If you're looking for studies on the topic, check out these two videos:
http://video.google.com/videoplay?docid=-847196066367535747
http://video.google.com/videoplay?docid=-1719204869171202407
It's basically a survey paper in video form, presented by one of the researchers. It has actual graphs! With error bars!
The corresponding book is pretty good too, it's called the China study.
Personally, I trust statisticians on health much more than biologists. It's nice that there's a biological basis for the conclusion, but trying to argue diet based on the metabolic process seems like a stretch, especially when it conflicts with what's observed.