Multi-Species Synbiotic Supplementation Enhances Gut Microbial Diversity, Increases Urolithin A and Butyrate Production, and Reduces Inflammation in Healthy Adults: A Randomized, Placebo-Controlled Trial

Background: In healthy adults, probiotic supplementation alone does not increase Urolithin A (UroA) and rarely increases butyrate, both microbiome-derived metabolites that influence key biological functions involved in regulating gastrointestinal symptoms. Accordingly, this clinical trial evaluated key biological functions of a multi-species synbiotic with 24 probiotic strains and a polyphenol-based prebiotic using capsule-in-capsule delivery technology. Methods: We conducted a randomized, placebo-controlled trial among healthy participants (n = 32). Participants were administered a daily synbiotic (53.6 billion AFU multi-species probiotic and 400 mg Indian pomegranate extract: DS-01) or matching placebo for 91 days. Samples were obtained at baseline Day 0, and Days 7, 14, 49, and 91. Endpoints included changes in fecal microbiome composition, urinary UroA, fecal butyrate, serum CRP, and safety. Results: The synbiotic significantly increased alpha-diversity of Bifidobacterium and Lactobacillus spp. at all timepoints, including at end-of-study (Day 91, p &lt: 0.0001) and increased native beneficial microbes. UroA production was significantly increased in the synbiotic arm at short-term (Day 7, 12-fold, p &lt: 0.02) and long-term (Day 91, 49-fold, p &lt: 0.001) timepoints. A higher proportion of synbiotic participants were capable of converting polyphenols into UroA (Day 91, 100% vs. 44.4%: p &lt: 0.01). Mechanistically, synbiotic participants showed an increased abundance of Lactobacillus species involved in UroA precursor metabolism and UroA-producing Gordonibacter species. The synbiotic also significantly increased fecal butyrate levels (p &lt: 0.03), and butyrate-producing species, in low-baseline butyrate producers, through Day 91, and was associated with reduced systemic inflammation. Conclusions: This multi-species synbiotic significantly increases diversity and abundance of key beneficial bacteria, enhances UroA production and butyrate levels, and is associated with lowered systemic inflammation. This is the first synbiotic to increase both UroA and butyrate.