If it's a concern the buy the non carbonated version. Non carbonated mineral water is called 'still' mineral water. Whole foods has one that's reasonably priced, if you've got one of those near you. Mineral water is great, esp if you workout outside, or you sweat alot (loss of electrolytes).
I was having cramping issues on days following my crossfit routines, and the mineral water helped a great deal with that. I was sweating out too much of the minerals (I train throughout the year in Houston, so July/August is kind of rough). This can be a problem if the multi you take is mineral deficient, as was mine during this period.