e.g. Bitter cassava is a staple crop in parts of South America and Africa. Unlike apple seeds, it contains substantial quantities of cyanide. It's a great crop because you can plant it and forget it. No need for fences. Animals won't eat it. A chemist would be hard-pressed to come up with a more effective method for removing cyanide from it than some of the traditional methods of cooking it. However, problems arise when people cook and consume it in non-traditional ways.
Traditional knowledge can be both constraining and protective. It's like a fence whose purpose you don't know. Tearing it down is a gamble. You might win. You might lose. It's probably not a bad idea to try to figure out why a tradition is there before you mess around.