What is the pH of the gastric acid in the stomach? Does it change when you get heartburn?

S.

The pH (a measurement of acid levels) in the stomach is normally very low, indicating a high level of acid. The acid, which is released by cells in the stomach, is necessary to help break down foods and aid digestion. Although high levels of acid can injure other areas of the digestive tract, such as the esophagus, the stomach itself is protected by the mucus that coats its walls.

In patients with heartburn or gastroesophageal reflux disease (GERD), the pH of the stomach does not change from its usual state. Instead, there is a problem with the sphincter that keeps acid from washing up from the stomach into the esophagus. The esophagus normally has a higher pH than the stomach (indicating a lower amount of acid). When reflux occurs, the pH of the esophagus drops as the stomach contents enter it. This sudden change in pH is the cause of the irritation and injury to the esophagus, and can lead to heartburn, regurgitation, chest pain and other symptoms of GERD.

Treatment of GERD involves medications that prevent acid production by the stomach. Less acid in the stomach means that stomach fluid has a higher pH. Then, when reflux occurs, the stomach contents washing up into the esophagus are less irritating because they contain much less acid.

Keep in mind that some patients still complain of symptoms of GERD despite adequate acid suppression. It is likely that other substances in the refluxed stomach contents can also irritate the esophagus. Although pH testing of the stomach or esophagus is not routinely done by gastroenterologists, sometimes such a test is performed (through a probe placed into the stomach through the nose) to check whether a patient's symptoms are really caused by GERD or to evaluate response to medications.