Just as heat can denature enzymes, so can a change in the pH. Enzymes that normally work in an acidic environment in the body can become denatured if the pH becomes too alkaline. And enzymes that normally work in alkaline environments in the body can become denatured if the pH becomes too acidic. Taking an antacid to reduce the acidity (and increase the pH) of the stomach and to relieve heartburn can make a person more comfortable. What would be the major drawback to taking too many antacids?

It will create an alkaline environment and can lead to denaturation of acidic enzymes.

Explanation:

Taking too much antacids will significantly increase the pH of the stomach and create an alkaline environment within it. Consequently, enzymes that normally work in acidic environments in the body can become denatured or rendered inactive. This will create another problem for the individual.

Too much antacid which then cause a major decrease in acidity which would cause the enzymes in the stomach (which operate optimally at high acidity) to be denatured.

Explanation:

Enzymes in the stomach function optimally at high acidity. Antacids are generally basic solution which reduces the acidity in the stomach hence relieve heartburn. Excess antacid will cause the operating conditions to be basic, hence lead to denature of the enzymes.