Microbiome diversity (alpha / Shannon index)

Microbiome diversity measures how rich and even your gut community is. 'Alpha diversity' is within one sample. 'Beta diversity' is across samples. The Shannon index is a popular alpha measure. It weighs two things: how many species there are, and how evenly they are spread. A higher Shannon value means a more complex community. In it, no single microbe dominates. Higher alpha diversity is broadly tied to good things. Those include resilience, metabolic health, and lower risk of bowel disease. But it is not a universal rule. Some diseases feature more diversity, just in the wrong place. Population studies do show one clear trend. Alpha diversity falls with age, especially after your 70s. And that decline tracks with frailty, hospital stays, and shorter survival. Still, read diversity carefully on its own. Thanks to 'functional redundancy', a diverse community can still lack key pathways. And the lab method (16S sequencing depth and primers) strongly shifts the numbers.

Last reviewed: June 22, 2026

This definition is educational and is not medical advice, a diagnosis, or treatment. Talk to a doctor about any health decisions. Read our full medical disclaimer