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 occur, 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 water 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 narrowed colons due to strictures or adhesions (scar tissue from previous surgery), 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 stool 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.