Dietary Fiber

Dietary Fiber

PEP Topic 
Constipation
Description 

Dietary fiber includes both insoluble and soluble fiber.

Insoluble fiber passes through the intestinal tract largely intact, adding bulk and weight to the stool. It is nonfermentable and helps food to pass more quickly through the stomach and intestines. Insoluble fiber is found in wheat bran, fruit and root vegetable skins, whole wheat, and whole-grain products, as well as seeds and nuts. Other sources include pumpernickel breads; all-bran cereal; butter, lima, pinto, and white beans; split and black-eyed peas; blackberries; boysenberries; raspberries; dried figs and prunes; artichokes; asparagus; Brussels sprouts; corn; parsnips; spinach; winter squash; and turnip greens.

Soluble fiber absorbs liquid to form a gel that eases stool movement. Sources of soluble fiber include fruits, vegetables, beans, barley, and oat bran. Soluble fibers include pectins, gums, starches, some hemicelluloses, and other polysaccharides.

Dietary fiber has been evaluated for effectiveness in constipation.

Effectiveness Not Established

Guideline/Expert Opinion

Bharucha, A.E., Pemberton, J.H., & Locke, G.R., 3rd. (2013). American Gastroenterological Association technical review on constipation. Gastroenterology, 144, 218–238.

doi: 10.1053/j.gastro.2012.10.028
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Purpose & Patient Population:

To identify rational, effective, and cost-effective treatment approaches for patients with constipation.

Type of Resource/Evidence-Based Process:

In this evidence-based guideline, material was selected from reviews and focused literature searches of peer-reviewed published studies.

Databases searched, search keywords, and inclusion criteria were not stated.

Studies were excluded if they reported on children or patients with constipation as a secondary symptom caused by problems such as spinal cord injury.
 

Phase of Care and Clinical Applications:

The study has clinical applicability to older adult and palliative care.

Results Provided in the Reference:

Evidence was categorized according to the U.S. Preventive Services Task Force grading system. Rome II criteria were used to define constipation. The resource identified causes of constipation, approaches for assessment, and recommendations for management based on evidence review. In addition to opiates, other causative agents associated with constipation in patients with cancer were antidepressants, anticholinergic agents, vinca alkaloids, vincristine, and cyclophosphamide.

Guidelines & Recommendations:

  • No evidence suggests increasing fluid intake improves constipation.
  • Increased physical activity is associated with less constipation.
  • Data are limited regarding the impact of probiotics on constipation.
  • Dietary fiber has potential therapeutic benefits, and fiber supplementation should be considered as a first step in patients with chronic constipation. However, the quality of evidence in this area is low.
  • If needed, osmotic agents should be used regularly and supplemented with stimulant laxatives as rescue medication, although the quality of evidence is moderate at best.

Limitations:

Limited high-quality evidence exists for effective interventions in managing constipation.

National Comprehensive Cancer Network. (2012). NCCN Clinical Practice Guidelines in Oncology: Palliative Care [v.2.2012]. Retrieved from http://www.nccn.org/professionals/physician_gls/pdf/palliative.pdf

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Purpose & Patient Population:

The objective of the guidelines is to provide palliative care practice guidelines for patients with cancer, facilitating the appropriate integration of palliative care into oncology practice.

Type of Resource/Evidence-Based Process:

These are consensus-based guidelines.

Phase of Care and Clinical Applications:

Included in the guidelines are multiple phases of care with palliative care applications. 

Guidelines & Recommendations:

The NCCN made recommendations on the following symptoms.

Anorexia
Nutritional support, including enteral and parenteral feeding, should be considered. Appetite stimulants such as megestrol acetate and corticosteroids can be used when appetite is an important aspect of quality of life.

Chemotherapy-Induced Nausea and Vomiting (CINV)
Recommendations include prochlorperazine, haloperidol, metoclopramide, or benzodiazepines. Adding 5-HT3 receptor agonists, anticholinergics, antihistamines, corticosteroids, antipsychotics, and cannabinoids also can be considered. Palliative sedation can be considered as a last resort.

Constipation
Increase fluid intake, dietary fiber, and physical activity. Opioid-induced constipation should be anticipated and treated prophylactically with laxatives.

Dyspnea
Pharmacologic interventions include opioids or benzodiazapines. Scopolamine, atropine hyoscyamine, and glycopyrrolate are options to reduce excessive secretions.

