Everyone gets an upset stomach on occasion—from, say, overindulging in greasy burgers, fatty fries, pizza, or Alfredo-topped pasta. But an estimated 10 to 15 percent of adults in the U.S. suffer from chronic tummy troubles in the form of irritable bowel syndrome (IBS), a cluster of symptoms that can include cramping, bloating, gas, and diarrhea or constipation, often triggered by certain foods and stress. Only one-third to one-half of them have been diagnosed with IBS, however, according to the American College of Gastroenterology.
The most common disorder seen by gastroenterologists, IBS accounts for more than 3 million doctor visits a year in the U.S. It usually begins in early adulthood, with onset typically before age 50, and affects about twice as many women as men; symptoms may worsen during menstruation. IBS also strikes an estimated 6 to 14 percent of adolescents.
IBS can significantly affect work and quality of life. People with IBS who tend to get unpredictable and severe diarrhea may even fear venturing far from home if they won’t have quick and easy access to a bathroom. The good news—or at least news that may make it somewhat easier to bear—is that IBS is a “functional” disorder, meaning that despite how uncomfortable it is, there is no structural damage to the gastrointestinal tract (also called the gut), and it does not lead to colon cancer or any serious digestive disorders.
IBS is complex, however, and despite advances in knowledge, especially over the past decade, the research has often been inconsistent or is still preliminary, and many questions remain, all of which makes treatment a challenge. That said, here’s what we know about this disorder.
What causes IBS?
Largely considered a psychiatric illness some decades ago (“nervous colon”), IBS is today recognized as a very real bowel disorder related to altered functioning of the muscles and nerves in the gut that control bowel motility and pain sensations. That is, IBS sufferers not only have altered bowel function, they also perceive sensations in the intestines differently than do people without IBS, with heightened sensitivity to normal bowel contractions and intestinal gas.
Though the exact cause of IBS is still unknown, many factors may play a role, including the bacterial population in the gut (the microbiome), the gut’s immune system, interactions between the brain and the gut (the “brain-gut axis”), altered intestinal permeability, overgrowth of bacteria in the small intestine, changes in neurotransmitter levels, food sensitivities, hormone imbalances, genetics, and psychological issues.
In recent years, researchers have found that some cases of IBS may occur in the aftermath of an acute attack of bacterial or viral gastroenteritis (“post-infectious IBS”)—for example, from food poisoning. This is thought to lead to an immune reaction that predisposes the intestines to become hypersensitive.
Traumatic events early in life may also trigger this effect, particularly in women who have been physically or sexually abused. Thus, gut physiology, environmental factors, and psychosocial factors may all interact to produce IBS.
Many people with IBS also have reflux symptoms, fibromyalgia, myalgic encephalomyelitis (commonly known as chronic fatigue syndrome), depression, and anxiety, suggesting that there might be some shared biological mechanisms.
What are the symptoms of IBS?
IBS involves a variety of intestinal issues that typically come and go, with pain often relieved by defecating (though in some cases, pain may be worse after defecating). Along with abdominal pain, there is a change in bowel pattern: either IBS with diarrhea (if motility in the intestines is increased, called IBS-D) or with constipation (if motility is decreased, called IBS-C)—or alternating bouts of each (IBS-M, for “mixed”).
There may also be mucus in the stool and a feeling of incomplete evacuation after bowel movements. Then, everything may go back to normal, for no apparent reason, with symptoms returning at some later point.
What’s the difference between IBS and IBD?
These two intestinal conditions are sometimes confused because of the similarities in their names and initials, as well as in some symptoms—for example, abdominal cramps, diarrhea, and sometimes constipation. IBD (inflammatory bowel disease) is an autoimmune disease, and it includes ulcerative colitis and Crohn’s disease. While IBS is a functional disorder that has no structural changes, IBD is an organic disorder characterized by ulcerations in the intestines and other structural changes that can be seen on radiological imaging and endoscopic exams, including colonoscopy, plus biochemical changes that can be detected with specialized blood tests, all of which are normal in IBS.
When should you see a doctor?
Because the symptoms noted above are fairly nonspecific, IBS can be confused with other conditions such as lactose intolerance, celiac disease, and IBD, which can make diagnosis tricky. Thus, it’s important to see your primary health care provider for evaluation; you may also be referred to a gastroenterologist. Red flags that warrant further evaluation include abdominal pain or diarrhea that wakes you from sleep; symptoms that worsen or start after age 50; unexplained weight loss; rectal bleeding, bloody discharge, or black stools; unexplained iron-deficiency anemia; or a family history of IBD, celiac disease, or colon cancer.
