As the saying goes, disease enters through the mouth, and cancer is no exception. Especially in recent years, more and more scientific experiments have confirmed that about 80% of cancer patients are related to their dietary habits. For example, liver cancer, nasopharyngeal cancer, intestinal cancer, esophageal cancer and other malignant tumors with high incidence are inextricably linked to various bad eating habits, and even breast cancer, cervical cancer, prostate cancer and other cancers are closely related to diet! The eating habits of young people will also have an impact on the future. For example, teenagers who seldom eat animal food will have a premature decrease in digestive enzyme secretion function after 40 years old, resulting in poor digestion of the stomach and intestines, and if they eat too roughly during childhood, the gastric mucosa will begin to degenerate at the age of 20 and the chance of developing chronic atrophic gastritis will increase accordingly. These are the risk factors of digestive tract cancer. When it comes to digestive tract cancer, we have to talk about obesity. Obesity can increase the chance of many diseases (such as cardiovascular diseases), and it is also closely related to cancer. Like gallbladder, pancreatic cancer, esophageal cancer, uterine body cancer, etc. are related to obesity. Research results show that: obesity leads to insulin resistance, cell sensitivity to insulin is reduced, and high concentrations of insulin in the blood will stimulate the growth of cancer cells. Ovarian cancer and breast cancer are common tumors in women, which are related to early menarche, and early menarche is related to excessive fat intake. Hormones are necessary for the development of breast cancer, and both estrone and estradiol have certain carcinogenic effects. Fat can promote the activity of aromatase in the body and make the adrenal cortex produce androgens, which can increase the level of estrogen in the blood through the regulation of pituitary and ovary; high sugar diet can also promote the development of breast tumor because high sugar and high fat diet makes the body obese, and high fat diet increases the secretion of bile and produces estrogen accordingly. If a high-fat diet lacks the trace elements selenium and fiber, it is very easy to develop intestinal cancer. Because high-fat diet can increase the secretion and excretion of bile acids, and the metabolism of bile acids caused by coliform bacteria contains carcinogenic active substances, that is to say, high-fat diet will increase the potential carcinogenic activity of bile acids. In addition, bladder cancer is related to alcohol and tobacco addiction, so the incidence is higher in men; where the food is heavily contaminated with aflatoxin, the incidence of liver cancer and kidney cancer is higher in areas with high intake; choriocarcinoma is related to low protein intake and poor nutrition. Therefore, it is easy to see that many cancers are related to eating and are caused by long-term poor dietary structure and habits. Therefore, we must pay attention to them in our daily life and develop good and reasonable dietary habits, because this will not only maintain the body balance, but also prevent cancer from invading.