May 2021 Issue

New Guidance for IBS
By Carrie Dennett, MPH, RDN, CD
Today’s Dietitian
Vol. 23, No. 5, P. 32

The American College of Gastroenterology publishes its first-ever guidelines for diagnosis and dietary management of irritable bowel syndrome.

Management of irritable bowel syndrome (IBS) has come a long way from advice to reduce stress and eat more fiber. Today, there are dietary, pharmacological, and psychological strategies available to manage symptoms of this chronic disorder of gut-brain interaction (previously called functional gastrointestinal disorders).

IBS affects up to 1 in 10 Americans, depending on the assessment source. While IBS doesn’t damage the bowels, its symptoms can significantly impair quality of life. Given its prevalence and impact, it’s perhaps surprising that the American College of Gastroenterology (ACG) has never released guidelines on how to diagnose and treat this condition until the end of last year. The new ACG guidelines assessed 25 clinically important questions based on rigorous GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) methodology, covering screening exams, diagnosis, dietary management, and medical and psychological treatment options.1

What Is IBS?
As mentioned, IBS is what’s now termed as a disorder of gut-brain interaction, with symptoms stemming from a complex interplay between the gut microbiota, altered mucosal immune function, visceral hypersensitivity (altered gut signaling) and dysregulation of gut signaling, and motor function by the central nervous system. While this class of disorders has been present throughout human history, they’ve been studied only over the last several decades. And because there’s no structural basis for IBS as there is for bowel disorders, such as Crohn’s disease, colitis, and celiac disease, it falls more within the realm of the growing field of neurogastroenterology and can be understood through an interdisciplinary biopsychosocial model, which looks at the interconnection between biology, psychology, and socioenvironmental factors.2

Rome IV criteria classify IBS as involving symptoms of abdominal pain at least once per week on average over the past three months, associated with a change in stool frequency, stool form, and/or relief or worsening of abdominal pain related to defecation. These symptoms should have started at least six months previously, with bloating often present, but isn’t a mandatory symptom for diagnosis. The Rome criteria are developed by a panel of international experts in the field of disorders of gut-brain interactions.2

People with IBS may experience diarrhea (IBS-D), constipation (IBS-C), or both (IBS-M, for “mixed”). Symptoms can so strongly impair quality of life that one study reported that IBS patients would be willing to give up an average of 15.1 years of life (about 25% of their remaining life expectancy) for an instant cure to their condition, and 13.5% of patients would accept at least a 1 in 1,000 chance of sudden death from taking a hypothetical medication if that medication could cure their IBS symptoms.3 Another study found that IBS patients would accept a median 1% risk of sudden death for a 99% chance of cure from a hypothetical medication.4

Recommendations for Diagnosis
Traditionally, an IBS diagnosis tended to be a “diagnosis of exclusion.” In other words, extensive testing often was done to exclude organic diseases such as inflammatory bowel disease, celiac disease, or colon cancer. The ACG guidelines call for doctors to make a positive diagnosis based on symptom history and minimal diagnostics provided there are no “alarm features,” symptoms that may indicate the presence of organic disease. These symptoms include blood in the stool, anemia, unintentional weight loss, fever, nighttime bowel movements, a family history of other bowel diseases, and symptoms that are severe or getting progressively worse. Onset of what appear to be IBS symptoms after the age of 50 also is a red flag.

Patsy Catsos, MS, RDN, LD, author of The IBS Elimination Diet and Cookbook, based in Portland, Maine, says if a patient has alarm symptoms or the clinician isn’t confident the patient has IBS, then they should exclude organic disease through the diagnostic process, but when that’s not a factor, she sees real benefits to the positive diagnosis model. “Rather than saying, ‘You might have IBS,’ or ‘You probably have IBS,’ health care providers can practice confident messaging about IBS that will provide patients with both insight and hope,” she says. “A positive diagnosis can reduce illness and symptom anxiety significantly and pave the way for more effective efforts toward symptom management.”

Diana Reid, MPH, RDN, owner of The Global Dietitian, based in Luxembourg, also sees benefits to the positive diagnosis strategy. “Most IBS patients don’t get to this diagnostic stage until they’ve had symptoms for several years. They are uncomfortable, they don’t feel well, they are frustrated, and their quality of life is likely suffering. Having a proper diagnosis helps them begin to understand the next steps in terms of treatment, to advocate and research on their own behalf, and to find community and support from others.” Reid says IBS patients deserve a clear diagnosis—not an “I guess you might have IBS” discussion with a doctor—so there’s comfort and accuracy in the diagnosis. “Also, doctors and other care providers really need to stop saying, ‘You just have IBS’ or calling it a diagnosis of exclusion. There are indeed proper guidelines to diagnose it, and it’s a real illness. Many patients feel marginalized or told they just need to relax or reduce stress. This is unhelpful to say the very least.”

