I have used Prodiem, and found that it works OK, but both that and Metamucil give me incredible amounts of bloating. My Dr. a few years ago told me to take one tablespoon of whole flax seeds at bed each night followed by a large glass of water. I do this faithfully every night and for the most part it works well. When I am having a really bad bout of IBS-C, it does not help much, but at other times it keeps me very regular. I like taking the flax better because it is all natural, not refined or anything, and it costs very little. I found Prodiem to be very expensive.