The Facts

Irritable bowel syndrome (IBS) is a common disorder of the intestine, causing abdominal pain with constipation, diarrhea, or alternating periods of both. IBS is also known as spastic colon or spastic bowel (terms that have fallen out of favour now) and functional bowel disorder. It's sometimes mistaken for colitis, an inflammatory bowel disease that is actually a more serious condition involving damage to the colon. IBS doesn't do any damage to the colon.

IBS affects about 20% of the population and is second only to the common cold as the most frequent cause of days lost to work and school. IBS symptoms can disappear for periods of time and then return.

Unlike inflammatory bowel disease (ulcerative colitis and Crohn's disease), IBS brings no extra risk of cancer of the colon. However, if symptoms of IBS begin in people over age 50, it's best to rule out polyps and colon cancer by having a direct inspection of the lower bowel done by a doctor.


The cause of IBS isn't known, but it's currently thought to be due to the large and small intestines over- or under-sensing factors that may lead to abnormal bowel function. For people with IBS, some situations may trigger pain and discomfort:

  • emotional stress
  • eating
  • excessive gas
  • female hormones (for women with IBS, symptoms often worsen during their periods)
  • certain medications and food (e.g., alcohol, chocolate, coffee, dairy products, fructose, carbohydrates)
  • after a bout of gastroenteritis
  • an overgrowth of bacteria in the small intestine

Symptoms and Complications

Symptoms of IBS include:

  • abdominal pain and cramps, which may come in "on-again, off-again" bouts or as a continuous dull ache
  • constipation or diarrhea, or alternating periods of both
  • urgent need to have a bowel movement
  • excessive gas
  • bloating
  • changes in bowel habits
  • mucus in the stool

Blood in the stool is never a symptom of IBS. People who have blood in their stool, constant pain, or who have a fever should see a doctor. For other possible causes of these symptoms, refer to our disease articles on Crohn's disease, ulcerative colitis, and hemorrhoids.

Making the Diagnosis

A doctor will get a medical history and perform a physical exam, looking for "alarm" symptoms like fever, bleeding, or drastic weight loss that could be due to something more serious.

X-rays or lower gastrointestinal endoscopy (using a tube with a tiny camera on the end) may be used to look inside the colon, especially for older individuals. Sometimes, abdominal ultrasounds or X-rays of the intestines are done.

Treatment and Prevention

People with IBS can usually manage symptoms by making adjustments to their lifestyle. Eating a healthy diet can lessen the symptoms. Some people find that following the diet recommended by Canada's Food Guide to be helpful. Dietary fibre (such as whole-grain breads and cereals, beans, fruits, and vegetables) prevents stools from drying out too much and helps to keep things moving regularly in the colon. Switching to a high-fibre diet might cause bloating and gas at first, but this usually goes away in a few weeks and can be reduced by making a gradual change to the amount of fibre consumed. It's also important to drink plenty of fluids, particularly water, to prevent or reduce constipation. Other people find that avoiding certain food triggers can lessen their symptoms. Eating smaller, more frequent meals can also help reduce cramping and diarrhea.

Since stress can bring on symptoms of IBS, stress management is an important way to deal with this condition. Exercise and some kind of relaxation training (such as meditation) are often recommended. Your doctor might also suggest talking with a counsellor to learn how to cope better. If you experience other symptoms such as anxiety, talk to your doctor on how to manage your condition.

Medication for IBS is aimed at treating symptoms. Medications are available to slow down the movement of food through the digestive system and to control diarrhea. Laxatives are sometimes helpful for problem constipation, but people should not depend on them for regular bowel movements. Antidiarrhea medications (e.g., loperamide*) may be helpful for people who have mostly diarrhea as a symptom. Many other medications are available and your doctor can discuss them with you.

Probiotics are bacteria that normally live in your intestines and found in certain foods, so they are considered "good" bacteria. Some studies suggest that IBS may be due to an imbalance or disruption of the normal "good" bacteria that's present in the intestines. Probiotics may help the symptoms experienced by people with IBS by restoring this balance. However, further research into the use of probiotics in IBS needs to be done.

