A Prebiotic Supplement Increases Bifidobacteria Abundance And Microbial Acetate Synthesis Gene In Participants Consuming Low-Fiber Diets

Many Americans consume diets that are deficient in fiber, for reasons that range in nature from financial constraints to personal taste preferences. Yet, it is well known that dietary fiber, which is degraded by certain gut microbes, may increase the overall diversity of the gut microbiome and the abundance of beneficial microbial taxa including Bifidobacterium and Lactobacillus spp. The objective of this study was to determine whether a novel fiber supplement consumed by apparently healthy individuals with a habitual diet low in fiber (< 15 g/day) improves the gut microbiome by increasing the proportion of Bifidobacterium and/or Lactobacillus spp. and increases the production of short chain fatty acids (SCFA) in stool. Twenty individuals were enrolled in this double-blinded, randomized order, placebo-controlled, cross-over study. Participants were young, apparently healthy, normal to overweight (BMI 23.0-32.0) and consumed <15 g/day of fiber. All participants consumed a fiber and placebo supplement for a period of 4 weeks each, with a 4-week washout between intervention arms in random order. Participants recorded their diet for 3 days using dietary records twice during each 4-week segment. The fiber packets contained 12 g/serving per day as a powder containing resistant starch, fructooligosaccharide, sugarcane fiber, and inulin while the placebo packets contained 12 g/serving per day of a powder that matched the fiber supplement in taste and appearance. The powder packet was mixed with water for consumption. Stool samples were collected every 2 weeks throughout the study, and metagenomic sequencing and SCFA analysis was performed. The fiber supplement was well tolerated, and all participants complied with the study protocols, indicating the general acceptability of the supplement formulation. The fiber supplement resulted in an increase in the relative abundance of several Bifidobacterium species (B. bifidum, B. adolescentis, B. catenulatum, B. longum) but did not affect the abundance of Lactobacillus species. The gene, poxB, related to SCFA production, specifically acetate formation, was increased however acetate concentrations in the stool samples were unchanged. Even a small amount of daily fiber supplement, supplied as a convenient powder mix added to water, resulted in measurable increases in beneficial Bifidobacterium species in apparently healthy individuals consuming diets low in fiber.