The American Gastroenterological Association (AGA) released a Clinical Practice Update, published in Gastroenterology, about the role of diet in irritable bowel syndrome (IBS).
IBS is a disorder of the gut-brain interaction, characterized by altered gastrointestinal (GI) motility, visceral sensation, intestinal permeability, and mucosal immune activation. Current therapeutic strategies are effective among fewer than half of patients, and the therapeutic gain is only 7% to 15% over placebo.
Most patients (>80%) with IBS associate their symptoms of abdominal pain, bloating, and altered bowel habits with eating food. The most common culprit foods are carbohydrates, which are short-chain sugars that are both poorly digested and poorly absorbed.
Mounting evidence suggests that dietary modifications, such as the low-fermentable oligo-, di-, and monosaccharides and polyols (FODMAP) diet (LFD), may be an effective intervention for IBS.
Before deciding whether to recommend a dietary intervention to patients, clinicians should gauge how often their patient consumes FODMAP foods. The committee recommends that dietary modifications should be recommended to patients who have insight into meal-related GI symptoms and are motivated to make necessary changes.
Dietary interventions should be attempted for a predetermined length of time. If the diet does not produce a clinical response in the allotted time, it should be abandoned.
Currently, an LFD is the most evidence-based dietary intervention. The LFD has 3 stages: up to 4 to 6 weeks of restriction, 6 to 10 weeks of reintroducing FODMAP foods, and dietary personalization based on reaction to reintroduced foods.
In addition, soluble fiber has been associated with improved global symptoms of IBS, especially among those with constipation-dominant disease. In general, the United States (US) Food and Drug Administration (FDA) recommends for people to consume 25 to 35 g of total fiber daily.
For patients who do not consume many culprit foods, are food insecure, at risk for malnutrition, have an eating disorder, or have an uncontrolled psychiatric disorder, the committee recommends for these patients to be screened for an eating disorder and for malnutrition.
To screen for an eating disorder, the committee suggests practical, open-ended questions to ask patients who are at risk, such as:
- Have you changed your diet recently? Why?
- What feelings do you have when you look at food?
- Are you or is anyone else concerned with your weight loss?
- How often and how long do you exercise?
- How often do you eat to the point of feeling sick?
- Do you use laxatives even when not constipated?
The committee recommends screening for malnutrition using the Malnutrition Screening Tool. This is a validated instrument comprising 2 questions about appetite and weight loss. Patients with high scores should be referred to a GI registered dietitian nutritionist (RDN) for a comprehensive nutritional assessment.
When referring patients to an RDN, clinicians should provide the patient with a symptom chart and to advise them to keep a food diary for at least 3 days before consultation with the RDN.
An RDN evaluation is a 4-step process comprising nutrition assessment, diagnosis, intervention, and monitoring. Medical nutrition therapy from an RDN is associated with improved outcomes in weight management and metabolic health. The committee recommends for patients with IBS who are attempting a dietary intervention to have a consultation with an RDN.
Clinicians should be aware that although observational studies have found that patients with IBS report symptom improvement after switching to a gluten-free diet, randomized clinical trials have found mixed results. Altogether, there is a lack of strong evidence to support efficacy of a gluten-free diet for the treatment of IBS symptomology. Similarly, there remains limited evidence of biomarkers that predict patient response to dietary interventions. Additional research of dietary interventions in IBS is needed.
The statement authors concluded, “Diet has assumed an increasingly prominent role in our understanding and treatment of IBS. Identifying the appropriate patients for dietary treatments, particularly elimination diets, is an important first step. Partnering with [an] RDN to provide integrated, multidisciplinary care is essential for the successful management of IBS symptoms.”
Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.
Chey WD, Hashash JG, Manning L, Chang L. AGA clinical practice update on the role of diet in irritable bowel syndrome: expert review. Gastroenterology. Published online March 22, 2022. doi:10.1053/j.gastro.2021.12.248