Consternation About Constipation - Medical Myths - Harvard Commentaries

Constipation — so common, but often it is an unsolved mystery for the person who becomes constipated. Common advice is typically unhelpful, misunderstanding is nearly universal, and people rarely want to talk about it. No wonder, then, that "common knowledge" about constipation is frequently wrong and the usual advice may actually make things worse.

While most people might say they "know what it is when they have it," defining constipation is not easy. One reason is that bowel habits vary widely even among perfectly healthy people. Some have bowel movements once or twice a day (or even more often) while for others, it's once every three days. Some describe constipation as a problem with hard stools that are difficult to pass, while others complain about pain, bloating or feeling the urge to go without being able to do so.

In research studies, a common definition for constipation relies on the fact that "normal" bowel movement frequency (that is, the frequency reported by 95% of the healthy population) is between three times a week and three times a day. Studies also have described constipation as fewer than two or three bowel movements a week, or as having significant and persistent distress (such as pain or straining) in attempting to pass stools more than 25% of the time. There are many ways to describe the problem and no one way that's perfect.

Regardless of how it's defined, constipation is unpleasant. Although often no explanation can be found, it's worthwhile to look for one. Among the conditions recognized to trigger or contribute to constipation are:

Hypothyroidism (underactive thyroid) — The hormones made by this golfball-sized gland that sits just below the Adam's apple have many effects on the body's metabolism. When the thyroid makes too little of these hormones, metabolism slows and constipation can be a prominent symptom.

Nerve or intestinal muscle disorders — Impaired nerve signals to the intestine or abnormal intestinal muscle activity can slow the movement of stool. Diabetes, multiple sclerosis and spinal cord injury are examples of diseases associated with this type of problem.

Abdominal surgery — After an operation, the intestines are usually much less active than normal, a condition called "ileus." It may last several days or more.

Medications — The most common examples include narcotics, iron, aluminum-containing antacids, calcium and certain antidepressants and blood pressure medicines (such as verapamil).

A disrupted routine — Travel, alteration in diet, limited access to bathroom facilities or delaying a bowel movement can lead to constipation.

Irritable Bowel Syndrome — This is a condition of unknown cause marked by alternating periods of constipation, diarrhea and abdominal discomfort.

Obstruction — Diverticulitis and gastrointestinal tumors are examples of disorders that can obstruct the intestinal tract, causing constipation. These more serious conditions usually have additional symptoms such as pain, fever or blood in the stool.

When a cause if found, the underlying condition often can be treated and the constipation will resolve. For example, a daily pill containing thyroid hormone can promptly reverse constipation related to hypothyroidism.

For many people, occasional constipation is simply a fact of life. When it is only intermittent, it's more of an annoyance than a serious health problem. However, for others, constipation is chronic and has a significant impact on quality of life. Even in these cases, the cause is often uncertain.

Once the common causes (as above) are considered and excluded, many patients with chronic constipation will undergo extensive testing and referral to a specialist in digestive disease (called a gastroenterologist). Even then, the cause may still be mysterious and the focus will turn to treatment.

That leads to a question: Without a cause that can be identified and treated, what can be done? Several safe and common remedies may be suggested by friends, family members or doctors, yet many are unhelpful, untested or may even make matters worse.

A recent review of the world's scientific literature looked at some of the common treatments for constipation and found remarkably little support for them. Researchers from several countries (including the United States, England, Germany and Italy) published their findings in the January 2005 edition of the American Journal of Gastroenterology. They found that the evidence did not support some very common assumptions.

The following statements offer a more accurate assessment of possible treatments:

Increasing fluid intake helps only some people with constipation.

Although dehydration may contribute to constipation, research studies suggest no clear benefit to increasing fluid intake in people who are not dehydrated. Studies also have noted no difference in estimated fluid intake between constipated and non-constipated adults. However, in a study of more than 21,000 elderly nursing home residents, decreased fluid intake was mildly correlated with constipation.

Increasing your dietary fiber does not consistently improve constipation.

While studies confirm that fiber increases the volume of stool and the frequency of bowel movements in healthy adults, less than half of people who report constipation respond to increases in dietary fiber. So although fiber does help some people with constipation, the overall effect is less than is commonly assumed. In addition, fiber may lead to increased gas production, which can make some people actually feel worse.

More exercise and physical activity often does not help with constipation.

Multiple studies demonstrate an association between constipation and inactivity. However, the relationship is not necessarily one of cause and effect. For example, a medical condition (such as pain) could contribute to reduced physical activity while a medication for that condition (such as a pain reliever) could contribute to constipation. Studies suggest little or no benefit from increased physical activity to reduce chronic constipation. Programs for the elderly that offer an array of medical and rehabilitation services — including increased activity and fiber, with fluids for those who are dehydrated — may improve or even reverse constipation. However, the increased activity alone is of uncertain benefit.

Laxatives are not dangerous when used properly.

While any drug can be psychologically addictive (which is often more a function of personality than the drug), laxatives appear to have remarkably low addictive potential. There is also no clear evidence for the common belief that laxative use frequently leads to an ever-escalating dose to maintain effectiveness. Limited use of stimulant laxatives at recommended doses does not cause colon cancer, nerve damage or other harmful effects on the digestive system. If laxatives need to be used frequently, this should be done only with medical supervision.

Constipation, without other symptoms, is not likely due to an underactive thyroid.

Inadequate thyroid hormone may cause constipation, but among all people with constipation, thyroid disease is rarely the cause.

As is true for most medical myths, there is some degree of truth to each of these. For example, even though there is little evidence that increased dietary fiber or increased exercise reliably improve constipation, some people do respond. And some people with prominent constipation do turn out to have hypothyroidism.

If these common concepts and recommendations about constipation are not supported by medical evidence, what's a constipated person to do?

Do the simple things that are safe, easy and might work. These include increasing dietary fiber, fluid intake and physical activity. Some people respond well to one or more of these, and you might be one of them. Using an over-the-counter laxative (such as Milk of Magnesia) or even an antacid that contains magnesium (as in Mylanta and many others) may be helpful.

If you don't improve, see your doctor for evaluation. A general check-up and review of your medications could lead to the discovery of a cause that is reversible.

Ask about the safety and advisability of laxatives, stool softeners and enemas. Each person's situation is slightly different, so the best person to discuss the risks and benefits of treatment with you is a physician familiar with your health status.

Constipation is a common and bothersome symptom. Much remains unknown and much of what has been considered true turns out to be only partly so or outright false.

When it comes to bowel movements, keep an open mind about what constitutes "normal." If your bowel movements aren't regular, frequent or easy to pass, your digestive tract may still be perfectly healthy. Don't expect instant relief from the common advice that may come your way — just as the cause of constipation is uncertain in most cases, so is the cure.

Robert H. Shmerling, M.D., is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.