Systematic Reviews
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Aug 7, 2015; 21(29): 8952-8963
Published online Aug 7, 2015. doi: 10.3748/wjg.v21.i29.8952
Effects of cereal fiber on bowel function: A systematic review of intervention trials
Jan de Vries, Paige E Miller, Kristin Verbeke
Jan de Vries, De Vries Nutrition Solutions Inc., 7213 CE Gorssel, The Netherlands
Paige E Miller, Center for Epidemiology, Biostatistics, and Computational Biology, Exponent, Inc., Chicago, IL 60661, United States
Paige E Miller, Nutrition and Food Service, Edward Hines Jr. VA Hospital, Hines, IL 60141, United States
Kristin Verbeke, Department of Clinical and Experimental Medicine, KU Leuven, 3000 Leuven, Belgium
Author contributions: de Vries J contributed substantially to conception and design, acquisition of data, analysis of data and drafting the article; Miller PE contributed substantially to drafting the article; Verbeke K contributed to conception and design, analysis of data and drafting of the article.
Supported by funding from Kellogg Company, Battle Creek, MI, United States.
Conflict-of-interest statement: Dr. de Vries J has received fees for systematically reviewing the literature reported in this publication from Kellogg Company, Battle Creek, MI, USA. Dr. Miller PE received fees while working at Exponent, Inc from Kellogg Company, Battle Creek, MI, USA, to support the writing process of the manuscript. Professor Verbeke K, PhD, is co-beneficiary of the WK Kellogg Chair in Cereal Sciences and Nutrition (Kellogg Company, Battle Creek, MI, USA).
Data sharing statement: No additional data are publically available. Interested readers can contact the first author.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Correspondence to: Dr. Jan de Vries, De Vries Nutrition Solutions Inc., Reuvekamp 26, 7213 CE Gorssel, The Netherlands.
Telephone: +31-6-54224148
Received: January 29, 2015
Peer-review started: January 30, 2015
First decision: March 10, 2015
Revised: April 15, 2015
Accepted: June 10, 2015
Article in press: June 10, 2015
Published online: August 7, 2015

AIM: To comprehensively review and quantitatively summarize results from intervention studies that examined the effects of intact cereal dietary fiber on parameters of bowel function.

METHODS: A systematic literature search was conducted using PubMed and EMBASE. Supplementary literature searches included screening reference lists from relevant studies and reviews. Eligible outcomes were stool wet and dry weight, percentage water in stools, stool frequency and consistency, and total transit time. Weighted regression analyses generated mean change (± SD) in these measures per g/d of dietary fiber.

RESULTS: Sixty-five intervention studies among generally healthy populations were identified. A quantitative examination of the effects of non-wheat sources of intact cereal dietary fibers was not possible due to an insufficient number of studies. Weighted regression analyses demonstrated that each extra g/d of wheat fiber increased total stool weight by 3.7 ± 0.09 g/d (P < 0.0001; 95%CI: 3.50-3.84), dry stool weight by 0.75 ± 0.03 g/d (P < 0.0001; 95%CI: 0.69-0.82), and stool frequency by 0.004 ± 0.002 times/d (P = 0.0346; 95%CI: 0.0003-0.0078). Transit time decreased by 0.78 ± 0.13 h per additional g/d (P < 0.0001; 95%CI: 0.53-1.04) of wheat fiber among those with an initial transit time greater than 48 h.

CONCLUSION: Wheat dietary fiber, and predominately wheat bran dietary fiber, improves measures of bowel function.

Keywords: Comprehensive review, Dietary fiber, Wheat bran, Cereal, Bowel function

Core tip: This comprehensive review evaluates available data on the effects of intact cereal dietary fiber on bowel function and provides a quantitative summary of the effect of intact wheat fiber on bowel function using weighted regression analysis. Insufficient observations were available from non-wheat cereals for quantitative analysis. Results found an increase in total stool weight of 3.7 ± 0.09 g per gram intact wheat fiber. Transit time decreased by approximately 45 min per gram intact wheat fiber when initial transit time was greater than 48 h. Therefore, intact wheat dietary fiber, predominantly from wheat bran, improves bowel function.