Lack of evidence of harm is not evidence of harmlessness, for it suffices to find one instance of harm to invalidate claims of harmlessness.

Paracetamol wrecks livers, one instance is sufficient, but it took 20

years of "no evidence of harm"

That aligns with logic in other places, for example, courts. We don't ask the defendant to prove they are innocent. That's impossible. We demand to find evidence of harm. Then we have a verdict. No earlier.

Harmlessness, in light of lack of evidence requires time: we can trust drinking water because:

a) no evidence of it being harmful

b) lots of time and instances of people drinking it.

That is a robust method, not the reverse, yet people get bamboozled by the fraudulent claims.