They say that all plants have evolved with inherent defense mechanisms (sublte phytochemical "poisons") that are meant to ward off animals from eating them. It is in turn very hard on the body to consume these raw foods that are full of the defense phytochemicals.
If you consult Tony Issacs, he referenced an article that you shouldn't eat immature nightshade vegetables. These vegetables, such as green peppers, have toxins in them so animals won't eat them in their immature states. It is fine to eat them when they are ripe.
In all honesty, everybody that I have ever seen that has ever been a raw foodie for many many years looks absolutely TERRIBLE.
Unless they are lying to me, this is not the case that I have seen. I am a 70-80% raw foodist. I know a some people who eat nothing but raw foods. People don't took terrible because they are suffering from a cooked food deficiency. Are their raw foods nutritionally deficient? Nutritionally deficient foods are one of our major problems. Are the foods fresh? Are they consuming to much of some types of raw food and not enough of others?