Hydrochloric Acid in the Stomach and Digestive Problems
Hydrochloric Acid Made by the Stomach
The inside of the stomach is a very acidic environment, especially after food has just been eaten. The acidic pH is created by hydrochloric acid, which is secreted by cells in the stomach lining. The chemical is needed in order to activate an enzyme that digests the proteins in food. Hydrochloric acid also kills many harmful bacteria that enter the stomach.
Stomach acid is a helpful substance but is potentially harmful as well. Fortunately, our body has ways to protect us from any harmful effects. The lining of the stomach is coated with mucus, which prevents the acid from reaching the lining and damaging it. In addition, when the mixture of food and acid leaves the stomach and enters the small intestine, it's neutralized by the basic environment of the intestine.
Too much or too little acid can cause problems. A circular muscle called a sphincter closes the entrance to the stomach. If the sphincter doesn't work properly, food and acid may move up into the esophagus, creating a burning sensation known as heartburn. Stomach acid can also aggravate ulcers, making them more painful. Sometimes cells in the stomach lining are unable to make hydrochloric acid. Without enough acid, protein digestion in the stomach is difficult and bacterial overgrowth can occur.
Functions of the Stomach
Hydrochloric acid (HCl) plays an important role in food digestion. The acid is made by parietal cells in the gastric glands of the stomach lining. (The glands are shown in the illustration below.) HCl does its job in the stomach cavity, or lumen. The parietal cells also secrete intrinsic factor, which is necessary in order for vitamin B12 to be absorbed in the small intestine.
Other cells in the gastric glands known as chief cells make a substance called pepsinogen. Hydrochloric acid converts pepsinogen into an enzyme called pepsin. Pepsin begins the digestion of protein in our food, breaking up the long, folded chains of amino acids into shorter and simpler structures. The enzyme requires an acidic environment to do its job. Enzymes in the small intestine complete the breakup of the protein molecules, allowing individual amino acids to enter the bloodstream.
The pH in the stomach varies. If a person hasn't eaten for a long time, the pH of stomach fluid is generally around 4. When food enters the stomach, hydrochloric acid production increases and the pH may fall to as low as 1 or 2, a very acidic condition. Components of the food often raise the pH slightly as digestion proceeds. The acid not only provides a suitable environment for pepsin to work but also kills many potentially harmful microbes that enter the stomach in our food.
The gastric glands secrete a liquid called gastric juice. Around two to three litres of this liquid are secreted each day. Gastric juice contains water, a protein called mucin, hydrochloric acid, pepsinogen, intrinsic factor, and other chemicals. In the stained sample of stomach lining below, the gastric glands are the indentations on the right that open to the outer environment (or the lumen of the stomach).
Making Hydrochloric Acid: The Proton Pump
The production and secretion of hydrochloric acid is a complex process. A major contributor to the process is a proton pump in the membrane of the parietal cells. A proton pump is a special protein inside a membrane, which is either the cell membrane or the membrane of an organelle in the cell. The protein transports protons across the membrane by active transport, a process that requires energy.
A hydrogen atom is made of a positively charged proton and a negatively charged electron. When the atom loses its electron to form a hydrogen ion, all that remains is a proton. A hydrogen ion (H+) is therefore the same thing as a proton.
Hydrogen ions are moved through the membrane of a parietal cell and into the duct of a gastric gland by a proton pump known as H+/K+ ATPase. Chloride ions (Cl-) move through the parietal cell membrane by diffusion, a process that doesn't require a protein carrier or added energy. (Hydrochloric acid consists of hydrogen ions and chloride ions.) The video below shows the process in more detail.
The information below is given for general interest. Anyone with unexplained digestive problems or with symptoms that may be related to stomach acid should visit a doctor.
Acid Reflux and GERD
The entrance to the stomach is protected by the lower esophageal sphincter, or the LES. A sphincter is a circular muscle that closes or opens the entrance or exit of a tubular structure. Under normal circumstances, the LES closes the entrance to the stomach once food has entered its lumen. If the LES doesn't close or if it opens while food is still in the stomach, the churning, acidic mix in the stomach may be pushed up into the esophagus. The hydrochloric acid may then irritate the wall of the esophagus, producing pain and a condition known as heartburn. There may also be a sour taste in the mouth.
Acid reflux and GERD (gastroesophageal reflux disease) are closely related conditions, but GERD is more serious than acid reflux. Many people seem to experience acid reflux occasionally. In GERD, the reflux is experienced regularly. The regurgitated acid produces heartburn, a sour taste, and sometimes additional symptoms, including coughing, wheezing, chest pain, and difficulty in swallowing. Anyone with these symptoms should visit a doctor for a diagnosis.
