Prebiotics Affect the Fecal Microbiota and Gastrointestinal Health of Adults Participating in a Randomized, Double-Blind, Placebo-Controlled, Crossover Trial

Abstract

Abstract Objectives Prebiotics are defined as substrates that are selectively utilized by host microorganisms conferring a health benefit. We aimed to determine the effects of the prebiotics fructooligosaccharides (FOS) and galactooligosaccharides (GOS) on the fecal microbiota and gastrointestinal health in adults. Methods We conducted a randomized, double-blind, placebo-controlled, crossover trial in healthy adults (n = 26) 25–45 years of age. Participants consumed two 4-week treatments in a randomized, counterbalanced order. The prebiotic beverage (PRE) was 8 oz low-fat lactose-free milk with 5 g FOS and 5 g GOS. The control beverage (CON) was 8 oz low-fat lactose-free milk without the added prebiotics. Each condition was separated by a 4-week washout. Fecal samples were collected at baseline and end of each condition. Fecal short-chain fatty acid (SCFA) concentrations were quantified using gas chromatography-mass spectrometry (GC-MS). Fecal pH was measured using a pH meter. Gastrointestinal health was assessed using the Bristol stool scale and a stool frequency and ease of passage log before the first and during the last week of each condition. SAS 9.4 was used to conduct general linear mixed modeling with treatment as a fixed effect and participant and period as random effects. Normality was assessed using the Shapiro-Wilk test and log and arcsine transformations were applied as needed. Results There was a 153% increase in fecal bifidobacteria relative abundances in the prebiotic group compared to control (CON: 2.8 ± 0.6, PRE: 6.9 ± 1.7; P = 0.002). No differences were detected between the groups in fecal acetate (CON: 278 ± 30.1, PRE: 231 ± 24.4; P = 0.2), butyrate (CON: 68.4 ± 10.1, PRE: 62.9 ± 12.2; P = 0.4), or propionate (CON: 76.5 ± 7.5, PRE: 76.7 ± 12.5; P = 0.4) concentrations, or fecal pH (CON: 6.86 ± 0.10, PRE: 6.91 ± 0.14; P = 0.5). Stool frequency (stool/day) increased by 26% in PRE compared to CON (CON: 1.0 ± 0.1, PRE: 1.3 ± 0.1; P = 0.01). Ease of stool passage tended to improve in PRE compared to CON (CON: 2.2 ± 0.1, PRE: 2.0 ± 0.1; P = 0.1). There was no difference in stool consistency (CON: 3.7 ± 0.3, PRE: 3.7 ± 0.2; P = 0.8). Conclusions These findings are suggestive of the beneficial health effects of consumption of the prebiotics FOS and GOS on gastrointestinal health in adults. Funding Sources USDA National Institute of Food and Agriculture, Hatch Project 1009249.