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Fiber has long been proclaimed an essential element of a healthful diet,and evidence continues to show that fiber reduces the risk for a number ofhealth problems, including heart disease and diabetes.
Dietary fiber consists of nondigestible carbohydrates and lignin that areintrinsic and intact in plants, and functional fiber consists of isolatednondigestible carbohydrates that have beneficial physiological effects inhumans (e.g., fibers that manufacturers add tofoods).1 The majorsources of fiber are fruits, vegetables (especially legumes), and grains.
The American Dietetic Association recommends that healthy adults consume20–35 g of dietary fiber each day from a variety of plant foods, andnutrition labels list daily goals of 25 g for diets of 2,000 kcal/day and 30 gfor diets of 2,500 kcal/day. The Institute of Medicine's (IOM) DietaryReference Intakes indicates that adequate consumption for total fiber is38 g per day for young men and 25 g per day for youngwomen.1
However, Americans generally consume just half the recommended daily intakeof dietary fiber. According to the IOM, median intakes of dietary fiberaverage 16.5–17.9 g per day for men and 12.1–13.8 g per day forwomen.1
Low fiber consumption persists, despite the fact that the Food and DrugAdministration (FDA) has conferred a "health claim" status tocertain fibers because of the strong scientific evidence showing that oatbran, oat flour, rolled oats, psyllium, and whole grains, or components inthese fibers, may reduce the risk of coronary heartdisease.2 InDecember 2005, the FDA added whole-grain barley and barley-containing productsto thelist.3
Daily intakes within the recommended ranges also may help normalize bloodglucose and insulin levels, reduce blood cholesterol, and reduce bloodpressure slightly.4Additionally, fiber-rich foods help prevent weight gain and obesity becausethey break down slowly, usually contain less fat and added sugar than otherfoods, and promotesatiety.5
FIGHTING HEART DISEASE
Researchers have linked high intake of dietary fiber to a lower risk ofheart disease in several large, long-term studies. In a meta-analysis of 10prospective cohort studies, researchers at University of Minnesota's School ofPublic Health in Minneapolis found fiber from cereals and fruits is inverselyassociated with the risk of coronary heartdisease.6 In 1997,the American Heart Association's Nutrition Committee published a statementrecommending dietary fiber intake of 25–30 g per day from foods, notsupplements, to maximize the cholesterol-lowering impact of a fat-modifieddiet.7
A recent study showed that consuming more than six servings per week ofwhole grains—including dark bread; popcorn; oatmeal; wheat germ; brownrice; other grains such as bulgur, kasha, and couscous; or breakfast cerealswith 
25% whole grain or bran by weight—proved beneficial forpostmenopausal women with established coronary artery disease(CAD).8 (Adistinction should be made between fiber and whole grain. Whole grain containsfiber, but also a number of other nutrients, such as vitamins andminerals.)
Over 3.2 years, the rate of atherosclerosis progression was slower in womenwhose median cereal fiber intake was 4 g/1,000 kcal compared with women whoseintake was 2 g/1,000 kcal, reports Alice H. Lichtenstein, DSc, director andsenior scientist at the Jean Mayer USDA Human Nutrition Research Center onAging at Tufts University in Boston.
OATS, BARLEY SHARE SPECIAL INGREDIENT: BETA GLUCAN
Beta glucan, the soluble component contributing to the cholesterol-loweringbenefits of oat fibers, is found in several other whole grains. Researchchemist Kay M. Behall, PhD, at the Agricultural Research Service of theDepartment of Agriculture (USDA), focused her recent research on barley, whichcontains a level of beta glucan similar to that of oats.
Behall and colleagues at the Beltsville (Md.) Human Nutrition ResearchCenter compared diets containing various levels of beta glucan—low(whole wheat/brown rice), medium (half whole wheat/brown rice and halfbarley), and high (all barley)—over 5 weeks in moderatelyhypercholesterolemicmen.9 All threediets resulted in cholesterol benefits from baseline, but the allbarley diet,which had the most beta glucan, conferred the greatest benefit. The respectiveeffects of the low, medium, and high beta glucan diets were as follows: totalcholesterol fell 14%, 17%, and 20%; LDL cholesterol fell 17%, 17%, and 24%;triglycerides fell 6%, 10%, and 16%; and HDL cholesterol rose 9%, 7%, and18%.
Behall suggests eating a minimum 3 g of soluble fiber as part of one'stotal daily fiber intake. A hot cereal breakfast of a half-cup of barleyflakes provides at least 3 g of beta glucan and confers the minimum lipidbenefit. Additional beta glucan consumed throughout the day could helpmaximize the cholesterol-lowering benefits, she says.
