The microbiome is the collective community of bacteria, archaea, viruses, and fungi inhabiting the body. Primarily the gut, but also skin, oral cavity, and other surfaces.
Mechanism: Gut microbes ferment fiber into short-chain fatty acids (butyrate, propionate, acetate), produce neurotransmitter precursors, modulate immune cells, and influence systemic inflammation. Diversity is the consistent marker of a healthy gut.
Use case: Eat 30+ different plant species per week, fermented foods regularly, sufficient fiber (30+ g/day). Avoid unnecessary antibiotics. Test via stool sequencing (Viome, Ombre) for trends.
Caveats: The science is younger than the marketing. Most commercial probiotics don't colonize. Diet and fiber outweigh supplements.