Animals / Human Biology / Nature

Acid in our stomach

Vulture (Photo:Beks-X)

Acid reflux or acidity problems, a heart burn sensation which is felt after having a large meal, lying down soon after a meal, during pregnancy or taking certain medications. There is a valve at the entrance of the stomach called lower esophageal sphincter (LES) which usually closes after the food passes through. However, when this muscle doesn’t seal the entrance tightly, the acid in the stomach travels to the esophagus resulting in the burning sensation. This acid is secreted by epithelial cells called parietal cells of the stomach and its main job is to aid digestion by creating optimal pH (a scale which used to specify acidity or basicity of water) for enzymes pepsin, gastric lipase and stimulates pancreatic bicarbonate secretion to break down food and thus help in absorption of nutrients by the cells. The pH range of gastric acid in humans is between the range of pH 1.5-2.0. Acid secretion is present at birth and reaches adult quantity by the age of 2. Here are some interesting information about the acid in our stomach

Man (Photo:Karl Magnuson)

  • The pH of the acid in the human stomach is much lower than that of other animals and is closer to scavengers.  It is hypothesized that when humans hadn’t evolved stable bipedal walking they had to eat leftover carcasses as hunting animals without tools was difficult. This scavenging trait probably helped the evolution of stomach acid with a lower pH than most animals which can efficiently disinfect food. 
  • pH levels are the highest in herbivore animals and gradually decrease in carnivores and omnivores with the lowest levels found in scavengers such as vultures. 
  • Researchers hypothesized that the diversity and type of gut microbiome is determined by the acidic environment of the stomach. Stomach acid is very effective in getting rid of opportunistic bacteria which otherwise can absorb nutrients thus preventing the host stomach from maximal amount of nutrients from food. 
  • Researchers have found that both gastric acid concentration and output is decreased in children who are malnourished and it has been hypothesised that this impairment probably leads to bacterial overgrowth and diarrhea.  
  • It has be found that malnourished children have  
  • The awareness that the stomach contains acid and is necessary for digestion was present as early as the 16th century. 
  • Stomach acid is composed of hydrochloric acid.
  • The stomach lining is rich in lipoproteins which are resistant to acid attack, thus protecting the stomach from getting corroded. 
  • Herbivores such as camels and llamas have stomach juice in the range of 6.4-7.0 thus indicating that diet played a major role in the pH of the gastric juice.

Camel (Photo: Wolfgang Hasselmann)

Whenever I watched documentaries on vultures I was in awe of their digestive capabilities. Little did I know that in theory atleast  that I can get a seat at their dinner table as well. 


Royalty free images were used.

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