Epidemiological studies have shown that GI tract tumors are among the most sensitive to improved diet. The mechanisms of dietary carcinogenesis are divided into several categories: direct DNA damage (e.g. nitrites), cytochrome activation or inhibition (e.g. alcohol), carcinogen activation (e.g. pickled foods), direct cytotoxicity (e.g. mycotoxins), oxidative damage (e.g. saturated fats) physiological alterations (e.g. rice, dietary fiber) and hormonal effects (e.g. phytoestrogens). The following are risk factors that have been confirmed by research to cause digestive system tumors i. Nitrosamines A variety of nitrosamines can induce esophageal and gastric cancer in animals. When nitrosamines in ingested food (e.g. sauerkraut, barbecued food) are easily synthesized by amines and nitrites under acidic conditions in the stomach, especially when vitamin C intake is insufficient. At the same time, nitrite at pH 1~4 and amines in the stomach can easily form nitrosamines, which can directly induce tumors in the stomach without any metabolic activation. Polycyclic aromatic hydrocarbons are also produced when grilling fish and meat, which increase the occurrence of gastric cancer. Fungal toxins Some fungi and their metabolites in food, sauerkraut and moldy food are important risk factors for esophageal and gastric cancers. These fungi (e.g. aflatoxin) can not only reduce nitrate to nitrite, but also decompose protein, increase the content of amines in food and promote the synthesis of nitrosamines. High-salt, high-fat and high-cholesterol diets Eating large amounts of saturated fat and high salt (salted fish, cured meat, etc.) can corrode the gastric mucosa, destroy the gastric mucosal barrier and increase the incidence of gastric cancer. The carcinogenic effect of high cholesterol and fat may be mediated by bile acids. High-fat diet can stimulate the secretion and excretion of bile acids and cholesterol, and promote the development of colorectal cancer. Dietary stimulation, such as rough food, overly hot food, overeating and irregular meals, causes chronic physical and chemical stimulation of esophageal mucosa, mechanical gastric mucosal damage and gastric juice secretion disorder, which increase the incidence of digestive system tumors. Epidemiological investigation shows that low content of molybdenum, copper, boron, zinc, magnesium and iron in food, drinking water and soil may be indirectly related to the occurrence of esophageal cancer. Molybdenum is an important component of certain oxidase and nitrate reductase enzymes, and molybdenum deficiency can cause nitrate accumulation in food. A hospital investigated the relationship between 97 pairs of case-control serum vitamin A and the incidence of gastric cancer, and found that the vitamin A level in the gastric cancer group was significantly lower than that in the control group, and there was a significant dose-dependent relationship between vitamin A level and the risk rate of gastric cancer. Investigation of 600 patients aged 35-64 with gastric mucosal intestinal hyperplasia in areas with high incidence of gastric cancer in China showed that the blood levels of vitamin C, β-C and vitamin E were significantly lower. Alcohol consumption Epidemiology found that many patients with esophageal cancer have a history of heavy alcohol consumption. Alcohol can be used as a solvent of carcinogen, which can promote carcinogen to enter the esophagus and cause mucosal damage to food, creating conditions for the occurrence of esophageal cancer. Smoking Chemicals in tobacco are not only related to esophageal cancer, but also can increase the incidence of stomach cancer. Animal experiments have proved that tobacco smoke contains a variety of carcinogenic substances specific to the pancreatic organs. Secondly, nicotine in tobacco can promote the release of catecholamines in the body, leading to a significant increase in blood cholesterol levels. In some way, hyperlipidemia can induce pancreatic cancer. Four ways to prevent digestive system tumors I. Condiments and tea Research shows that garlic can inhibit the synthesis of N-ethylnitrosamines. The consumption of garlic can increase the function of gastric acid secretion. Garlic has a killing effect on bacteria, especially HP. The sulfur-containing complex in garlic can protect the DNA of mammalian epithelial cells, and the thiosulfate in garlic can inhibit the growth of HP. And it is rich in flavonols (especially tetrahydroxyflavonoids) which help in the removal of carcinogens. Consumption of green tea may prevent a variety of intestinal tumors. The main component of green tea, EGCG (gallocatechin gallate), has various mechanisms of action, such as intracellular antioxidant effect, inhibition of carcinogen formation and angiogenesis and cancer cell proliferation. Vitamin A: Vitamin A is mainly an antioxidant and increases intercellular connection traffic, and can enhance the defense function of epithelial cells and protect the mucosa to assist in recovery. Giving animals a high vitamin A diet can significantly inhibit the cancer-inducing effects of DMH and aflatoxin B. Studies have also indicated that carotenoids have a stronger cancer-preventive effect. Foods rich in vitamin A include: pig liver, duck liver, duck egg yolk, chicken liver, western blueberry, carrot (red), etc. 2.Folic acid: Folic acid is composed of glutamic acid, para-aminobenzoic acid and chitosan; it is mainly involved in SAM methylation process to maintain methylation status, gene regulation and suppression of oncogene expression. A case-control study in Mexico showed that folic acid reduced the incidence of gastrointestinal-type cancer. Folic acid is widely found in animal and plant foods, such as: pork liver, beef, asparagus, rape, orange, strawberry, etc. 3.Vitamin C: Vitamin C is an antioxidant that can scavenge free radicals, and can stimulate the immune system and activate gap junction traffic through retinol and vitamin A acid, maintain the normal state of cell differentiation, inhibit the formation of nitrosamines, and enhance liver detoxification. It has been proved through experiments that vitamin C can indeed prevent the formation of N-nitroso radicals, a carcinogen in the stomach, thus reducing the risk of gastric cancer. Foods with high vitamin C content include: sour dates, fresh dates, kiwi, alfalfa, radish tassels (white), kale, etc. 4.Vitamin D: Research shows that vitamin D is an important factor in preventing malignant changes of colon epithelial cells and regulating their growth and differentiation. Vitamin D is mainly obtained through meat, egg yolk and exposure to sunlight, most foods do not contain vitamin D. 5, vitamin E: vitamin E, in addition to antioxidants to inhibit the formation of free radicals, but also before and after the genetic mutation to prevent malignant transformation of cells or excessive proliferation. Vegetable oil is the main source of vitamin E. Eggs, meat, fruits and vegetables contain less. 6, selenium: selenium can change the metabolism and detoxification of carcinogenic agents, which can prevent damage to DNA by inhibiting the oxidation process of glutathione peroxidase inhibitors such as DMH and lipid peroxidation, thus maintaining the integrity of cell membrane structure and function. Increasing the blood selenium level can improve its immune status and the body’s antioxidant function, which helps to play the body’s own anti-cancer function. Lipids The lunosilicic acid in coconut oil can inhibit the growth of Helicobacter pylori, so coconut oil can strengthen the ecosystem of intestinal mucosa. Dietary fiber High dietary fiber can significantly inhibit the carcinogenic effect of AOX on the large intestine. Cereal plant fiber has a strong scavenging effect on nitrosamines in an acidic environment, significantly reducing the concentration of nitrite in the stomach. In addition, phytoestrogens, phenolic complexes, anti-starch, and oligofructose in plants have antitumor components. Cancer often takes several years to develop and is caused by a combination of factors. And good lifestyle habits and balanced diet are the best way to stay away from cancer.