An antacid is a substance which neutralizes stomach acidity.

Reduced stomach acidity may result in an impaired ability to digest and absorb certain nutrients, such as iron and the B vitamins.

These drugs work by reducing stomach acidity.

Known as Heidelberg capsules, they provide a record of stomach acidity during digestion.

For example, both normal and disease-causing intestinal bacteria may grow when antacids or other medication alter the stomach acidity.

Grigori Rasputin may have survived a potassium cyanide poisoning because his stomach acidity was unusually low.

Since cyanide works better with higher stomach acidity, it should, in theory, work best with an empty stomach.

Ginger has been used in the treatment and prevention of motion sickness, to increase appetite, and to reduce stomach acidity.

But the pH of food generally would not impact stomach acidity (although other properties of food can affect digestion).

Infection most likely occurs in people with malnutrition due to the low stomach acidity or people with immune compromised systems.