question: Is our stomach acid the same acid we’ve had since we were born?
comment: It is constantly being secreted by parietal cells in the stomach wall.
passages: Bile acids may have some importance in the development of colorectal cancer. Deoxycholic acid (DCA) is increased in the colonic contents of humans in response to a high fat diet. In populations with a high incidence of colorectal cancer, fecal concentrations of bile acids are higher, and this association suggests that increased colonic exposure to bile acids could play a role in the development of cancer. In one particular comparison, the fecal DCA concentrations in Native Africans in South Africa (who eat a low fat diet) compared to African Americans (who eat a higher fat diet) was 7.30 vs. 37.51 nmol/g wet weight stool. Native Africans in South Africa have a low incidence rate of colon cancer of less than 1:100,000, compared to the high incidence rate for male African Americans of 72:100,000.
   BULLET::::- Gastrin: This is an important hormone produced by the "G cells" of the stomach. G cells produce gastrin in response to stomach stretching occurring after food enters it, and also after stomach exposure to protein. Gastrin is an endocrine hormone and therefore enters the bloodstream and eventually returns to the stomach where it stimulates parietal cells to produce hydrochloric acid (HCl) and Intrinsic factor (IF).
  
  Of note is the division of function between the cells covering the stomach. There are four types of cells in the stomach:
  
  BULLET::::- Parietal cells: Produce hydrochloric acid and intrinsic factor.
   Section::::Clinical studies.:Portal hypertension.
  
  Animal studies suggest that OCA improves intrahepatic vascular resistance and so may be of therapeutic benefit in portal hypertension. An open label phase 2a clinical study is under way.
  
  Section::::Clinical studies.:Bile acid diarrhea.
   In the fetus, the normal range differs based on which umbilical vessel is sampled (umbilical vein pH is normally 7.25 to 7.45; umbilical artery pH is normally 7.20 to 7.38). In the fetus, the lungs are not used for ventilation. Instead, the placenta performs ventilatory functions (gas exchange). Fetal respiratory acidemia is defined as an umbilical vessel pH of less than 7.20 and an umbilical artery PCO of 66 or higher or umbilical vein PCO of 50 or higher.
  
  Section::::See also.
  
  BULLET::::- Acid–base homeostasis
  
  BULLET::::- Acid–base imbalance
  
  BULLET::::- Alkalinizing agent
  
  BULLET::::- Alkaline diet
  
  BULLET::::- Arterial blood gas
  
  BULLET::::- Chemical equilibrium
   Excess concentrations of bile acids in the colon are a cause of chronic diarrhea. It is commonly found when the ileum is abnormal or has been surgically removed, as in Crohn's disease, or cause a condition that resembles diarrhea-predominant irritable bowel syndrome (IBS-D). This condition of bile acid diarrhea/bile acid malabsorption can be diagnosed by the SeHCAT test and treated with bile acid sequestrants.
  
  Section::::Clinical significance.:Bile acids and colon cancer.
   The highest concentration that gastric acid reaches in the stomach is 160 mM in the canaliculi. This is about 3 million times that of arterial blood, but almost exactly isotonic with other bodily fluids. The lowest pH of the secreted acid is 0.8, but the acid is diluted in the stomach lumen to a pH between 1 and 3.
  
  There is a small continuous basal secretion of gastric acid between meals of usually less than 10 mEq/hour.
  
  There are three phases in the secretion of gastric acid which increase the secretion rate in order to digest a meal:
   Older methods such as the C-glycocholic breath test are no longer in routine clinical use.
  
  Measurement of 7α-Hydroxy-4-cholesten-3-one, (C4), a bile acid precursor, in serum, shows the increased bile acid synthesis found in bile acid malabsorption. This test is an alternative diagnostic means when available. Fasting blood FGF19 values may have value in the recognition of the disease and prediction of response.
   BULLET::::2. The gastric phase: About sixty percent of the total acid for a meal is secreted in this phase. Acid secretion is stimulated by distension of the stomach and by amino acids present in the food.
  
  BULLET::::3. The intestinal phase: The remaining 10% of acid is secreted when chyme enters the small intestine, and is stimulated by small intestine distension and by amino acids. The duodenal cells release entero-oxyntin which acts on parietal cells without affecting gastrin.
  
  Section::::Regulation of secretion.
   Experimental studies also suggest mechanisms for bile acids in colon cancer. Exposure of colonic cells to high DCA concentrations increase formation of reactive oxygen species, causing oxidative stress, and also increase DNA damage. Mice fed a diet with added DCA mimicking colonic DCA levels in humans on a high fat diet developed colonic neoplasia, including adenomas and adenocarcinomas (cancers), unlike mice fed a control diet producing one-tenth the level of colonic DCA who had no colonic neoplasia.
   The various biomarkers give similar diagnostic yields of around 25% in patients with functional bowel disorders with diarrhea. In countries such as the USA, where SeHCAT is not available, fecal bile acids and C4 are available to make the diagnosis.
  
  Section::::Treatment.
   As of March 15, 2016, Novartis Pharmaceuticals is conducting a phase II clinical study involving a farnesoid X receptor agonist named LJN452.
  
  Section::::Epidemiology.
  
