From the Guidelines
The normal pH of the stomach is typically between 1.5 and 3.5, making it highly acidic. This strong acidity is primarily due to the secretion of hydrochloric acid (HCl) by parietal cells in the stomach lining. The acidic environment serves several important functions:
- it activates pepsinogen to form pepsin (an enzyme that breaks down proteins)
- kills many ingested microorganisms
- denatures proteins to begin digestion
- facilitates the absorption of certain nutrients like iron and calcium. Although the provided study 1 discusses the importance of pH in the context of bleeding ulcers and the use of acid-suppressing drugs, it does not directly address the normal pH range of the stomach. However, it mentions that a pH greater than 6 is necessary for platelet aggregation, implying that the normal stomach pH is indeed lower than this threshold. The stomach's ability to maintain this acidic environment is crucial for proper digestion and protection against pathogens, while a specialized mucus layer protects the stomach itself from being damaged by its own acid. In clinical practice, understanding the normal pH of the stomach is essential for managing conditions like gastroesophageal reflux disease (GERD) and peptic ulcers, where acid suppression may be necessary to alleviate symptoms and promote healing 1.
From the Research
Normal pH of the Stomach
The normal pH of the stomach is a topic of interest in various medical studies.
- The study 2 measured gastric pH in ambulatory esophageal pH monitoring and defined the normal range of gastric pH as 0.3-2.9.
- Another study 3 discussed the gastrointestinal pH profile of healthy subjects, stating that the intraluminal pH is rapidly changed from highly acid in the stomach to about pH 6 in the duodenum.
- However, the exact normal pH of the stomach is not explicitly stated in all studies, but it is generally considered to be acidic, with a pH range of around 1.5-3.5, as inferred from the study 2 which found a median gastric pH of 1.7 in patients.
Factors Affecting Gastric pH
Several factors can affect gastric pH, including:
- Diet, which primarily affects the colonic pH, whereas drugs might affect both small intestinal and colonic pH, as described in the study 3.
- Gastrointestinal diseases, such as chronic pancreatitis and cystic fibrosis, which seem to decrease pH of the proximal small intestine, as mentioned in the study 3.
- Medications, such as proton-pump inhibitors and H2 blockers, which can inhibit gastric secretion and relieve symptoms of diarrhea and postprandial urgency associated with irritable bowel syndrome or functional diarrhea, as found in the study 4.