Dietary fiber, bulk-forming and lubricant laxatives, and stool softeners
The best way of adding fiber to the diet is increasing the quantity of fruits and vegetables that are eaten. This means a minimum of five servings of fruits or vegetables every day. For many people, however, the amount of fruits and vegetables that are necessary may be inconveniently large or may not provide adequate relief from the condition. In this case, fiber supplements can be useful.
Fiber is defined as material made by plants that is not digested by the human gastrointestinal tract. It is one of the mainstays in the treatment. Many types of fiber within the intestine bind to water and keep the water within the intestine. It adds bulk (volume) to the stool and the water softens it.
There are different sources of fiber, and the type varies from source to source. Types can be categorized in several ways, for example, by their source.
The most common sources include:
- Fruits and vegetables
- Wheat or oat bran
- Psyllium seed (for example, Metamucil, Konsyl)
- Synthetic methyl cellulose (for example, Citrucel)
- Polycarbophil (for example, Equalactin, Konsyl Fiber)
Polycarbophil often is combined with calcium (for example, Fibercon). However, in some studies, the calcium-containing polycarbophil was not as effective as the polycarbophil without calcium.
A lesser known source of fiber is an extract of malt (for example, Maltsupex). However, this extract may soften the material in ways other than increasing fiber.
Increased gas (flatulence) is a common symptom and side effect of high-fiber diets. The gas occurs because the bacteria normally present within the colon are capable of digesting fiber to a small extent. The bacteria produce gas as a byproduct of their digestion it. All fibers, no matter what their source, can cause flatulence. However, since bacteria vary in their ability to digest the various types of fiber, the different sources of it may produce different amounts of gas. To complicate the situation, the ability of bacteria to digest one type can vary from individual to individual. This variability makes the selection of the best type of fiber for each individual more difficult.
Different sources of fiber should be tried one by one. It should be started at a low dose and increased every one to two weeks until either the desired effect is achieved or troublesome flatulence interferes. Fiber does not work overnight, so each product should be tried over a few weeks, if possible. If symptoms of flatulence occurs, the dose can be reduced for a few weeks and the higher dose can then be tried again. It generally is said that the amount of gas that is produced by fiber decreases when it is ingested for a prolonged period of time, although, this has never been studied. If flatulence remains a problem and prevents the dose of fiber from being raised to a level that affects the stool satisfactorily, it is time to move on to a different source of fiber.
When increasing amounts of fiber are used, it is recommended that greater amounts of water be consumed (for example, a full glass with each dose). In theory, the water prevents "hardening" of the fiber and blockage (obstruction) of the intestine. This seems like simple and reasonable advice. However, ingesting larger amounts of water has never been shown to have a beneficial effect on constipation, with or without the addition of fiber. There is already a lot of water in the intestine and any extra ingested will be absorbed and excreted in the urine. Nevertheless, it is reasonable to drink enough fluids to prevent dehydration that would cause reduced intestinal water.
There are reasons not to take fiber or to take specific types of them. Due to concern about obstruction, if individuals have narrowings (strictures) or adhesions (scar tissue from previous surgery) of the intestines, they should talk to their doctor or other health care professional before making any dietary changes. Some products contain sugar, so individuals with diabetes may need to select sugar-free products.
Lubricant laxatives contain mineral oil as either the plain oil or an emulsion (combination with water) of the oil. The oil stays within the intestine, coats the particles of stool, and presumably prevents the removal of water from the material. This retention of water results in softer stool. Mineral oil generally is used only for the short-term treatment since its long-term use has several potential disadvantages.
The oil can absorb fat-soluble vitamins from the intestine and, if used for prolonged periods, may lead to deficiencies of these vitamins. This is of particular concern in pregnancy during which an adequate supply of vitamins is important for the fetus. In the very young or very elderly in whom the swallowing mechanism is not strong or is impaired by strokes, small amounts of the swallowed oil may enter the lungs and cause a type of pneumonia called lipid pneumonia. Mineral oil also may decrease the absorption of some drugs such as warfarin (Coumadin) and oral contraceptives, thereby decreasing their effectiveness. Despite these potential disadvantages, mineral oil can be effective when short-term treatment is necessary.
