+1 on this book. Goes into a great deal of detail about the relationship between agribusiness and the regulatory agencies (FDA and USDA).

I've been mostly vegetarian for seven or eight years now, and don't think it's especially hard to get enough protein. Grains, legumes, nuts, dairy. Chocolate. I usually bring a Clif bar or two along on a ride. My wife does weightlifting and likes whey powder, but not soy powder.