High-Fiber Diet
Manual of Clinical Nutrition Management D- 6 Copyright © 20 13 Compass Group, Inc.
abnormalities are generally absent (12). Patients who present with rectal bleeding, weight loss, iron deficiency
anemia, nocturnal symptoms, and a family history of selected organic diseases (colon cancer, inflammatory
bowel disease, or celiac disease) should undergo medical testing to exclude underlying causes (12).
Microscopic colitis can masquerade as IBS (12). IBS is a prevalent and expensive condition that is associated
with a significantly impaired health-related quality of life and reduced work productivity (12). Based on strict
criteria, 7% to 10% of people worldwide have IBS (12). Approximately 60% of IBS patients believe that
certain foods exacerbate their symptoms, and research suggests that allergies to certain foods could trigger
IBS symptoms (12). However, based on an extensive review of the literature, there is no correlation between
foods that patients identify as a cause of their IBS symptoms and the results of food allergy testing (12).
Psyllium hydrophilic mucilloid (ispaghula husk) is moderately effective and can be given a conditional
recommendation for managing IBS (12). Wheat bran or corn bran is no more effective than placebo in the
relief of global symptoms of IBS and cannot be recommended for routine use (12). Certain antispasmodics
(hyoscine, cimetropium, pinaverium, and peppermint oil) may provide short term relief of abdominal pain
and discomfort (12). However, evidence of long-term efficacy, safety, and tolerability is limited (12). Probiotics
possess a number of properties that may prove to be beneficial for patients with IBS (12). Although studies of
Lactobacilli have repeatedly shown no effect on symptoms, probiotics combinations including strains of
Lactobacillis Bifidobacteria infantis (eg, AlignTM) and Saccharomyces boulardii may improve symptoms of IBS
(12,13). A position statement from the Academy of Nutrition & Deitetics suggests that fiber intake shows
inconsistent results in IBS. Dietary fiber should be considered as a therapy for bowel syndromes, but it
should not be regarded as a proven therapy that is suitable for all individuals with bowel syndromes (1). A
reduction in lactose and foods sources of fermentable oligo-di-and monosaccharides and polyols (FODMAPs)
have also been suggested to improve symptoms. These include fruits, dried fruits, fruit juice, fructose as
added sweetener, high fructose corn syrup, honey, coconut, fortified wines, onion, leek, asparagus, artichokes,
cabbage, brussel sprouts, beans, legumes, sorbitol, mannitol, isomalt, and xylitol (14, 15).
Cardiovascular disease and hypercholesterolemia: Dietary fiber intake from whole foods or supplements
may lower blood pressure, improve serum lipid levels, and reduce indicators of inflammation such as C-
reactive protein (Grade II) (1). Benefits may occur with daily fiber intakes of 12 to 33 g from whole foods or up to
42.5 g from supplements (Grade II) (1). The DRI recommendations for dietary fiber intake are based on
protection against cardiovascular disease (1). The one characteristic common to all cholesterol-lowering
fibers is viscosity (16). Fiber that lowers blood cholesterol is found in foods such as apples, barley, beans and
other legumes, fruits, vegetables, oatmeal, oat bran and rice hull. Purified sources of cholesterol-lowering
fiber include beet fiber, guar gum, karaya gum, konjac mannan, locust bean, gum, pectin, psyllium seed husk,
soy polysaccharide, and xanthan gum (1,17). The US Food and Drug Administration has studied two fibers,
beta glucan in oats and psyllium husk, to authorize a health claim that foods meeting specific compositional
requirements and containing 0.75 g of beta glucan or 1.7 g of psyllium husk per serving can reduce the risk of
heart disease (18). Viscous fibers lower cholesterol because their viscosity interferes with bile acid absorption
from the ileum. In response, low-density lipoprotein cholesterol is removed from the blood and converted
into bile acids by the liver to replace the bile acids lost in the stool. Evidence also indicates that cholesterol
synthesis is dampened by changes in the composition of the bile acid pool that accompany the ingestion of
viscous fibers (1,19). Fiber ingestion also affects the levels of blood pressure and C-reactive protein, which are
both biomarkers linked to the risk of cardiovascular disease (Grade II) (1). A secondary benefit of a high-fiber
diet is a lower dietary content of energy, fat, and simple sugars; these reductions are effective dietary
intervention strategies for weight management and hypertriglyceridemia associated with cardiovascular
disease (1,20).
Diabetes mellitus: Diets providing 30 to 50 g of fiber per day from whole food sources consistently produce
lower serum glucose levels compared to a low-fiber diet. Daily fiber supplements providing 10 to 29 g may
have some benefit in terms of glycemic control (Grade III) (1). The addition of viscous dietary fibers slows gastric
emptying rates, digestion, and the absorption of glucose to benefit immediate postprandial glucose
metabolism and long-term glucose control in individuals with diabetes mellitus (1). The American Diabetes
Association has determined that the consumption of soluble fiber independent of total fiber has limited
documented effects on glycemic control in individuals with diabetes (21). Although large amounts of dietary
fiber (>50 g/day) may have beneficial effects on glycemia, insulinemia, and lipemia, it is not known whether
such high levels of fiber intake can be maintained long-term (21). According to the American Diabetes
Association and evidence-based nutrition practice guidelines, fiber consumption recommendations for people
with diabetes are the same as for the general population (1,21). The DRI recommends consumption of 14 g of
dietary fiber per 1,000 kcal, or 25 g for adult women and 38 g for adult men. For general health benefits, the