How we assign an A–F grade

Every compound × outcome on Vallydia carries a single letter, A through F. The letter is about the evidence, not our catalogue — and never about whether we happen to sell something. This note explains the weighting behind each grade.

What the letters mean

• A — Consistent, higher-quality human evidence for this specific outcome.
• B — Supportive human or strong animal evidence, with meaningful limitations.
• C — Preclinical or small/mixed human evidence; a real but uncertain signal.
• D — Weak, conflicting, or largely mechanistic evidence.
• F — Marketed or anecdotal claims with no controlled support.

The three inputs

A grade is a judgement over three things, in order of weight:

1. Study quality — randomised human trials and meta-analyses outrank animal and in-vitro work, which outrank case reports and anecdote.
2. Effect size — a reliable but tiny effect is graded honestly as small.
3. Replication — a finding that one group reports and no one reproduces is treated with suspicion.

What a grade is not

A grade is not a recommendation, and it is not a dose. Where humans have not been studied, we say so plainly rather than borrowing an animal result to imply a human benefit. The preclinical never poses as proven.