Irritable Bowel Syndrome
On this page:
- What causes IBS?
- What are the symptoms of IBS?
- How is IBS diagnosed?
- What is the treatment for IBS?
- How does stress affect IBS?
- Can changes in diet help IBS?
- Is IBS linked to other diseases?
- Hope Through Research
- Points to Remember
Irritable bowel syndrome (IBS) is a disorder that interferes with
the normal functions of the large intestine (colon). It is
characterized by a group of symptoms--crampy abdominal pain,
bloating, constipation, and diarrhea.
One in five Americans has IBS, making it one of the most common
disorders diagnosed by doctors. It occurs more often in women than
in men, and it usually begins around age 20.
IBS causes a great deal of discomfort and distress, but it does
not permanently harm the intestines and does not lead to intestinal
bleeding or to any serious disease such as cancer. Most people can
control their symptoms with diet, stress management, and medications
prescribed by their physician. But for some people, IBS can be
disabling. They may be unable to work, go to social events, or
travel even short distances.
What causes IBS?
What causes one person to have IBS and not another? No one knows.
Symptoms cannot be traced to a single organic cause. Research
suggests that people with IBS seem to have a colon that is more
sensitive and reactive than usual to a variety of things, including
certain foods and stress. Some evidence indicates that the immune
system, which fights infection, is also involved. IBS symptoms
result from the following:
- The normal motility of the colon may not work properly. It can
be spasmodic or can even stop temporarily. Spasms are sudden
strong muscle contractions that come and go.
- The lining of the colon (epithelium), which is affected by the
immune and nervous systems, regulates the passage of fluids in
and out of the colon. In IBS, the epithelium appears to work
properly. However, fast movement of the colon's contents can
overcome the absorptive capacity of the colon. The result is too
much fluid in the stool. In other patients, colonic movement is
too slow, too much fluid is absorbed, and constipation develops.
- The colon responds strongly to stimuli (for example, foods or
stress) that would not bother most people.
In people with IBS, stress and emotions can strongly affect the
colon. It has many nerves that connect it to the brain. Like the
heart and the lungs, the colon is partly controlled by the autonomic
nervous system, which has been proven to respond to stress. For
example, when you are frightened, your heart beats faster, your
blood pressure may go up, or you may gasp. The colon responds to
stress also. It may contract too much or too little. It may absorb
too much water or too little.
Research has shown that very mild or hidden (occult) celiac
disease is present in a smaller group of people with symptoms that
mimic IBS. People with celiac disease cannot digest gluten, which is
present in wheat, rye, barley, and possibly oats. Foods containing
gluten are toxic to these people, and their immune system responds
by damaging the small intestine. A blood test can determine whether
celiac disease is present. (For information about celiac disease,
see the Celiac
Disease fact sheet from the National Institute of Diabetes
and Digestive and Kidney Diseases (NIDDK).)
The following have been associated with a worsening of IBS
- large meals
- bloating from gas in the colon
- wheat, rye, barley, chocolate, milk products, or alcohol
- drinks with caffeine, such as coffee, tea, or colas
- stress, conflict, or emotional upsets
Researchers have also found that women with IBS may have more
symptoms during their menstrual periods, suggesting that
reproductive hormones can exacerbate IBS problems.
What does the colon do?
The colon, which is about 5 feet long, connects the small
intestine with the rectum and anus. The major function of the colon
is to absorb water, nutrients, and salts from the partially digested
food that enters from the small intestine. Two pints of liquid
matter enter the colon from the small intestine each day. Stool
volume is a third of a pint. The difference in volume represents
what the colon absorbs each day.
Colon motility (the contraction of the colon muscles and the
movement of its contents) is controlled by nerves and hormones and
by electrical activity in the colon muscle. Contractions move the
contents slowly back and forth but mainly toward the rectum. During
this passage, water and nutrients are absorbed into the body. What
remains is stool. A few times each day, strong muscle contractions
move down the colon, pushing the stool ahead of them. Some of these
strong contractions result in a bowel movement. The muscles of the
pelvis and anal sphincters have to relax at the right time to allow
the stool to be expelled. If the muscles of the colon, sphincters,
and pelvis do not contract in a coordinated way, the contents do not
move smoothly, resulting in abdominal pain, cramps, constipation or
diarrhea, and a sense of incomplete stool movement.
