Cancer is a common and frequent disease that seriously endangers people’s lives and health, and the annual number of cancer cases in China is about 1.6 million. Cancer is overtaking cardiovascular diseases as the first cause of death. The esophagus, stomach and large intestine in the digestive tract are the most common sites of cancer, and cancer patients in these three areas account for more than a quarter of common malignant tumors. Among the top five deaths due to cancer, stomach, esophagus and colon cancer occupy the first, third and fifth places; in the world, China has the highest incidence and mortality rate of esophageal cancer, and half of the patients with esophageal cancer are Chinese. In Asia, the incidence rate of stomach cancer in China is among the top three, and due to the large population in China, 160,000 people die from stomach cancer every year. Colorectal cancer, including colon cancer and rectal cancer, ranks second in Europe and the United States in terms of incidence rate, while China ranks fifth among various cancers, and the incidence rate has increased significantly in recent years. How can we change the high incidence rate of digestive tract cancer, many deaths and great harm to people’s health? First of all, we should take measures against cancer-causing factors, among many cancers, digestive tract cancer is most closely related to environmental factors. “Early detection, early diagnosis, and early treatment are all important. To achieve this goal, medical personnel and people need to act together, change customs, change unreasonable dietary habits, protect the environment, raise awareness, recognize and detect cancer at an early stage. 1.Esophageal cardia cancer Risk factors causing esophageal cardia cancer: (1) Smoking and alcohol: long-term smoking and alcohol consumption are related to the occurrence of esophageal cancer. It has been found that the incidence of esophageal cancer is 50 times higher in heavy drinkers than in basic non-drinkers, 7 times higher in smokers than in non-smokers, and 156 times higher in alcoholics and smokers than in non-drinkers and non-smokers. Although alcohol itself has no carcinogenic effect, alcohol is the solvent of some carcinogenic substances, and strong alcohol may also cause esophageal mucosal damage, and wine may be contaminated with nitrosamines, creating conditions for the occurrence of esophageal cancer. (2) Local damage of esophagus: long-term consumption of coarse and hard food, hot soup, hot porridge, hot tea or irritating food such as chili pepper, or poor hygiene habits such as fast swallowing, poor chewing and overeating. These factors can cause mechanical or physical stimulation and damage to the esophageal mucosa, creating conditions for the entry of carcinogenic substances, thus promoting the occurrence of cancer. (3) Nitrosamines: Nitrosamines are very strong carcinogens and more than ten kinds of nitrosamines are known to cause esophageal cancer in animals. High levels of nitrates and nitrites can be detected in grain, sauerkraut and well water in Lin County, an area with a high incidence of esophageal cancer, and their levels are positively correlated with local esophageal epithelial hyperplasia and the prevalence of esophageal cancer. (4) Mold: It has been found that more than 10 kinds of mycotoxins can induce tumors in different organs of animals. Epidemiology found that mold contamination in areas with high incidence of esophageal cancer is 2 to 15 times higher than in low incidence areas. (5) Nutrition and micronutrients: the areas with high incidence of esophageal cancer in the world are generally poor and backward areas, and the diet lacks vitamins, proteins and essential fatty acids. The lack of these ingredients can cause the epithelial proliferation and interstitial degeneration of esophageal mucosa, which can further cause cancer. The lack of trace elements such as iron, molybdenum and zinc is also related to the occurrence of esophageal cancer. (6) Genetic susceptibility: Clinical epidemiological study found that esophageal cancer has certain family aggregation, which does not exclude the involvement of genetic factors. Early signs of esophageal cancer: (1) Choking: there is resistance when swallowing food, poor swallowing, blocked feeling or foreign body feeling, which is progressively aggravated and occurs occasionally once or twice at the beginning and cures itself without treatment, but occurs again in the following days or months, and the frequency of occurrence and the degree of choking gradually increases, which is a common manifestation of early esophageal cancer. (2) Difficulty in swallowing: when swallowing, there is mild stuffy, distended discomfort or hidden pain behind the sternum, and the degree of pain is not necessarily related to the hardness of eating. After swallowing, this sensation will gradually subside. (3) Swallowing foreign body sensation: when swallowing, you feel that there is a foreign body in the esophagus, like rice grains or tea leaves fragments adhering to the esophagus, which cannot be swallowed and cannot be spit out. Sometimes, when taking the first bite of food, it always feels obstructed and the movement of food in the esophagus seems to be felt. The incidence of the above three symptoms accounts for more than 80% of all early esophageal cancer symptoms, and the feeling of swallowing discomfort accounts for more than 30% of all symptoms. 