Irritable Bowel Syndrome

Author, Frank W. Jackson MD
Updated 2014


Irritable bowel syndrome (IBS) is known by a variety of other terms: spastic colon, spastic colitis, mucous colitis and nervous or functional bowel. Usually, it is a disorder of the large intestine (colon), although other parts of the intestinal tract even up to the stomach can be affected.

When IBS occurs, the colon does not contract normally. Instead, it seems to contract in a disorganized, at times violent, manner. The contractions may be terribly exaggerated and sustained, lasting for prolonged periods of time. One area of the colon may contract with no regard to another. At other times, there may be little bowel activity at all. These abnormal contractions result in changing bowel patterns with constipation being common.

The colon, the last five feet of the intestine, serves a number of important functions in the body. First, it dehydrates and stores the stool so that, normally, a well-formed soft stool occurs. Second, it quietly propels the stool from the right side over to the rectum, storing it there until it can be evacuated. This movement occurs by rhythmic contractions of the colon. A third very important function is to provide and produce a large number of health benefits if fed properly with prebiotic plant fibers. The best way to nourish these bacteria is with a prebiotic fiber supplement.

What Are the Symptoms?

Weight ControlMost IBS symptoms – abdominal pain, diarrhea, constipation, and bloating – are due to abnormal patterns of bowel contraction.  Abdominal discomfort or pain often moves around the abdomen rather than staying in one area. These disorganized, exaggerated and painful contractions lead to certain problems. The pattern of bowel movements is often altered. Diarrhea may occur, especially after meals, as the entire colon contracts and moves liquid stool quickly into the rectum. Or, localized areas of the colon may remain contracted for a prolonged time. When this occurs in the section of colon just above the rectum, the stool may be retained for a prolonged period (constipation) and be squeezed into small pellets. Excessive water is removed from the stool which becomes hard.

Also, colon gas may accumulate behind these localized contractions, causing the bowel to swell. So bloating and abdominal distress may occur.

Some patients see gobs of mucous in the stool and become concerned. Mucous is a normal secretion of the bowel, although most of the time it cannot be seen. IBS patients sometimes produce large amounts of mucous, but this is not abnormal nor a problem.

IBS is Not a Disease

Although the symptoms of IBS may be severe, the disorder itself is not a serious one. There is no actual disease present in the colon. In fact, an operation performed on the abdomen would reveal a perfectly normal appearing bowel.

Rather, it is a problem of abnormal function. The condition usually begins in young people, often below 40. It is not uncommon in the teens. The symptoms may wax and wane, be particularly severe at some times and absent at others. Over the years, the symptoms tend to become less intense.

IBS is very common and is present in perhaps half the patients that see a specialist in gastroenterology. It tends to run in families. The disorder does not lead to cancer. Prolonged contractions of the colon, however, may lead to diverticulosis, a disorder in which balloon-like pockets push out from the bowel wall because of excessive, prolonged contractions.


While our knowledge is still incomplete about the function and malfunction of the large bowel, some facts are well-known. Certain foods, such as coffee, alcohol, spices, some raw fruits and vegetables, and, in some people, even milk can cause the gut to malfunction. In these instances, avoidance of these foods is the simplest treatment.

The colon contains a very large number of bacteria types. This is normal and healthy. Very surprisingly, in 2007 it was found that IBS patients had a significantly different makeup of bacteria within the colon. It is likely that a key part of IBS treatment is changing this bacterial makeup by the use of prebiotics

Infections, illnesses and even changes in the weather somehow can be associated with a flare-up in symptoms. So can the premenstrual cycle in the female.

By far, the most common factor associated with symptoms of IBS is the interaction between the brain and the gut. The bowel has a rich supply of nerves that are in communication with the brain. Virtually everyone has had, at one time or another, some alteration in bowel function when under intense stress, such as before an important athletic event, school examination, or a family conflict. However, people with IBS seem to have an overly sensitive bowel, and perhaps an overabundance of nerve impulses flowing to the gut, so that the ordinary stresses and strains of living somehow result in colon malfunction.

These exaggerated contractions can be demonstrated experimentally by placing pressure-sensing devices in the colon. Even at rest, with no obvious stress, the pressures tend to be higher than normal. With the routine interactions of daily living, these pressures tend to rise dramatically. When an emotionally charged situation is discussed, they can reach extreme levels not attained in people without IBS. These symptoms are due to real physiologic changes in the gut – a gut that tends to be inherently overly sensitive, and one that overreacts to the stresses and strains of ordinary living.

