How we source and rate the evidence
Where the associations come from
Every organism–condition link is drawn from the published research and from curated microbiome–disease databases — principally Disbiome, gutMDisorder, and GMrepo — which compile microbial composition changes reported across human studies. Organism names are normalized to standard taxonomy; conditions are mapped to standard medical vocabularies.
What the evidence tiers mean
Every claim carries an evidence rating, because "a study found X" and "this is consistently replicated" are very different things:
- Well-replicated — consistent across many studies, often with mechanistic support.
- Moderate — repeated findings, but with meaningful variation between studies.
- Preliminary — early or small studies; treat as a signal, not a conclusion.
- Disputed / mixed — studies genuinely disagree, sometimes on the direction itself. We show the conflict rather than pick a side.
Direction, not verdicts
We show whether an organism is elevated or reduced in a condition — not a "good" or "bad" label. The same organism can move in opposite directions across conditions (Akkermansia rises in Parkinson’s but falls in metabolic disease), and many "parasites" are commensal or even protective. Context is everything, and a verdict would erase it.
We flag what the evidence doesn’t support
A guide you can trust has to say when a popular idea isn’t backed by research. Claims like the "full-moon parasite cleanse" are kept on the site, clearly marked as folklore, with an explanation of what the evidence actually shows. Omitting them would be less honest, not more.
On composition by weight
The gut’s composition looks completely different by cell count than by weight, because fungal cells are roughly 100× larger than bacterial cells. We show both, and we’re explicit that the by-weight split is a cell-size-corrected estimate — the exact figures are genuinely under-measured.
This is not medical advice
BiotaMD is a research reference, not a diagnostic tool. Associations are overwhelmingly correlational. If you have symptoms, please see a qualified clinician.