Although
fructose was discovered in 1794, it was realised in recent decades only that its malabsorption can lead to intestinal symptoms while its excessive consumption induces metabolic disturbances.
Fructose is a
monosaccharide found naturally in most fruits and vegetables. Dietary intake of
fructose has gradually increased in the past decades, especially because of the consumption of
high fructose corn syrup. With its 16.4 kg/year consumption, Hungary ranks secondly after the United States.
Fructose is absorbed in the small intestine by facilitated transport mediated by
glucose transporter proteins-2 and -5, and arrives in the liver cells. Here it is transformed enzymatically into
fructose-1-phosphate and then, fructose-1,5-diphosphate, which splits further into
glyceraldehyde and
dihydroxyacetone-phosphate, entering the process of glycolysis,
triglyceride and
uric acid production. The prevalence of
fructose intolerance varies strongly, depending on the method used. The leading symptoms of
fructose intolerance are similar, but less severe than those of
lactose intolerance. Multiple secondary symptoms can also occur. A symptom-based diagnosis of
fructose intolerance is possible, but the gold standard is the H2 breath test, though this is less accurate than in
lactose testing. Measuring fructosaemia is costly, cumbersome and not widely used.
Fructose intolerance increases intestinal motility and sensitivity, promotes biofilm formation and contributes to the development of gastrooesophageal reflux. Long-term use of
fructose fosters the development of
dental caries and non-
alcoholic steatohepatitis. Its role in
carcinogenesis is presently investigated. The cornerstone of dietary management for
fructose intolerance is the individual reduction of
fructose intake and the FODMAP diet, led by a trained dietetician. The newly introduced
xylose-isomerase is efficient in reducing the symptoms of
fructose intolerance. Orv. Hetil., 2016, 157(43), 1708-1716.