Emollient laxatives (stool softeners)
Emollient laxatives are generally known as stool softeners. They contain a compound called docusate (for example, Colace). Docusate is a wetting agent that improves the ability of water within the colon to penetrate and mix with the material in the bowel. This increased water within it softens the stool, although studies have not shown docusate to be consistently effective in relieving constipation. These softeners often are used in the long-term management of the condition. It may take a week or more for docusate to be effective. The dose should be increased after one to two weeks if no effect is seen.
Although docusate generally is safe, it may increase the absorption of mineral oil and some medications from the intestine. Absorbed mineral oil collects in tissues of the body, for example, the lymph nodes and the liver, where it causes inflammation. It is not clear if this inflammation has any important consequences, but it generally is felt that prolonged absorption of mineral oil should not be allowed. The use of emollient products is not recommended together with mineral oil or with certain prescription medications. Emollient products are commonly used when there is a need to soften it temporarily and make defecation easier (for example, after surgery, childbirth, or heart attacks). They are also used for patients with hemorrhoids or anal fissures.
Hyperosmolar laxatives are indigestible, unabsorbable compounds that remain within the colon and retain the water that already is in the colon. The result is softening of it. The most common hyperosmolar products are lactulose (for example, Kristalose), sorbitol, and polyethylene glycol (for example, MiraLax). Some are available by prescription only. These products are safe for long-term use and are associated with few side effects.
Hyperosmolar laxatives may be digested by colonic bacteria and turned into gas, which may result in unwanted abdominal bloating and flatulence. This effect is dose-related and less with polyethylene glycol. Therefore, gas can be reduced by reducing the dose of the laxative. In some cases, the gas will decrease over time.
Over-the-counter (OTC) laxatives
Saline laxatives contain non-absorbable ions such as magnesium, sulfate, phosphate, and citrate [for example, magnesium citrate (Citroma), magnesium hydroxide, sodium phosphate). These ions remain in the colon and cause water to be drawn into the colon. Again, the effect is soften feces.
Magnesium also may have mild stimulatory effects on the colonic muscles. The magnesium in magnesium-containing products is partially absorbed from the intestine and into the body. Magnesium is eliminated from the body by the kidneys. Therefore, patients with impaired kidney function may develop toxic levels of magnesium from chronic (long duration) use of magnesium-containing products.
Saline laxatives act within a few hours. In general, potent saline products should not be used on a regular basis. If major diarrhea develops with the use of saline products and the lost fluid is not replaced by the consumption of liquids, dehydration may result. The most frequently-used and mildest of the saline products is milk of magnesia. Epsom Salt is a more potent saline laxative that contains magnesium sulfate.
Stimulant laxatives cause the muscles of the small intestine and colon to propel their contents more rapidly. They also increase the amount of water in it, either by reducing the absorption of the water in the colon or by causing active secretion of water in the small intestine.3
The most commonly-used stimulant products contain cascara (castor oil), senna (for example, Ex-Lax, Senokot), and aloe. Stimulant products are very effective, but they can cause severe diarrhea with resulting dehydration and loss of electrolytes (especially potassium). They also are more likely than other types of laxatives to cause intestinal cramping. There is concern that chronic use of stimulant laxatives may damage the colon and worsen the condition, as previously discussed. Bisacodyl (for example, Dulcolax, Correctol) is a stimulant laxative that affects the nerves of the colon which, in turn, stimulate the muscles of the colon to propel its contents. Prunes also contain a mild colonic stimulant.
