FPIN's Help Desk Answers

Effect of Dietary Changes on IBS Symptoms


Am Fam Physician. 2018 Sep 1;98(5):online.

Clinical Question

What dietary changes are effective in relieving the symptoms of irritable bowel syndrome (IBS)?

Evidence-Based Answer

A diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FOD-MAPs) decreases IBS symptoms and improves quality of life compared with usual diet. (Strength of Recommendation [SOR]: A, based on a meta-analysis of randomized controlled trials [RCTs].) Soluble fiber supplementation improves IBS symptoms such as abdominal pain. (SOR: B, based on a low-quality meta-analysis of RCTs.) Patients with IBS whose symptoms improve with a gluten-free diet—even without evidence of gluten-sensitive enteropathy—are better off continuing to avoid gluten. (SOR: B, based on an RCT.)

Evidence Summary

A 2016 meta-analysis of 22 RCTs and nonrandomized clinical interventions (N = 934) compared the effects on IBS symptoms of a low-FODMAP diet vs. usual diet.1 FODMAPs contain short-chain carbohydrates, which can lead to excess gas production in the small intestine. Patients ranged from seven to 74 years of age and met Rome III or National Institute for Health and Care Excellence criteria for IBS. Outcome measures included scores on the IBS Severity Scoring System and IBS Quality of Life scale. The IBS Severity Scoring System assesses abdominal pain severity and frequency, abdominal bloating, bowel habit dissatisfaction, and interference with quality of life on a 0- to 500-point scale; a decrease of 50 points indicates clinical improvement. The IBS Quality of Life scale measures 41 IBS-specific factors; a decrease of 9 points indicates clinical improvement. Follow-up was conducted over three to six weeks in the RCTs and over two days to 35 months in the nonrandomized interventions. Patients who followed a low-FODMAP diet had a greater chance of achieving at least a 50-point improvement on the IBS Severity Scoring System (six RCTs; N = 354; odds ratio [OR] = 0.44; 95% confidence interval [CI], 0.25 to 0.76; and 16 nonrandomized trials; N = 580;

Author disclosure: No relevant financial affiliations.

Address correspondence to Michael Erlandson, MD, at michael.erlandson@healthonecares.com. Reprints are not available from the authors.


1. Marsh A, Eslick EM, Eslick GD. Does a diet low in FODMAPs reduce symptoms associated with functional gastrointestinal disorders? A comprehensive systematic review and meta-analysis. Eur J Nutr. 2016;55(3):897–906.

2. Moayyedi P, Quigley EM, Lacy BE, et al. The effect of fiber supplementation on irritable bowel syndrome: a systematic review and meta-analysis. Am J Gastroenterol. 2014;109(9):1367–1374.

3. Biesiekierski JR, Newnham ED, Irving PM, et al. Gluten causes gastrointestinal symptoms in subjects without celiac disease: a double-blind randomized placebo-controlled trial. Am J Gastroenterol. 2011;106(3):508–514.

Help Desk Answers provides answers to questions submitted by practicing family physicians to the Family Physicians Inquiries Network (FPIN). Members of the network select questions based on their relevance to family medicine. Answers are drawn from an approved set of evidence-based resources and undergo peer review. The strength of recommendations and the level of evidence for individual studies are rated using criteria developed by the Evidence-Based Medicine Working Group (http://www.cebm.net).

The complete database of evidence-based questions and answers is copyrighted by FPIN. If interested in submitting questions or writing answers for this series, go to http://www.fpin.org or e-mail: questions@fpin.org.

This series is coordinated by John E. Delzell Jr., MD, MSPH, Associate Medical Editor.

A collection of FPIN's Help Desk Answers published in AFP is available at https://www.aafp.org/afp/hda.



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