From the Journals

AGA Clinical Practice Update: Expert review of dietary options for IBS



The American Gastroenterological Association has published a clinical practice update on dietary interventions for patients with irritable bowel syndrome (IBS). The topics range from identification of suitable candidates for dietary interventions, to levels of evidence for specific diets, which are becoming increasingly recognized for their key role in managing patients with IBS, according to lead author William D. Chey, MD, of the University of Michigan, Ann Arbor, and colleagues.

“Most medical therapies for IBS improve global symptoms in fewer than one-half of patients, with a therapeutic gain of 7%-15% over placebo,” the researchers wrote in Gastroenterology. “Most patients with IBS associate their GI symptoms with eating food.”

Dr. William D. Chey of Ann Arbor, Michigan, University of Michigan

Dr. William D. Chey

According to Dr. Chey and colleagues, clinicians who are considering dietary modifications for treating IBS should first recognize the inherent challenges presented by this process and be aware that new diets won’t work for everyone.

“Specialty diets require planning and preparation, which may be impractical for some patients,” they wrote, noting that individuals with “decreased cognitive abilities and significant psychiatric disease” may be unable to follow diets or interpret their own responses to specific foods. Special diets may also be inappropriate for patients with financial constraints, and “should be avoided in patients with an eating disorder.”

Because of the challenges involved in dietary interventions, Dr. Chey and colleagues advised clinical support from a registered dietitian nutritionist or other resource.

Patients who are suitable candidates for intervention and willing to try a new diet should first provide information about their current eating habits. A food trial can then be personalized and implemented for a predetermined amount of time. If the patient does not respond, then the diet should be stopped and changed to a new diet or another intervention.

Dr. Chey and colleagues discussed three specific dietary interventions and their corresponding levels of evidence: soluble fiber; the low-fermentable oligo-, di-, and monosaccharides and polyols (FODMAP) diet; and a gluten-free diet.

“Soluble fiber is efficacious in treating global symptoms of IBS,” they wrote, citing 15 randomized controlled trials. Soluble fiber is most suitable for patients with constipation-predominant IBS, and different soluble fibers may yield different outcomes based on characteristics such as rate of fermentation and viscosity. In contrast, insoluble fiber is unlikely to help with IBS, and may worsen abdominal pain and bloating.

The low-FODMAP diet is “currently the most evidence-based diet intervention for IBS,” especially for patients with diarrhea-predominant IBS. Dr. Chey and colleagues offered a clear roadmap for employing the diet. First, patients should eat only low-FODMAP foods for 4-6 weeks. If symptoms don’t improve, the diet should be stopped. If symptoms do improve, foods containing a single FODMAP should be reintroduced one at a time, each in increasing quantities over 3 days, alongside documentation of symptom responses. Finally, the diet should be personalized based on these responses. The majority of patients (close to 80%) “can liberalize” a low-FODMAP diet based on their responses.

In contrast with the low-FODMAP diet, which has a relatively solid body of supporting evidence, efficacy data are still limited for treating IBS with a gluten-free diet. “Although observational studies found that most patients with IBS improve with a gluten-free diet, randomized controlled trials have yielded mixed results,” Dr. Chey and colleagues explained.

Their report cited a recent monograph on the topic that concluded that gluten-free eating offered no significant benefit over placebo (relative risk, 0.46; 95% confidence interval, 0.16-1.28). While some studies have documented positive results with a gluten-free diet, Dr. Chey and colleagues suggested that confounding variables such as the nocebo effect and the impact of other dietary factors have yet to be ruled out. “At present, it remains unclear whether a gluten-free diet is of benefit to patients with IBS.”

Dr. Chey and colleagues also explored IBS biomarkers. While some early data have shown that biomarkers may predict dietary responses, “there is insufficient evidence to support their routine use in clinical practice. ... Further efforts to identify and validate biomarkers that predict response to dietary interventions are needed to deliver ‘personalized nutrition.’ ”

The clinical practice update was commissioned and approved by the AGA CPU Committee and the AGA Governing Board. The researchers disclosed relationships with Biomerica, Salix, Mauna Kea Technologies, and others.

This article was updated May 19, 2022.

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