Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder characterized by abdominal pain or discomfort associated with altered bowel habit (diarrhea, constipation or both) symptoms in the absence of structural, major inflammatory or biochemical abnormalities. These symptoms can significantly impair quality of life, reduce work productivity and increase utilization of health care resources.
The Rome IV diagnostic criteria for IBS include recurrent abdominal pain, on average, at least one day a week in the past three months, associated with two or more additional criteria:
- Discomfort related to defecation
- A change in frequency of stool
- A change in form (appearance) of stool
Criteria should be fulfilled for the last three months with symptom onset of at least six months before diagnosis.
Three distinct subtypes of IBS have been described:
- IBS with constipation (IBS-C) has a 28 percent prevalence in the U.S.
- IBS with diarrhea (IBS-D) has a 26 percent prevalence in the U.S.
- IBS with a mixed bowel pattern (IBS-M) has a 44 percent prevalence in the U.S.
Given that the gastrointestinal symptoms associated with IBS have both physical and psychosocial impacts, it's important to tailor treatment to the individual patient and factor in the severity of disease. Therapeutic options for IBS focus on alleviating symptoms. This article addresses the role of diet, exercise and sleep modifications in the treatment of IBS.
Individuals with diarrhea-predominant IBS experience an exaggerated gastro-colonic motor response to ingestion of food that causes postprandial pain and rectal urgency. Although these symptoms are invariably related to meals, individuals with IBS do not commonly have true food allergies. However, sensitivities are frequently reported. In an article published in Gastroenterology Clinics of North America in 2016, authors note that up to 90 percent of patients with IBS restrict their diets to prevent or improve their symptoms; formal blinded food challenge studies have shown that only 11 to 27 percent of these patients pinpoint which agent stimulates symptoms.
Some researchers hypothesize that disturbances in tryptophan metabolism may contribute to gastrointestinal symptoms and mood disturbances. Histamine, via histamine receptor 1, may potentiate visceral hypersensitivity.
Some researchers theorize that immune-mediated responses to food components may play a role in IBS. Using confocal endomicroscopy, they have detected subtle structural changes in the duodenal mucosa in the small intestines after exposure to specific food antigens. The clinical significance, if any, of this finding is unclear. In addition to an exaggerated gastro-colonic motor response, some patients with IBS also have increased colonic perception of distention after a meal.
Emerging evidence supports some form of dietary management for IBS symptoms and generally focuses on modifying intake of the following food constituents:
Caffeine and fat
Because caffeine intake stimulates gut motility, reducing caffeine intake is often recommended. A low-fat diet is often recommended, as fatty foods may cause painful contractions in patients with IBS.
Fiber and fiber-based supplements accelerate colon transit, increase stool bulk and facilitate passage, resulting in an increase in stool frequency. This increase can benefit patients with chronic constipation and IBS-C. Often used as a first line therapy, fiber should be gradually increased to a total daily intake of 20 to 30 grams. A subgroup analysis reported that soluble fiber (psyllium and ispaghula husk) but not insoluble fiber (wheat bran) was associated with improved IBS symptoms.
Several studies have demonstrated that gluten may contribute to symptoms in IBS, even in patients without celiac disease (non-celiac gluten sensitivity), and that at least a subset of IBS patients might benefit from a diet containing no gluten, or a reduced amount. It's important to rule out celiac disease before testing a gluten-restricted diet.
In a four-week, randomized controlled trial patients with IBS-D and without celiac disease who were fed a diet containing gluten reported increased stool frequency and altered intestinal permeability (measured by urine lactulose-to-rhamnose ratio) and immune activation. Patients randomized to a gluten-free diet experienced less bowel movement frequency than patients consuming gluten, and this effect was amplified in patients with either of the celiac-associated genes HLA-DQ2 or HLA-DQ8.
In a randomized, double-blind, placebo-controlled re-challenge trial in 34 patients with IBS with a history of non-celiac gluten sensitivity (NCGS), 68 percent of patients receiving gluten versus 40 percent receiving a gluten-free diet had IBS symptoms that were not adequately controlled. NCGS is characterized by one or more IBS-type symptoms precipitated by ingestion of gluten-containing foods. Although not well-understood, NCGS may result from gluten's effect on mucosal integrity or cellular adherence, or when the amylase trypsin inhibitor enzymatic family present in wheat triggers the innate immune system stimulating the release of proinflammatory cytokines in cells. Diagnostic criteria or serologic testing are not currently available for NCGS.
It's also possible that fructans, nonabsorbable carbohydrate components of wheat, may cause IBS symptoms often attributed to gluten. Diets low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs) may be appropriate for patients with IBS. Wheat, onions, some fruits and vegetables, sorbitol, and some dairy products are some of the foods that contain FODMAPs.
In a 2017 review article published in Therapeutic Advances in Gastroenterology, authors note that recent clinical trials testing restricted diets low in FODMAPs have shown significant beneficial clinical effects on IBS. However, low-FODMAP diets are as effective as traditional dietary advice for IBS. Moreover, since a low-FODMAP diet is quite restrictive, long-term adherence may be difficult and may adversely influence the gut microbiome. Thus, patients attempting to reduce their FODMAP intake should consult with an experienced dietitian and gradually reintroduce FODMAP foods to identify and restrict only those foods needed to maintain symptom benefit.
Regular exercise has been shown to decrease IBS symptoms. Physically active individuals have more-frequent bowel movements and more-rapid colon transit than sedentary individuals. A randomized clinical trial showed a significant reduction in IBS symptoms in patients who performed 20 to 60 minutes of moderate to vigorous physical activity threes times a week for 12 weeks.
A growing body of research suggests that yoga might be a safe and beneficial adjunct treatment for people with IBS. A qualitative analysis of results from six randomized controlled trials involving 273 patients showed that patients performing yoga experienced significantly decreased bowel symptoms, IBS severity and anxiety, compared with conventional treatment. The patients who performed yoga also showed significant improvements in quality of life, global improvement and physical functioning, compared with no treatment.
"I tell my patients that irritable bowel syndrome is like having an irritable child in your belly," says Lucinda A. Harris, M.D., a gastroenterologist who cares for patients with IBS at Mayo Clinic's campus in Scottsdale, Arizona. "That child is going to behave much better if you establish a schedule of eating frequent small meals, getting enough sleep and doing regular exercise. Further treatments may be needed, but that good foundation is important."
For more information
Harris LA, et al. Irritable bowel syndrome and female patients. Gastroenterology Clinics of North America. 2016;45:179.
Lucak S, et al. Current and emergent pharmacologic treatments for irritable bowel syndrome with diarrhea: Evidence-based treatment in practice. Therapeutic Advances in Gastroenterology. 2017;10:253.