I. Dietary interventions 1. High-fiber diet to prevent colon cancer Hill reviewed 58 epidemiological papers and found that there is a correlation between high-fiber diet and the risk of colorectal cancer, and that cereals provide protection against colorectal cancer. An analysis of 13 case-control studies of colon and rectal cancer found that dietary fiber did have a preventive effect on this type of cancer, as well as a significant reduction in the incidence of gastric, esophageal, and pancreatic cancers. However, Fuchs’ study did not support this view, as a 16-year observation of 88,000 nurses did not find a preventive effect of fiber on colon cancer or polyps; a prospective study of 16,500 men also did not find a correlation between fiber (overall, cereals and vegetables) and adenomas, and fruit fiber intake reduced the risk of adenomas, but not in a statistically significant way. Randomized interventional trials also did not support a protective effect of fiber on colorectal adenoma development. Soluble vegetable fiber has almost no effect on stool weight and dilution, but soluble fiber can ferment in the large intestine and produce short-chain fatty acids, including butyrate, which seems to promote cell differentiation and reduce the occurrence of intestinal cancer. Epidemiological studies recommend that reducing the intake of red meat in the Western diet may lead to a reduction in the incidence of colorectal cancer. Some case-control studies have shown that the correlation between red meat or fat intake and colorectal cancer may be due to the formation of heterocyclic amines during high-temperature cooking, which are carcinogenic to animals and form DNA adducts in humans. However, a case-control study conducted in Sweden failed to show a correlation between heterocyclic amine intake and colorectal cancer, and the risk may be mediated by enzymes that metabolize heterocyclic amines. Two of these enzymes have genetic polymorphisms: CYP1 A2 (cytochrome p4501 A2) catalyzes N-oxidation, and NAT2 (N-acetyltransferase type 2) catalyzes N- and O-acetylation. Evidence suggests that the risk of colorectal cancer is increased in those with rapid acetylation. Milk is an indispensable part of nutritious food, and Turks who are meat-eating people often consume milk and cheese products, and have a low rate of colorectal cancer. Experiments have proved that milk has a direct relationship with cancer inhibition. After injecting carcinogenic elements in two groups of laboratory rats, the growth rate of cancer cells in the group that did not consume milk was twice that of the group that consumed milk. The linoleic acid protein and whey protein enzymes in milk have the function of inhibiting the occurrence of cancer cells and tumor growth. In addition, the antioxidant vitamins, vitamin A, D and carotene contained in milk also have the function of preventing the growth of cancer cells. 4, wine can reduce the risk of colon cancer Many Americans already drink a glass of wine a day to reduce the risk of heart disease, and now a new study reports that drinking wine can also reduce the risk of colon cancer. Researchers believe that drinking wine helps reduce the risk of colon cancer, but drinking other alcohol such as beer and vodka does not have this protective function. Only 4.5 percent of wine drinkers developed polyps, three times that number for beer drinkers and twice that number for non-drinkers. Second, colon cancer chemoprevention Since the mid-1950s, chemoprevention has made some progress in finding foods or drugs that prevent or terminate carcinogenic processes. The main mechanisms of action of chemopreventive agents include: (1) reversal of abnormal differentiation (e.g. heteroproliferative lesions); (2) inhibition of cell replication and proliferation; (3) induction of apoptosis; (4) prevention of metabolic activation of carcinogens or blocking the binding of carcinogens to DNA; (5) anti-angiogenesis and prevention of cancer cell infiltration and metastasis. (1) Malignancy blockers: they prevent malignant transformation or overproliferation of cells before and after gene mutation. (2) Differentiation or apoptosis inducers: their role is to induce differentiation of transformed cells back to a normal non-cancerous state or induce them to undergo apoptosis. Those belonging to this category include vincristine, N-(4-phenyl)vincristine (4-HPR or Femetinide) and NSAIDs, etc. Folic acid is essential for nucleotide synthesis and DNA methylation, and its deficiency will lead to malfunction of DNA synthesis, methylation and repair, thus leading to colorectal cancer. Evidence shows that insufficient intake of folic acid will increase the risk of colon cancer, and supplementation of folic acid can reduce the risk. 2.Vitamin D/Calcium As the role of vitamin D in inhibiting proliferation and promoting differentiation of colorectal tumors has been increasingly affirmed, vitamin D as a chemopreventive or therapeutic agent for colorectal cancer has become an important issue, but the toxic reactions caused by excessive intake of vitamin D, especially hypercalcemia and its serious consequences, have limited its application. Therefore, in recent years, research has been conducted abroad on synthetic derivatives of vitamin D in the hope of obtaining drugs that can effectively inhibit cancer without causing hypercalcemia. Calcipotriol (MC903), a synthetic derivative of vitamin D, significantly reduced the CCRP of colonic tissue epithelium by 62% without causing hypercalcemia and hypercalcemia in urine, and similar results were obtained with another synthetic derivative, DD003. In addition, in an AOM-induced rat colon tumor model, administration of derivative R024-5531 resulted in a significant decrease in cancer incidence and no significant difference in blood calcium from the control group, and similar results were obtained with derivative OTC. The authors concluded that vitamin D has a better pro-differentiation and anti-proliferation response only for colorectal cancer with high VDR expression. Vitamins C and E are considered to have antioxidant properties and can be used for tumor prevention. Vitamin C has the advantage of being safe and easy to obtain, but large clinical trials have not found vitamins C and E to be beneficial in preventing tumor development. Many new compounds derived from citrus products, Asian foods and spices have been shown to have chemopreventive effects in preclinical studies. (1) Curcumin: showed significant colorectal cancer chemopreventive activity in animal models; in vitro studies showed that it significantly reduced the proliferation of colorectal cancer cell lines HT-29 and HCT-15 in a dose-dependent manner; (2) Perillyl alcohol: present in citrus, lavender and peppermint, and its addition to the diet significantly reduced tumorigenesis in experimental animals; (3) Another citrus extract, hesperidin, significantly reduced colon tumors in experimental animals. In conclusion, epidemiological and experimental studies have confirmed that the occurrence of colorectal cancer is closely related to dietary nutritional factors. Future studies should focus on the discovery of human-specific colon carcinogens and further elucidate the relationship between dietary structure and certain specific dietary habits and colorectal carcinogenesis. Since the results of previous studies were mostly derived from epidemiological survey data, the conclusions reached were unclear and even contradictory, and future laboratory studies could be focused on verifying and clarifying these conclusions. Since dietary structure and certain specific dietary habits are not as strong as carcinogenic effects and may not induce tumors in the short term, or even throughout the life cycle of animals, the use of transgenic animals (specific metabolic types) for such tests will be a new area of research in the future. The development of non-nutrients in food to provide efficient and non-toxic chemopreventive agents for the chemoprevention of colorectal cancer will be the focus of research in the coming period.