Calcium carbonate. This is the main ingredient in the most common mainstream antacids, and it is essentially ground-up limestone. This mineral certainly helps reduce acid, but it cannot be absorbed or digested by the body to any great degree.  Recently there’s been concern that all that calcium carbonate or limestone might contribute to kidney stones and build-up in the arteries, which could lead to an increased risk of heart attack. To learn more, go to our Learning Center, About calcium carbonate.

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