my breath gets nasty too, i can tell cause my toungue starts feelin like a dirty ashtray.
i drink 3-4 protien drink along with over a gallon of water and 8-10 cups of coffee a day(i work afternoons and i wake up early).
I brush and use mouthwash 3-4 times a day, i need to cut the coffee to 2 cups in the am and thats it, i think this causes it more than the protien.
I'd rather have to brush all the time than have protien gas, i have a buddy who farts a;ll day long from protien powder.