LACTOSE-MALABSORPTION AND IRRITABLE-BOWEL-SYNDROME - EFFECT OF A LONG-TERM LACTOSE-FREE DIET

Lactose malabsorption may induce abdominal symptoms indistinguishable from those of the irritable bowel syndrome (IBS), however the exact re lationship between the two conditions and the optimal differential dia gnostic workup are still to be defined, We prospectively studied the p revalence of lactose malabsorption (by means of a hydrogen breath test ) and the clinical effect of a long-term lactose-free diet in 230 cons ecutive patients with a suggested diagnosis of irritable bowel syndrom e, no organic disease of the GI tract, and no history of milk intolera nce, Lactose malabsorption was diagnosed in 157 patients (68.2%), In 4 8 (43.6%) of the 110 patients who complied with the diet symptoms subs ided, in 43 they were somewhat reduced and in 17 they remained unchang ed. Symptoms never fully subsided in lactose malabsorbers non-complian t with the diet or in normal lactose absorbers who adhered to a lactos e-free regimen, Partial improvement was observed in 20% of these subje cts. No relation was demonstrated between pre-trial symptoms and the o utcome of the diet, The occurrence of symptoms during the lactose brea th test strongly suggested a favorable response to diet, but did not h elp in predicting whether symptoms would subside or be reduced, Conver sely, their absence during the test was not associated with an accepta ble negative predictive value, The high prevalence of lactose malabsor ption in the patients under study suggests that in Italy IBS and lacto se malabsorption are frequently associated, A test for diagnosing lact ose malabsorption should always be included in the diagnostic workup f or IBS and a long-term lactose-free regimen recommended if the test is positive.