What You Need to Know About Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome (IBS) is classified as a functional bowel disorder that causes abdominal pain. That means there is no visible damage to the tissues, but there is a disorder of functioning.

Woman with abdominal cramps laying on a couch
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A 2019 study conducted of 5,931 people in the United Kingdom, Canada, and the United States found that almost 30% of adults have a functional bowel disorder, with approximately 5% of people having IBS. The severity of IBS symptoms varies, and may be described as anything from a mild annoyance to debilitating.

The symptoms of IBS can include:

  • Abdominal pain
  • Bloating
  • Constipation
  • Diarrhea
  • Gas (belching or flatulence)


IBS is often diagnosed only after other possible digestive disorders and diseases that cause pain or diarrhea have been ruled out. To do that, people with IBS are often tested for food insensitivities (like lactose or gluten), bacterial or parasitic infections, or other inflammatory digestive diseases like ulcerative colitis or Crohn's disease.

The American College of Gastroenterology (ACG) would like to change that. According to their 2021 guidelines for treating irritable bowel syndrome, a "positive diagnostic strategy" rather than a strategy of exclusion would improve both patient satisfaction and cost-effectiveness, allowing patients to get appropriate treatment sooner and get on with their lives more quickly.

The Rome IV Diagnostic Criteria

According to the ACG, it's best to use the simplified international diagnostic criteria for IBS called Rome IV ("Rome 4"). To meet the Rome IV criteria for IBS, you must have recurrent abdominal pain at least one day a week, associated with two or more of the following:

  1. The pain is related to defecation.
  2. The pain is associated with a change in the frequency of stool.
  3. The pain is associated with a change in the form (appearance) of the stool.

To be diagnosed with IBS, you must have these symptoms for the last three months consistently, and they must have started at least six months before your diagnosis.

If you don't meet these diagnostic criteria, it is possible that you have a different functional bowel disorder (FBD) or a medical issue unrelated to functional gastrointestinal disorders (FGDs) entirely.

Other functional bowel disorders addressed by the Rome IV criteria include:

IBS Subtypes

The ACG also stresses that people understand their subtype of IBS. That's because most treatments for IBS are geared to a specific subtype. If treatment is given for the wrong subtype, it may make symptoms worse. They note that over half of patients change their predominant subtype over the course of a year, so it's important to assess IBS subtype routinely.

There are four main subtypes of IBS, and ACG recommends typing them based on predominant stool type on the days of abnormal bowel movements, as identified on the Bristol Stool Form Scale (BSFS).

  • IBS-D is where the predominant stool type is diarrhea. Over 25% of stools are mushy or liquid (6 or 7 on the BSFS) and less that 25% are hard/constipated (1 or 2 on the BSFS).
  • IBS-C is where the predominant stool type is constipation. Over 25% of stools are hard/constipated (1 or 2 on the BSFS) and less than 25% are mushy or liquid (6 or 7 on the BSFS).
  • IBS-M is where the predominant stool type is mixed. Both constipation and diarrhea feature heavily. Over 25% of stools are BSFS 1 or 2, and over 25% of stools are BSFS 6 or 7.
  • IBS-U is where the pattern is unknown. There isn't a significant pattern to the abnormal stools, so the type can't be determined.

Blood in the stool, fever, weight loss, vomiting bile, and persistent pain are not symptoms of IBS and may be the result of some other serious problem.

Dietary Triggers

Many people with IBS experience symptoms shortly after, or even during, meals. Fatty foods, alcohol, caffeine, and gas-producing foods (such as broccoli or beans) have regularly been things that are pinpointed as worsening IBS symptoms.

However, it can be difficult for some people to track down which particular foods can trigger their IBS. Making the issue even more complicated, not every person with IBS will have symptoms after eating the same foods, and each person's response can change over time.

Keeping a food diary and a symptom diary is a good way to trace foods that lead to IBS symptoms. Starting with a bland diet of "safe foods" and gradually adding new foods can also help in the search for specific food triggers. The food diary can then be discussed with a doctor or dietitian for help in treatment.

Some people with IBS also find a low-FODMAP diet to be helpful, because the fermentable compounds abbreviated as FODMAPs can aggravate their symptoms. Because starting and following a low-FODMAP diet can be complicated, the ACG recommends working with a nutritionist for best results.

