Irritable bowel syndrome. Role of lactase deficiency.

In adults with the irritable bowel syndrome who had no history of milk intolerance, the prevalence of lactase deficiency and the value of lactose restriction were determined. Eighty subjects with the irritable bowel syndrome who were white, non-Jewish, and of northern-western European background were screened for lactase deficiency by means of the hydrogen breath test. Lactase deficiency was found in 5 of the 80 subjects with the irritable bowel syndrome and in 6 of the 100 subjects without intestinal symptoms who were of comparable ethnic background. After exclusion of milk from the diet, three of the five subjects with lactase deficiency and the irritable bowel syndrome had partial to complete relief of symptoms for 3 weeks, and two of these had sustained relief for 1 year (one with complete and one with 75% improvement). Lactase deficiency was found to be a relatively uncommon cause of irritable bowel symptoms among non-Jewish whites who are of northern-western European background.