  Bile acid malabsorption is common in Crohn's disease but not always recognized. Most people with previous ileal resection and chronic diarrhea will have abnormal SeHCAT tests and can benefit from bile acid sequestrants.
   Digestion is a complex process controlled by several factors. pH plays a crucial role in a normally functioning digestive tract. In the mouth, pharynx and esophagus, pH is typically about 6.8, very weakly acidic. Saliva controls pH in this region of the digestive tract. Salivary amylase is contained in saliva and starts the breakdown of carbohydrates into monosaccharides. Most digestive enzymes are sensitive to pH and will denature in a high or low pH environment.
   A typical adult human stomach will secrete about 1.5 liters of gastric acid daily. Gastric acid secretion happens in several steps. Chloride and hydrogen ions are secreted separately from the cytoplasm of parietal cells and mixed in the canaliculi. Gastric acid is then secreted into the lumen of the gastric gland and gradually reaches the main stomach lumen. The exact manner in which the secreted acid reaches the stomach lumen is controversial, as acid must first cross the relatively pH neutral gastric mucus layer.
   Physiologically, the "Chaetogaster" species have already long been known as invertebrates with acid stomach content, just like vertebrates.
  
  Section::::The special case of "Chaetogaster limnaei".
   BULLET::::- Gastric lipase: Gastric lipase is an acidic lipase secreted by the gastric chief cells in the fundic mucosa in the stomach. It has a pH optimum of 3–6. Gastric lipase, together with lingual lipase, comprise the two acidic lipases. These lipases, unlike alkaline lipases (such as pancreatic lipase), do not require bile acid or colipase for optimal enzymatic activity. Acidic lipases make up 30% of lipid hydrolysis occurring during digestion in the human adult, with gastric lipase contributing the most of the two acidic lipases. In neonates, acidic lipases are much more important, providing up to 50% of total lipolytic activity.
   Sources of acid loss include:
  
  BULLET::::1. Use of hydrogen ions in the metabolism of various organic anions
  
  BULLET::::2. Loss of acid in the vomitus or urine
  
  BULLET::::3. Gastric aspiration in hospital
  
  BULLET::::4. Severe diarrhea
  
  BULLET::::5. Carbon dioxide loss through hyperventilation
  
  Section::::Compensation.
   About 20,000 protein coding genes are expressed in human cells and nearly 70% of these genes are expressed in the normal stomach. Just over 150 of these genes are more specifically expressed in the stomach compared to other organs, with only some 20 genes being highly specific. The corresponding specific proteins expressed in stomach are mainly involved in creating a suitable environment for handling the digestion of food for uptake of nutrients. Highly stomach-specific proteins include GKN1, expressed in the mucosa; pepsinogen PGC and the lipase LIPF, expressed in chief cells; and gastric ATPase ATP4A and gastric intrinsic factor GIF, expressed in parietal cells.
   BULLET::::- Diagnosis/exclusion of pancreatic involvement in association with gastrointestinal symptoms, abdominal pain or osteoporosis, for example.
  
  Method of detection:
  
  BULLET::::- Sandwich ELISA with two monoclonal antibodies highly specific for human pancreatic elastase 1
  
  BULLET::::- The ELISA kit is based on a microtiter plate (96 well format) with 12 breakable single strips x 8 wells suitable for up to 42 samples in duplicate
  
  Reference concentration to interpret Pancreatic Elastase results:
  
  For adults and children after the first month of life
  
  BULLET::::- Values  200 µg elastase/g stool indicate normal exocrine pancreatic function
   Total food intake and absorbance rate of food will rapidly decline after gastric bypass surgery, and the number of acid-producing cells lining the stomach increases. Doctors often prescribe acid-lowering medications to counteract the high acidity levels. Many patients then experience a condition known as achlorhydria, where there is not enough acid in the stomach. As a result of the low acidity levels, patients can develop an overgrowth of bacteria. A study conducted on 43 post-operative patients revealed that almost all of the patients tested positive for a hydrogen breath test, which indicated an overgrowth of bacteria in the small intestine. Bacterial overgrowth causes the gut ecology to change and induces nausea and vomiting. Recurring nausea and vomiting eventually change the absorbance rate of food, contributing to the vitamin and nutrition deficiencies common in post-operative gastric bypass patients.
   A fourth phase of acid secretion is known as the basal state which occurs in the times between meals (interdigestive phase). The level of acid secretion during these times is regulated by body weight, individual, number of parietal cells, and time of day. Acid secretion is lowest in the morning before awakening and highest at night.
  
  Section::::Cephalic Phase.
   BULLET::::- Bile salt breath test (C-glycocholate) to determine bile salt malabsorption.
  
  BULLET::::- Schilling test to establish cause of B deficiency.
  
  Section::::Management.
  
  Treatment is directed largely towards management of underlying cause:
   Several methods have been developed to identify the disorder but there are difficulties with all of them. Diagnosis of bile acid malabsorption is easily and reliably made by the SeHCAT test. This nuclear medicine test involves two scans a week apart and so measures multiple cycles of bile acid excretion and reabsorption. There is limited radiation exposure (0.3 mSv). Retention of SeHCAT at 7 days is normally above 15%; values less than 15%, 10% and 5% predict respectively mild, moderate and severe abnormal retention and an increasing likelihood of response to bile acid sequestrants. This test is not licensed in the USA, and is underutilized even where it is available. 
   Dietary factors are not proven causes and the association between stomach cancer and various foods and beverages is weak. Some foods including smoked foods, salt and salt-rich foods, red meat, processed meat, pickled vegetables, and bracken are associated with a higher risk of stomach cancer. Nitrates and nitrites in cured meats can be converted by certain bacteria, including "H. pylori", into compounds that have been found to cause stomach cancer in animals.
   Bile acid
  
  Bile acids are steroid acids found predominantly in the bile of mammals and other vertebrates. Different molecular forms of bile acids can be synthesized in the liver by different species. Bile acids are conjugated with taurine or glycine in the liver, and the sodium and potassium salts of these conjugated bile acids are called bile salts.
   Section::::Clinical studies.:Primary biliary cholangitis.
  