is presumably due to a defective transport mechanism in the small intestine. The specific transport protein responsible for the absorption of fructose is inoperative owing to hereditary or external factors so that fructose is not absorbed and reaches the colon. This results mainly in two complaints: a. water accumulates through osmosis in the small intestine causing diarrhoea because this surplus liquid cannot be absorbed in the colon. b. Fructose is decomposed in the colon by bacteria forming short-chain fatty acids and gases, and this causes complaints such as flatulence, bloating, abdominal pain and headache. Fructose malabsorption is often wrongly diagnosed, just like other kinds of carbohydrate malabsorptions, e.g. lactose malabsorption is diagnosed as irritable bowel syndrome (IBS).
Fructose malabsorption can be diagnosed simply and painlessly by the Hydrogen Breath Test (HBT). Great care should be taken, however, if somebody is suspected of suffering from HFI because the Hydrogen Breath Test can be extremely risky in this case, see below.
At the moment there is no therapy for fructose malabsorption. People suffering from it should stick to a low-fructose or, in severe cases, fructose-free diet.
Hereditary Fructose Intolerance (HFI)
Hereditary Fructose Intolerance is a very rare congenital defect of the fructose metabolism which results in serious damage to liver ánd kidneys and to hypoglycaemia. HFI patients suffer severely, starting usually in their first year as soon as they are given supplementary food. A great many but by no means all of them take a dislike to anything sweet (fruit or vegetables) which protects them against eating fructose. In contrast to fructose malabsorption, a low-fructose diet is of no use if somebody suffers from fructose intolerance; their intake must be strictly fructose-free.
People suspected of suffering from HFI should be warned against taking a Hydrogen Breath Test before any suspicious factors are cleared up; serious hypoglycemic reactions may occur during the test.
Hereditary fructose intolerance can, among other things, be diagnosed by molecular genetic analysis.
Diet for Fructose Intolerance
Completely fructose-free nutrition is nearly impossible. It is important, therefore, to stick to a well-balanced diet while eating as little fructose as possible (see “fructose content”). The foodstuffs offered here will be helpful.
For forbidden and permitted kinds of sugar/sugars please see > sugars.
