I haven't seen anyone mention systemic enzymes for digestive problems. It seems to me like this would help with leaky gut, since from what I can tell the therapy is quite powerful. The enzymes can eat away internal scar tissue, for example. I listened to a CD by Dr. Will Wong on systemic enzyme therapy and a product called Vitalzyme that sounded promising. He is selling a product, but he is also a licensed doctor (a naturopath, I believe).
I also read Burton Goldberg's, "Alternative Medicine Guide to Weight Loss," which has a whole section on enzymes. It describes how enzymes are crucial for proper digestion.