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Nutrition 411: Managing Diarrhea and Constipation

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Nutrition 411: Managing Diarrhea and Constipation

  Bathroom habits are not something most people feel comfortable discussing, but as healthcare practitioners it is important that we not overlook this topic when speaking with patients. When questioned, a large percentage of patients admit to problems with diarrhea, constipation, or alternating bouts of both. These problems not only may affect a patient’s nutritional intake, but also may interfere with wound healing. Caring for and dressing wounds on the sacrum and coccyx can be much more difficult if the patient has frequent bouts of diarrhea. Constipation can cause straining, hemorrhoids, and much suffering if not resolved. For these reason both of these conditions deserve a closer look.


  Diarrhea is characterized by frequent loose or liquid stool and is a symptom of many disorders and diseases. The first step in treating diarrhea is to identify its cause. Table 1 lists several common causes of diarrhea. The three most common types of diarrhea are watery, fatty, and small-volume. Identifying the type of diarrhea may help determine its cause.1

  Watery diarrhea occurs when the amount of water and electrolytes moving into the intestinal mucosa exceeds the amount absorbed into the bloodstream. Watery diarrhea may be classified into two subtypes: osmotic or secretory. To determine which type is present, determine whether the diarrhea abates with fasting. Osmotic diarrhea is relieved by fasting; secretory diarrhea is not. Watery osmotic diarrhea usually accompanies lactose intolerance, dumping syndromes, and enteral feeding intolerances. Watery secretory diarrhea is a sign of bacterial enterotoxins and viruses.

  Fatty diarrhea, or steatorrhea, usually accompanies conditions associated with malabsorption, such as chronic pancreatitis or short-bowel syndrome. Small-volume diarrhea may accompany diverticulosis of the colon. Bloody stool or black tarry stool may indicate a more serious condition and should not be confused with common diarrhea. Black tarry stool, or melena, usually indicates that blood is coming from the upper part of the gastrointestinal tract. Maroon or red bloody stool, called hematochezia, usually suggests that blood is coming from the large intestine or rectum. These conditions warrant prompt medical attention and testing. Occasionally, the ingestion of black licorice, lead, iron supplements, or blueberries can cause black stool and false melena. A fecal occult blood test can be administered to rule out false melena.

Preventing Dehydration

  The main goal in the treatment of diarrhea is to prevent dehydration and electrolyte imbalance. Potassium and sodium loss should be corrected as soon as possible by providing a proper oral rehydration solution. Water does not contain the necessary electrolytes for oral rehydration therapy and sugary juices, such as apple juice, may worsen diarrhea. Caffeinated and alcoholic beverages also should be limited. Proper solutions may be homemade or purchased from a medical nutrition supplement company. Sports drinks such as Gatorade also may be used for rehydration. Sodium, potassium, chloride, blood urea nitrogen/creatinine ratio, and albumin should be carefully monitored. Patients with a history of hypertension or heart failure should be monitored closely when given high-sodium solutions.


  Constipation is a symptom; it is not a disease unto itself. Constipation is defined in many ways. One common definition states that constipation is a decrease in the frequency of bowel movements, accompanied by prolonged or difficult passage of stools. There is no accepted rule or correct number of bowel movements per week. Many people think they are constipated when in fact they are following their own individual pattern. It is not mandatory to have a bowel movement every single day. For some people, regularity may be a bowel movement only three times per week; for others, it may be daily bowel movements.

  Sometimes, patients express concern when they don’t have a bowel movement every single day. Reassurance should be given but it is also important to remember that after 3 or 4 days without a bowel movement intestinal contents may harden and may be harder to pass. For this reason, it is imperative to take these concerns seriously and provide some useful tips to relieve the situation.

Causes of Constipation

  Constipation can be caused by many different problems and situations. A diet low in fiber is often the easiest cause to identify and luckily, easy to correct. The Institute of Medicine2 recommends that children and adults consume 14 g of fiber for every 1,000 calories of food they eat each day. That means a person who eats 2,500 calories each day should consume at least 35 g of fiber daily, while a person who eats 1,700 calories each day needs somewhat less fiber (about 24 g). According to the Harvard School of Public Health,3 the average American consumes only 14 to15 g of fiber each day. This is well short of the recommendation and may lead to many other health concerns such as colon cancer, heart disease, diverticulitis, and type 2 diabetes. Table 2 details recommended amounts of fiber.   Inadequate fluids are another common cause of constipation. Liquids add fluid to the colon and bulk to the stools, making bowel movements softer and easier to pass. Table 3 lists many other causes of constipation. Table 4 lists some of the medications that may cause constipation.