2.Gastric cancer is a multifactorial disease, and the cause of which is still not very clear. According to current research data, the occurrence of gastric cancer is related to the following factors: (1) Diet and living habits: In poor mountainous areas, the incidence of gastric cancer is significantly higher among residents who take pickled vegetables, cured meat and smoked food as their main side dishes. If residents have good economic conditions and consume more protein, fresh vegetables and fruits as side dishes, the incidence of stomach cancer is significantly lower. The incidence of stomach cancer is significantly higher in long-term smokers, and smoking has carcinogenic and cancer-promoting effects on the stomach. Long-term alcohol consumption has synergistic and promoting effects with other factors that cause gastric cancer. (2) Environmental factors: Epidemiological surveys have found that the incidence of gastric cancer increases in areas where there is a lack of trace elements (such as copper, manganese, zinc, selenium and magnesium) in the soil and drinking water. Residents living in mining areas or asbestos mining areas have a significantly higher incidence of stomach cancer. (3) Immune factors: The incidence of gastric cancer is relatively higher in those with low immune function, because immune dysfunction can reduce the immune surveillance effect on cancer. (4) Genetic factors: Most of the retrospective survey data suggest that the role of genetic factors in the etiology of gastric cancer is relatively certain, and there is an obvious tendency of family gathering. It is generally believed that the incidence of gastric cancer among relatives of gastric cancer patients is four times higher than that of the control group. According to the data, Napoleon’s grandfather, father, sister and himself all died of gastric cancer. (5) Infectious factors: The risk of gastric cancer is 6 times higher in people at high risk of H. pylori infection than in those with low infection. H. pylori infection is a causative factor of peptic ulcer and a risk factor of gastric cancer. (6) Other factors: Many diseases are considered to be related to the occurrence of gastric cancer, such as chronic atrophic gastritis, chronic gastric ulcer, gastric polyps, etc. Early signs of gastric cancer: (1) Age 40 or above, no previous history of gastric disease, sudden loss of appetite, fullness after meals, vague pain in upper abdomen or wasting, especially belching with sour smell or egg odor. (2) History of previous gastric disease, sudden change in the regular pain previously manifested, or change to persistent vague pain, and poor results of treatment according to gastric ulcer. (3) Usually low stomach acidity, love of acidic food or diagnosed atrophic gastritis or atypical hyperplasia, with a long history of disease and sudden weight loss, anemia, fear of eating greasy food or worsening of indigestion symptoms. (4) Age 40 years or older, history of gastric disease, sudden gastrointestinal bleeding (vomiting blood or black stool), or continuous positive stool test for occult blood for more than two weeks. (5) Gastric ulcer that does not heal after more than two months of regular treatment. (6) Progressive wasting and anemia, accompanied by dyspepsia symptoms. 3.Colorectal cancer The age of colorectal cancer is generally between 50 and 70 years old, and there are more men than women. The cause of colorectal cancer is not clear, but there are intrinsic and extrinsic factors. Intrinsic factors such as genetic inheritance; extrinsic factors such as long-term inflammation, chronic irritation, dietary habits, etc. The development of colorectal cancer is the result of the synergistic effect of internal and external factors. There are mainly the following aspects: (1) Dietary factors: Currently, it is believed that high fat, high animal protein and low fiber diet are the main dietary factors for the development of colorectal cancer. (2) precancerous lesions: the malignant tendency of colon adenomas, papillomas and polyps is a certain fact, and the incidence of colorectal cancer is significantly higher in those with colon and rectal polyps than in normal people. (3) Chronic inflammation: some chronic inflammatory stimuli are also one of the factors of colorectal cancer, such as chronic ulcerative colitis, schistosomiasis, etc. (4) Adverse stimulation: the development of colorectal cancer is related to constipation, smoking and other stimulating factors. In addition, the status of nitrosamines in the etiology of colorectal cancer has been increasingly emphasized in recent years. These compounds can form certain amines with carcinogenic function under the action of bacteria in the colon. (5) Genetic factors: The death rate of family members of colorectal cancer patients from colorectal cancer is four times higher than that of general family members, which may be related to the same dietary habits or the existence of genetic factors. Some data show that the misdiagnosis rate of colorectal cancer can be 40% to 60% or even higher, and the average time from the appearance of symptoms to diagnosis is about 1 year. Early symptoms of colorectal cancer are not typical and often confused with intestinal dysfunction, indigestion, enteritis and dysentery. The symptoms are different due to the different sites of cancer occurrence. Early signs of colorectal cancer: (1) When feces with fresh blood and cannot be explained by hemorrhoids. (2) Persistent or repeated episodes of pus and blood stool, with a feeling of incomplete evacuation, and when treatment as dysentery is not effective. (3) Change in bowel habits, abnormal number of bowel movements or stools with mucus, etc., constipation, diarrhea or both alternately, more than 3 weeks should be paid extra attention. (4) Change in stool shape, thinning, flattening or grooving. (5) The presence of anemia, repeated stool examinations or persistent occult blood. (6) Persistent lower abdominal discomfort, vague pain or abdominal distension, abdominal mass, weight loss. The occurrence and development of cancer does not appear in one morning, it has a long and sufficient time for us to intervene. As long as we change our bad habits, pay attention to and be alert to the early signs of cancer, the cure rate and survival rate of cancer will definitely have a big improvement.