Linda's right - the carbonate helps bind stuff up. But in addition to that effect, the calcium itself helps regulate muscle and nerve function. And we all know how important nerve and muscle function is in IBS.There were also some studies done that show women's calcium levels drop near the time of their periods, which can contribute to moodiness, diarrhea, and cramping. So calcium is important for a lot of reasons.BTW - I told my doc about the calcium, and he had never heard of any studies that deal with it's effect on IBS-D. Typical, huh? The medical community is more willing to spend research dollars on new and expensive drugs rather than a mineral we can all get off the shelf, huh?------------------Fear can hold you prisoner. Hope can set you free.Missycat