Pain
Do not reduce opioid dose for symptoms such as decreased blood pressure or respiratory rate. Palliative sedation can be considered for refractory pain.

Sleep/Wake Disturbances
For refractory insomnia with no underlying physiologic cause, pharmacologic management includes diazepam, zolpidem, and sedating antidepressants. Cognitive behavioral therapy may be effective. If present, restless leg syndrome can be treated with ropinirole.

Limitations:

  • Recommendations are predominantly consensus- rather than evidence-based. 
  • Recommendations are generally based on low-level evidence. 
  • Recommendations regarding CINV seem particularly out of date and are not in concert with current evidence.

Nursing Implications:

Recommendations provide expert opinion/consensus-level suggestions for management of various symptoms. Many recommendations, such as those for CINV, do not agree with current evidence in these areas.

Research Evidence Summaries

Griffenberg, L., Morris, M., Atkinson, N., & Levenback, C. (1997). The effect of dietary fiber on bowel function following radical hysterectomy: A randomized trial. Gynecologic Oncology, 66, 417–424.

doi: 10.1006/gyno.1997.4797
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Study Purpose:

To evaluate the effect of fiber on bowel function by comparing increased fiber intake with instructions versus regular diet.

Intervention Characteristics/Basic Study Process:

Women were randomized into two groups: high fiber (treatment) or regular diet (control). Both groups were evaluated at one, four, and seven months after surgery.

The treatment group received dietary counseling with instructions to increase their dietary intake to 30 to 40 g per day. Patients received all-bran cereal (unmarked) containing 15 g of fiber per bowl. Patients also were encouraged to increase their intake of insoluble fibers (eg, whole-grain, whole-wheat, and pumpernickel breads; all-bran cereal; butter; lima, pinto, and white beans; split and black-eyed peas; blackberries; boysenberries; raspberries; dried figs and prunes; artichokes; asparagus; Brussels sprouts; corn; parsnips; spinach; winter squash; turnip greens).

Sample Characteristics:

The study reported on a sample of 35 women with cervical cancer who had a type II or III radical hysterectomy.

Setting:

University of Texas MD Anderson Cencer Center

Study Design:

This was a randomized controlled trial (RCT).

Measurement Instruments/Methods:

  • Use of medications to achieve regularity was measured in terms of straining and pain with elimination.
  • Patients completed subjective questionnaires, exercise log (seven days), food diary (three days), and bowel function assessment (seven days) at intervals. 

Results:

  • Mean daily dietary fiber intake was 22.4 g in the treatment group and 12.4 g in the control group.
  • Insoluble fiber intake for the treatment and control groups was 16.2 g and 8.1 g, respectively.
  • Caloric intake was discussed.
  • Patients in the control group had a significant increase in the amount of medications used to achieve regularity; no other significant changes existed pre-/postoperation in either group.

Conclusions:

Patients with higher fiber intake had significantly less cramping abdominal pain and reports of straining, bowel-movement retention, more bowel movements with gas, and made in less than three minutes.

Limitations:

  • The sample size was small (fewer than 100). Although this was an RCT, the sample size of 35 could be considered a major flaw and, therefore, decreased the impact level of evidence.
  • The sample comprised women only.
  • Findings were postsurgical only; presurgical fiber intake for the control group (10 g) was significantly higher than in the treatment group (7 g, p = 0.005).

Holma, R., Hongisto, S.M., Saxelin, M., & Korpela, R. (2010). Constipation is relieved more by rye bread than wheat bread or laxatives without increased adverse gastrointestinal effects. Journal of Nutrition, 140, 534–541.

doi: 10.3945/jn.109.118570
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Study Purpose:

To investigate the effects of rye bread and cultured buttermilk on bowel function, colon metabolism, and gastrointestinal symptoms in adults with constipation.

Intervention Characteristics/Basic Study Process:

For three weeks before the beginning of the study, participants were instructed not to use products containing Lactobacillus rhamnosus GG (LGG). At the end of the baseline period, participants were randomized into one of five groups.

  1. Rye bread: minimum of 240 g per day of whole-grain rye bread
  2. LGG: 400 g per day of cultured buttermilk with LGG
  3. Rye bread plus LGG: minimum 240 g per day of whole-grain rye bread and 400 g per day cultured buttermilk with LGG 
  4. Laxative: laxative use as usual and maximum of 192 g per day of white wheat bread 
  5. Control: maximum of 192 g per day of white wheat bread

Foods considered to have laxative effects (e.g., prunes, flax, fiber products) were only allowed for the laxative group. All participants were permitted laxative use as necessary after first contacting the principal investigator. Participants were to exclude products containing other lactic acid bacteria.