Diagnosing Constipation

  Most people with constipation do not require extensive diagnostic tests; a medical history and a physical exam usually suffice. However, sometimes more extensive testing may be necessary if symptoms are severe or a sudden change in bowel movements occurs or blood appears in the stool. Most physicians will begin with routine blood tests and a digital rectal exam. The stool will be tested for occult blood. If further testing is required, a barium enema x-ray and a sigmoidoscopy or colonoscopy may be performed. A barium enema x-ray allows viewing of the rectum, colon, and lower part of the small intestine. The night before the exam, bowel cleansing is necessary because even a small amount of stool can obscure proper results. During the exam, the bowel is filled with barium so it will be visible on the x-ray. A sigmoidoscopy allows viewing of the rectum and lower colon; a colonoscopy views the rectum and entire colon. Both of these procedures use a flexible, lighted tube inserted through the anus and rectum into the colon.

Treating Constipation

  The first line of constipation treatment is usually a change in diet. Adding additional fiber to the diet is often the key to keeping regular. This means additional whole grain breads, fresh fruits and vegetables, bran cereals, oatmeal, and lentils and beans. Processed foods should be slowly replaced with high-fiber foods because there may be a temporary increase in bloating, fullness, and gas as the body adjusts to the additional fiber. This feeling will go away if the high-fiber diet is continued but it is advisable to increase fiber slowly. Drinking plenty of fluids with the new high-fiber diet is equally important.

  Commercial bulking agents (fiber supplements) are sources of natural or synthetic fiber. These products generally are considered safe but are not a substitute for a proper diet. Taken with water, the products absorb the water in the intestine and make stool bulkier and softer. Products in this category include Metamucil® (Procter and Gamble) and Citrucel® (Bayer Health Care LLC).

  There are many other types of laxatives. Laxatives are for short-term use only; extended use can cause dependency. The healthcare practitioner should determine which type of laxative to use and for how long. Stimulants cause rhythmic muscle contractions in the intestines. These products include Correctol® (Schering-Plough), Dulcolax® (Boehringer Ingelheim Pharmaceuticals, Inc), and Senokot® (Purdue Products L.P.). Stool softeners provide moisture to the stool. This type of laxative includes Colace® (Purdue Products L.P.) and Surfak® (Pfizer). Lubricants grease the stool, enabling it to move through the intestine. Mineral oil is a common example. The final category of laxatives is saline laxatives. These act like a sponge to draw water into the colon for easier passage of stools. Examples of this type are milk of magnesia and Phillips’ M-O (Bayer HealthCare LLC).

  Regular exercise is also a part of the treatment plan. Many patients with wounds and other health challenges may not be able to vigorously exercise but regular activity should be encouraged as tolerated. Creating a regular bathroom routine also has proven useful for many people. For example, setting aside 15 minutes every day after breakfast for undisturbed visits to the bathroom may encourage regularity. The urge to defecate should not be ignored.

Practice Points

    • Ask patients if they are having problems with diarrhea and/or constipation.
    • Suggest oral rehydration beverages to prevent dehydration with acute or prolonged diarrhea.
    • Encourage patients with diarrhea to eat small meals and snacks rather than big meals.
    • Suggest foods such as bananas, white or brown rice, applesauce, toast, (ie, the BRAT diet) and crackers. These foods contain soluble fiber, which is helpful in the digestion and absorption process.
    • Caution patients about eating greasy, fried, or fatty foods and adding butter, oil, or other fats to foods, which can worsen certain types of diarrhea.
    • Tell patients to avoid foods that may be hard to digest. The gastrointestinal tract may be affected by foods that are high in insoluble fiber (raw fruits and vegetables and bran products), dried beans, cabbage, onions, nuts, and carbonated beverages. Patients should avoid them if they worsen symptoms.
    • For constipation, encourage patients to increase fiber.
    • Encourage regular bathroom time.
    • Consider substituting medications if that is deemed to be the cause of the problem. For example, one of the newer and less constipating antidepressant medications such as fluoxetine (Prozac, Eli Lilly) may be substituted for amitriptyline and imipramine.

Coming next month: Nutrition for the Ostomy Patient

Nancy Collins, PhD, RD, LD/N, FAPWCA, is founder and executive director of and For the past 20 years, she has served as a consultant to healthcare institutions and as a medico-legal expert to law firms involved in healthcare litigation. Correspondence may be sent to Dr. Collins at

This article was not subject to the Ostomy Wound Management peer-review process.