Gut Microbiome Responses to a 4-Week High-Fiber Feeding: Preliminary Findings

OBJECTIVES: Dietary components high in fiber have been shown to uniquely influence the gut microbiome through growth of beneficial bacteria. To determine if fiber from a pulse source (pea fiber) improves microbiome profiles, we tested the hypothesis that a high-fiber (HiFi) diet will result in improvements in microbial composition and diversity compared to a low-fiber (LowFi) diet. METHODS: In a parallel arm, repeated-measures design, overweight or obese adult males and females with at least one characteristic of the metabolic syndrome, were randomly assigned to consume a standard diet consisting of 25g/d (HiFi) or 5g/d (LowFi) of added pea fiber for 4 weeks (HiFi: n = 5, mean ± SD, BMI 30.1 ± 2.4 kg/m(2), 30.6 ± 9.9 y; LowFi: n = 5, BMI 28.6 ± 3.4 kg/m(2), 32.2 ± 11.7 y). The intervention meals were matched for palatability, energy, and macronutrient composition. Fecal sampling was performed on days 0, 7, 14, 21, and 28 of the intervention for a total of 50 samples. Gut microbiome composition was assessed by 16S rRNA amplicon sequencing. RESULTS: Alpha diversity as assessed by the Shannon index remained unchanged in both the HiFi and LowFi groups after 4 weeks. Beta diversity analysis (by Principal Coordinates) demonstrated that there was a statistically significant difference in microbial composition between the HiFi and LowFi group (p = 0.0001, F = 4.04) but no significant effect of time (p = 1, F = 0.28). There were differences seen in the microbial taxa in both groups at day 0 in comparison to the days after. For example, members of the genus Blautia, and Subdoligranulum (belonging to the phylum Firmicutes, known producers of short chain fatty acids (SCFA)) were low at day 0 in the HiFi group but increased from day 7 through day 28. These genera were unchanged in the LowFi group. CONCLUSIONS: These preliminary results provide evidence of differential effects of HiFi compared to LowFi diets on the gut microbiome, particularly an increase in SCFA producers with HiFi. FUNDING SOURCES: University of Missouri and NIH-K01- NHLBI.