The lining of the stomach is uniquely designed to withstand the extremely acidic liquids released by the stomach cells to break down and digest food. The main component of stomach fluid is hydrochloric acid, chemically abbreviated as HCl. Stomach fluids must be acidic to break down food for absorption. Disturbances in stomach acid production can cause pain along with gastrointestinal symptoms such as bloating, belching and gas.
Mechanism
Hydrochloric acid is the main ingredient of stomach acid, which also contains pepsinogen, which is converted into the enzyme pepsin. Pepsin, which can work only in an acidic environment, breaks down proteins by breaking the bond between the different amino acids found in proteins so they can be absorbed in the small intestine. Stomach acid also contains potassium chloride and sodium chloride. Sstomach acid has a pH of between 1 and 2. A neutral pH, which is neither acidic nor alkaline, is 7. The parietal cells that line the stomach produce stomach acid.
Purpose
The purpose of stomach acid is to break down nutrients for easier absorption in the small intestine. Food that enters the small intestine without being broken down will not be well absorbed; nutritional deficiencies or malnutrition can develop. The acidity of the stomach also destroys bacteria and other pathogens that can cause illness such as E. coli and C difficile.
Timing
As much as 30 percent of the acid in your stomach is secreted when you think about, smell or see food, called the cephalic phase. In the gastric phase, when food enters the stomach, parietal cells release around 60 percent of the acid needed for digestion. Proteins produced by the breakdown of food stimulate the release of additional stomach acid. In the intestinal phase, around 10 percent of the acid produced enters the stomach in response to chyme, the mixture of broken down food, entering the small intestine.
Abnormalities
Two of the common abnormalities that can arise with stomach acid are excessive acid production and insufficient acid production. A decrease in stomach acid production occurs commonly as people age; as many as 30 percent of people over age 60 have atrophic gastritis caused by hypochlorhydria, low levels of stomach acid, or achlorhydria, an absence of stomach acid, according to Nutrition Review. People with acid reflux, a condition in which acid backs up from the stomach into the esophagus, causing heartburn and pain, often take drugs that reduce stomach acid production. However, low acid production can also cause heartburn and symptoms of acid reflux.
References
- Colorado State University; The Parietal Cell: Mechanism of Acid Secretion; R. Bowen; March 2010
- Nutrrition Review; Gastric Balance: Heartburn Not Always Caused by Excess Acid; Jim English
- Clinical Education; The Role of HCL In Gastric Function And Health; Michael Ash, D.O.; January 2011
- Harvard Medical School Family Health Guide; Do PPIs have Long-Term Side Effects?; February 2009
- Tahoma Clinic; The Digestive Theory Of Aging Part 2; Jonathan Wright, M.D.
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