Objective: The relationship between lactose intolerance and post-infectious irritable bowel syndrome (IBS) in adults is uncertain. Bowel symptoms may persist after bacterial gastroenteritis and as post-infectious IBS. Acquired lactose intolerance may follow viral enteric infections in children. We compared the frequency of lactose intolerance after bacterial gastroenteritis in adults with and without symptoms of IBS or functional diarrhoea at 3-6-months' follow-up.
Design: A prospective cohort study was conducted.
Methods: All subjects with bacterial gastroenteritis confirmed by stool culture from the microbiology laboratory and without prior IBS or functional diarrhoea were eligible to participate. IBS and functional diarrhoea were diagnosed via self-completed Rome II modular questionnaires. Lactose intolerance was determined from a rise in breath hydrogen and plasma glucose and symptoms.
Results: One hundred and twenty-eight subjects with bacterial gastroenteritis were followed prospectively, from which a smaller cohort of 42 subjects took part in this study. The cohort was comprised of 24/25 subjects who developed post-infectious IBS (n = 16) or functional diarrhoea (n = 8) (9 male, 15 female) and 18 random controls (8 male, 10 female) chosen from the group without IBS or functional diarrhoea. The mean age of the subjects was 44.4 years (range 25-76 years). In the group with functional diarrhoea or IBS, four subjects had failure of the plasma glucose to rise but none had abnormal glucose hydrogen breath tests. In the control subjects, one had a positive combined test and six had failure of plasma glucose to rise alone. No subject developed symptoms during the test.
Conclusions: Bacterial gastroenteritis did not cause persistent lactose intolerance in our study population. Lactose intolerance does not appear to be implicated in the aetiology of post-infectious bowel symptoms, including IBS. Advice to avoid dairy products in patients presenting with post-infectious IBS on the basis that they may have lactose intolerance appears unnecessary in patients from northern England.