I read this book a few years ago but I (conveniently) forgot about much of what I read, except for one main message which stuck in my head. I saw the movie last night and it remined me of that message. Its simple, there's shit in the meat. I remember that that had a huge impact on me when I read that line in the book.
Bruce Willis plays his part very well in the movie. His answer is that every now and them you have to eat some shit. So every time you tuck into a super mac muggy meal, remember that there's a teeny tiny piece of shit in there somewhere. Its really small, you probably won't see it or smell it, but it's there!