Yes you can, in the book he tells you that you to get your proper protein you just add "Protein rich vegetarian foods" such as firm and extra firm Tofu and isoloated soybean protein powder. also eating hot dogs, hamburgers and sausage..Soy style, Tofu burgers gardenburgers, soy dogs etc etc. "Beans have exceptionally high amount of carbs for the amount of protein they provide, which makes it impossible to acheive the desired protien to carb ratio needed for the Zone"

Hope that helps, Mel