William 
> What I read is in the "excerpts" at
> http://www.thechinastudy.com/about.html
> he says it's the casein.

It's interesting that Chris Masterjohn of the WAPF doesn't dispute
Campbell's finding of a link between casein and cancer, but he speculates
that the type of processing used could affect the carcinogenic properties of
casein (for example, fermenting casein might make it less cancerous).


The Truth About the China Study
The China Study: Startling Implications for Diet, Weight Loss, and Long-Term
Health by T. Colin Campbell
http://www.cholesterol-and-health.com/China-Study.html

"Other questions, such as what effect different types of processing have on
casein's capacity to promote tumor growth, remain unanswered.
Pasteurization, low-temperature dehydration, high-temperature spray-drying
(which creates carcinogens), and fermentation all affect the structure of
casein differently and thereby would affect its physiological behavior."