There are many different types of enemas. By distending the rectum, all enemas (even the simplest type, the tap water enema) stimulate the colon to contract and eliminate the material. Other types of enemas have additional mechanisms of action. For example, saline enemas cause water to be drawn into the colon. Phosphate enemas (for example, Fleet phosphosoda) stimulate the muscles of the colon. Mineral oil enemas lubricate and soften hard stool. Emollient enemas (for example, Colace, Microenema) contain agents that soften it.
Enemas are particularly useful when there is impaction, which it hardens in the rectum. In order to be effective, the instructions that come with the enema must be followed. This requires full application of the enema, appropriate positioning after the enema is instilled, and retention of the enema until cramps are felt. Defecation usually occurs between a few minutes and one hour after the enema is inserted.
Enemas are meant for occasional rather than regular use. The frequent use of enemas can cause disturbances of fluids and electrolytes in the body. This is especially true of tap water enemas. Soapsuds enemas are not recommended because they can seriously damage the rectum.
As is the case with enemas, different types of suppositories have different mechanisms of action. There are stimulant suppositories containing bisacodyl (for example, Dulcolax). Glycerin suppositories are believed to have their effect by irritating the rectum. The insertion of the finger into the rectum when the suppository is placed may itself stimulate a bowel movement.
There are many products that combine different laxatives. For example, there are oral products that combine senna and psyllium (Perdiem), senna and docusate (Senokot-S), and senna and glycerin (Fletcher's Castoria). One product even combines three laxatives, senna-like casanthranol, docusate, and glycerin (Sof-lax Overnight). These products may be convenient and effective, but they also contain stimulant products. Therefore, there is concern about permanent colonic damage with the use of these products, and they probably should not be used for long-term treatment unless non-stimulant treatment fails.
Biofeedback, exercise, and surgery
Most of the muscles of the pelvis surrounding the anus and rectum are under some degree of voluntary control. Thus, biofeedback training can teach patients with pelvic floor dysfunction how to make their muscles work more normally and improve their ability to defecate. During ano-rectal biofeedback training, a pressure-sensing catheter is placed through the anus and into the rectum. Each time a patient contracts the muscles, the muscles generate a pressure that is sensed by the catheter and recorded on a screen. By watching the pressures on the screen and attempting to modify them, patients learn how to relax and contract the muscles more normally.
People who lead sedentary lives are more frequently constipated than people who are active. Nevertheless, limited studies of exercise on bowel habit have shown that exercise has minimal or no effect on the frequency of how often you go to the bathroom. Thus, exercise can be recommended mostly for its many other health benefits, but not for its effect on constipation.
For patients with problematic constipation that is due to diseases of the colon or laxative abuse, surgery is the ultimate treatment. During surgery, most of the colon, except for the rectum (or the rectum and part of the sigmoid colon), is removed. The cut end of the small intestine is attached to the remaining rectum or sigmoid colon. In patients with colonic inertia, surgery is reserved for those who do not respond to all other therapies. If the surgery is to be done, there must be no disease of the small intestinal muscles. Normal small intestinal muscles are evidenced by normal motility studies of the small intestine itself.
Electrical pacing is still in its experimental phases. Electrical pacing may be done using electrodes implanted into the muscular wall of the colon. The electrodes exit the colon and are attached to an electrical stimulator. Alternatively, stimulation of the sacral skin can be used to stimulate nerves going to the colon. These techniques are promising, but much more work lies ahead before their role in treating the condition, if any, has been defined.
Prescription drugs to treat constipation
Lubiprostone (Amitiza) is a selective chloride channel activator that increases secretion of chloride ions from the cells of the intestinal lining into the intestinal lumen. Sodium ions and water then follow the chloride ions into the lumen, and the water softens the stool. The FDA approved lubiprostone for the treatment of chronic constipation in both men and women in February 2006. At a dose of 24 micrograms twice a day, lubiprostone significantly and promptly increased bowel movements, improved stool consistency, and decreased straining. The most common side effect of initial clinical studies was mild to moderate nausea in 32% of patients treated with lubiprostone, compared to 3% of the controls.
