Starch-entrapped microsphere fibers improve bowel habit but do not exhibit prebiotic capacity in those with unsatisfactory bowel habits: a phase I, randomized, double-blind, controlled human trial

Abstract

Approximately one-third of individuals in the United States experience unsatisfactory bowel habits, and dietary intake, especially one low in fiber, could be partly responsible. We hypothesized that intake of a fermentable fiber (starch-entrapped microspheres, SM) that has a delayed, slow fermentation profile in vitro would improve bowel habit while exhibiting prebiotic capacity in those with self-described unsatisfactory bowel habits, all with minimal adverse effects. A total of 43 healthy volunteers completed a 3-month, double-blind, parallel-arm randomized clinical trial to assess the ability of a daily dose (9 or 12 g) of SM vs psyllium (12 g) to improve bowel habit, including stool consistency and frequency, and modify gut milieu through changes in stool microbiota and short-chain fatty acids while remaining tolerable through minimal gastrointestinal symptoms. All outcomes were compared before and after fiber treatment. Stool frequency significantly improved (P=.0003) in all groups after 3 months, but stool consistency improved only in both SM groups compared with psyllium. In addition, all groups self-reported a similar improvement in overall bowel habit with fiber intake. Both SM and psyllium resulted in minimal changes in microbiota composition and short-chain fatty acid concentrations. The present study suggests that supplementation with a delayed and slow-fermenting fiber in vitro may improve bowel habit in those with constipation, but further investigation is warranted to determine capacity to alter microbiota and fermentation profiles in humans. This trial was registered at ClinicalTrials.gov as NCT01210625.

Keywords: Clinical trial; Constipation; Dietary fiber; Microbiota; Prebiotics.

Copyright © 2017 Elsevier Inc. All rights reserved.

Figures

Fig. 1. Fecal butyrate concentrations (n=3) before and after 4 weeks of 9 g starch-entrapped microsphere supplementation in a one-group, open-label pilot study

Butyrate concentrations analyzed by Mann-Whitney U Test and expressed as μmol/g of dry fecal weight. Values are means ± SD.

Fig. 2. Participant screening, enrollment, and attrition

SM, starch-entrapped microspheres

Fig. 3. Change in abdominal pain and bloating during supplementation at months 1-3 with either psyllium, 9 g SM, or 12 g SM

Change in symptoms scores were compared to baseline symptoms before treatment (Visit 1). Symptom change reported as summed scores from a 7-day symptom diary and analyzed by GEE. SM; starch-entrapped microspheres. Values are means ± SD.

Fig. 4. Microbial taxonomic composition of fecal samples based on 16S rRNA gene amplicon sequencing from genomic DNA extracts

Raw sequence data (rarefied to 2,000 sequences/sample) were clustered (97%) and annotated as described in the text. Annotation data were summarized at the taxonomic level of genus, and the number of sequences from each taxon for each sample are presented as a bar plot. Samples are grouped by treatment group (psyllium, 9 g SM, 12 g SM) and visit (2 or 3). For each group, the average Shannon index and standard deviation is shown. SM; starch-entrapped microspheres