Ms. Terrie is a clinical pharmacy writer based in Haymarket, Virginia.
Daily intake of an adequate amount of dietary fiber is the most common recommendation for the prevention and treatment of constipation and has an important role in the maintenance of normal bowel function.1 Results from various studies have demonstrated that adequate fiber intake has many additional health benefits and may prevent or decrease an individual’s risk of developing coronary disease, stroke, hypertension, diabetes, obesity, and colon cancer.2-5 Increased fiber intake may also lower serum cholesterol levels and be of benefit in gastrointestinal disorders, such as gastroesophageal reflux disease, duodenal ulcer, diverticulitis, and hemorrhoids.2,3 Studies also indicate that adequate intake of soluble fiber may promote better glycemic management for patients with diabetes.3-5 Other health benefits of adequate fiber intake include improved management of irritable bowel syndrome, promotion of weight loss, and restoration of regularity for individuals on low-carbohydrate diets.3-5
Current Recommended Daily Intake of Fiber
An estimated 95% of Americans do not get enough fiber in their diets and fail to meet the recommended daily intake.6 Obtaining dietary fiber through eating fruits, vegetables, whole grains, legumes, and beans is considered the ideal option; however, many individuals may find it difficult to do so through dietary means alone. Therefore, they may elect to take various fiber supplements, also known as bulk-forming laxatives, to meet their daily fiber intake requirement as well as to help maintain normal bowel function and prevent or decrease episodes of constipation. In general, the typical American diet includes an average daily intake of 14 to 15 g of fiber. According to the recommendations of the American Dietetic Association, healthy adults should ideally have a daily intake of 25 to 30 g of dietary fiber, and children older than 2 years should have a daily intake equal to their age plus 5 g.2
According to the National Academy of Sciences Institute of Medicine (IOM), the recommended intake of total fiber for adults 50 years and younger is 38 g for men and 25 g for women. For men and women older than 50 years, the recommended intake of fiber is 30 and 21 g per day, respectively, because of the decreased food consumption common in older individuals. 7 The IOM also recommends that individuals should consume at least 14 g of fiber for every 1000 calories.2,5 The American Heart Association recommends that at least 50% of daily grain intake come from whole-grain food sources.4 Dietary fiber can be divided into 2 basic categories: soluble and insoluble.5,6 Characteristics of these types of fiber are outlined in the Table.5,8
A variety of fiber supplements containing active ingredients, such as wheat dextrin, methylcellulose, psyllium husk, inulin, and calcium polycarbophil, are available. Pharmacists can assist patients in the proper selection of fiber supplements as well as provide the necessary information for using these products appropriately. Fiber supplements come in a variety of dosage formulations, including sugar-free, taste-free, and fruit-flavored versions in the form of shakes, caplets, chewable tablets, capsules, wafers, and dissolvable powders. Many powder formulations can be mixed with 4 to 8 oz of water or noncarbonated beverage or mixed into soft foods, such as applesauce. Some fiber supplements contain vitamins, calcium, and other minerals as well.
The use of certain pharmacologic agents, such as anticonvulsants, antidepressants, and analgesics, may be associated with constipation; therefore, pharmacists are in a pivotal position to identify and inform those patients at risk, encouraging patients to discuss the issue with their physician. Constipation is common among older patients for a variety of reasons, including adverse drug effects, decreased intestinal motility, decreased dietary intake, and dehydration. Fiber supplements are often used to treat or prevent constipation in this population.9
Optimizing Administration of Fiber Products
Patients should be reminded to gradually increase fiber intake over several weeks to avoid or reduce the incidence of adverse effects, such as intestinal flatulence, bloating, diarrhea, and cramping. If possible, patients should also increase water intake, because inadequate fluid intake can reduce the effectiveness of fiber products and may cause intestinal or esophageal obstruction. 1 Many manufacturers of fiber supplements have reminders on the product label that recommend taking fiber supplements with 8 oz of water to avoid choking.1,10-12 Patients with comorbidities that require restricting fluid intake, such as significant renal dysfunction or congestive heart failure,3 or those taking additional agents for other medical conditions, should be advised to discuss these supplements with their primary health care provider before initiating use.
Patients with intestinal ulcerations, stenosis, or disabling adhesions should avoid fiber supplements because of the possibility of fecal impaction or intestinal obstruction.1 Fiber supplements can decrease the absorption of many drugs; thus patients should be advised to avoid ingesting these supplements within 1 to 2 hours of taking other medications and to report any concerns to their physicians.1 The use of fiber supplements should never be a substitute for a fiber-rich diet containing the essential vitamins and minerals necessary for optimal health. It is important to remind patients to try to obtain most of their daily intake of fiber through dietary means. ■
1. Curry C, et al. Constipation. In: Berardi R, Newton G, McDermott JH, et al, eds. Handbook of Nonprescription Drugs. 16th ed. Washington, DC: American Pharmacists Association;2009:263-272.
2. Marlett J, McBurney MI,Slavin JL, for the American Dietetic Association. Position of the American Dietetic Association: health implications of dietary fiber. J Am Diet Assoc.2002;102(7):993-1000.
3. Anderson JW, Baird P, Davis RH Jr, et al. Health benefits of dietary fiber. Nutr Rev. 2009;67(4):188-205.
4. Fiber. American Heart Association Web site. Available at: www.americanheart.org/presenter.jhtml?identifier=4574. Accessed October 29, 2009.
5. Rollins C. Functional and meal replacement foods. In: Berardi R, Newton G, McDermott JH, et al, eds. Handbook of Nonprescription Drugs. 16th ed. Washington, DC: American Pharmacists Association;2009:425-433.
6. Inulin fiber benefits. Proctor & Gamble Web site. Available at:www.metamucil.com/clear-and-natural.php?ref=f. Accessed November 1, 2009.
7. Trumbo P, Schlicker S, Yates AA, Poos M, for the Food and Nutrition Board of the Institute of Medicine, The National Academies. Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids.J Am Diet Assoc. 2002;102(11):1621-1630.
8. Soluble versus insoluble fiber. Medline Plus Encyclopedia. Available at: www.nlm.nih.gov/medlineplus/ency/article/002136.htm. Accessed October 28, 2009.
9. Bouras EP, Tangalos EG. Chronic constipation in the elderly.Gastroenterol Clin North Am. 2009;38(3):463-480.
10. Metamucil product information. Proctor & Gamble Web site. Available at: www.metamucil.com. Accessed October 29, 2009.
11. Fibercon product information. Wyeth Consumer Healthcare Web site. Available at: www.fibercon.com. Accessed October 29, 2009.