Evidence literacy
Evidence tiers A–G, explained
Every plant entry in Myto Intelligence carries a letter, A through G. That letter grades one thing only: how much and what kind of research exists. It is not a quality score, not a safety rating, and not a recommendation. Here's how to read it.
The scale, top to bottom
The tiers describe the strongest form of evidence available for a plant's studied uses:
- A — systematic review or meta-analysis of human studies: multiple human trials, formally synthesized.
- B — randomized controlled human trials: at least one well-designed RCT.
- C — small or uncontrolled human studies: pilot trials, open-label studies, small cohorts.
- D — case reports and observational human data.
- E — animal studies only.
- F — in-vitro (test tube / cell culture) findings, or documented traditional-use records without modern study.
- G — hypothesis or in-silico only: an idea from theory or computer modeling, not yet tested in living systems.
What a low tier does — and doesn't — mean
A tier-F plant is not a debunked plant. It means the modern research simply hasn't been done — which is true for the majority of the world's documented ethnobotanicals. Absence of evidence is a research-funding fact, not a pharmacological verdict.
The reverse also holds: a high tier is not an endorsement. A plant can carry tier-B evidence for one studied context and still have meaningful interaction concerns, quality problems in commercial products, or negative trial results. The tier tells you how much weight the literature can bear — what the literature says is a separate question, and that's what the entry itself documents.
Why grading honestly matters
Most botanical content online inflates: a single mouse study becomes "proven," a tradition becomes a claim. Grading the evidence honestly — including saying "this has never been studied in humans" — is the entire point of a claim-safe reference. When an entry here says tier G, that's not hedging; it's the most useful thing a reference can tell you.
Every entry pairs its tier with citations you can open yourself. The grade is our reading of the literature; the literature is right there to check.
Sources & further reading
Keep reading
Want the evidence itself?
Myto Intelligence maps 1,173 medications to 705plants, fungi & ethnobotanicals by shared mechanism — every result with an evidence tier and a citation. It teaches, compares, and cites; it never tells anyone what to take.