As the saying goes, “disease enters through the mouth”, so is there any relationship between breast cancer and diet or not? What are the things you eat that increase the risk of breast cancer? What are the dietary concerns of breast cancer patients during the different stages of treatment? Is there any relationship between certain foods and the recurrence of breast cancer after surgery? Let’s talk about these concerns. According to scientists’ long-term research, “eating” is one of the major recognized risk factors for breast cancer. High-fat diet, obesity (especially post-menopausal obesity), lack of calcium and vitamin D, long-term alcohol consumption, and long-term use of estrogen and progesterone containing foods and drugs all contribute to the increased risk of breast cancer. Epidemiological surveys show that the incidence of breast cancer in the United States is much higher than in China, and the total daily fat intake per person is 2.5 times higher for Americans than for Chinese. Surveys in six major cities in China also suggest that as the monthly intake of meat, eggs and dairy increases, the incidence of breast cancer also increases accordingly. Studies have proven that meat, fried eggs, butter, cheese, sweets, and animal fat increase the risk of breast cancer, while vegetables, fruits, fresh fish, and low-fat dairy products can reduce the risk of breast cancer. A diet high in fiber has a protective effect on the breast and the higher the intake, the more pronounced the protection. Research also shows that calcium is an important medium for regulating cell function, while vitamin D is involved in regulating the body’s absorption and metabolism of calcium, and improving the level of calcium in the body can help prevent and treat breast cancer. Therefore, it is very beneficial to supplement calcium-containing foods, such as bone marrow, cartilage-containing foods and tender shrimp skin, etc. In the dietary guidelines for oncology patients jointly formulated by breast cancer experts from many countries, there is information that casein in milk is related to breast cancer, and it is recommended to drink yogurt as much as possible because acidification can break down casein in milk. It has been affirmed that alcohol can increase the risk of breast cancer, and the previous view that an alcohol intake of less than 7 grams per day does not increase the risk of breast cancer has been disproved. Therefore, for the sake of health, it is better not to drink alcohol or alcoholic beverages, even if it is one small glass per day. In addition, statistics show that only one out of every 100 breast cancers is in men, indicating that estrogen and progesterone are an important factor in causing breast cancer. The level of hormones in women is influenced by the endogenous hormones they produce and the exogenous hormones they take. About two-thirds of breast cancers are hormone-dependent. Therefore, it is important not to take too much estrogen-containing foods and medications, such as oral contraceptives and the use of certain breast enhancement products. Some artificially farmed aquatic products such as turtle and river eel should not be consumed excessively. For a patient diagnosed with breast cancer, he or she has to go through preoperative preparation, surgery, postoperative chemoradiotherapy, endocrine therapy and postoperative rehabilitation, etc. What should we pay attention to in terms of diet? For a person with normal diet, there is generally no malnutrition before surgery, so it is not recommended to use nutritious food before surgery, such as high protein diet, which will tend to promote faster tumor growth, but after surgery, because of the need to recover physical strength for better wound healing, some high protein diet can be increased appropriately, but it is not advisable to take large supplements, and it is better to have easy to digest, non-greasy, diversified, meat and vegetarian. During chemotherapy, as various chemotherapeutic drugs have different degrees of gastrointestinal reactions, including nausea, vomiting, constipation, diarrhea, anorexia, etc., the diet emphasizes eating less and more meals, replenishing enough water to help the excretion of chemotherapy drugs, eating more easily digestible foods rich in vitamins and trace elements, such as fruits and vegetables, noodles, rice, beans, etc. The protein supplement is based on fresh fish, live shrimps, eels, loach, pigeons, ducks, sea cucumbers, etc. Duck, sea cucumber, etc. are good. In addition, there are some misconceptions about the diet of cancer patients, such as chicken and eggs cannot be eaten, seafood cannot be eaten, soy milk and soy products cannot be eaten, etc. These things will make cancer recurrence. There is no such reference in the authoritative tumor diet guidelines, and no scientific basis to support this statement can be found in various literature on diet and tumor. Therefore, chicken and eggs can be eaten and they do not increase the risk of cancer recurrence. Of course, some “fast food” chicken meat has an impact on human body due to the use of growth hormones and other feeds, so it is recommended not to eat them. Similarly, seafood can enrich our recipes and is rich in nutrients, safer than some artificially farmed river fish, so why should we refuse to eat it? But for some shellfish is not recommended to eat more, because shellfish is a relatively low-level organisms, metabolism is poor, easy to absorb polluting substances such as heavy metals and not easy to excrete. And soy milk soy products for a very good source of plant protein, as long as the natural beans soy products can be eaten. In conclusion, reasonable and scientific dietary habits and methods are the guarantee of human health and the basis for breast cancer patients’ recovery.