How is IBS diagnosed?
For the most part, diagnosis is based on symptoms and made after excluding other conditions such as celiac disease and IBD, with clinical judgment on the part of the doctor playing a major role. Experts have defined criteria for making the diagnosis, which include the presence of abdominal pain at least once a week for the past three months, with onset at least six months prior. Stool, blood, and breath tests may sometimes be done, and possibly an upper endoscopy and a colonoscopy, to help with the differential diagnosis and treatment plan.
Researchers are looking for biomarkers that may accurately distinguish IBS from IBD. For example, a paper in the American Journal of Gastroenterology in 2012 found that IBS patients have different levels of specific proteins (granins) in feces that could be used as a biomarker. And a relatively new blood test (IBSDetex) detects two biomarkers that may be present in some people who developed IBS-D following an episode of acute gastroenteritis, though its accuracy and usefulness are not clear (the results can be positive for some people with celiac disease and for some people with normal gut functioning). In any case, such a test is not needed to diagnose post-infectious IBS—a good medical history goes a long way in doing that.
Mapping Out a Diet Plan for IBS
IBS sufferers frequently report that their symptoms worsen after meals and often get some relief by avoiding certain foods. But one specific diet has been meriting a lot of attention in recent years, called "low FODMAP."
How is IBS treated?
Depending on the symptoms and severity of the condition, management can include everything from dietary modifications (see inset, "Mapping Out a Diet Plan for IBS") to cognitive behavioral therapy and medications. Generally, a broad yet individualized approach is recommended. In some studies exercise has been shown to improve symptoms. Getting adequate sleep and reducing stress—for example, through mindfulness training or “gut-directed hypnotherapy”—may also help.
Many drugs can be used to manage (but not cure) IBS, based on which symptoms are most troubling. These include anti-diarrheals, laxatives, antispasmodics, antibiotics, and antidepressants (which, in addition to improving mood, may affect intestinal motility and pain perception).
Selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine, are antidepressants that can improve abdominal pain and bowel function in people with IBS-C; they are thought to increase food transit speed. For IBS-D, low-dose tricyclic antidepressants, such as nortriptyline, may reduce pain and diarrhea.
The antibiotic rifaximin (Xifaxan), approved by the FDA in 2015 specifically for IBS-D, has been found to be effective when there is bacterial overgrowth in the small intestine (which can be confirmed with a breath test) and when symptoms of bloating and increased flatulence are present. The drug eluxadoline (Viberzi) was also approved by the FDA in 2015 for IBS-D, with clinical research showing it reduces abdominal pain and improves stool consistency. Other drugs specifically target IBS-C, including linaclotide (Linzess) and lubiprostone (Amitiza).
There are safety concerns with some IBS drugs, however. For instance, as the FDA warns, eluxadoline may increase the risk of pancreatitis in people who have had their gallbladder removed. Another drug, alosetron, was withdrawn from the market in 2000, the same year it was approved, due to infrequent but serious intestinal side effects. It was brought back two years later with a black-box warning and restrictions in sales and should be used only for severe cases of IBS-D if other treatments don’t work.
Other promising drugs and treatments are on the horizon. For instance, probiotic supplements, on the whole, “improve global symptoms, bloating, and flatulence in IBS,” by modifying the gut microbiome, according to a 2014 monograph from the American College of Gastroenterology. There’s growing evidence that Bifidobacteria infantis bacteria, in particular, may help. But the studies are hard to evaluate overall because they’ve used different strains, formulas, and doses for varying durations, and no single type may work for everyone.
More research on probiotics for IBS is needed. Still, a trial of VSL#3 (which contains B. infantis and other strains and is sold as a medical food) is worth considering, or even just good-quality kefir (a yogurt drink that contains live probiotic organisms) or Activia brand yogurt.
As an IBS clinician and researcher said in a clinical roundtable monograph regarding potential probiotic therapy, “The concept of manipulating the microbiome is one of the most promising new ways in which to treat patients with IBS, but there is still much to learn.”
Peppermint (in enteric-coated capsules) also has some evidence to support its benefits. Among several mechanisms, it may activate a specific anti-pain process in the gut, thus countering pain-sensing nerve fibers, such as those activated by spicy foods.
Bottom line: IBS is a frustrating condition to deal with, but with support from doctors and nutritionists, it can usually be well managed with a combination of strategies, even if it may take some trial and error. Dietary and other lifestyle modifications are often the first line of treatment. If those don’t help enough, medication is a reasonable option.
Also see Flatulence: Causes and Treatments.
Published March 01, 2018