Digestion and acid attack

Carbonic acid is formed when carbon dioxide reacts with the water present in the cells. 

This in turn produces H+ ions, which have to be dealt with and neutralized by the buffer system to keep the pH at the best working value. 

The proteins in the blood (namely that of the haemoglobin and particularly the histidine and cysteine amino acids of the proteins) are excellent buffers and keep the blood working at its most effective pH of 7.4. 

After eating too much food or drinking too much alcohol, the stomach sometimes becomes overloaded with the tasks it has to perform, particularly that of maintaining a steady constant working pH. The buffer system becomes overloaded and overworked and an excess of stomach acid builds up. This can lead to indigestion. 

The re-stabilizing of the stomach pH can be helped by taking stomach powders Rennies , Alkaseltzer or small amounts of bicarbonate of soda , etc. These materials add a small amount of basic OH ions or bicarbonate, HC03, ions in order to react with the excess acid. Unfortunately the bicarbonate ions produce C02 gas which causes you to burp. 

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