# Dysbiosis

Dysbiosis is when your gut microbial community drifts away from a healthy state. The drift can be in its makeup, its diversity, or its chemical output. It is a working term, not a precise one. That is because there is no single 'healthy' reference community to compare against. Typical signs include a few things. You lose beneficial microbes (like the fatty-acid-making Firmicutes). Potential troublemakers (pathobionts) overgrow. Alpha-diversity drops. Or the community's function shifts. These changes are linked to inflammatory bowel disease, metabolic syndrome, type 2 diabetes, and colorectal cancer, among others. Cause and effect is hard to pin down in people. Most evidence is correlational, and dysbiosis can be both a driver and a result of inflammation. It was named a hallmark of aging in the 2023 López-Otín update. Age-related dysbiosis is increasingly seen as a contributor to inflammaging and frailty.

## Sources

- Sonnenburg JL, Backhed F. (2016). Diet-microbiota interactions as moderators of human metabolism. Nature. https://doi.org/10.1038/nature18846

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_Canonical: https://longevity-switzerland.com/en/glossary/dysbiosis · Part of Longevity Cities · Updated 2026-06-22_