Symptomatic fructose malabsorption in irritable bowel syndrome: A prospective study

Introduction: Fructose can trigger or worsen symptoms in irritable bowel syndrome (IBS) patients. The aim of this study was to determine the prevalence of symptomatic fructose malabsorption in IBS patients and to test whether the patient's characteristics can help to detect a fructose malabsorption.

Materials and methods: Ninety Rome III IBS patients (predominant diarrhoea (IBS-D): 31%, predominant constipation (IBS-C): 18%, mixed type (IBS-M): 51%) were included prospectively. After exclusion of a small intestinal bacterial overgrowth by a glucose breath test, fructose malabsorption was assessed by a five-hour breath test, with symptom monitoring, after a 25 g load of fructose. An increase of more than 20 ppm of hydrogen (H2) or methane (CH4) levels in the exhaled air led to the diagnosis of malabsorption.

Results: Fructose test was abnormal in 20/90 patients among whom only 35% were intolerant, with a simultaneous rise of H2/CH4 levels and the onset of abdominal discomfort or diarrhoea. IBS characteristics were not predictive even if young (p = 0.031) and male IBS patients (p = 0.029) were at higher risk of malabsorption. At variance, 18 additional patients experienced intestinal symptoms during the test despite normal fructose absorption.

Discussion: After a 25 g fructose load, symptomatic fructose malabsorption and intolerance without malabsorption were detected in 22% and 28% of IBS patients respectively.