I found drinking kefir made me regular like nothing else. It was quite remarkable, and that's coming from somone who exercises and eats loads of vegetable and still manage to not be regular.

I used to buy these huge jugs of kefir from Washington, but stores in Canada only sells them in small containers that are much too expensive to buy regularly so I haven't had kefir in a while. Needless to say I'm not as regular as I was when I was consuming it.

You can also make kefir quite easily by buying the kefir grains. The bonus is kefir's good for your gut and immune system, too.