I like metamucil the best, it will cause gas in the begining but if you start with a tsp and gradually increase the dose as your body adjusts. I take it at bedtime so I dont have problems with gas.
There are different types of fiber and this one is very helpful with colon problems. It makes the stool easier to pass, it helps to bulk things up and absorb the water in the colon.
I have tried benefibre and citrucelle but went back to the metamucil(with sugar) the sugar free one has aspartame and can cause diahrea.