The Health Benefits of Fiber

W. Steven Pray, PhD, DPh

Disclosures

US Pharmacist. 2006;31(6):20-28. 

In This Article

Fiber's Health Benefits

Through its OTC Review, the FDA evaluated fiber products for use in regulating bowel function. Several plant-derived bulk-forming fiber laxatives were found to be safe and effective--such as psyllium, malt soup extract, and bran. Bran and malt soup extract are not often marketed as nonprescription ingredients, but psyllium is widely available in a variety of dosage forms and options. The patient seeking a sugar-free psyllium product may use such products as Metamucil Sugar-Free Powder (3 g of dietary fiber per teaspoonful) or Konsyl Original Powder (6 g of psyllium per teaspoonful). Several non-plant-derived ingredients also were found safe and effective as bulking agents, including methylcellulose (e.g., Citrucel) and polycarbophil (e.g., FiberCon Caplets, Phillips' FiberCaps, Konsyl Fiber Tablets).

A new fiber ingredient is being marketed in a product known as Fibersure. The product contains inulin-type fructans, chicory-derived carbohydrate polymers characterized by fructosyl- fructose linkages.[10] The linkages do not allow digestion in the upper digestive tract. Thus, they are fermented in the colon, increasing the mass and water content of stools. Inulin-type fructans are known as "functional foods" and thus have not been evaluated by the FDA. Fiber supplementation is encouraged by physicians and nurses to treat and prevent constipation.[11,12]

Little is known about hydrolyzed guar gum, as found in Benefiber. The ingredient has not been approved by the FDA as a nonprescription ingredient but is being marketed as a dietary supplement. The National Academy of Sciences, in its Dietary Reference Intakes for Fiber, states that guar gum has "little effect on fecal bulk or laxation."[13]

The FDA considers seven days to be the safe time limit for use of laxatives without physician consultation. However, stimulant laxatives cause many patients to become habituated to them because of their nonphysiologic and drastic action; some patients might use laxatives for years once they become reliant on them. This practice can lead to changes in the colon that are carcinogenic and may result in death of colonic tissues located in the myenteric plexus. Patients should be urged to replace habitual use of stimulant laxatives with bulking agents. However, abrupt discontinuation in habitual laxative overusers may result in an inability to evacuate the bowels. The colon may not respond normally as a result of years of artificial stimulation. The patient may benefit from a gradual withdrawal. In this method, the pharmacist may recommend short-term stimulant use until the fiber begins to exert its own effect. A combination of a stimulant and fiber (e.g., SennaPrompt) might be useful for a 30-day period to boost colonic function and bridge the transition from stimulant addiction to natural facilitation of bowel movements with fiber. After that period, the goal should be permanent discontinuation of stimulants in favor of fiber intake.

The 1990 Nutrition Labeling and Education Act gave FDA authority to regulate health claims on food labels.[14] As a result, manufacturers submitted research attempting to demonstrate the effect of various fibers on health. Two fibers have been proven safe and effective for the claims submitted. Beta-glucan soluble fiber from whole oats met the standard for reduction of risk from coronary heart disease.[15,16] Psyllium husk is also able to reduce the risk of coronary heart disease as it contains a soluble fiber similar to beta-glucan.[17,18] Researchers quantified this outcome by determining the effect of psyllium (5 g three times daily) in lowering cholesterol as an adjunct to 10 mg of simvastatin, as compared to doubling the dose of simvastatin to 20 mg.[19] They discovered that dietary supplementation with psyllium in patients taking 10 mg of simvastatin was as effective in lowering cholesterol as 20 mg of simvastatin alone. As a result of this research and FDA findings, pharmacists can recommend ingesting psyllium supplements daily to consumers who wish to attain regularity of bowel movements while simultaneously lowering their risk of coronary heart disease.

The popular media has given ample coverage to the epidemic of obesity in America. Almost 100 million Americans are either obese or overweight.[20] The figures climb each year, so that the toll of obesity will also continue to rise. Obesity has been linked to such morbid conditions as osteoarthritis in weight-bearing joints, type 2 diabetes, heart disease, cancer, and many other conditions. While hundreds of dietary supplements purported to be obesity cures are launched each year, the rising incidence of the condition attests to their inefficacy. The cure for obesity is actually quite simple. The overweight patient must eat less and exercise more, beginning immediately and continuing over the span of a lifetime.

Stomach distension (feeling full) signals a person to stop eating. It is in this area that fiber can yield lasting benefits through several mechanisms. Fiber is a bulky food, more difficult to digest than fatty foods, fried foods, and candies. Once ingested, fiber enhances satiety and prolongs satiation after a meal through distending the stomach and by prolonging retention of gastric contents.[21] The stomach is distended after a fiber-containing meal because it promotes secretion of saliva and of gastric acids, both of which distend the stomach. Ingestion of fiber must be accompanied by water intake, which further serves to distend the stomach during a meal.[22] Prolonging gastric retention decreases the absorption rate of nutrients, so that hunger does not return as rapidly.

Fiber also yields dietary benefit through energy displacement or energy dilution. A person who ingests little fiber in an average day usually has a diet of high-energy foods such as fats. However, the bulk that fiber adds to the diet makes it impossible to eat the same quantity of high-energy foods. Research bears this out. If a patient adds 14 g of fiber to the diet, energy intake will be reduced by approximately 10%.[22] Further, observational studies of obese people and those who are thin confirm that thin people ingest more fiber and obese people ingest more high-fat foods.

Researchers explored the link between dietary fiber/fat intake and excess weight in young and middle-aged adults.[21] They discovered that only 5% of the sample consumed adequate fiber. Further, in women, consumption of a low-fiber, high-fat diet was associated with the highest incidence of obesity when compared to those consuming a high-fiber, low-fat diet.

Fiber may help prevent colon cancer. The possible link stems from observational studies in the 1970s demonstrating that natives of Africa consuming high-fiber diets had reduced risk of colorectal carcinoma.[23] Studies carried out to explore this link have been contradictory. Some seem to confirm a protective effect, but others show little to no effect.[24] There is little risk to fiber consumption. Therefore, with no clearly negative data about fiber, it makes sense to increase fiber intake just in case the positive studies did reveal an actual link. The patient will also experience the ancillary benefits of fiber consumption, such as reduction in cholesterol (with psyllium), prevention of constipation, and reducing risk of hemorrhoids.

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