Barrett, J. S. et al. Comparison of the prevalence of fructose and lactose malabsorption across chronic intestinal disorders. Aliment. Pharmacol. Ther. 30, 165–174 (2009).
Malabsorption of short-chain carbohydrates and an early rise in breath hydrogen after lactulose challenge do not necessarily indicate a chronic intestinal disorder. “Fructose malabsorption is a normal event,” say lead researchers Jacqueline Barrett and Peter Gibson. “Many have considered a positive breath hydrogen test (which indicates fructose malabsorption) in a healthy person a 'false positive' result. This is not the case.”
Symptoms of functional gastrointestinal disorders have been attributed to poorly absorbed short-chain carbohydrates. “While we knew a lot about lactose malabsorption, previous studies had not clearly defined whether fructose malabsorption is abnormal or normal and [its] relevance ... in a variety of gut diseases,” Barrett explains.
Breath hydrogen tests were carried out after challenges with lactulose, fructose and lactose in 91 patients with Crohn's disease, 56 with ulcerative colitis, 201 with functional gastrointestinal disorders, 136 with celiac disease and 71 healthy volunteers.
“People with IBS and other functional gut disorders are no more likely to have fructose malabsorption than are healthy people,” Barrett reports. However, sugar malabsorption was more common in patients with Crohn's disease than in other patients or healthy individuals, a finding that Barrett believes supports the hypothesis that poorly absorbed short-chain carbohydrates are involved in the pathogenesis of this disorder.
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Richards, L. Carbohydrate malabsorption in chronic intestinal disorders. Nat Rev Gastroenterol Hepatol 6, 501 (2009). https://doi.org/10.1038/nrgastro.2009.132