Boston-based dietitian and author Kate Scarlata, MPH, RDN, sees some pros and cons to this model. “Having a positive diagnosis can help the patient get right to work on existing treatments to mitigate symptoms and avoid the stress of trying to ‘figure out’ if something else is missing.” She says, overall, data show that doing extra testing in patients who present with IBS but don’t have alarm signs rarely yields evidence to support a diagnosis of something other than IBS. However, she says the positive diagnosis model may not work when general gastrointestinal specialists haven’t kept up with the latest data, which means they may miss an alternative diagnosis, such as sucrase isomaltase deficiency, a condition with symptoms that mimic IBS-D but that isn’t well known among gastroenterologists who work with adult patients.

Diagnostic Testing Guidelines
So when is additional testing warranted? The guidelines recommend against routine colonoscopy in patients younger than 45 without alarm features, against testing for food allergies and sensitivities unless there are reproducible symptoms suggesting a food allergy, and against routine stool testing for pathogens. However, the guidelines do recommend patients with suspected IBS-D but no alarm features have their levels of C-reactive protein and either fecal lactoferrin or fecal calprotectin tested to rule out inflammatory bowel disease. C-reactive protein is a measure of systemic inflammation, while fecal lactoferrin and fecal calprotectin are two fecal-derived markers of intestinal inflammation.

The guidelines also recommend blood testing to rule out celiac disease in people with symptoms of IBS-D, based on moderate evidence that patients presenting with these symptoms are more likely to test positive for celiac disease than the general population. “Before embarking on a low- FODMAP diet, patients should absolutely first be screened for celiac disease,” Scarlata says. “RDNs should always ask their patients if they’re consuming wheat, barley, and rye—and how often and what amounts.”

Catsos says she wouldn’t initiate a gluten-free diet or a gluten-free modified low-FODMAP (fermentable oligo-, di-, and monosaccharides and polyols) diet for a gastrointestinal patient who hasn’t had celiac disease ruled out. “In fact, I make a point of asking them to continue eating gluten until they can discuss the rule-out process with their provider.”

What happens when IBS patients already have been avoiding gluten, perhaps because they noticed their symptoms seem to be triggered by consumption of gluten-containing grains, but it’s unclear whether this is because they have celiac disease or because the oligosaccharides in these grains are triggering IBS symptoms?

Scarlata says if a patient has self-removed gluten from his or her diet, the clinician can recommend a genetic test for the celiac-related genes HLA-DQ2 and HLA-DQ8. “If the gene test is negative, this provides good evidence that celiac disease is not a risk factor in this patient,” she says. If the patient does test positive for one or both genes, it’s possible they have or can develop celiac disease. At this point, Scarlata says the patient has two choices. One is to reintroduce gluten via two slices of wheat bread per day for a month before receiving the celiac blood test and/or undergoing an endoscopy, as advised by their gastroenterologist. The other option is to follow a gluten-free diet for life, including being careful with gluten cross-contamination. She says following a so-called “gluten-lite” diet, in which a person reduces but doesn’t follow a rigid gluten-free diet, isn’t recommended, because if the patient does have celiac disease, allowing any gluten can be harmful.

Reid says asking patients to reintroduce gluten so they can be accurately tested for celiac disease is challenging, but it’s nothing new to dietitians who practice in the digestive space. “Sometimes it’s just a question of properly explaining to patients that if they have undiagnosed celiac disease and they’re still eating gluten here and there—because most patients I see are—they’re at risk of long-term and sometimes irreversible health concerns,” she says. “We know that even small amounts of gluten can have lasting effects. In my practice, we discuss a lot of the differences between an intolerance and an allergy or immune-mediated disorder, and the pathology and risks of each.”

Reid says she’s had some patients who refuse to eat wheat again for fear of triggering symptoms, even if they test positive for the celiac disease genes and would benefit from confirming whether they already have developed celiac disease. “We talk a lot about fears, symptoms, health risks, and how to manage these if it becomes a scenario where a patient really doesn’t want to reintroduce,” she says. “I also encourage patients to pursue stress reduction strategies, such as meditation, yoga, and/or gut-directed hypnotherapy to help deal with symptoms if they do need to reintroduce wheat and gluten.”

