Gastric cancer is one of the most common malignant tumors, and its incidence rate ranks first among all types of tumors in China. Among the malignant tumors of stomach, adenocarcinoma accounts for 95%, which is also the most common malignant tumor of digestive tract and even ranks among the top of all human malignant tumors. Early stage gastric cancer is mostly asymptomatic or has only mild symptoms. When the clinical symptoms are obvious, the disease is already in advanced stage. Therefore, we should be very alert to the early symptoms of stomach cancer to avoid delaying the diagnosis and treatment. Five warning signs of stomach cancer: 1. Upper abdominal pain: This is the most common symptom of stomach cancer. It starts as intermittent vague pain and is often diagnosed as gastritis or ulcer disease. 2.Upper abdominal discomfort: It is mostly a feeling of fullness or burning. It can be temporarily relieved and recurring. 3, loss of appetite, belching and other indigestion symptoms: manifested as a feeling of fullness after eating and active restriction of diet, often accompanied by recurrent belching. 4, black stool or positive fecal occult blood: If black stool occurs without eating blood tofu, taking bismuth and other drugs, you should come to the hospital for examination as soon as possible. 5.Lack of energy, emaciation and anemia: This is another common but non-specific symptom of stomach cancer. Patients often show fatigue and weakness due to loss of appetite and blood loss in digestive tract. In case of stomach pain, stomach area discomfort or digestive tract discomfort, one should promptly go to the gastroenterology department of hospital for gastroscopy or laboratory examination to figure out the cause of the disease. Those who live irregularly, work intensely and busy, and eat pickled or moldy food for a long time should have timely medical checkups and regular screening. Although many people’s stomach pain is the general gastritis, there are few people who eventually develop gastric cancer. Certain chronic gastric diseases such as gastric ulcer, atrophic gastritis and gastric polyps are now recognized as pre-cancerous lesions. This reminds people with a family history of gastric disease and recurrent stomach pain symptoms to be more alert. The incidence of stomach cancer is much higher in men than in women. In addition to the fact that men smoke and drink more alcohol, scientists have found that estrogen has a protective effect on the stomach. One study showed that women who received hormone replacement therapy (which includes estrogen) had a 48% reduction in the incidence of gastric cancer, including a 66% reduction in the risk of non-cardia gastric cancer and a 32% reduction in cardia gastric cancer. Middle-aged men are the mainstream group of gastric disease.” The main reasons for the decline of stomach function in middle-aged men are hunger, excessive smoking and drinking, and irregular life. Secondly, middle-aged men work under stress and live under relatively high pressure, these repeated bad stimulation of the cerebral cortex, but also easy to contribute to the stomach lesions. Most middle-aged men suffer from gastric diseases to varying degrees, especially gastric ulcers, such as gastric polyps, gastric ulcers, chronic atrophic gastritis and pernicious anemia, all of which have the potential to turn into gastric cancer. Early gastric cancer symptoms are not obvious and can be easily misdiagnosed. Early gastric cancer does not have characteristic symptoms, which are often manifested as hidden pain in upper abdomen, abdominal distension, loss of appetite, nausea and vomiting. Since these symptoms are not unique to early gastric cancer, it is easy to be diagnosed as general gastric disease. This is the main reason why patients are diagnosed late. It is reminded that once there is persistent stomach discomfort, especially those with the above-mentioned poor lifestyle, family history of gastrointestinal cancer, gastric ulcer, gastric polyp, chronic atrophic gastritis, Helicobacter pylori infection and other gastric cancer risk factors, they should go to regular hospitals for gastroscopy in a timely manner. It is recommended that people with risk factors for gastric cancer should have gastroscopy once a year after 40 years old (35 years old for smokers), which is the most effective way to detect gastric cancer at an early stage. Selenium supplementation helps prevent gastric cancer in clinical practice, which can improve the activity of selenium-containing enzymes in human body, enhance the antioxidant function of the body, effectively remove the free radicals generated during human metabolism, prevent necrosis of gastric mucosa, promote the repair of gastric mucosa and healing of ulcers, and prevent cancer. You can eat more selenium-rich foods in your daily diet. There are a lot of selenium-containing foods in nature, with high content of fish, shrimp and other aquatic products, followed by animal heart, kidney and liver. The highest content in vegetables are capers, garlic, mushrooms, followed by peas, cabbage, pumpkin, radish, leek, onion, tomato, lettuce, etc.