Participants collected all feces for five days during the baseline week, one day during week 1, and five days during week 3. The samples were kept frozen until taken to the study center. Sitzmarks® Radiopaque capsules were used to determine total intestinal transit time (TITT) measurements.

Sample Characteristics:

  • The study reported on a sample of 51 patients.
  • Mean patient age was 46 years (range 22–78).
  • The sample comprised 47 women and four men.
  • Patients self-reported constipation and laxative use.

Setting:

A metropolitan area in Helsinki, Finland

Study Design:

This study had a randomized, unblended, 2 x 2 factorial design (LGG given, LGG not given, rye bread given, rye bread not given).

Measurement Instruments/Methods:

Patients self-reported the following.

  • Stool consistency (-1 = loose, 0 = normal, 1 = hard)
  • Ease of defecation (-1 = easy, 0 = normal, 1 = straining)
  • Rank of abdominal symptoms (i.e., abdominal pain, flatulence, borborygmi, abdominal bloating, constipation, diarrhea) (0 = no symptoms, 1 = mild, 2 = moderate, 3 = severe)

Results:

  • Rye bread, compared with white wheat bread, shortened TITT by 23% (p = 0.04), increased weekly defecations by 1.4 (p = 0.014), softened feces (odds ratio [OR] = 3.98, p = 0.037), eased defecation (OR = 5.08, p = 0.018), increased fecal acetic acid by 24% (p = 0.044), increased fecal butyric acid by 63% (p < 0.001), and reduced fecal enzyme (β-glucuronidase) activity by 23% (p = 0.014).
  • Rye bread, compared with laxatives, reduced TITT by 41% (p = 0.006), reduced fecal enzyme (β-glucuronidase) activity by 38% (p = 0.033), and reduced fecal pH by 0.31 units (p = 0.006).
  • LGG did not significantly improve bowel function or affect colonic metabolism.
  • Adverse abdominal symptoms did not significantly differ among the study groups.

Conclusions:

In adults with constipation, bowel function and colonic metabolism may improve more with rye bread consumption than with wheat bread consumption or common laxative use without causing adverse abdominal symptoms. Cultured buttermilk with LGG did not significantly improve bowel function or affect colonic metabolism in this population.

Limitations:

  • The sample size was small (fewer than 100). In addition, the study design was 2 x 2 factorial with a control, so five groups existed. Therefore, the already small total sample size (N = 51) was distributed into very small study groups of only 8 to 12 participants each. 
  • The study was not blinded.
  • The ratio of women to men was not balanced.

Nursing Implications:

Rye bread consumption may be more effective in relieving constipation than wheat bread or commonly used laxatives in adults. However, the convenience sample of volunteers was small, comprised predominately men, and did not include patients with cancer. Additional study is warranted in a larger population that includes patients with cancer, as well as a balanced number of women and men.

Sturtzel, B., & Elmadfa, I. (2008). Intervention with dietary fiber to treat constipation and reduce laxative use in residents of nursing homes. Annals of Nutrition and Metabolism, 52(Suppl. 1), 54–56.

doi: 10.1159/000115351
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Study Purpose:

To determine whether the addition of oat bran to the diets of older adult residents of a long-term care facility would lead to a reduction in laxative use.

Intervention Characteristics/Basic Study Process:

The control group (15 patients assigned) received usual diet.

The intervention group had oat fiber containing 8.3 g of nondigestible fermentable fiber and 9.7 g of nondigestible nonfermentable fiber per 100 g incorporated into their diet for 12 weeks.

Sample Characteristics:

  • The study reported on a sample of 30 older adult patients.
  • Patient age ranged from 57 to 98 years. Mean age was 86 years (SD = 9) in the intervention group and 84.6 years (SD = 11.4) in the control group.
  • Gender information was not provided.
  • Patients were excluded if they were receiving parenteral or enteral nutrition or any medication that would alter transit time through the gut.

Setting:

Single ward of a long-term care facility in Vienna, Austria

Phase of Care and Clinical Applications:

The study has clinical applicability to older adult care.

