Hi - Do you alreadly have IBS? I've had IBS for almost all my life, and I can attest to the fact that smoking does make it worse for some people. It did for me; and one of my college roommates, who didn't smoke but was constipated, was instructed by her doctor to smoke a cigarette after breakfast while sitting on the toilet. It did help with her constipation. However, because I had no problem with constipation, the cigarettes caused me to have diarrhea, and often! I think taking Metamucil helps with IBS - at least it's worth a try if you are not able to stop smoking. Good luck. mabent