There is one more aspect of the causes of cancer and certain types of disease that hasn't been written about in this thread. This is bottled up stress in various forms. I have heard and read about reports time and time again about how people have cured themselves of cancer by addressing conscious conflicts and forgiving others. Energy therapy touches on this subject. I recently heard something about an author named Louise Haye. She apparently cured herself of cancer by addressing her stress. I will probably read at least one of her books sooner or later.
Of course the reason why some of us haven't heard about this is because there is no money in it for businesses.