Study Design:

This was a controlled, parallel, blind intervention trial.

Measurement Instruments/Methods:

  • Nursing staff began recording laxative use after 10 days.
  • Body weight was recorded on days 1, 42, and 84.
  • Kilojoule (calorie) and fluid intake were recorded daily.
  • Observations concerning patients' eating habits were used to adapt recipes to ensure compliance.

Results:

  • The intervention group increased fiber intake by 5.1 g over the 12-week study period.
  • The intervention group had a 59% reduction in laxative use (p < 0.001), with a constant body weight (p = 0.455). 
  • The control group had a decrease in fiber intake by 1.8 g. Mean energy intake was 5,203 kilojoules (SD = 1,285) per day, and mean fluid intake was 1.794 ml (SD = 276 ml) per day.
  • The control group increased laxative use by 8% (p = 0.218), and their body weight decreased significantly (p < 0.005).

Conclusions:

Fiber supplementation with oat bran may be an alternative to laxatives for treating constipation in an older adult population.

Limitations:

  • The study used a small convenience sample that did not include patients with cancer.
  • Whether simple or double blinding was used is unclear.
  • Exercise may have decreased constipation, but patients' activity level was not noted.

Nursing Implications:

Increasing fiber supplementation with oat bran may be an alternative to laxative use for treating constipation in older adults. Additional study is warranted in a larger population that includes patients with cancer.

Sutton, D., Dumbleton, S., & Allaway, C. (2007). Can increased dietary fiber reduce laxative requirement in peritoneal dialysis patients? Journal of Renal Care, 33, 177–178.

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Study Purpose:

To explore the extent to which peritoneal dialysis (PD) patients are affected by constipation, how many laxatives they use on a regular basis, and barriers to managing constipation when their dietary fiber is increased.

Intervention Characteristics/Basic Study Process:

In stage 1, the investigators established current bowel habits and laxative use. In stage 2 (N = 23), fiber intake was increased by 6 to 12 g per day using a dietary fiber supplement, partially hydrolyzed guar gum (PHGG). Finally, in stage 3 (N = 17), patients' daily diet was modified to include foods naturally high in fiber, aiming for 6 to 12 g per day more than their current intake, and bowel habits and laxative use were monitored.

A stool-and-laxative recording diary was sent to 126 PD patients. Forty-six reported using laxatives. All respondents using laxatives were invited to use a soluble dietary fiber supplement for four weeks, followed by dietary advice to see whether they could achieve the same effect using high-fiber foods.

Sample Characteristics:

  • The study reported on a sample of 23 PD patients using laxatives.
  • Patients were included in the study if they had received PD at home for at least three months.

Setting:

United Kingdom

Study Design:

This was a descriptive study with a three-stage audit and intervention project.

Measurement Instruments/Methods:

A stool-and-laxative diary was used to measure number of bowel movements per day.

Results:

  • In stage 1, a recording diary was sent to 126 patients with PD. Seventy patients returned the diary, and 46 reported using laxatives.
  • In stage 2, 23 of 46 patients entered the intervention stage. Seventeen succeeded in replacing prescribed laxatives with the fiber supplement. All 23 patients successfully increased fiber and reduced laxative use within a four-week period.
  • In stage 3, 17 patients were asked to increase dietary fiber by modifying their daily food intake. Sixteen tried to increase their intake of high-fiber foods; of them, 8 succeeded. However, only two patients were able to reduce their fiber supplement intake.

Conclusions:

Fiber supplementation may be as effective as laxative treatment in preventing constipation. In addition, fiber supplementation was preferred by patients in this study, as many felt it improved bowel habits without the side effects of stimulant laxatives.

Fiber supplements cost much more than standard laxatives.

Limitations:

  • The sample size was small.
  • Only eight patients tried to increase their dietary fiber intake, limiting the value of the study. 
  • The fiber supplement was used as a thickening and stabilizing agent. It helped renal patients on fluid restriction because psyllium and methyl cellulose require a lot of fluids to be effective. In addition, PHGG has negligible potassium and phosphate. This is not transferable to patients with cancer unless they are in renal compromise.
  • The research design had flaws.
  • The study did not compare the use of bulk-forming fiber or dietary with soluble fiber.
  • A subjective patient-preferred questionnaire was administered. No tool was presented for patient outcomes assessed, which can be subjective for the clinicians evaluating the study.

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