GERD requires medical treatment. If the esophagus is exposed to acid frequently over a long period of time, its cells may be damaged or its lining may change its nature and resemble the tissue that lines the intestine. The latter condition is known as Barrett's esophagus. It's linked to a slightly increased risk of esophageal cancer. Patients should visit a doctor regularly so that any precancerous cells can be treated.
Stomach Ulcers, H. pylori, and Acid
An ulcer is a sore that forms on the stomach lining or on the lining of the duodenum (the first part of the small intestine). Ulcers in the stomach are known as stomach, gastric, or peptic ulcers. Ulcers in the duodenum are known as peptic or duodenal ulcers.
It used to be thought that a person under stress produced excess stomach acid and that this acid damaged the stomach lining and caused an ulcer. It's now known that stomach ulcers are usually caused by a bacterium called Helicobacter pylori, or H. pylori. They may also be caused by long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs), which reduce the amount of protective mucus made in the stomach. Aspirin is an NSAID. Although stomach acid doesn't cause an ulcer, it may make it more painful.
H. pylori is an interesting creature, even though it can cause pain. It evades the acid that kills most bacteria and lives in the mucus coating on the stomach lining. Strangely, in some people the bacterium lives harmlessly in the digestive tract while in others it causes stomach ulcers or inflammation of the stomach lining (gastritis).
Possible Treatments for Excess Stomach Acid
Doctors often treat an H. pylori infection by prescribing antibiotics as well as medications that suppress acid production in the stomach. A popular medication is a type known as a proton pump inhibitor, which blocks the production of hydrochloric acid. It joins to the protein pump, preventing the pump from attaching to hydrogen ions and transporting them to the duct of the gastric gland.
Sometimes other types of drugs called H2-receptor antagonists are prescribed to reduce the acid level in the stomach. These drugs block the receptor on the parietal cell membrane that normally binds to histamine. Histamine joins to parietal cells to trigger the process that makes hydrochloric acid. Proton pump inhibitors and H2-receptor antagonists are also prescribed for some people who suffer from GERD.
Proton pump inhibitors are powerful reducers of stomach acid. They are often prescribed instead of H2-receptor antagonists because they are thought to be more effective, but their long-term use may increase the risk of osteoporosis and bone fractures. A limited amount of evidence suggests that proton pump inhibitors may block hydrogen ion transport in the bones as well as the stomach.
Some people take simple antacids to neutralize the acidity in their stomach. These aren't as effective as the more modern drugs because they don't prevent the acid from being made. They may provide temporary relief from a mild case of acid reflux or pain caused by acid in the stomach, but anyone who finds themselves repeatedly taking antacids needs to visit a doctor for a diagnosis and treatment.
In some places, proton pump inhibitors and H2-receptor antagonists are sold over the counter without a prescription. If someone is tempted to use these because antacids aren't working, it's very important that they see a doctor to get his or her advice instead of performing self-treatment.
Hypochlorhydria and Achlorhydria
Significant hypochlorhydria (low stomach acid) seems to be uncommon. It‘s more prevalent in elderly people than in younger ones, however. In severe cases, acid production stops and the condition is called achlorhydria.
Hyochlorhydria and achlorhydria are often associated with other disorders, including some autoimmune ones that affect the stomach. In an autoimmune disorder, the immune system mistakenly attacks the body’s own tissues. Some evidence suggests that medications that are designed to reduce acid production in the stomach may sometimes cause hypochlorhydria.
Some Possible Consequences of the Disorders
Without activated pepsin in the stomach, protein will pass into the small intestine in an undigested form. An enzyme called trypsin is present in the small intestine after we eat and does the same job as pepsin. It works in the basic environment of the intestine, where most nutrient absorption takes place. Other intestinal enzymes complete the digestion of proteins into individual amino acids, which are then absorbed into the bloodstream. Nevertheless, without the action of pepsin, digestion may be reduced.
Although the small intestine as a whole is basic, at the start of the duodenum (the section connected to the stomach), the pH is still slightly acidic. This acidity helps the absorption of certain nutrients. People with low stomach acid may need to take specific supplements to compensate for the lack of acid.
Chronic hypochlorhydria may reduce bone density. A low level of hydrochloric acid in the stomach cavity can lead to an overgrowth of bacteria, including Helicobacter pylori. The bacteria may travel into the small intestine. Here they may compete with human cells for the absorption of nutrients, including the calcium and other minerals needed to make strong, dense bones.
Trypsin is made in the pancreas in the form of trypsinogen, which is inactive. (The pancreas can be seen in the first illustration in this article.) Trypsinogen is sent to the duodenum, where it’s converted to trypsin. Like pepsin, trypsin digests proteins.
Possible Symptoms and Treatment
Symptoms of low stomach acid may include stomach discomfort, bloating, heartburn, and/or nausea. These symptoms can also be caused by other conditions, however. A doctor should be consulted if the symptoms are present in order to receive a diagnosis for the problem.
