The logic behind antacids is that people who are suffering from heartburn, acid-reflux, GERD (GastroEsophageal Reflux Disease), etc. must be producing too much stomach acid.
So antacids work by neutralizing the acid in your stomach. But your stomach needs acid to digest proteins. So if the acid gets neutralized, your digestion stops.
Then your stomach, sensing something's wrong, secretes more acid to digest the food ...and the antacid neutralizes it again, thus stopping digestion again. Vicious cycle? (wasted money?) Havoc on your health?