Although some products containing psyllium will call themselves a laxative (ie. Metamucil)...psyllium is a soluble fiber and absorbs 40X its weight in water! Since many people are chronically dehydrated to begin with...and many who use the P&B cleanse don't drink nearly enough water with the shakes...the result can be constipation. You are essentially making bricks inside your body if you don't add enough water into a fiber mix!!! Not everyone will become constipated...but it happens not too infrequently. Psyllium is a good fiber to use to KEEP you going...provided you drink enough water, but not the best choice to GET you going!