Someone with either hypochlorhydria or achlorhydria should be under a doctor’s care. Treatment will likely be aimed at removing the cause of the low acid production and/or at compensating for any chemical or nutritional deficiencies.
A Very Useful Chemical
Like the myriad of other processes that occur in the amazing human body, hydrochloric acid production and action generally occur as required and without our awareness. The chemical is very useful in our lives. Unfortunately, sometimes people are aware of the effects of too much or too little acid in the stomach. Luckily, methods to relieve or help these conditions exist, although a doctor's aid is generally required.
- Anatomy and physiology of the stomach from the Canadian Cancer Society
- Mechanism of hydrochloric acid secretion in the stomach from Colorado State University
- Acid reflux and GERD information from WebMD
- Peptic ulcer information from the Mayo Clinic
- Barrett's esophagus information from the Mayo Clinic
- Facts about proton pump inhibitors from Harvard Health Publishing
- Facts about achlorhydria and hypochlorhydria from the NIH (National Institutes of Health)
This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.
Questions & Answers
The digestive juice in our stomach contains HCl. It normally doesn't damage the stomach lining. Sometimes it does and causes considerable pain. What is the name given to the damaged area?
The mucus layer covering our stomach lining normally protects the stomach from an acid attack. If the mucus is removed by some factor, the acid may damage the lining of the stomach and cause a sore. A sore on the stomach lining is called a gastric, stomach, or peptic ulcer. Most gastric ulcers are caused by a bacterium called Helicobacter pylori, or by the long-term use of medications known as NSAIDs (non-steroidal anti-inflammatory drugs).Helpful 10
Are vitamins K and B made with bacteria?
Yes, vitamin K and the B vitamins—including vitamin B12— are made by certain bacteria. The situation in the human digestive tract needs some further explanation, however.
The nutrients from digested food—including the vitamins—are absorbed in the small intestine. The main functions of this organ are digestion and absorption. Most of the bacteria that release are potentially helpful vitamins for us live in the large intestine, which is located beyond the small one. Some vitamins are absorbed in the large intestine. There is uncertainty about the quantity of vitamins that are absorbed in this location, however.
Absorption of vitamin B12 from food is a particular problem. It requires the presence of a chemical called intrinsic factor, which is made by glands in the stomach lining. The intrinsic factor enables the vitamin to be absorbed in the last part of the small intestine, which is called the ileum.
Vitamin B12 is found in foods from animals but not in those from plants. Vegans who fail to take vitamin B12 supplements can develop serious health problems. This indicates that we don’t absorb enough vitamin B12 from the bacteria in our large intestine to be helpful. People whose stomach doesn’t make enough intrinsic factor can also develop problems if they fail to take supplements.
Obtaining sufficient vitamin K may be less of a problem. It's found in food from plants and to a lesser extent in certain types of food from animals and a few fermented foods. Also, it doesn’t require intrinsic factor to be absorbed. Obtaining a small quantity of the vitamin from the bacteria in our large intestine may be a bonus.
Vitamin K2 exists in different forms. Plants make vitamin K1 or phylloquinone. Leafy green vegetables are a good source of this vitamin. Food from animals contains vitamin K2 or menaquinone, which exists in slightly different forms. Intestinal bacteria also make vitamin K2. Our body can convert vitamin K1 into the form of vitamin K2 that we require.Helpful 1
How can the effect of hydrochloric acid be cured?
If you are suffering from an excessive amount of hydrochloric acid in your stomach, you need to visit your doctor for a diagnosis and treatment. Your doctor should be able to discover why you are making too much acid and will prescribe the most appropriate treatment for your problem and overall state of health.Helpful 19
I have been taking a magnesium chloride supplement recently, and my gastritis has become worse lately. Could the chloride part of the supplement somehow cause my stomach acid production to increase and cause this issue?
Since your gastritis has become worse, you should visit your doctor to find out why. WebMD says that a magnesium chloride supplement may cause a stomach upset as a side effect, but this may not be the reason for your increased discomfort. It's important that you discuss the advisability of taking the supplement with your doctor (if you haven't already done so) and get his or her recommendations for relieving your pain.Helpful 11
If we have natural buffering systems in our stomachs, why would we have to take antacids?
The stomach lining produces sodium bicarbonate, which helps to reduce the acidity in the stomach up to a point. Gastric fluid must be acidic in order for protein to be digested. The pancreas also produces sodium bicarbonate in order to neutralize the stomach acid that enters the small intestine and produces a basic environment so that intestinal enzymes can work.
If the stomach fluid contains a lot of acid, the natural sodium bicarbonate production in the organ may not be of much help. Under these circumstances, a person may take antacid tablets, which often contain sodium bicarbonate.Helpful 8
© 2013 Linda Crampton