What to eat during chemotherapy is one of the most important concerns of patients, especially their families. While chemotherapy kills tumor cells, it also has certain toxicity to normal cells. It leads to poor appetite, loss of appetite, tasteless mouth, and even nausea and vomiting. When encountering this situation, family members are often anxious and worry about the lack of nutrition, hoping to supplement nutrition as soon as possible to strengthen the body so that the patient can pass through chemotherapy successfully. However, there are rules on how to eat, not too hasty, if the method is not appropriate, often counterproductive. For patients whose gastrointestinal reactions are not obvious (the same applies to healthy people), it is recommended to: eat a variety of foods, mainly cereals, coarse and fine; eat more vegetables and fruits and potatoes; eat milk, soybeans or their products every day; eat an appropriate amount of fish, poultry, eggs and lean meat; light and less salt; moderate activity; and drink enough water. For patients with poor appetite, nausea and vomiting, it is recommended that: a light, easily digestible diet should be the mainstay. Carbohydrates, the usual rice and noodles, are the mainstay, because coarse grains are difficult to digest and are not recommended to be consumed too much during chemotherapy. Moderate consumption of protein foods, eggs are easier to digest and absorb, giving preference to eggs. The amount of meat should be controlled because meat is relatively difficult to digest; especially beef and lamb. Eat less fatty foods for the time being because they are difficult to digest. Eat vegetables appropriately. A small amount of fruit. If gastrointestinal discomfort or even diarrhea occurs after consuming fruit, stop eating it temporarily.