Coffee is highly acidic and can trigger the hypersecretion of gastric acids. Decaffeinated coffee increases acidity to a higher level than either ordinary coffee or caffeine alone.
Acidic substances or chemicals are those that have the characteristics of an acid. Acidity is the level of acid in substances. An acid refers to a chemical substance whose aqueous solutions are dotted by a sour taste. Aqueous solutions of acidic nature have a pH of less than 7, with a lower pH indicating a greater acidity. The acidity of coffee can irritate the stomach. Both caffeine and coffee encourage gastric acid production, and decaffeinated coffee elevates gastrin levels.