A Controlled Trial of Gluten-Free Diet in Patients With Irritable Bowel Syndrome-Diarrhea: Effects on Bowel Frequency and Intestinal Function

Abstract

Background & Aims Patients with diarrhea-predominant irritable bowel syndrome (IBS-D) could benefit from a gluten-free diet (GFD). Methods We performed a randomized controlled 4-week trial of a gluten-containing diet (GCD) or GFD in 45 patients with IBS-D; genotype analysis was performed for HLA-DQ2 and HLA-DQ8. Twenty-two patients were placed on the GCD (11 HLA-DQ2/8–negative and 11 HLA-DQ2/8–positive) and 23 on the GFD (12 HLA-DQ2/8−negative and 11 HLA-DQ2/8–positive. We measured bowel function daily, small bowel (SB) and colonic transit, mucosal permeability (by lactulose and mannitol excretion), and cytokine production by peripheral blood mononuclear cells (PBMCs) following exposure to gluten and rice. We collected rectosigmoid biopsies from 28 patients, analyzed levels of mRNAs encoding tight junction proteins, and performed hematoxylin and eosin staining and immunohistochemical analyses. Analysis of covariance models was used to compare data from the GCD and GFD groups. Results Subjects on the GCD had more bowel movements/day (P=.04); the GCD had a greater effect on bowel movements/day of HLA-DQ2/8–positive than −negative patients (P=.019). The GCD was associated with higher SB permeability (based on 0–2 hr levels of mannitol and lactulose:mannitol ratio); SB permeability was greater in HLA-DQ2/8–positive than −negative patients (P=.018). No significant differences in colonic permeability were observed. Patients on the GCD had a small decrease in expression of ZO-1 in SB mucosa and significant decreases in expression of ZO-1, claudin-1, and occludin in rectosigmoid mucosa; the effects of the GCD on expression were significantly greater in HLA-DQ2/8–positive patients. GCD vs GFD had no significant effects on transit or histology. PBMCs produced higher levels of interleukin-10, granulocyte colony-stimulating factor, and transforming growth factor-a in response to gluten than rice (unrelated to HLA genotype). Conclusion Gluten alters bowel barrier functions in patients with IBS-D, particularly in HLA-DQ2/8–positive patients. These findings reveal a reversible mechanism for the disorder.