LOWERING BLOOD PRESSURE AND GLUCOSE
Other research compares diets containing recommended amounts of daily fiberintake from either insoluble fibers (brown rice/whole wheat) or soluble barleyfiber in healthy nonhypertensivemen.10 Bloodpressure decreased after 5 weeks on these diets, Behall notes, whether theycontained insoluble or soluble fibers. Blood pressure fell from an average ofabout 120 mmHg systolic and 75 mmHg diastolic to about 113 mmHg systolic and72 mmHg diastolic.
In addition, Agricultural Research Service chemists have found thatconsuming barley beta glucan is more effective in regulating peak glucoseresponse than eating wheat with no betaglucan.11 Glucoseand insulin benefits occur when the soluble fiber is consumed in a meal,Behall explains, "not as a between-meal supplement."
INCREASING PATIENT AWARENESS
Rather than focusing on just one aspect of a healthy diet, generalpractitioners should "look at the whole package," Lichtensteinsuggests.
Clinicians should ask about the types of food patients eat and makereasonable suggestions within the patient's normal diet to bring them in linewith healthy recommendations. Clinicians can continue to assess dietarypatterns as well as exercise and other healthy lifestyle practices at eachfollow-up visit. Patients are more likely to take recommendations seriouslywhen clinicians make notes and take the time to discuss and follow up onhealthy lifestyle habits, Lichtenstein adds.
Fiber Found in Common Foods
Consuming the recommended 20–35 g of fiber each day from a variety offoods is not difficult. A breakfast of 100% bran cereal and a banana providesabout 12 g of fiber. A cup of chili with beans and a corn muffin at lunch addabout 10 g. Snacks of an apple or a handful of almonds or pistachios add 3 geach. Including a sweet or regular potato, or a serving of green peas,couscous, or whole wheat bread, and a salad at dinner boosts one's daily fiberintake by another 7 g, for a grand total of 35 g.
For a detailed breakdown of foods' dietary fiber content, see theDepartment of Agriculture's National Nutrient Database for Standard Reference,Release 18, available to download atwww.nal.usda.gov/fnic/foodcomp/Data/SR18/nutrlist/sr18w291.pdf.
References
2. Food and Drug Administration: Code of Federal Regulations21CFR101.81. Available online atwww.gpoaccess.gov/cfr/retrieve.html.Accessed January 18, 2006.
3. Food and Drug Administration: FDA allows barley products to claimreduction in risk of coronary heart disease. December 23, 2005 news releaseavailable online athttp://origin.www.fda.gov/bbs/topics/news/2005/NEW01287.html.Accessed January 18, 2006.
4. Streppel MT, Arends LR, van't Veer P, et al.: Dietary fiber andblood pressure: A meta-analysis of randomized placebo-controlled trials.Arch Intern Med 165:150–156, 2005.
5. Harvard School of Public Health: The nutrition source: Knowledgefor healthy eating: Fiber. Available atwww.hsph.harvard.edu/nutritionsource/fiber.html.Accessed November 22, 2005.
6. Pereira MA, O'Reilly E, Augustsson K, et al.: Dietary fiber andrisk of coronary heart disease: A pooled analysis of cohort studies.Arch Intern Med 164:370–376, 2004.
7. Van Horn L: Fiber, lipids, and coronary heart disease. A statementfor healthcare professionals from the Nutrition Committee, American HeartAssociation. Circulation 95:2701–2704, 1997.
8. Erkkila AT, Herrington DM, Mozaffarian D, et al.: Cereal fiber andwhole-grain intake are associated with reduced progression of coronary-arteryatherosclerosis in postmenopausal women with coronary artery disease.Am Heart J 150:94–101, 2005.[Medline]
9. Behall KM, Scholfield DJ, Hallfrisch J: Lipids significantlyreduced by diet containing barley compared to whole wheat and brown rice inmoderately hypercholesterolemic men. J Am Coll Nutr 23: 55–62, 2004.
10. Hallfrisch J, Scholfield DJ, Behall KM: Blood pressure reduced bywhole grain diet containing barley or whole wheat and brown rice in moderatelyhypercholesterolemic men. Nutrition Research 23: 1631–1642, 2003.
11. Kim H, Behall KM, Conway JM: Consumption of whole grains containingbeta-glucan altered short-term satiety and glycemic response in overweightwomen (Abstract). Cereal Foods World 50: 276–277, 2005.
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