What are the symptoms of IBS?
Abdominal pain or discomfort in association with bowel
dysfunction is the main symptom. Symptoms may vary from person to
person. Some people have constipation (hard, difficult-to-pass, or
infrequent bowel movements); others have diarrhea (frequent loose
stools, often with an urgent need to move the bowels); and still
others experience alternating constipation and diarrhea. Some people
experience bloating, which is gas building up in the intestines and
causing the feeling of pressure inside the abdomen.
IBS affects the motility or movement of stool and gas through the
colon and how fluids are absorbed. When stool remains in the colon
for a long time, too much water is absorbed from it. Then it becomes
hard and difficult to pass. Or spasms push the stool through the
colon too fast for the fluid to be absorbed, resulting in diarrhea.
In addition, with spasms, gas may get trapped in one area or stool
may collect in one place, temporarily unable to move forward.
Sometimes people with IBS have a crampy urge to move their bowels
but cannot do so or pass mucus with their bowel movements.
Bleeding, fever, weight loss, and persistent severe pain are not
symptoms of IBS and may indicate other problems such as inflammation
or rarely cancer.
How is IBS diagnosed?
If you think you have IBS, seeing your doctor is the first step.
IBS is generally diagnosed on the basis of a complete medical
history that includes a careful description of symptoms and a
No particular test is specific for IBS. However, diagnostic tests
may be performed to rule out other diseases. These tests may include
stool or blood tests, x rays, or endoscopy (viewing the colon
through a flexible tube inserted through the anus). If these tests
are all negative, the doctor may diagnose IBS based on your
symptoms: that is, how often you have had abdominal pain or
discomfort during the past year, when the pain starts and stops in
relation to bowel function, and how your bowel frequency and stool
consistency are altered.
Criteria for IBS Diagnosis
- Abdominal pain or discomfort for at least 12 weeks out of the
previous 12 months. These 12 weeks do not have to be
- The abdominal pain or discomfort has two of the following
- It is relieved by having a bowel movement.
- When it starts, there is a change in how often you have a
- When it starts, there is a change in the form of the stool
or the way it looks.
What is the treatment for IBS?
No cure has been found for IBS, but many options are available to
treat the symptoms. Your doctor will give you the best treatments
available for your particular symptoms and encourage you to manage
stress and make changes to your diet.
Medications are an important part of relieving symptoms. Your
doctor may suggest fiber supplements or occasional laxatives for
constipation, as well as medicines to decrease diarrhea,
tranquilizers to calm you, or drugs that control colon muscle spasms
to reduce abdominal pain. Antidepressants may also relieve some
symptoms. Medications available to treat IBS specifically are the
- Alosetron hydrochloride (Lotronex) has been re-approved by the
U.S. Food and Drug Administration (FDA) for women with severe
IBS who have not responded to conventional therapy and whose
primary symptom is diarrhea. However, even in these patients, it
should be used with caution because it can have serious side
effects, such as severe constipation or decreased blood flow to
- Tegaserod maleate (Zelnorm) has been approved by the FDA for
the short-term treatment (usually 4 weeks) of women with IBS
whose primary symptom is constipation.
With any medication, even over-the-counter medications such as
laxatives and fiber supplements, it is important to follow your
doctor's instructions. Laxatives can be habit forming if they are
not used carefully or are used too frequently.
It is also important to note that medications affect people
differently and that no one medication or combination of medications
will work for everyone with IBS. You need to work with your doctor
to find the best combination of medicine, diet, counseling, and
support to control your symptoms.
How does stress affect IBS?
Stress--feeling mentally or emotionally tense, troubled, angry,
or overwhelmed--stimulates colon spasms in people with IBS. The
colon has a vast supply of nerves that connect it to the brain.
