How LYO grades evidence

Every outcome on this site carries a grade from A to D. The grade is not about whether a compound "works" — it is about how much human evidence exists and how consistent it is. A compound can be genuinely promising and still be a D, because promising is not the same as proven.

Grades only count studies in humans. A hundred rodent papers do not move a grade above D. That rule alone explains most of what you'll see here.

The four grades: A — several well-run randomised trials in people, pointing the same way. B — human trials exist and mostly agree, but there are too few, they are too small, or the biggest one is still unpublished. C — a few small or poorly controlled human studies. D — animal studies, cell studies or anecdotes only.

Two rules people find surprising. First, adverse effects are graded too: a well-documented side effect earns an A exactly like a well-documented benefit, so that you can weigh one against the other. Second, effect size is separate from grade. The three squares next to a grade say how big the effect is; the letter says how sure we are it is real. A large uncertain effect and a small certain one look different on purpose.

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