Influence of Leuconostoc mesenteroides OL3621 on cognitive performance in community-dwelling older adults.

Age-related cognitive vulnerability has been linked to redox imbalance, low-grade inflammation, and gut microbiota remodeling. In a randomized, double-blind, placebo-controlled pilot trial, we evaluated whether 12-week supplementation with Leuconostoc mesenteroides OL3621 improves cognition and aging-related biomarkers in female-predominant, community-dwelling older adults. Relative to baseline, the probiotic group improved in the ACE-III attention domain, alongside a redox shift (lower malondialdehyde and advanced oxidation protein products, higher superoxide dismutase activity) and reduced fecal calprotectin, with no change in fecal zonulin. 16S rRNA profiling showed microbiota remodeling with increased abundance of putative short-chain fatty acid–associated taxa (e.g., Roseburia, Lachnospiraceae_UCG-008), and PICRUSt2 suggested enrichment of carbohydrate utilization pathways. These preliminary findings support a gut–immune–redox link in aging and warrant larger, mechanistic studies.