Gastric acid
The main constituent of gastric acid is hydrochloric acid which is produced by parietal cells (also called oxyntic cells) in the gastric glands in the stomach. Its secretion is a complex and relatively energetically expensive process. Parietal cells contain an extensive secretory network (called canaliculi) from which the hydrochloric acid is secreted into the lumen of the stomach. The pH of gastric acid is 1.5 to 3.5 in the human stomach lumen, the acidity being maintained by the proton pump H/K ATPase. The parietal cell releases bicarbonate into the bloodstream in the process, which causes a temporary rise of pH in the blood, known as an alkaline tide.
Alkaline diet
These diets have been promoted by alternative medicine practitioners, who propose that such diets treat or prevent cancer, heart disease, low energy levels, and other illnesses. Human blood is maintained between pH 7.35 and 7.45 by acid–base homeostasis mechanisms. Levels above 7.45 are referred to as alkalosis and levels below 7.35 as acidosis. Both are potentially serious. The idea that these diets can materially affect blood pH for the purpose of treating a range of diseases is not supported by scientific research and makes incorrect assumptions about how alkaline diets function that are contrary to human physiology.