There's an old joke - you've probably heard it - about the body parts arguing over which of them is most important. The eyes, ears, nose and mouth all make fun of the rectum, because of the nature of its function, and so the rectum stops working. Within a few days, all of the others find they no longer work properly, and they realize the importance of this seemingly lowly body part.

If the colon and rectum aren't healthy, the body isn't healthy, but it's very easy to get into habits that aren't good for the colon. In theory, keeping the colon in top shape is simple: eat fiber-rich whole foods, drink lots of water, and exercise regularly. In practice, we tend to eat too much processed food, we're not sufficiently hydrated, and many of us lead sedentary lifestyles. When the colon does back up, many of us turn to chemical laxatives, which offer only temporary relief and may make the problem worse.

A sluggish colon affects more than just the bowels: it can also result in reduced liver and kidney functions, dull-looking skin and hair, hemorrhoids, and fatigue. Straining to pass impacted stools can cause fainting or even heart attacks in those with cardiovascular problems. And while not all of the causes are fully understood, this is clear: colon cancer is the second-deadliest cancer in the U.S., with an estimated 142,500 new cases of colon or rectal cancer diagnosed each year, and more than 51,300 men and women dying of it. Cleansing the colon - cleaning it, and keeping it clean - is a cornerstone of good health.

The colon is the first four to five feet of the large intestine; the last several inches are the rectum, which opens into the anus. Its main function is to take digested food from the small intestine and turn it into stool (feces). It absorbs vitamins and nutrients, and contains beneficial bacteria - probiotics - to help break down any undigested material. Mainly, though, it soaks up water from the runny small-intestine contents, helping to maintain the body's ideal fluid balance.

If food passes too quickly through it, not enough fluid is absorbed, and the result is watery diarrhea. More commonly, if it stays in the colon too long, the stool becomes dry and hard, and difficult to pass. This is constipation.

There are many reasons for constipation, the most common being poor diet and lack of exercise. Fruits, vegetables and whole grains contain fiber, which the body cannot digest. Both soluble fiber, which dissolves easily in water and becomes a soft gel in the intestine, and insoluble fiber, which passes through the body almost unchanged, bulk up the stool, keeping it soft and easy to pass. Most Americans eat too much meat, fat and processed food, and not enough fiber; this diet creates dense stools that clog the colon.

Other causes of a sluggish colon include not drinking enough water, prescription or over-the-counter medications, diseases and conditions such as diabetes, stroke, Parkinson's disease, irritable bowel syndrome and hypothyroidism, and life changes such as pregnancy or aging.

Many people try to solve constipation by using chemical laxatives, which can make the problem worse. While very occasional use of a laxative or stool softener isn't harmful, frequent use may make the colon dependent on them, making it very difficult for the intestine to work normally on its own.

To get a sluggish colon back into working order, start at the source: fiber-rich foods and plenty of water. The recommendation is 20 to 35 grams of fiber per day, but most Americans eat an average of only 5 to 14 grams. Much of this is due to eating too many refined and processed foods, which have had most of the fiber removed, and not consuming enough foods that are naturally rich in fiber, such as fresh fruits and vegetables, and whole grains. Dehydrating liquids, such as alcohol, coffee and caffeinated soft drinks, can also increase the likelihood of hard, dry stools.

Unfortunately, many people have to combine a fast pace with a sedentary lifestyle, and it can be difficult to eat a completely balanced diet. Fiber supplements, such as psyllium, add extra fiber naturally. Unlike chemical laxatives, they add the soft bulk necessary to move stools efficiently through the colon. The body also needs probiotics, beneficial bacteria found in the colon lining, which help with digestion and boost the immune system. These "good bacteria" are found in dietary supplements and in certain fermented foods, such as yogurt.

It's usually a gradual process to return the colon to its optimum health, and many start with a "cleanse," which clears away any impacted fecal matter and returns the intestinal lining to its normal levels of beneficial bacteria. Cleansing can take many forms, and can include a fiber-concentrated diet, a raw-food diet, a series of dietary supplements, or irrigating the bowel with fluids. How long it takes depends on the system used, and can be anything from a single treatment to several weeks. It's a good idea to ask a practitioner to determine the best method for your situation.