Diagnosing Irritable Bowel Syndrome

The diagnosis of IBS often can be suspected just by a review of the patient’s medical history. In the end, however, it is a diagnosis of exclusion; that is, other conditions of the bowel need to be ruled out
before a firm diagnosis of IBS can be made. This process of elimination occurs when the lower gut appears normal but nevertheless produces uncomfortable symptoms that require medical attention.

Irritable Bowel Syndrome Diagnostic Criteria

In general, a person who suffers from IBS notices chronic pain and discomfort over an extended period of time. These symptoms may occur intermittently or over several consecutive weeks. During this period, changes in the stool – including quality and consistency – occur. The changes may include more frequent loose stools or constipation. Bloating and straining is common, as is feeling unable to empty the bowels. If these symptoms are accompanied by weight loss, abdominal pain that isn’t relieved by passing stool, fever or bleeding, then additional testing may be required.

A number of diseases of the gut, such as inflammation, cancer, and infection, can mimic some or all of the IBS symptoms. Certain medical tests are helpful in making this diagnosis, including blood, urine and stool exams, x-rays of the intestinal tract and a lighted tube exam of the lower intestine. This exam is called endoscopy, either sigmoidoscopy or colonoscopy. Sigmoidoscopy reviews the lower colon, while colonoscopy examines the entire length of the colon. Additional tests may be required, depending on the specific circumstances in each case. Checking for lactose intolerance, order a CT scan of the lower internal organs, and blood tests also rule out other lower gut health issues. If the proper medical history is obtained and if other diseases are ruled out, a firm diagnosis of IBS can then usually be made.

Treating IBS

Eating a fiber-rich diet helps the lower gut produce the bacteria and hormones that improve overall health. Prebiotic fiber, in particular, has been proven to fertilize the beneficial bacteria that strengthen the bowel walls, improve mineral absorption and regularity, positively affect appetite control and hormone production, and more. If IBS appears to be a possibility, discuss with your physician how prebiotics and other fibers can aid in the treatment of IBS.


The treatment of IBS is directed to both the psyche and the gut. One key element is diet. For a complete review of the most current thoughts on diet in IBS patients, go to Irritable Bowel Syndrome Dietary Therapy.

Current medical thinking about diet has changed a great deal in recent years. There is good evidence to suggest that, where tolerated, a high roughage and bran diet is helpful. To review the many benefits of a high fiber diet, go to the High Fiber Diet page. This diet can result in larger, softer stools which seem to reduce the pressures generated within the colon. In particular, you should select vegetables, fruits and whole grains that are high in insoluble fiber as these fibers do not promote gas. Go to Fiber Content of Foods for information.

Irritable BowelPrebiotics are a more recently discovered form of soluble plant fibers. These specially formulated soluble fibers stimulate the growth of good bacteria in the colon producing certain well-defined health benefits. Therefore a prebiotic fiber supplement is indicated as part of the diet. Initially, excessive colon gas may occur. The best thing to do is try small amounts and see what the response and symptoms are.

As many people have already discovered, the simple act of eating may, at times, activate the colon. This action is a normal reflex, although in IBS patients it can be exaggerated. In these instances, it is sometimes helpful to eat smaller, more frequent meals to reduce this reflex.

There are certain medications that help the colon by relaxing the muscles in the wall of the colon, thereby reducing the bowel pressure. These drugs are called antispasmodics. Since stress and anxiety may play a role in these symptoms, it can at times be helpful to use a mild sedative, often in combination with an antispasmodic.

Physical exercise, too, is helpful. During exercise, the bowel typically quiets down. If exercise is used regularly and if physical fitness or conditioning develops, the bowel may tend to relax even during non-exercise periods. The invigorating effects of conditioning, of course, extend far beyond the intestine and can be recommended for general health maintenance.

As important as anything else in controlling IBS is learning stress reduction, or at least how to control the body’s response to stress. It certainly is well-known that the brain can exert controlling effects over many organs in the body, including the intestine.


Patients with IBS can be assured that nothing serious is wrong with the bowel. Prevention and treatment may involve a simple change in certain daily habits, reduction of stressful situations, eating better, carefully trying fiber foods and supplements, and exercising regularly.

Perhaps the most important aspect of treatment is a reassurance. For most patients, just knowing that there is nothing seriously wrong is the best treatment of all, especially if they can learn to deal with their symptoms on their own.