These nerves control the normal rhythmic contractions of the colon
and cause abdominal discomfort at stressful times. People often
experience cramps or "butterflies" when they are nervous
or upset. But with IBS, the colon can be overly responsive to even
slight conflict or stress. Stress also makes the mind more tuned to
the sensations that arise in the colon and makes the stressed person
perceive these sensations as unpleasant.
Some evidence suggests that IBS is affected by the immune system,
which fights infection in the body. The immune system is also
affected by stress. For all these reasons, stress management is an
important part of treatment for IBS. Stress management comprises
- stress reduction (relaxation) training and relaxation
therapies, such as meditation
- counseling and support
- regular exercise such as walking or yoga
- changes to the stressful situations in your life
- adequate sleep
Can changes in diet help IBS?
For many people, careful eating reduces IBS symptoms. Before
changing your diet, keep a journal noting the foods that seem to
cause distress. Then discuss your findings with your doctor. You may
also want to consult a registered dietitian, who can help you make
changes to your diet. For instance, if dairy products cause your
symptoms to flare up, you can try eating less of those foods. You
might be able to tolerate yogurt better than other dairy products
because it contains bacteria that supply the enzyme needed to digest
lactose, the sugar found in milk products. Dairy products are an
important source of calcium and other nutrients. If you need to
avoid dairy products, be sure to get adequate nutrients in the foods
you substitute or take supplements.
In many cases, dietary fiber may lessen IBS symptoms,
particularly constipation. However, it may not help pain or
diarrhea. Whole grain breads and cereals, fruits, and vegetables are
good sources of fiber. High-fiber diets keep the colon mildly
distended, which may help prevent spasms. Some forms of fiber also
keep water in the stool, thereby preventing hard stools that are
difficult to pass. Doctors usually recommend a diet with enough
fiber to produce soft, painless bowel movements. High-fiber diets
may cause gas and bloating, but these symptoms often go away within
a few weeks as your body adjusts. (For information about diets for
people with celiac disease, there is a fact sheet from NIDDK.)
Drinking six to eight glasses of plain water a day is important,
especially if you have diarrhea. But drinking carbonated beverages,
such as sodas, may result in gas and cause discomfort. Chewing gum
and eating too quickly can lead to swallowing air, which again leads
Also, large meals can cause cramping and diarrhea, so eating
smaller meals more often or eating smaller portions should help IBS
symptoms. It may also help if your meals are low in fat and high in
carbohydrates, such as pasta, rice, whole-grain breads and cereals
(unless you have celiac disease), fruits, and vegetables.
Is IBS linked to other diseases?
IBS itself is not a disease. As its name indicates, it is a
syndrome - a combination of signs and symptoms. But IBS
has not been shown to lead to any serious, organic diseases,
including cancer. Through the years, IBS has been called by many
names, among them colitis, mucous colitis, spastic colon, or spastic
bowel. However, no link has been established between IBS and
inflammatory bowel diseases such as Crohn's disease or ulcerative
Hope Through Research
The NIDDK conducts and supports research into many kinds of
digestive disorders, including IBS. Researchers are studying
gastrointestinal motility and sensitivity to find possible
treatments for IBS. These studies include the structure and
contraction of gastrointestinal muscles as well as the mechanics of
fluid movement through the intestines. Understanding the influence
of the nerves, hormones, and inflammation in IBS may lead to new
treatments to better control the symptoms.
Points to Remember
- IBS is a disorder that interferes with the normal functions of
the colon. The symptoms are crampy abdominal pain, bloating,
constipation, and diarrhea.
- IBS is a common disorder found more often in women than in men
and usually begins around age 20.
- People with IBS have colons that are more sensitive and react
to things that might not bother other people, such as stress,
large meals, gas, medicines, certain foods, caffeine, or
- IBS is diagnosed by its symptoms and by the absence of other
- Most people can control their symptoms by taking medicines
(laxatives, antidiarrhea medicines, tranquilizers, or
antidepressants), reducing stress, and changing their diet.
- IBS does not harm the intestines and does not lead to cancer.
It is not related to Crohn's disease or ulcerative colitis.
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