This whipping boy of humanity is regularly insulted by all sorts of concoctions dictated by our taste buds and psyche, not to mention the many drugs required to treat our poor health. It is amazing how much abuse it can absorb with minimal complaint.
The stomach has evolved as a “fiery pit” of high acid content to intercept various bacterial invaders. Fortunately a few escaped to populate our intestinal tracts, where they are mostly beneficial. One bacterium in particular evolved to tolerate the high acidic conditions of the stomach, like extremophile bacteria tolerate the “smoking vents” underneath the sea. This is the famous helicobacterium pylori, which caused most gastric ulcers in the early days of my medical career. Ulcers were then treated by an ongoing special diet. Now they are treated by a simple course of antibiotics.
The stomach evolved a special lining to tolerate the acid, and a valve to keep it in place. Over time this valve may weaken, allowing the acid to reflux back into the swallowing tube, the esophagus. This produces the familiar heartburn that most of us have experienced, and if chronic, can produce inflammation and the condition called Barrett’s esophagus, which frequently leads to gastric cancer.
Gastric cancer comprises only about 1.5% of cancers in the United States, but in Korea it is the most common cancer. This may be because of the Korean diet, Which often finds nitrites in close proximity to proteins, which donate an amine group to form the carcinogen nitrosamine.
I have begun a time restricted eating program, where I eat my entire days food within a six hour window. My stomach has seemed to tolerate this, but I have noticed that when I eat a lot of fat late in the day (I like half-and-half on my oatmeal) my stomach will object. Alcohol does the same thing, and when I was in medical school we used to give a dose of alcohol to stimulate stomach acid production, as a test.
If you have a lot of pain in the area of the stomach (the epigastrium), chronic heartburn or trouble swallowing chunks of meat, you may well need to see a gastroenterologist, who will look into the esophagus and stomach to check for problems.
Please check the following Mayo clinic articles for more information.