Gastric acid

Gastric acid is a fluid mixture secreted by glands in the stomach to aid the body in the digestion of food. Also called stomach acid or gastric juices, gastric acid is primarily made up of hydrochloric acid, digestive enzymes, water, mucus, proteins, and electrolytes. While its main function is to break down food so that it can be digested by the body, gastric acid also helps slow the growth of bacteria and sends signals to the small intestine that food is on the way. Too little gastric acid in the stomach can lead to infection or problems with digestion; too much can cause acid reflux disease or ulcers in the stomach or small intestine.

Background

The human digestive system is a series of organs responsible for consuming and processing food so that its nutrients can be absorbed by the body. It is also responsible for disposing of waste products resulting from the process. The digestive system consists of the gastrointestinal tract, or GI tract, and the liver, pancreas, and gallbladder. The GI tract is a system of hollow organs through which food travels as it passes through the body. It consists of the mouth, esophagus, stomach, small intestine, large intestine, and anus.

Food enters the body through the mouth, where it is chewed, mixed with saliva, and passed along through the esophagus. Muscles in the esophagus move the food down to the stomach where it mixes with gastric acid, breaking it down further to make it easier to digest. The stomach then pushes the processed food into the small intestine where it mixes with digestive enzymes produced by the liver, pancreas, and gallbladder. The walls of the small intestine absorb water and other nutrients from the food for use by the body. The waste products caused by the process are then pushed into the large intestine where excess water is absorbed, turning the liquid waste into a solid form. This solid waste is stored in the lower part of the large intestine called the rectum where it is eventually expelled from the body through the anus.

Overview

Gastric acid is a substance produced by the stomach that prepares food for digestion by the small intestine. Gastric acid is made up of several different substances that are produced by various cells in the GI tract and stomach. The most prominent ingredient is hydrochloric acid (HCl), a strong acid with highly corrosive properties. Hydrochloric acid is produced by the parietal cells, which are found in glands in the upper part of the stomach. The acid helps break down food into a more easily digestible form and kills unwanted bacteria that enter the stomach. Hydrochloric acid also converts the compound pepsinogen into pepsin, a digestive enzyme that breaks down proteins found in food. Pepsinogen is another component of gastric acid. It is produced by gastric chief cells found in the stomach lining. Because these cells are themselves made of proteins, pepsin cannot be released directly or it would consume its parent cells. Pepsinogen is released as an inactive substance and only becomes pepsin when it is triggered by hydrochloric acid.

Another element of gastric acid is gastric lipase, a digestive enzyme that is also released by the chief cells. This enzyme breaks down certain types of fats. Intrinsic factor is a type of protein produced by the parietal cells that binds to the vitamin B-12. When the food reaches the small intestine, intrinsic factor helps the body absorb B-12, which is vital for the production of red blood cells. Mucus is a thick, slimy substance secreted by cells in the mouth, neck, and stomach. Mucus acts as a coating agent to protect the lining of the stomach from the corrosive hydrochloric acid. Water is also present in gastric acid to provide a liquid environment that allows food and other substances to better mix together. Other components of gastric acid are amylase, an enzyme produced by saliva in the mouth; bicarbonate, a compound that controls HCl levels in the stomach; and various hormones and electrolytes. Electrolytes are minerals that conduct electric currents when dissolved in liquid. They are necessary in helping the body perform various functions.

In addition to breaking down food for digestion, gastric acid also sends chemical signals to the muscles that connect the stomach to the small intestine. These signals instruct the muscles to open so that food can pass through. The acid also sends signals to the pancreas instructing it to begin producing digestive enzymes.

The human body produces about three to four liters of gastric acid a day. Before the body begins eating, the stomach has a pH level of about 5.0 to 6.0. A pH level is the measure of acidity in an environment; the lower the pH number, the more acidic the environment. A level of 5.0 to 6.0 is considered slightly acidic to neutral. When the body smells, tastes, or even anticipates food, the stomach begins producing more gastric acid and the pH level begins to drop to between 1.0 and 2.0. Certain digestive triggers can only occur when the pH levels fall within a specific range. For example, pepsinogen can only be converted to pepsin when the pH level is between 1.0 and 3.0.

As people age, their body can produce lower levels of gastric acid. This condition, known as hypochlorhydria, can cause health problems as the body is not able to properly break down the nutrients from food. It can also allow bacteria on the food to survive longer in the stomach, potentially causing an infection. Too much gastric acid can also lead to several health-related issues. A common problem is acid reflux, in which stomach acid backs up and enters the esophagus. This can cause irritation and a burning sensation in the chest area. A more severe and chronic form of the problem is called gastroesophageal reflux disease (GERD). Too much gastric acid can also cause ulcers, painful open sores on the walls of the stomach or small intestine.

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