An antacid is a compound that absorbs and neutralizes stomach acid. The use of antacids has declined because of the availability of many very potent drugs that are more effective and much less troublesome to take than antacids. Still, these drugs can be helpful in relieving intermittent, infrequent heartburn and indigestion. If these symptoms occur frequently such as multiple times a day or at night, then the cause should be sought, as a more serious disorder may be present.
Calcium carbonate is a good antacid but it also provides calcium, which is desirable.
Adults need 1500 mg of calcium a day and post menopausal females even more. Unless you drink a quart of milk a day, you likely do not get enough calcium from your food. If taken with food, the protective effect may be 2 or 3 hours. To get as much acid reduction as prescription medicines produce is expensive as the antacid must be taken frequently during the day and night. It is probably cheaper to take an acid-reducing pill once or twice a day.