Chronic atrophic gastritis is associated with many factors, such as dietary habits, autoimmunity, and bacterial infections. Currently, Helicobacter pylori infection is the most important cause of chronic atrophic gastritis. In our country, most H. pylori infections are acquired in childhood, and some of these infections progress from non-atrophic gastritis to chronic atrophic gastritis. So, how exactly does H. pylori cause atrophic gastritis? To answer this question, we need to understand our stomach first. The stomach is like a pouch, with the upper end connected to the esophagus and the lower end connected to the duodenum. The stomach consists of four main parts: the cardia, the fundus, the body and the pylorus (including the pyloric duct and pyloric sinus). The cardia is the entrance of the stomach and the pylorus is the exit of the stomach. When Helicobacter pylori (Hp for short) enters the stomach, the flagellum at the end is like the tail of a fish, and by swinging it is able to propel the bacterium forward, through the mucosal layer of the stomach to the surface of the epithelial cells, and settle down. This spiral-shaped or rod-shaped bacteria is mainly distributed in the pylorus region of the stomach, so it is named H. pylori. H. pylori is a group of stubborn molecules that are not only hardy and can withstand the erosion of gastric acid, but also very “home-loving” and will not leave easily once they settle on the surface of the epithelial cells of the gastric mucosa. On the one hand, H. pylori have to absorb nutrients from the stomach to sustain a large family. On the other hand, they also discharge waste everywhere on the gastric mucosa – toxins, inflammatory factors, etc., destroying the structure and function of the gastric mucosa; this slowly causes the gastric glands in the gastric mucosa to shrink in size, decrease in number and even become intestinalized (the normal epithelial cells in the gastric mucosa become diseased and turn into a new type of epithelial cells similar to those in the small intestine or colon mucosa). (the normal epithelial cells in the gastric mucosa are transformed into a new type of cell similar to the epithelial cells in the small intestine or colon mucosa). Chronic atrophic gastritis occurs when the gastric mucosa becomes atrophic or intestinalized, and patients with chronic atrophic gastritis have an increased risk of developing gastric cancer.