Clinical Question

Does a gluten-free diet improve gastrointestinal symptoms in patients with irritable bowel syndrome (IBS)?

Evidence-Based Answer

The evidence is conflicting on whether gluten-free diets improve symptoms of IBS. Gluten-free diets may improve symptoms such as abdominal pain, stool consistency, and tiredness, and they can be recommended to patients with IBS. (Strength of Recommendation: B, based on inconsistent, small, randomized controlled trials [RCTs].)

Evidence Summary

A 2011 RCT included 34 patients 29 to 59 years of age who had IBS and no celiac disease and whose symptoms were controlled on a gluten-free diet.¹ They were randomized to remain on a gluten-free placebo diet or to switch to a gluten-containing diet. Patients recorded overall symptoms, abdominal pain, bloating, satisfaction with stool consistency, tiredness, wind, and nausea using a 0- to 100-mm visual analog scale at baseline and weekly for six weeks. Patients on the gluten-containing diet had statistically significant increases in mean scores at week 1, including overall symptoms (+28 vs. +9.2 for placebo; P = .047), abdominal pain (+28 vs. +5; P = .016), bloating (+26 vs. +5.8; P = .031), satisfaction with stool consistency (+24 vs. +2.5; P = .024), and tiredness (+25 vs. −5; P = .001). At six weeks, scores for abdominal pain (+40 vs. +18.3; P = .02), stool consistency (+30 vs. +16; P = .03), and tiredness (+34 vs. +8; P = .01) increased significantly from baseline in the gluten group. Significantly more patients on the gluten diet answered “no” to the question “Over the last week, were your symptoms adequately controlled?” (68% vs. 40%; P = .001).

A 2013 double-blind crossover RCT examined 37 patients 24 to 61 years of age with nonceliac gluten sensitivity and IBS whose self-reported symptoms improved with a gluten-free diet.² Patients were started on a two-week diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs), which has been proven to improve IBS symptoms. They were then randomized to high-gluten (16 g per day), low-gluten (2 g per day plus 14 g whey protein per day), and control (16 g whey protein per day) diets for one week. All patients participated in each diet arm with a two-week run-in diet of reduced FODMAPs before each one-week trial. At the end of each week, patients graded overall symptoms, abdominal pain, bloating, satisfaction with stool consistency, tiredness, and wind using a 0- to 100-mm visual analog scale. Compared with baseline, no group had the predefined clinically significant decrease of 20 mm or more for overall symptoms at seven days. A secondary three-day trial was repeated in similar fashion, and no statistically or clinically significant changes were noted between diet arms.