ABSTRACT Phenolic-rich prebiotic fiber has been correlated with a number of positive health outcomes, despite low bioavailability. A large portion of the gut microbiota metabolize these fibers releasing a range of phenolic acids, which are believed to be salient bioactive components driving reduction in disease risk. Despite this, little evidence exists linking specific gut bacteria with the metabolites they produce and the downstream biological effects that these compounds exert. We therefore propose to assemble a cohort of individuals that will receive prebiotic supplementation during comprehensive, longitudinal characterization of the microbiota and host changes with multiple omics assays (Aim 1). We will then integrate these multiomic data (Aim 2), generating unique biological signatures that define the role microbial metabolites from specific bacteria play in host biological activity. To find associations between multiomic systems biology, fiber supplementation, and cognition we propose to add cognitive tests to out longitudinal study. Through this study we expect to gain a detailed and clear understanding of the physiological changes that occur in the microbiome and host in response to dietary supplementation with prebiotic fiber.