This is a fallacy. All sorts of things are time-tested, in some cases over a millennium, and turn out to be carcinogenic: lutefisk, for instance, or the scalding hot tea Iranians drink.
I'm talking conditional probabilities here. Conditioned on the natural, our track record isn't bad. Conditioned on synthetic substances, just in the last century we have thalidomide, high-fructose corn syrup and this wonderful collection: https://en.wikipedia.org/wiki/Category:Withdrawn_drugs
