As people age, shifts in the gut microbiome influence inflammation, metabolism, and cognitive health. A growing body of evidence links specific bacterial taxa and microbial metabolites to markers of healthy aging — including preserved gut barrier function, balanced immune responses, and improved metabolic profiles. For an overview of practical implications, see [gut microbiome and healthy aging](https://www.innerbuddies.com/blogs/longevity-healthy-aging/gut-microbiome-healthy-aging-bacteria-pathways). Key microbial players repeatedly associated with longevity include Akkermansia muciniphila, Faecalibacterium prausnitzii, members of the Christensenellaceae family, Roseburia spp., and Coprococcus spp. Akkermansia supports the mucous layer of the gut and is linked to lower inflammation and better metabolic outcomes. Faecalibacterium is a major butyrate producer; butyrate nourishes colonocytes and exerts anti-inflammatory effects by modulating NF-κB signaling and regulatory T-cell differentiation. Christensenellaceae correlates with leanness and favorable metabolic phenotypes and is more abundant in some long-lived populations. Butyrate, propionate, and acetate — short-chain fatty acids (SCFAs) produced by fiber-fermenting microbes — are central mediators of these benefits. Butyrate supports intestinal barrier integrity and limits systemic inflammation, while propionate and acetate influence lipid metabolism and gluconeogenesis and modulate cytokine balance. Through these pathways, microbial metabolites can reduce chronic low-grade inflammation, a hallmark of biological aging. The gut–brain axis provides another mechanism linking microbes to age-related cognitive outcomes. Microbial metabolites, immune signaling, and vagal pathways can alter brain function and behavior. Trials in older adults with mild cognitive impairment have reported cognitive improvements after probiotic supplementation with certain Lactobacillus strains, likely via changes in neuroactive compound production and systemic inflammation. These findings are early but suggest a plausible route for microbiome-influenced cognitive resilience. Lifestyle factors strongly shape the microbial communities that mediate these effects. Diets rich in diverse, fiber-containing plant foods promote SCFA-producing taxa; prebiotics such as inulin and galacto-oligosaccharides selectively feed beneficial microbes. Fermented foods can introduce live microbes that transiently alter community composition. Regular physical activity is associated with greater microbial diversity and higher levels of health-promoting bacteria, and time spent in natural environments may broaden microbial exposure, supporting immune resilience. Research syntheses and longitudinal studies continue to refine which strains and pathways are most causally linked to healthy aging. Translating findings into public health recommendations will require consistent, well-controlled trials and mechanistic studies. For readers who want deeper context on how diet specifically influences the microbiome and aging, see Diet and the gut microbiome: adding years to life. For foundational information on gut microbiota and its importance, consult What is gut microbiota and why it matters. Additional resources and testing options are available for those tracking their microbiome over time: microbiome test. Continued, evidence-based research will clarify actionable strategies to preserve microbial functions that support healthy aging without overstating current clinical certainty.