You can't. One either goes through it themselves as I did and learns from it or is simply shut off to even the idea of it.
I have an uncle that has been systematically starving himself (fasting) since fasting does stop the dumping of toxins, primarily into the lymph, everyone feels better on it. I once tried to explain to him that eventually he will suffer for this and talked about what happened to me, but like teenagers even adults can be narrow-minded.