Acid that is called hydrochloric acid (HCI) is always present in a healthy stomach. It is important for the body because the stomach acid helps digestion and also acts as a shield against harmful microbes in the gastrointestinal system.
Many people suffer from vague stomach trouble, at least from time to time. The symptoms may vary and can be caused, for example, by too little acid secretion leading to an anacidic stomach, or, excessive acid secretion. An anacidic stomach can be caused by either a chronic inflammation of the mucosa (i.e. atrophic gastritis), or long-term use of antacids such as proton-pump inhibitors (PPIs) which block the action of the acid-forming cells.
It is important to identify the exact causes of these problems, because even insignificant disorders may predispose to gastric diseases.