Reasonable nutrition should include the intake of food that can meet and ensure the caloric needs, the selection of reasonable recipes and the establishment of a reasonable dietary system. Reasonable nutrition is closely related to the development of cancer. 45% of the occurrence of cancer is related to dietary factors and 35% is related to frequent smoking and drinking a lot of strong alcohol. Diet is the basis of nutrition, and nutrition is the root of health. Cancer prevention is best to start from scientific and nutritionally reasonable diet. 1. Balanced diet A balanced diet means that the nutrients contained in food are complete, sufficient in quantity and in proper proportion, and the nutrients supplied in the diet are in basic balance with the needs of the organism. The appropriate ratio of protein, fat and carbohydrate consumption is 1:1 and 5:5, and the distribution of caloric energy is 10%-15% for protein, 20%-25% for fat and 60%-70% for carbohydrate. The ratio of essential and non-essential amino acids in protein is 4:6. In order to achieve this requirement, we should first establish a balanced dietary pattern, which is the basic premise of nutrition and cancer prevention. （Except for breast milk, no natural food can provide all the nutrients required by human body. A balanced diet must consist of a variety of foods in order to meet various nutritional needs of human body, achieve reasonable nutrition and promote health. Therefore, we should advocate people to eat a wide range of foods. A variety of food should include the following five categories: The first category is cereals and potatoes. Cereals include rice, noodles, grains, potatoes including potatoes, sweet potatoes, cassava, etc., mainly to provide carbohydrates, protein, dietary fiber and B vitamins. The second category is animal food. Including meat, poultry, fish, milk, eggs, etc., mainly to provide protein, fat, minerals, vitamin A and B vitamins. The third category is legumes and their products. Including soybeans and other dry legumes, mainly provide protein, fat, dietary fiber, minerals and B vitamins. The fourth category is vegetables and fruits. Including fresh beans, roots and tubers, leafy vegetables, eggplant and fruit, mainly providing dietary fiber, minerals, vitamin C and carotene. The fifth category is pure caloric foods. It includes animal and vegetable oils, starch, edible sugar and alcohol, which mainly provide energy, and vegetable oils also provide vitamin E and essential fatty acids. In the Yellow Emperor’s Classic of Internal Medicine? It is also stated that people should eat cereals as the main food, a variety of meat and vegetables as side dishes, and fresh fruits as appropriate. From the viewpoint of modern nutrition, this dietary composition is relatively scientific. Cereals are the mainstay of the traditional Chinese diet. With economic development and improvement of life, people tend to consume more animal-based foods. This western-style diet provides too much energy and fat, and too little dietary fiber, which is not good for the prevention of some chronic diseases. (2) Reasonable mix Reasonable mix is based on the premise of “food diversity” in the dietary pattern, each kind of food contains different nutrients, and must rely on a variety of food mix to meet all the nutritional needs of the human body. Cereals mainly provide carbohydrates, protein, dietary fiber and B vitamins, and are the main source of energy and protein, but some of their protein amino acid content is relatively low, if the intake of animal food or legumes at the same time, can play a complementary role to further improve the nutritional value of protein. According to the dietary situation in China, it is recommended that the daily supply of nutrients should be: 20%-25% of total energy from fat for adults, 25%-30% for children, 10%-15% of total energy from protein, and 60%-70% of energy from carbohydrates. In accordance with the nutrient and caloric energy requirements, a reasonable daily diet for an adult engaged in the medium workforce can be determined as follows: 500 to 600 grams of food, accounting for 41% of the total diet; 50 to 100 grams of meat, one egg, 50 grams of soy products, accounting for 16% of the total diet; not less than 500 grams of vegetables, of which the best half are green leafy vegetables, accounting for 41% of the total diet; 25 to 35 grams of oils and fats, accounting for 10% to 15% of the total energy. 25~35 grams of oils and fats, accounting for about 2% of the total diet. 2. Food selection (1) Basic requirements: control fat intake; eat more fresh vegetables and fruits; improve food preservation conditions; promote low-salt, vitamin-rich food; avoid eating food that is too hot, burnt or moldy; and quit smoking and drinking. If the above requirements can be met, the incidence of stomach, esophageal and liver cancers in China can be reduced by 10%. (2) Specific choices: Foods not suitable to be eaten: charcoal grilled meat, sausages, grilled loin, smoked and cured meats, foods containing more additives and preservatives. Foods to be eaten sparingly: baked foods, wine, coffee and soft drinks, sweets, foods with much salt, high-fat foods, fried fish, canned fish in oil. Foods to eat more: wheat, barley, brown rice, cabbage, bok choy, radish, spinach, cauliflower, potatoes, soybeans, red beans, black beans, mung beans, lentils, apples, apricots, pears, bananas, strawberries, oranges, grapes, grapefruit. 3, reasonable cooking of food The purpose of reasonable cooking of food is to make food easy to digest and absorb and increase the utilization of nutrients, improve the color, aroma and taste of food, prevent the destruction and loss of nutrients, kill pathogenic microorganisms and parasitic eggs, and avoid the production of carcinogenic substances and other harmful substances. (1) to prevent the production of harmful substances: in the cooking process of food, avoid directly baking food with fire to prevent the production of mutagenic substances to cells, as well as coal tar, polycyclic aromatic hydrocarbons and other harmful substances to food pollution; advocate steaming, boiling, stewing, stewing, can avoid the production of mutagenic substances, and food is easy to digest and absorb; frying food should be avoided too high oil temperature or frying too old char, grease should also avoid repeated Deep-frying should be avoided. (2) Cooking principles and methods of preserving nutrients: the principles of reasonable cooking should be under the requirements of ensuring harmless changes in food and good taste, shortening the heating time and controlling the appropriate temperature as much as possible; rice and other grains should not be overwashed, vegetables should not be soaked in water for too long, major side dishes should not be abandoned in soup, and vegetables should not be juiced to avoid large losses of water-soluble vitamins. 4, a reasonable meal system (1) regular and quantitative: for a long time, most of China has developed a daily three-meal system of eating habits is more reasonable. Under normal circumstances, breakfast should account for 25%-30% of the total calories of the whole day, lunch accounts for 40%, dinner accounts for 30%-35%, which can basically adapt to the physiological condition and the needs of work. The arrangement of three meals should be appropriate, the interval between meals to 4-5 hours is appropriate, too long can cause a high degree of hunger, resulting in a decline in body resistance, too short not only can not cause a good appetite, and the food has not been emptied, the accumulation of large, will increase the burden on the stomach and intestines, leading to a variety of gastrointestinal diseases, and even can induce stomach cancer. (2) avoid overeating: often overeating, and the intake is too hot, too rough food, will directly damage the esophageal mucosal epithelium, so that the mucosal epithelium is broken, ulcerated, bleeding and other lesions. If the mucosal epithelium is repeatedly stimulated for a long time, the mucosal epithelium will mutate in the frequent process of repeated proliferation and repair, and finally cancer will occur. In addition, the intake of large amounts of fat and protein will increase the risk of malignant tumors such as breast cancer, colon cancer and pancreatic cancer.