Drinking prune juice for constipation isn't just an old wives' remedy – there's truth behind the lore. A glass of prune juice, dark, thick and distinctively bittersweet in flavor, might not be the most tempting solution to your temporary problem. But prunes and prune juice contain a special ingredient that makes your bowels move along: fiber.

Constipation can arise for any number of reasons. According to the National Digestive Diseases Information Clearinghouse, or NDDIC, it can be caused by stress, a low-fiber diet, inadequate liquid intake or a change in your normal eating habits and level of physical activity. Constipation can also be caused by taking calcium or iron supplements or taking certain medications, such as codeine, diuretics, antidepressants and antacids. One of the best things you can do when your bowel movements are fewer than normal is to bump up the fiber in your diet – and prunes are a high-fiber food.

Fiber is abundant in many fruits, according to an article published in the July 2008 issue of "Today's Dietitian." A half-cup of prunes contains 6 g of fiber, on par with the fiber content in a medium-sized pear. Bananas, oranges and apples have between 3 and 4 g fiber, by comparison. Prunes are rivaled in fiber content only by figs and fresh raspberries, which contain 8 g fiber for every half-cup and cup, respectively.

Although whole fruit is a natural source of fiber, the Center for Science in the Public Interest points out that most fruit juices, such as grape and orange juice, have little to no fiber at all. Not so with prune juice, which contains 2.5 g of fiber for every 8-oz. glass. In 2009, Johns Hopkins Bloomberg School of Public Health published results of a study in the "The Internet Journal of Nutrition and Wellness, Vol. 7 No. 2," comparing the effectiveness of plum juice – prunes are made from dried plums – with a psyllium-based fiber supplement. After studying 36 participants for two weeks, researchers concluded there was "preliminary evidence to support the daily use of ... plum juice ... as an accepted and effective treatment for stool softening and immediate relief of constipation symptoms."

In the vast world of detoxification kits and supplements, "colon cleanse" has a nebulous meaning. Proponents of colon cleansing sometimes advocate using fiber-based supplements and diets to purportedly get rid of burgeoning "toxins" in your bowels. However, Harvard Medical School indicates that there's no scientific research to suggest that colon cleansing for purposes of "detoxification" does anything to improve your health – MayoClinic.Org goes a step further and advises you not to cleanse your bowels unless your doctor recommends it.

Normal bowel movements fall within a wide range, says the NDDIC. You may have three a day or three a week – it all depends on the individual. Constipation is generally defined by three or less bowel movements a week coupled with stool that is dry, hard and difficult to pass. It's not uncommon to experience it from time to time. Prune juice is only one high-fiber food that can support regular bowel functioning. However, don't neglect other ways to address constipation. According to NDDIC, eating a diet rich in vegetables, fruits and whole grains, drinking plenty of liquids, exercising, and heeding nature's call whenever you have to go are other ways to keep yourself regular.