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Information, Symptoms, Treatments and Resources


Irritable Bowel Syndrome (IBS) Overview


A Common Bowel Condition

By Katherine Solem 

What Is Irritable Bowel Syndrome?

One in five Americans has symptoms of irritable bowel syndrome (IBS), a common disorder of the large bowel (also called colon, or large intestine). The large bowel gathers and transports indigestible waste (stool) from the small bowel (intestine), and absorbs most of the water from the waste before transporting it to the rectum. Researchers don't know exactly what causes IBS, but it occurs more often in women and symptoms usually appear before age 35. Though IBS symptoms cause pain and discomfort, no permanent damage is done to the large bowel and it won't lead to more serious diseases or conditions, like cancer.

Symptoms of IBS

IBS symptoms vary from person to person, but some of the more common ones include:

  • Abdominal pain, especially pain that:
    • Comes and goes
    • Is worse after eating
    • Is relieved by going to the bathroom
  • Abdominal or intestinal cramping
  • Excess gas
  • Bloating
  • Diarrhea
  • Constipation
  • Hard or loose stool
  • Loss of appetite
  • Changes in bowel movements, including bowel frequency and consistency

Causes of IBS

Researchers have not discovered a conclusive reason why people develop IBS, but there are a number of possible causes for this condition.

  • Large bowel muscle irregularities: The large bowel is lined with muscles that contract and relax to push waste through roughly five feet of tubing. In IBS patients, these contractions may be stronger than normal, in which case waste is transported too quickly, causing gas and diarrhea. On the other hand, if these contractions are weaker than normal, stool will be too dry and constipation may ensue.
  • Previous intestinal infection: Sometimes IBS develops after a person has already had an intestinal infection. This is called postinfectious IBS.
  • Intestine is sensitive: Stretching and movement through the intestine causes more discomfort than it should.
  • Excess serotonin in the GI tract: A large percentage of the body's serotonin is located in the GI tract. Serotonin helps regulate GI functioning, and people with IBS may have more serotonin in the GI tract because there aren't enough serotonin receptors. Excess serotonin may cause problems with bowel movement and pain in the intestines.

IBS Triggers

Some stimuli may worsen IBS symptoms.

  • Certain foods.Food triggers for IBS vary from person to person. Some common food triggers include:
    • Spicy foods
    • Fried foods
    • Milk products
    • Chocolate
    • Alcohol
    • Carbonated beverages
    • Caffeine
    • Wheat, rye and barley (they contain gluten)
  • Stress. Stress can intensify IBS symptoms. Stress activates nerves of the autonomic nervous system, which may increase the intensity of intestinal muscle contractions.
  • Other digestive illnesses may aggravate IBS symptoms as well.

Risk Factors for IBS

You are more likely to have or develop IBS if you are:

  • Female: Females are twice as likely to have IBS.
  • Young: Most people develop IBS as an adolescent or young adult. Fifty percent of cases begin before age 35.
  • Have a family history of IBS: People with a parent or relative with IBS have an increased risk of developing the condition.

Diagnosing IBS

IBS can usually be diagnosed by a doctor after a physical exam has been performed and medical history has been reviewed. Other tests, like blood tests, stool sample tests, lactose intolerance tests, CT scans, a colonoscopy (a visual examination of the colon with small camera called a colonoscope), or a flexible sigmoidoscopy (an examination of the sigmoid colon with a small camera) may be performed in order to rule out other potential causes of IBS symptoms.

Similar Conditions

The following conditions may have symptoms similar to IBS. Check with your doctor if you are experiencing symptoms of IBS so that your doctor can help determine the cause.

  • Celiac disease: People with celiac disease cannot tolerate gluten, a protein found in wheat, rye and barley. The symptoms are similar to IBS, but problems arise in the small bowel, where nutrients are absorbed.
  • Lactose intolerance: The small intestine cannot tolerate lactose, an enzyme found in milk products.
  • Colon cancer: Symptoms of colon cancer can include diarrhea, abdominal pain and narrow stool.
  • Ulcerative colitis: This inflammatory bowel disease is very similar to IBS. This disease is more likely to affect the lining of the rectum, but can be present in the large bowel.
  • Crohn's disease: Characterized by constant inflammation of the GI tract, this disease can occur anywhere from the mouth to the rectum.

Managing IBS

Managing IBS with Diet:
Try altering your diet by:

  • Eating less gas-inducing foods (such as broccoli, cabbage and beans), eating smaller meals and drinking plenty of water throughout the day.
  • Eating foods high in fiber may help regulate your bowels. Just don't eat too much fiber or it may over-stimulate your bowels and cause bloating; slowly increase your daily fiber intake to allow your body to adjust.
  • Taking probiotics or eating yogurt that contains probiotics. Probiotics are a type of healthy bacteria that normally live in your intestines and help digest food. One theory is that people with IBS do not have enough "good" bacteria and that adding probiotics can help relieve IBS symptoms. Some studies have found that probiotics may relieve abdominal pain and bloating, but more research is needed. Probiotics are naturally found in yogurt, and can also be taken as dietary supplements.

A registered dietitian can help implement an effective plan. If diet changes don't work, there are medications that can help.


Medications for IBS:
Two medications have been approved specifically for IBS:

  • Alosetron (Lotronex): slows the movement of waste through the lower bowel by relaxing the colon. Some serious complications are linked to this drug, so it should only be used if other treatments do not work.
  • Lubiprostone (Amitiza): increases fluid secretion in the small intestine to help move stool through the colon. This drug is prescribed to women with constipation from IBS. Its effectiveness has not been proven for men.

Other over-the-counter and prescription medications that may help include:

  • Fiber supplements (Metamucil): may help control constipation, but too much fiber may actually make IBS symptoms worse; find the amount that works best for you.
  • Laxatives: relieve constipation
  • Antidepressants: Depression can affect the neurons that control your intestines
  • Anti-diarrhea medications


Katherine Solem is a health writer and editor living in San Francisco.

See also:


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