I'm no nutritional expert but from what I understand: If you look at traditional food people ate very different around the world but by some miracle all of those traditional diets cover all angles of nutrition. It seems to suggest that in the long run only cultures who eat a complete diet survive. You can of course survive for a really long time with all kinds of deficiencies but apparently time will catch up. How this happens I don't know but it isn't actually important. The point I wanted to make is that poison isn't even required. Unless you have experimental success after perhaps thousands of years of trial and error we would have to actively monitor and adjust everything with an iron fist. Specially this idea that anything goes unless harm is proven needs to go. There is an enormous amount of low hanging fruit but to do the entire job entirely will be a humongous undertaking.