Linaclotide (Linzess) is an oral drug that is not absorbed from the intestine. It stimulates the cells lining the small intestine to secrete fluid into the intestine. The increase in fluid secretion leads to an increased number of bowel movements. In addition, when it is associated with the abdominal pain of IBS, the pain also is reduced. Although the improvement in pain may be due to the improvement, linaclotide has been shown also to reduce the sensitivity of intestinal pain nerves, and this mechanism of action also may account for the decrease in pain.
Linaclotide is moderately effective, and its effectiveness depends on how a favorable response is defined. In the studies leading up to its approval, linaclotide was associated with a predefined response of an increase in bowel movements and a decrease in pain in approximately one-third of patients as compared with 17% of patients who received placebo. The response was better when pain and constipation were considered separately, with responses of approximately 50% for either.
The only common side effect of linaclotide is diarrhea. It should not be used in children below the age of six because of serious toxicity (death) to very young mice in animal studies, and should be avoided in children ages six through 17.
Miscellaneous drugs to treat constipation
Several prescribed drugs that are used to treat medical diseases consistently cause (as a side effect) loose stools, even diarrhea. There actually are several small studies that have examined these drugs to treat the condition.
Colchicine is a drug that has been used for decades to treat gout. Most patients who take colchicine note a loosening of their stools. Colchicine has also been demonstrated to relieve constipation effectively in patients without gout.
Misoprostol (Cytotec) is a drug used primarily for preventing stomach ulcers caused by nonsteroidal anti-inflammatory drugs such as ibuprofen. Diarrhea is one of its consistent side-effects. Several studies have shown that misoprostol is effective in treating it short term. Misoprostol is expensive, and it is not clear if it will remain effective and safe with long-term use. Therefore, its role in treatment remains to be determined.
Orlistat (Xenical) is a drug that is used primarily for reducing weight. It works by blocking the enzymes within the intestine that digest fat. The undigested fat is not absorbed, which accounts for the weight loss. Undigested fat is digested by bacteria within the intestine and the products of this bacterial digestion promote the secretion of water. The products of digestion also may affect the intestine in other ways, for example, by stimulating the intestinal muscles. In fact, in studies, orlistat has been shown to be effective in treating constipation. Orlistat has few important side effects, which is consistent with the fact that only very small amounts of the drug are absorbed from the intestine.
It is unclear if these prescribed drugs should be used for to treat the condition. Although it is difficult to recommend them specifically just for the management it, they might be considered for patients who are constipated and are overweight, have gout, or need protection from nonsteroidal anti-inflammatory drugs.
Prucalopride (Resolor) is an oral drug. It is the only approved drug belonging to a new class of drugs, the dihydro-benzofuran-carboxamides. It attaches to receptors within the intestinal wall that promote intestinal motility, that is, contraction of the muscles of the wall that move stool through the intestine.
Prucalopride is effective in patients with chronic constipation. Randomized, placebo-controlled studies have shown that at maximum doses it increases the number of stools per week by one in approximately 50% of patients compared with approximately 25% of patients given placebo. It increases the number of stools per week to more than 3 in approximately 25% of patients compared with approximately 12% of patients given placebo. Most of the patients in the studies were having less than one stool per week before starting prucalopride.
The most common side effects of prucalopride are headache and gastrointestinal symptoms including nausea, diarrhea, and abdominal pain. These symptoms usually are mild, frequently resolve with continued treatment, and infrequently cause patients to discontinue treatment.
Home remedies for constipation relief
Start with the simple things.
- Don't suppress urges to defecate. When the urge comes, find a toilet.
- With the assistance of your physician and pharmacist, determine if there are drugs that you are taking that could be contributing to constipation. See if the drugs can be discontinued or changed.
- Increase the fiber in your diet by consuming more fruits, vegetables, and whole grains. (There are other health benefits from this recommendation as well.)