Dietary Management
The guidelines give a conditional recommendation for a limited trial of the low-FODMAP diet based on very low-quality evidence. This largely is due to a relative lack of placebo-controlled trials on the low-FODMAP diet and lack of high-quality long-term data, but the guidelines also highlight the perceived complexity of the diet, the potential for nutrient deficiencies if FODMAPs are restricted long-term, and the need for guidance to follow all three phases of the diet properly.

Catsos says the shortage of higher-quality studies is common among most types of diet trials due to expense and logistical concerns. “I don’t disagree that the FODMAP diet is complex and requires proper guidance. We certainly need to continue working toward more access to care and high-quality teaching materials, she says. “Well-planned low-FODMAP diets are entirely capable of meeting patients’ nutrient needs if the patient is willing to eat a wide variety of low-FODMAP foods.” She says in practice, the theoretical risks to nutrient intake on low-FODMAP diets are greatly overshadowed by individual patient decisions not to eat certain foods for one reason or another, and that patients who, for example, are vegan or follow a Paleo or dairy-free diet or don’t like vegetables are all at risk of not getting enough of certain nutrients. “Since patients with IBS have been restricting their diets long before FODMAPs ever came onto the scene, we often can help patients improve their diets using a FODMAP framework.”

Reid says she has mixed feelings about the dietary recommendations in the guidelines. “As a trained and experienced low-FODMAP dietitian, I know how powerful the diet can be in helping reduce even the most severe and/or long-standing IBS symptoms,” she says. “However, I also see many doctors just giving patients a handout of high-FODMAP foods—usually out of date—and telling patients to go follow the diet.” She says this usually results in three things: Symptoms aren’t properly reduced, the patient is incredibly stressed by the long list of restrictions—which can make symptoms worse due to the IBS gut-brain connection—and the patient never makes it to the reintroduction phase, which can adversely alter their gut bacteria and leave the patient exposed to nutrient deficiencies. “As with any kind of dietary treatment, personalization of the recommendation is key.”

Scarlata, who’s author of The Low-FODMAP Diet Step by Step, says the low-FODMAP diet can be life-changing from a symptom management point of view in the right patients, but she also agrees with the conditional recommendation. “I personally feel a trial of psyllium husk and/or diet instruction that focuses on balance to the plate, inclusion of mostly whole foods, and modification of high-fat foods, alcohol, sugar alcohols, and caffeine—along with a low-lactose diet, if the patient exhibits lactose intolerance—should be the first line therapy.” She says a trial of a low-FODMAP diet may be the next step if the patient doesn’t have any conditions that make it unwise, such as an active or recent eating disorder.

Reid says she agrees with the guidelines’ recommendation that IBS patients try the low-FODMAP diet only under the guidance of a properly trained dietitian but wishes the report also had stated that the diet may not be appropriate for certain populations—including children, individuals with eating disorders, and people with other dietary restrictions—in which other strategies should be tried first. “I think it’s incredibly important that screening for eating disorders should be a part of the diagnostic process and criteria for IBS, as it’s well understood that there’s a significant overlap between eating disorders and functional gastrointestinal disorders.”

Where dietary modification isn’t appropriate or doesn’t provide adequate symptom management, there also are medication options, which vary based on whether the patient has IBS-D or IBS-C.

Final Thoughts
“I thought overall this clinical guideline provided best practices for IBS at this time,” Scarlata says. “I do expect to see changes in diet recommendations from more broad to more personalized as this area is better explored.”

Reid says she’s glad to see an official guideline from the ACG. “Patients who suffer from long-term [gastrointestinal] issues often feel misunderstood or questioned about the reality or intensity of their symptoms. Having a more structured approach ensures proper, evidence-based diagnosis and treatment for these patients, offering peace of mind and improved quality of life.”

— Carrie Dennett, MPH, RDN, CD, is the nutrition columnist for The Seattle Times, owner of Nutrition by Carrie, and author of Healthy for Your Life: A Holistic Guide to Optimal Wellness.

1. Lacy BE, Pimentel M, Brenner DM, et al. ACG clinical guideline: management of irritable bowel syndrome. Am J Gastroenterol. 2021;116(1):17-44.

2. Drossman DA, Hasler WL. Rome IV-functional GI disorders: disorders of gut-brain interaction. Gastroenterology. 2016;150(6):1257-1261.

3. Drossman DA, Morris CB, Schneck S, et al. International survey of patients with IBS: symptom features and their severity, health status, treatments, and risk taking to achieve clinical benefit. J Clin Gastroenterol. 2009;43(6):541-550.

4. Lacy BE, Everhart KK, Weiser KT, et al. IBS patients' willingness to take risks with medications. Am J Gastroenterol. 2012;107(6):804-809.