A reasonable dietary structure can ensure the daily essential nutrients and trace elements for the human body, improve immunity, and play an important role in maintaining human health. At present, there is still a nutritional imbalance in our population, and long-term nutritional imbalance can lead to the occurrence and development of chronic diseases and cancer. In order to continue life, human beings must consume food that is good for health, and human beings are shaping their own body and health through diet. The World Health Organization (WHO) has evaluated many factors that affect human health, and the results show that the impact of dietary nutrition on human health is second only to genetic factors (15%) at 13%, and much higher than medical factors (8%), it is easy to see the importance of dietary nutrition on human health. The four cornerstones of a healthy lifestyle are: reasonable diet, moderate exercise, smoking cessation and alcohol restriction, and psychological balance, of which reasonable diet and nutrition are placed in the first place. A reasonable dietary structure plays an important role in maintaining health and preventing chronic diseases. I. Reasonable diet and nutrition is the foundation of health Reasonable diet and nutrition means the supply and proportion of food and nutrients suitable for various conditions (age, gender, physiological condition, labor, load, health status, etc.). Proper nutrition can maintain the normal physiological function of human body, promote health and growth and development, improve the body’s ability to work, resistance and immunity, and facilitate the prevention and treatment of certain diseases. Lack of proper nutrition will produce obstacles to the occurrence of nutritional deficiency diseases or over-nutrition diseases (obesity and atherosclerosis, etc.). According to modern nutritional research, various nutrients required by human body are divided into 6 categories, namely protein, fat, sugar (carbohydrates), inorganic salts (including trace elements), vitamins and dietary fiber. When nutrition is balanced, it can meet the body’s needs for caloric energy and various nutrients, promote the body’s ability to resist diseases, improve work and labor efficiency, and also prevent and treat certain diseases; when the dietary structure is not reasonable, the intake of caloric nutrients is not balanced, that is, nutritional disorders, because of a certain or certain nutrients intake is not enough to meet the needs of the body, after a long time, the body’s nutritional reserves are seriously depleted, then there are The corresponding pathological changes, followed by clinically visible nutritional deficiency disease. On the contrary, excessive intake of caloric energy and certain nutrients can lead to obesity, cardiovascular diseases, tumors, etc., or poisoning due to excess of certain nutrients, which is detrimental to health. The Chinese Nutrition Society has proposed: “Reasonable nutrition is the material basis of health, and balanced diet is the only basis of reasonable nutrition. Therefore, balanced diet and reasonable nutrition are the important conditions for maintaining human health and survival. Reasonable nutrition is not equal to high-grade exquisite food. If you think that eating more fish, meat, beans, fruits or vegetables is necessarily a scientific diet, the nutrient composition and biological characteristics of a certain kind of food or a certain type of food cannot fully meet all the human body’s needs for nutrition, and any monotonous dietary pattern or partial eating habits will cause the excess of some nutrients and the lack of others, thus leading to human Any monotonous dietary pattern or partial eating habits will cause excess of some nutrients and deficiency of others, thus leading to nutritional imbalance. The relationship between diet and tumor will lead to the occurrence and development of cancer if there is a long-term nutritional imbalance or poor dietary habits. A lot of epidemiological data prove that some cancers such as stomach, esophagus, colon and breast cancers are closely related to people’s dietary habits, and the survey found that the incidence of colon cancer in Western Europe and North America, where high-calorie and high-fat dietary pattern is the main, is significantly higher than that in Asia and Africa, where dietary fat is relatively low; the incidence of stomach cancer is related to eating fried food, stupid and castor, pickled and smoked food containing nitrite and nitrosamine, moldy food (containing aflatoxin), and the incidence of cancer in the stomach. The incidence of gastric cancer is positively correlated with eating fried food, stupid castor, pickled and smoked food containing nitrite, nitrosamines, moldy food (containing aflatoxin), and negatively correlated with milk intake, for example, the United States has the highest milk consumption and the lowest incidence of gastric cancer in the world, and the incidence of gastric cancer in Japan is gradually decreasing with the increase of milk consumption. Adequate amount of protein can not only maintain the normal physiological function of the body, but also enhance the immune ability of the body. Due to various reasons, tumor patients often have negative nitrogen balance which