Common Trigger Foods in IBS

Foods that may trigger symptoms of IBS in some people include:

  • Alcohol
  • Artificial fat (Olestra)
  • Artificial sweeteners
  • Carbonated beverages
  • Coconut milk
  • Coffee (even decaffeinated)
  • Dairy (especially if high in lactose, like milk and ice cream)
  • Egg yolks
  • Fried foods
  • Oils
  • Poultry skin and dark meat
  • Red meat
  • Sauces and gravies
  • Shortening
  • Solid chocolate


Treatment for IBS can include changes to diet, lifestyle, mind/body therapies, and medications. Often, a combination of modalities will help to provide the most relief. There is still much that is not understood about IBS, so it may take some experimentation with different therapies to achieve good results.


Medications for IBS are prescribed depending upon whether you have more constipation (IBS-C) or more diarrhea (IBS-D).

Medications for IBS-C are usually geared toward increasing fluid in the colon and also increasing movement of the intestines (peristalsis). Laxatives can be habit-forming and should be used under the close supervision of a physician. The ACG generally recommends against laxatives containing polyethylene glycol (PEG), as they have not been shown to improve the symptoms of IBS.

Medications for IBS-D are geared to slowing down the action of the colon, including stopping spasms that can worsen diarrhea. Stopping the spasms in the bowel can reduce pain and the feeling of urgency. An antibiotic called rifaximin also appears to help some people, possibly by adjusting problems with their gut microbiome.

Anti-diarrhea medications may also be used to slow down frequent, watery stools but they are not recommended for regular use.


Fiber supplements help with both constipation and diarrhea. Fiber bulks up the stool in cases of diarrhea, and also makes stool easier to pass in the case of constipation.

The ACG guidelines recommend soluble fiber that will not ferment in the colon and therefore cause gas. Soluble, low-fermenting fiber is found in psyllium (also known as "ispaghula husk").

Eating enough fiber in the diet may also help some people with IBS to reduce their symptoms. Often there is some trial and error in finding the right types of fiber and how much to eat each day. Because eating fiber can also lead to gas, gradually increase the fiber in your diet so your body can adjust to it.

Lifestyle Changes

Smaller portions at mealtimes may help to prevent bloating and cramping. Instead of three large meals every day, eating five smaller meals may help in reducing symptoms.

Eating a healthy diet, drinking plenty of water, and getting daily exercise are also helpful in reducing IBS symptoms. These changes can contribute to an overall healthy lifestyle.

Stress Reduction

Relaxation training, such as mindfulness-based approaches can help to reduce symptoms. It is important to note that stress is not the cause of IBS, but stress can cause the symptoms of IBS to worsen.

A Word From Verywell

The good news about IBS is that it is increasingly being seen under a new light. People with this common disorder can discuss symptoms with healthcare professionals without being told "it's all in your head." Treatment for IBS is better now than ever, but more research and awareness are needed to raise the quality of life for those who have IBS.

Frequently Asked Questions

  • What foods make IBS worse?

    Every person with irritable bowel syndrome is affected differently by foods. There are some common culprits, but not everyone with IBS is affected by these foods. 

    Fatty foods, alcohol, caffeine, dairy, beans, and certain vegetables can irritate some people with IBS. In addition, some people find fermentable compounds in FODMAPs can cause an IBS flare-up. 

  • Why does lettuce give me diarrhea?

    Some people with IBS find eating lettuce can cause a flare-up in symptoms. But getting diarrhea after eating a salad does not mean you have IBS.

    Lettuce has fiber, which promotes softer stools. More likely, lettuce is also a common source of contamination from food-borne illnesses, such as bacteria, parasites, and viruses from mishandled produce.

  • What are symptoms of IBS?

    Abdominal pain, bloating, constipation, diarrhea, and gas are the symptoms of IBS. To meet the diagnostic criteria, you must experience recurrent abdominal pain at least one day a week for three months straight, and symptoms need to have started at least six months before diagnosis.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1.  Palsson OS, Whitehead W, Törnblom H, Sperber AD, Simren M. Prevalence of Rome IV functional bowel disorders among adults in the United States, Canada, and the United Kingdom. Gastroenterology. 2020;158(5):1262-1273.e3. doi: 10.1053/j.gastro.2019.12.021

  2. National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of irritable bowel syndrome.

  3. Wald A. Patient education: Irritable bowel syndrome (Beyond the Basics).

  4. Lacy BE, Pimentel M, Brenner DM, et al. ACG clinical guideline: Management of irritable bowel syndrome. Am J Gastroenterol. 2021 Jan 1;116(1):17-44. doi:10.14309/ajg.0000000000001036

  5. Farzaei MH, Bahramsoltani R, Abdollahi M, Rahimi R. The role of visceral hypersensitivityin irritable bowel syndrome: Pharmacological targets and novel treatments. J Neurogastroenterol Motil. 2016;22(4):558-574. doi:10.5056/jnm16001

Additional Reading

By Amber J. Tresca
Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.