When it comes to diet, people will think of “taboo”, mistakenly thinking that only Chinese medicine is concerned, Western medicine is regardless. In fact, Chinese medicine and Western medicine are both concerned about “avoiding food”. Strictly speaking, avoidance of food is only part of the dietary regimen, which is about what not to eat, but the dietary regimen also needs to understand what can be eaten or can eat more. Different diseases have different dietary contraindications, and here we will only talk about the principles of dietary regulation for cancer patients. Some things have been proven to have carcinogenic effects, such as moldy cereals, soybeans, peanuts, corn, etc. contain aflatoxin, which is a strong carcinogen and can induce cancer and should never be eaten. Tobacco contains more than 6,000 kinds of harmful compounds, and there is a lot of evidence that smoking is the culprit of cancer, so smoking should be prohibited. Betel nut chewing can lead to oral cancer, and it is best to quit. Pickles, preserved vegetables, burnt fish or meat contain carcinogens such as nitrite and benzo(a)pyrene respectively, which should be avoided or eaten as little as possible. Eating large amounts of these things for a long time may easily cause cancer recurrence or induce second cancers. Some foods such as rooster, carp, shrimp, beef, mutton, dog meat, etc. (commonly known as “hairy foods”) are not absolutely inedible. These foods are nutritious and tasty, so eating them properly can help the body recover as soon as possible. However, those who have high blood pressure, high blood ester, obesity, indigestion and other diseases should eat less, and those who have obvious symptoms of “fire” (dry mouth, sore throat, sores on the tongue, fear of heat, fever, red tongue with yellow coating, knotted stool, yellow urine, etc.) should also eat less. These foods do not cause rapid recurrence or metastasis of cancer, but may cause “fire” symptoms in some patients. On the contrary, patients with Yang deficiency and fear of cold should eat more of them, but don’t eat too much and cause indigestion. Some foods have cancer prevention and anti-cancer effects, and some foods are originally medicines. For example, Coix rice (six grain rice, coix seeds) is a good product for both medicine and food, has the effect of cancer prevention and anti-cancer, promote digestion, improve appetite, can eat 50-250 grams per day. Carrots contain carotene and can be eaten raw or juiced (1-2 cups per day) to help fight cancer and prevent recurrence. Fungal foods such as shiitake mushrooms contain polysaccharides that are beneficial to cancer patients’ recovery and prevention of recurrence. Asparagus, sweet potato, sweet basketball and kiwi (vine pear) are considered to be anti-cancer foods and can be eaten more often. In general, as long as the fresh food such as meat, fish, fruits and vegetables can be eaten in general, but it is better to steam or stew them, avoid deep-frying and frying, and should also be avoided in excess. Patients undergoing radiotherapy, most of them will have “fire” performance, should eat more watermelon, pears and other cool fruits, and try to avoid oranges, cinnamon, litchi and other warm fruits. Patients undergoing radiotherapy and chemotherapy may cause a drop in blood, you can choose the red peanut rice stew with some red dates, which has the effect of replenishing blood and preventing the decline of white blood cells. Some foods are not directly related to the disease, but can affect the patient’s emotions or feelings, also need to pay attention to. Patients receiving radiotherapy and chemotherapy have poor appetite and other side effects, so the food should be colorful, fragrant and tasty, tasty, soft and easy to digest. Under the premise of ensuring that the total amount of food eaten is not reduced, it is possible to have a small amount, but not many meals. Chili, ginger and garlic will make patients with head and neck tumor radiotherapy more dry-mouthed, but they can improve the taste. Patients without symptoms such as dry mouth and sore throat can eat some in moderation, and there are reports that garlic mashed and eaten raw has anti-cancer effects. Patients with rectal cancer surgery rerouted to eat foods such as onion will make the stool stink, and should be avoided, and they should eat more coarse grains and vegetables containing fiber to increase the stool volume and prevent constipation. Coarse, bone-infused foods can easily damage the mouth, esophagus and gastrointestinal tract and cause bleeding. Patients with oral cancer, esophageal cancer, gastrointestinal cancer or leukemia and thrombocytopenia with bleeding risk should not eat them. There are also some contraindications related to drugs when taking medicines, such as iron is contraindicated to be served with tea; fish and fava beans are contraindicated when taking Yunnan Baiyao; ginseng and ripe earth are contraindicated to radish; licorice is contraindicated to kelp, etc. The pharmacist or physician should be consulted about the contraindications of medicine and food. In conclusion, diet should be based on the patient, condition, treatment and complications, combined with the patient’s dietary habits and economic status, and discussed by the patient, family members and experienced doctors, so as to formulate a plan that is conducive to cancer prevention and fight against cancer, as well as physical and mental recovery.