I was wondering if you were taking a prebiotic as well? I've read that by serving as "food" for the probiotics you find in yogurt it can increase their volume by 5-10 times. I think most studies have been done with inulin, but I assume (based on information Heather has provided here) that most SFS, like acacia or Benefiber (which I also take in addition to foods containing inulin), provide the same benefit. Is there any mention of this in the book you're reading?
I'm going to have to check out "Restoring Your Digestive Health." Sounds like an informative read!