leads to protein-calorie malnutrition, impaired immune function and weakened inhibition of cancer cell growth, resulting in further aggravation of the disease. Excessive alcohol consumption has a close relationship with the occurrence of some cancers. Modern medical research shows that the incidence of cancer in the mouth and throat is more than twice as high in excessive drinkers than in non-excessive drinkers, the incidence of thyroid cancer is 30-150% higher, the incidence of skin cancer is 20-70% higher, and the chance of breast cancer in women is 20-60% higher, and in patients with esophageal cancer, excessive drinkers account for 60%, while non-drinkers account for only 2%. The risk of liver cancer in hepatitis B patients is higher, and its incidence will increase significantly if they drink alcohol or drink too much. Therefore, good dietary habits are an important factor in cancer prevention. A survey on the diets of 132 adult acute and chronic leukemia cases revealed that the intake of legumes, vegetables, dairy and other foods of leukemia patients was significantly lower than the food intake recommended by the balanced diet pagoda of Chinese residents, and the intake of energy, protein, vitamin A, thiamine, riboflavin, ascorbic acid, calcium, zinc and selenium accounted for less than 80% of the recommended intake (RNI) and appropriate intake (AI). The intake levels of energy, vitamin A, thiamine, riboflavin, ascorbic acid, and calcium were severely deficient (60% of RNI and AI). Tumor patients are more likely to have inadequate or deficient intake of vitamins and minerals due to restricted nutritional intake and increased consumption. Multivitamin-mineral deficiencies are associated with tumorigenesis and may exacerbate cancer progression. Epidemiological data show that plasma vitamin A and E concentrations are significantly lower in bladder cancer patients than in the healthy population. Vitamin C deficiency is common in patients with advanced cancer, and plasma vitamin B6, vitamin B12, folic acid, vitamin C, and vitamin E are significantly lower in patients with liver cancer than in healthy individuals. Numerous studies have revealed that vitamin A has a tumor suppressive effect, which may be related to its regulation of cell differentiation, proliferation and apoptosis, as well as its antioxidant function. Feeding high amounts of vitamin A to rats with cancer inhibited the spread of their cancer cells, and their transplanted cancer cells stopped growing. Vitamin B has a protective effect against the production of many malignant tumors. 90% of people who die from Kwashiorkor disease have cancer, which usually occurs in Central and South Africa, mostly due to a severe lack of protein and vitamin B in the diet, and can recover if supplied with milk rich in protein and vitamin B6. Vitamin E has strong antioxidant effects. Clinical studies have found that derivatives of vitamin E such as vitamin E succinate can inhibit the growth of many tumor cells such as human leukemia cells, block the tumor cycle, inhibit tumor cell DNA synthesis, induce tumor cell apoptosis and promote tumor cell differentiation. Vitamin C can reduce NO2 to NO and block the synthesis of nitrosamines in the body, and is involved in the synthesis of “physiological hyaluronidase inhibitor” released by cancer cells, so it has anti-tumor effects. Epidemiological data also confirm that the occurrence of certain cancers in human body is related to vitamin C deficiency, for example, the vitamin C intake of residents in areas with high incidence of esophageal cancer and gastric cancer in China is lower than that of low incidence areas, and the incidence of cancer is inversely proportional to the daily intake of vitamin C. In northwestern Sichuan, the vitamin C content in the urine of residents in areas with high incidence of esophageal cancer is only 1/9-1/8 of that in low incidence areas. rats excrete 50-70 times more vitamin C in their urine than normal within 6 days after eating various drugs, chemicals or dyes, and have signs of producing cancer. A diet low in iodine not only causes goiter, but also thyroid cancer, and can promote hormone-related breast cancer, endometrial cancer and ovarian cancer. Rats fed iodine-deficient food on a continuous basis are prone to thyroid cancer. Selenium can promote normal cell proliferation and regeneration, improve the immune function of the body, block the damaging effects of reactive oxygen species and free radicals, and scavenge lipid peroxides in the body. Its content is significantly and negatively correlated with the mortality rate of digestive and urinary tract tumors, and also negatively correlated with the mortality rate of tumors. To sum up, only by learning and popularizing the knowledge of nutrition and accepting the viewpoint of balanced diet can we prevent the incidence of many chronic diseases and tumors, significantly reduce the incidence of diseases and mortality rates, and save the huge medical expenses. And scientific and reasonable dietary habits should be cultivated from childhood. Letting children accept the idea of balanced diet and cultivate good dietary habits from childhood will benefit them for a lifetime. This view of promoting health through balanced diets is very important for China.