THE CLINICAL RELEVANCE OF LACTOSE-MALABSORPTION IN IRRITABLE-BOWEL-SYNDROME

Objective: The prevalence of lactose malabsorption (LM) in the Caucasi an population of northern Europe is estimated to be low. Irritable bow er syndrome (IBS) is a very common diagnosis, and its symptoms are nea rly identical to those of LM. Therefore we investigated the prevalence of LM among IBS patients in comparison with healthy volunteers. Desig n: A double-blind clinical trial compared with healthy controls. Setti ng: One out-patient gastroenterology clinic in the Netherlands. Patien ts: 70 Caucasian IBS patients and 35 healthy volunteers (staff members ).Methods: All 105 underwent hydrogen (H-2) breath and blood glucose t ests, after an oral intake of 50 grams of lactose. The IBS patients we re treated with a lactose-restricted diet for 6 weeks. They completed a lactose intake score before, and a symptom score scored by six separ ate criteria, before, during and after treatment. Results: In 17 out o f 70 (24.3%) IBS patients LM was detected, in comparison with 2 out of 35 (5.7%) controls (P <0.009). There was no difference in the pre-ent ry mean lactose intake and symptom score between the LM positive and n egative IBS patients. The mean symptom score of the LM positive group showed a marked decrease after 6 weeks of dietary therapy (P <0.001). Conclusion: A substantial number of IBS patients showed a clinically u nrecognized lactose malabsorption, which could not be discriminated by symptoms and dietary history, and which can be treated with a lactose -restricted diet. Therefore LM has to be excluded before the diagnosis IBS is made.