Can switching from carbs to smart carbs cause stomach pain?

Possible...: I am assuming you are speaking of carbs that are low on the glycemic index.This can cause some stomach discomfort, as any diet change can cause for short periods of time. However, if it is more pain than discomfort, and if it does not improve after a short time after adjusting to diet, i would recommend assessment by your physician sooner than later. Hope that helps and best of luck.