The effect of a lactose-restricted diet in patients with a positive lactose tolerance test, earlier diagnosed as irritable bowel syndrome: a 5-year follow-up study

Design and methods Prospectively, the effect of a lactose-restricted diet w as evaluated among irritable bowel syndrome patients with lactose malabsorp tion. Lactose malabsorption was defined by a positive hydrogen breath test and a positive blood-glucose test. An analysis of symptoms was completed be fore, during, 6 weeks after and 5 years after starting the diet. In additio n, the number of visits made by the patients to the outpatient clinic was s cored during 6 years. Results In 17 out of 70 irritable bowel syndrome patients (24.3%), lactose malabsorption was detected. There was no difference in the symptom score be tween patients with a positive lactose tolerance test and patients with a n egative lactose tolerance test. After 6 weeks of the lactose-restricted die t, symptoms were markedly improved in lactose malabsorption-positive patien ts (P < 0.001). After 5 years, one patient was lost for follow-up, and 14 o ut of the remaining 16 lactose malabsorption patients (87.5%) still had no complaints during the lactose-restricted diet. Two patients chose not to fo llow the diet continuously and accepted the discomfort caused by lactose in take. Only two out of 16 patients (12.5%) no longer experienced any benefit from lactose restriction. In the 5 years before their diagnosis of lactose malabsorption, these 16 patients visited the outpatient clinic a total of 192 times (mean 2.4 visits per year per person; range 1-7 visits). In the 5 years after diagnosis, they visited the outpatient clinic a total of 45 ti mes (mean 0.6 visits per year per person; range 0-6 visits; P < 0.0001). Conclusions In a large majority of irritable bowel syndrome patients with l actose malabsorption, which was previously clinically unrecognized, a lacto se-restricted diet improved symptoms markedly both in the short term and th e long term. Furthermore, visits by all patients to the outpatient clinic w ere reduced by 75%. We conclude that diet therapy is extremely cost- and ti me-saving. Therefore, it is strongly recommended that lactose malabsorption , which is easily treatable, is excluded before diagnosing irritable bowel syndrome. Eur J Gastroenterol Hepatol 13:941-944 (C) 2001 Lippincott Willia ms & Wilkins.