(OR15-01-25) Effects of Fermentable Fiber and Polyphenol Supplementation on Fecal Bacteria Populations and Respiratory Mucosal Immunity in Healthy Adults

Objectives: Nutrition interventions targeting the gut-microbiota may reduce risk of respiratory tract infections but whether any effects are mediated through increased mucosal immunity is unclear. This study determined effects of dietary supplementation with a combination of prebiotic fibers and polyphenol sources on select gut bacteria populations and salivary secretory immunoglobulin A (SIgA), a potential biomarker of respiratory mucosal immunity and infection risk.

Methods: Healthy adults (n = 13, 22 ± 3 yr) participated in a randomized, double-blind crossover study including two, 2-wk phases separated by ≥1 wk. A supplement providing 1.25 g oligofructose-enriched inulin, 1.4 g Bimuno-galactooligosaccharide, 5.3 g high-amylose corn starch, and 525 mg total phenolics from blueberry powder and cocoa, green tea and cranberry extracts (FP) or matched placebo (PL) was consumed daily during each phase. Two supplement doses were consumed daily during week 1 and four daily during week 2. Salivary SIgA was measured as a secondary study outcome on day 13 of each phase using ELISA. Fecal bacteria populations were quantified immediately before and on day 11-12 of each phase using culture independent fluorescence in-situ hybridization.

Results: Bifidobacterium spp. cell counts were higher throughout FP compared to PL (mean difference log₁₀ cells/mL [95% CI]: 0.6 [0.1, 1.1], P-treatment = 0.02). Additionally, FP prevented (P > 0.25) the decreases in Lactobacillus and Enteroccous spp. (-0.6 [-1.0, -0.2], P = 0.01), Faecalibacterium prausnitzii (0.4 [-0.8, -0.1], P = 0.02) and Clostridium clusters I and II (-0.9 [-1.3, -0.4] P < 0.001) observed during PL (P-interaction < 0.06). However, no effects of FP on SIgA concentration (Cohen’s d = -0.02, P-treatment = 1.00) or secretion rate (Cohen’s d = -0.26, P-treatment = 0.36) relative to PL were observed and changes in bacteria populations were not correlated with changes in SIgA.

Conclusions: This prebiotic fiber and polyphenol supplement favorably impacted several beneficial gut bacteria populations, but also supported potentially harmful Clostridium groups and effects on bacteria populations did not appear to impact respiratory mucosal immunity.

Funding Sources: Supported by DHP JPC-5. Authors’ views not official U.S. Army or DoD policy.