Can tumors be prevented? This is a question that we are very concerned about, and it is no wonder that with the rapid development of science and technology, the worsening of environmental pollution and the change of people’s living habits, the incidence of tumors is increasing year by year, and since the 21st century, cancer has become the number one killer of human health. According to statistics, there are nearly 2 million new cancer patients in China every year, and about 1.5 million deaths due to cancer every year, while the incidence rate of cancer is still increasing at a rate of 2.5% per year. Among them, the incidence rate of lung cancer is the highest. A research report published by the International Agency for Research on Cancer (IARC) in October 2005 pointed out that, according to the current trend of cancer incidence, by 2020, the incidence of cancer worldwide will increase by 50% compared with the present, and the number of new cancer patients worldwide will reach 15 million each year, among which, the incidence of the highest lung cancer will reach 1.2 million. However, people know very little about cancer, and we all “talk about cancer”. Some people wrongly think that cancer is incurable, which makes the curable cancer miss the opportunity of treatment; some people only carry out a certain treatment, such as surgery, chemotherapy, or some unproven treatments by hearsay, which makes the treatment effect far from being effective. Although some cancers are cured, the remaining psychological diseases still cannot be recovered. According to the statistics of UICC (International Union Against Cancer), more than half of the cancer patients can be cured, and the other part of them can improve the quality of life and prolong the survival time through comprehensive treatment. Not only that, a large number of facts also show that 70% of cancers can be prevented in advance. Smoking is an important cause of lung cancer, esophageal cancer, oral and pharyngeal cancer; long-term alcoholism can lead to liver cancer, stomach cancer, etc.; pickled sauerkraut, overnight and repeated heating of vegetables can produce nitrite, nitrite has an obvious carcinogenic effect; moldy food produced by aflatoxin has a carcinogenic effect; food coloring, smoke and baked food has a carcinogenic effect; long-term consumption of high-fat diets and breast cancer and rectal cancer; many tumors are related to mental factors, over-suppression, over-expression and over-expression of food. Mental factors are related to over-repression and over-sadness are important factors leading to tumors. As long as people change their bad dietary and living habits and maintain mental hygiene, they can prevent most cancers! Based on a large number of facts, the World Cancer Research Fund (WCRF) released the 200-page “Cancer Prevention Policies and Actions” on February 26, 2009, which is a landmark document. Written by 23 world-renowned experts, it makes recommendations based on evidence from evidence-based medicine. The document provides statistics from various countries and concludes that 1/3 of the 12 common adult cancers are preventable in high-income countries (e.g., the United Kingdom and the United States), while about 1/4 are preventable in low-income countries (e.g., my country). This figure does not include the results of smoking bans, which alone can reduce cancer by 1/3, but because these factors are interrelated, the two figures cannot be simply added together. After controlling diet, strengthening activity and maintaining body weight, cancers in China can be prevented: 44% of esophageal cancer, 44% of oral cavity and pharynx cancer, 38% of lung cancer, 34% of endometrial cancer, 33% of gastric cancer, 20% of breast cancer, 17% of colorectal cancer, 14% of pancreatic cancer, 8% of renal cancer, 6% each of liver and gallbladder cancers, averaging about 27% in total, or 20% if all cancers are taken into account. In the United Kingdom and the United States, the prevention of endometrial cancer can reach 56% and 70%, colorectal cancer 43% and 45%, and breast cancer 42% and 38%, totaling 39% and 34% on average, or 26% and 24% for all cancers. In addition, early treatment of precancerous lesions is also the main method of tumor prevention. From this, we can see that most tumors can be prevented. As long as we change the bad living habits, change the bad dietary habits, keep a good mindset, and actively treat the precancerous lesions, we can prevent tumors very well.