- It may be difficult to get enough fiber in the diet to effectively treat constipation, so don't hesitate to take fiber supplements if necessary (wheat bran, psyllium, etc.).
- Use increasing amounts of fiber and/or change the type of fiber consumed until there is a satisfactory result.
- Don't expect fiber to work overnight. Allow weeks for adequate trials.
What if constipation does not respond to these simple, safe measures?
These efforts should not be discontinued but other measures should be added. If it is infrequent, that is, every few weeks (as it can be when due to the menstrual cycle), it probably doesn't matter what other measures are added-emollient, saline, or hyper-osmolar laxatives, enemas, and suppositories. Even stimulant laxatives every four to six weeks are unlikely to damage the colon. Unfortunately, the tendency when using stimulant products is to unconsciously increase the frequency of their use. Before you know it, you're taking them every week, or more often, and there is concern (though no proof) that permanent colonic damage might result.
If it is a continuous rather than an intermittent problem, probably the safest products to take on a regular basis are the hyper-osmolar laxatives. Their use should be supervised by a physician. As with fiber, increasing doses of different hyper-osmolar products should be tried over several weeks until a satisfactory type and dose of laxative is found. Hyper-osmolar laxatives, however, can be expensive. Milk of magnesia is the mildest of the saline laxatives, is inexpensive, and provides a good alternative. Most patients can adjust the dose of milk of magnesia to soften the stool adequately without developing diarrhea or leakage of stool.
Prunes and prune juice have been used for many years to treat mild constipation. There is no evidence that the mild stimulant effects of prunes or prune juice damage the colon.
Stronger stimulant products usually are recommended only as a last resort after non-stimulant treatments have failed.
Many people take herbs to treat the problem because they feel more comfortable using a "natural" product. Unfortunately, most of these herbal preparations contain stimulant products and their long term use raises the possibility that they also may damage the colon.
When should I seek medical care for chronic constipation?
If the main problem is straining to push the stool out, chronic constipation should probably be evaluated early. This difficulty might be due to pelvic floor dysfunction, and the treatment of choice is biofeedback training, not laxatives. If it is not responding to the simple measures discussed previously with the addition of hyper-osmolar products or milk of magnesia, it is time to consult a physician for an evaluation. If a primary doctor is not comfortable performing the evaluation or does not have confidence in doing an evaluation, he or she should refer the patient to a gastroenterologist. Gastroenterologists evaluate constipation frequently and are very familiar with the diagnostic testing described previously.
What is new in the treatment of constipation?
Each part of the intestine (stomach, small intestine, and colon) has a network of nerves that controls its muscles. A great deal of research is being done in order to gain an understanding of how these nerves control each other and ultimately the muscles. Much of this research involves the study of neurotransmitters. (Neurotransmitters are chemicals that nerves use to communicate with each other.) This research is allowing scientists to develop drugs that stimulate (and inhibit) the various nerves of the colon which, in turn, cause the muscles of the colon to contract and propel the colonic contents. Such drugs have great potential to treat constipation that is due to colonic inertia. The first of these drugs is in clinical trials and is likely to be available soon. These drugs are an exciting development because they offer a new treatment for a difficult-to-treat form of the problem. The most studied drug is prucalopride which has been approved for use in several countries but not the U.S.
Nevertheless, there are many questions about these types of drugs that must be answered. How effective are they? Will they work in many or only a few patients? Will they work in patients who have damaged their nerves with stimulant products? Since these medications are likely to be used for a lifetime, how safe will they be with many years of use? Will they be used indiscriminately in situations for which simple treatments (for example, fiber) or more appropriate treatments (for example, biofeedback training) should be used?
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Reviewed on 3/27/2017
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.
National Institutes of Diabetes and Digestive and Kidney Diseases. "Constipation."
National Institute of Diabetes and Digestive and Kidney Diseases. "Eating, Diet, & Nutrition for Constipation.