Objectives: This study estimates the prevalence of perceived food intolerance and its consequences in subjects with irritable bowel syndrome (IBS), evaluates the utility of common tests for food intolerance, studies the relation between perceived food intolerance and other disorders, and discusses the etiology.

Design: Cross-sectional study.

Setting: National health survey.

Subjects: A selection of the population (n=11,078) in Oppland county, Norway, was invited to a health screening, and a sample of subjects with IBS were included in the study.

Interventions: A medical history of food intolerance, musculoskeletal pain, mood disorders and abdominal complaints was taken, and tests were performed for food allergy and malabsorption. A dietician evaluated the dietary habits of the subjects.

Results: Out of 4,622 subjects with adequately filled-in questionnaires, 84 were included in the study, 59 (70%) had symptoms related to intake of food, 62% limited or excluded food items from the diet and 12% had an inadequate diet. The mean numbers of food items related to symptoms and the number of foods limited or excluded from the diet were 4.8 and 2.5, respectively. There were no associations between the tests for food allergy and malabsorption and perceived food intolerance. Perceived food intolerance was unrelated to musculoskeletal pain and mood disorders.

Conclusions: Perceived food intolerance is a common problem with significant nutritional consequences in a population with IBS. The uselessness of current antibody tests and tests for malabsorption and the lack of correlation to psychiatric co-morbidity make the etiology obscure.