Do food elimination diets improve Irritable Bowel Syndrome?
A double blind trial based on IgG antibodies to food.
Atkinson W, Gurney R, Sheldon TA, Whorwell PJ, “Do food elimination diets improve irritable bowel syndrome? A double blind trial based on IgG antibodies to food”, Gastroenterology. 2003;124:A-29.
Introduction: Many patients with irritable bowel syndrome (IBS) feel that they have some form of dietary allergy or intolerance. IgE mediated food reactions (classic allergies) are probably rare in IBS but little attention has been paid to the potential role of IgG responses. This study aimed to assess the efficacy of an exclusion diet based on testing for the presence of IgG food antibodies in patients with IBS.
Methods: A double blind randomized controlled trial was undertaken in which 150 unselected out-patients with IBS (all subtypes) were randomized to receive either a diet excluding, for 3 months, all foods to which they had IgG antibodies (titre > 3:1) or a sham diet excluding the same number of foods but not those to which they were sensitive. Symptom severity, non-colonic symptoms, anxiety/depression and quality of life were recorded at 0 and 3 months, and the primary outcome measure was a change in symptom severity score. Global outcome was also recorded on a seven point scale with only ‘better’ and ‘excellent’ regarded as an improvement. Patients who withdrew before the end of the study were also assessed after 3 months. Analysis was by ‘intention to treat’ using a generalized linear model for severity and ordinal regression for global outcomes in SPSS.
Results: The true diet was significantly superior to the shame diet in reducing symptom severity scores (average reduction 34; 95% Cl: 17.3, 68.6; p = 0.049). However, response to the diet was significantly affected by dietary adherence and the number of foods to which the patient was sensitive. When these factors were accounted for in the analysis, the difference in symptom scores rose to 89 (95% Cl :41, 137; p< 0.001). It is of interest that adherence to the diet affected the response observed in patients on the true diet, but not those on the sham diet (p=0.038). The analysis also revealed a significant difference in favor of the true diet with respect to global symptomatology (p=0.007). All other outcome measures showed a trend towards benefit, but did not reach statistical significance.
Conclusion: A clinically significant improvement can be achieved in patients with IBS using a food elimination diet based on IgG food antibodies.
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