If I said or implied that cancer is a certainty then I amend that. Lets say that in other cases where toxins are in long term contact with mucosa there's been increased incidence of cancer.
The digestive system is often thought of as an absorber of nutrients and eliminator of waste. That's a very simplistic and incorrect view.
link to abstract
The GI tract is now recognized having significant impact on the immune system. That wasn't known many years ago. What are the long term changes in flora and their effects?
Remember that colorectal cancer is an example. My problem is that people are taking an engineers view of this. Add all the nutrients and voila! Biological systems have never proven that simple and will never be. Consequently I have reservations based on more than "it can't work". I think the person who is attempting to popularize this is doing a great disservice and I expect a book "How to stop eating" or some such thing along with a commercial venture to package and sell. As one who saw how DES, a "perfectly safe" medication turned out I'm not cutting this guy any slack. It's my professional imperative to be highly skeptical.