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Background and Objectives: Irritable bowel syndrome is a functional gastrointestinal disorder. Despite heavy economic and psychological burdens and severe decreases in quality of life of the patients, no certain cure is available for this common disease. Glutamine can decrease intestinal permeability and possibly improve intestinal barrier function and intestinal-friendly microbiota. Therefore, the aim of this study was to assess effects of glutamine supplementation against iso whey protein on clinical symptoms and quality of life of the patients with irritable bowel syndrome.
 Materials & Methods: This study was a double-blind, randomized clinical trial; in which, 42 patients aged 18–70 years of the two sexes were participated for six weeks. Patients were randomized to receive glutamine (5 g, three times a day) or iso whey for six weeks. Scores of the irritable bowel syndrome symptom severity and quality of life scores were calculated at the beginning and end of the study.
Results: Total severity score of the irritable bowel syndrome (p = 0.015), dissatisfaction with bowel habit (p = 0.001) and abdominal pain frequency (p = 0.028) significantly decreased in the glutamine group, compared to the iso whey group. Moreover, the total score of the irritable bowel syndrome symptom severity, abdominal pain frequency and  dissatisfaction with bowel habits respectively decreased by 180, 32 and 38 points, compared to the glutamine group at the beginning of the intervention.
Conclusion: Based on the findings, glutamine supplementation can be suggested as an adjunct therapy with a low FODMAP diet (oligosaccharides, disaccharides, monosaccharides and fermentable polyols) to further relieve symptoms of the patients with irritable bowel syndrome.