Our food grade calcium carbonate is a naturally mined, ultra-pure form with typical assays greater than 99% – to meet demanding industry standards, and more specifically, your own high purity standards. Calcium Carbonate is approved for use in food with no limitations, according to the U.S. Food and Drug Administration. Calcium carbonate is a natural product, but doesn't naturally occur in foods. Calcium carbonate is a popular dietary supplement used to increase calcium levels. You might see it as a calcium supplement, as an ingredient in antacids, or as an additive in food