Combined effect of a probiotic (Bifidobacterium) and a prebiotic (polydextrose) on the fecal microbiota and stool parameters of healthy young women

Background: The beneficial effects of probiotics and probiotics on bowel health have been described in both healthy and constipated subjects. Recent research has investigated the effects of combinations of probiotics and prebiotics, which are termed synbiotics. This study aimed to investigate the effect of consuming probiotics together with prebiotics on the fecal microbiota and stool parameters of healthy young Japanese women. Methods: A randomized, double-blinded, placebo-controlled intervention study was conducted in 28 healthy young Japanese women. Subjects were randomly assigned to consume a placebo food containing 6.25 g dextrin (control) or a test food containing either 1 billion colony-forming units of Bifidobacterium lactis HN019 (probiotic), 6.25 g polydextrose (prebiotic), or both the probiotic and the prebiotic (synbiotic) daily for 2 weeks. Stool samples and records of stool parameters (frequency, amounts, Bristol scale) and nutrient intake were obtained during the trial. Results: The change in the proportion of Bacteroides spp. in both the polydextrose-fed groups (prebiotic and synbiotic) was significantly greater than that in both the dextrin-fed groups (control and probiotic), whereas the changes in the proportions of other microbes were not significantly different among the experimental groups. Stool parameters did not significantly differ among the experimental groups, but a significant correlation between the proportion of Bacteroides spp. and the stool amounts after 2 weeks of intake was observed in the synbiotic group. Conclusion: The intake of polydextrose for 2 weeks increased the proportion of fecal Bacteroides. The combined intake of probiotics and prebiotics may increase stool amounts via increasing the proportion of Bacteroides among the fecal microbiota. Abbreviations: BL: Bifidobacterium lactis; PDX: Polydextrose Introduction Probiotics are microorganisms that remain viable after being consumed and exert positive health effects [1]. Several strains of Bifidobacteria have been used as probiotics in Japan. The beneficial effects of probiotics include the normalization of the frequency of bowel movements and stool consistency [1] and the mechanisms often depend on interactions with the microflora of the host [2]. Bifidobacterium animalis ssp. lactis was reported to improve metabolic disorders by modulating the gut microbiota, resulting in an increased production of short-chain fatty acids in the colon [3]. Prebiotics were first defined as “nondigestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, thus improving host health” [4]. This definition was later refined as “a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microflora that confer benefits” [5]. Polydextrose (PDX) is a non-digestible oligosaccharide that is considered a soluble dietary fiber and is used widely in the food industry. In vitro studies have indicated that PDX has the potential to act as a prebiotic [6-10] and remains available as a carbon source throughout the colon [11]. The consumption of PDX was reported to produce a significant decline in the genotoxicity of the fecal water of volunteers, which coincided with an increased abundance of several bacteria including known producers of butyrate [12]. Recent research has highlighted the potential benefits of synergistic combinations of probiotics and prebiotics, which are called synbiotics [1]. This study aimed to investigate the effect of consuming a probiotic (Bifidobacterium lactis; BL) together with a prebiotic (PDX) on the fecal microbiota and stool parameters of healthy young Japanese women. Materials and methods Subjects Twenty-eight subjects were recruited among female students aged over 18 years from the Otuma Women’s University, Japan. The primary purpose of this study was to estimate the changes in stool parameters and the fecal microbiota after supplementation with test foods for 2 weeks. The inclusion criteria were: 1) aged more than 18 years at consent and must be an Otsuma Women’s University student and 2) understands the study procedures and agrees to participate in the study by giving informed consent prior to the study. The exclusion criteria were: 1) has a history of cardiovascular diseases, liver disease, kidney disease, digestive tract disease, respiratory disease, or diabetes; Correspondence to: Seiichieo Aoe, Ph.D, Department of Food Science, Fuculty of Home Economics, Otsuma Women’s University, 12 Sanban-cho, Chiyoda-ku, Tokyo, 102-8357, Japan