Meta-Analysis
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World J Gastroenterol. Dec 28, 2012; 18(48): 7378-7383
Published online Dec 28, 2012. doi: 10.3748/wjg.v18.i48.7378
Effect of dietary fiber on constipation: A meta analysis
Jing Yang, Hai-Peng Wang, Li Zhou, Chun-Fang Xu
Jing Yang, Li Zhou, Department of Clinical Nutrition, The First Affiliated Hospital of Soochow University, Suzhou 215006, Jiangsu Province, China
Hai-Peng Wang, Department of Cardiovascular, The First Affiliated Hospital of Soochow University, Suzhou 215006, Jiangsu Province, China
Chun-Fang Xu, Department of Gastroenterology, The First Affiliated Hospital of Soochow University, Suzhou 215006, Jiangsu Province, China
Author contributions: Yang J and Wang HP performed the majority of research and prepared the manuscript; Zhou L revised the manuscript; and Xu CF designed the study and revised the manuscript.
Correspondence to: Chun-Fang Xu, MD, PhD, Professor, Department of Gastroenterology, The First Affiliated Hospital of Soochow University, No. 188 Shizi Road, Suzhou 215006, Jiangsu Province, China. nutritionscience@163.com
Telephone: +86-512-67780357 Fax: +86-512-65222588
Received: August 12, 2012
Revised: October 1, 2012
Accepted: November 11, 2012
Published online: December 28, 2012
Processing time: 170 Days and 15.6 Hours
Abstract

AIM: To investigate the effect of dietary fiber intake on constipation by a meta-analysis of randomized controlled trials (RCTs).

METHODS: We searched Ovid MEDLINE (from 1946 to October 2011), Cochrane Library (2011), PubMed for articles on dietary fiber intake and constipation using the terms: constipation, fiber, cellulose, plant extracts, cereals, bran, psyllium, or plantago. References of important articles were searched manually for relevant studies. Articles were eligible for the meta-analysis if they were high-quality RCTs and reported data on stool frequency, stool consistency, treatment success, laxative use and gastrointestinal symptoms. The data were extracted independently by two researchers (Yang J and Wang HP) according to the described selection criteria. Review manager version 5 software was used for analysis and test. Weighted mean difference with 95%CI was used for quantitative data, odds ratio (OR) with 95%CI was used for dichotomous data. Both I2 statistic with a cut-off of ≥ 50% and the χ2 test with a P value < 0.10 were used to define a significant degree of heterogeneity.

RESULTS: We searched 1322 potential relevant articles, 19 of which were retrieved for further assessment, 14 studies were excluded for various reasons, five studies were included in the analysis. Dietary fiber showed significant advantage over placebo in stool frequency (OR = 1.19; 95%CI: 0.58-1.80, P < 0.05). There was no significant difference in stool consistency, treatment success, laxative use and painful defecation between the two groups. Stool frequency were reported by five RCTs, all results showed either a trend or a significant difference in favor of the treatment group, number of stools per week increased in treatment group than in placebo group (OR = 1.19; 95%CI: 0.58-1.80, P < 0.05), with no significant heterogeneity among studies (I2= 0, P = 0.77). Four studies evaluated stool consistency, one of them presented outcome in terms of percentage of hard stool, which was different from others, so we included the other three studies for analysis. Two studies reported treatment success. There was significant heterogeneity between the studies (P < 0.1, I2 > 50%). Three studies reported laxative use, quantitative data was shown in one study, and the pooled analysis of the other two studies showed no significant difference between treatment and placebo groups in laxative use (OR = 1.07; 95%CI 0.51-2.25), and no heterogeneity was found (P = 0.84, I2= 0). Three studies evaluated painful defecation: one study presented both quantitative and dichotomous data, the other two studies reported quantitative and dichotomous data separately. We used dichotomous data for analysis.

CONCLUSION: Dietary fiber intake can obviously increase stool frequency in patients with constipation. It does not obviously improve stool consistency, treatment success, laxative use and painful defecation.

Keywords: Dietary fiber; Constipation; Meta-analysis; Stool frequency; Stool consistency