We often see headlines like “XX foods can prevent cancer”, “YY diet can keep you away from cancer”, “ZZ do this and you can live to be more than 100 years old” on major websites and books. As a medical practitioner, I have to ask: Are these rumors based on science or not? The American Cancer Society (ACS), World Cancer Research Fund (WCRF) and American Institute for Cancer Research (AICR) have jointly issued a paper recommending five major lifestyles for cancer prevention. 1. Maintain normal weight BMI <25 kg/m2 Women with reduced risk of breast cancer This recommendation is not listed by the three departments out of thin air, but is based on the results of several recent randomized clinical trials. To prevent breast cancer, the ACS recommends that women get at least 150 minutes of moderate-intensity exercise per week, drink up to one standard glass of alcoholic beverage per day, and maintain a body mass index (BMI) <25 kg/m2. In one clinical trial (2905 women), women at high risk of developing breast cancer had a 44% reduction in risk of developing the disease after adopting the ACS recommendations. The Women's Health Initiative Watch (64,000 women) study found that a healthy diet (more fruits and vegetables, less meat, less alcoholic beverages) significantly reduced the risk of breast cancer in women: a 20% reduction in women with a BMI <25 kg/m2 and a 30% reduction in women with a BMI=25-29.9 kg/m2. You should note that a healthy diet does not reduce the risk of breast cancer in obese women. You may not be surprised to hear this, as high BMI is a cancer risk factor in itself. Excess body fat triggers insulin resistance, and elevated levels of insulin and growth factors can promote cancer. Obesity also promotes the production of estrogen, which in turn is a stimulant for many cancers. In addition, fat secretes cytokines that promote inflammation. A recent meta-analysis (involving 50 prospective observational studies) found that maintaining a normal weight in adults may prevent certain types of cancer, particularly those not amenable to hormone replacement therapy (HRT). For example, for every 5 kg increase in body weight in adult women, there is an 11% increase in the relative risk of postmenopausal breast cancer, a 39% increase in the risk of postmenopausal endometrial cancer, and a 13% increase in the risk of postmenopausal ovarian cancer. The key problem is that the weight of adults increases with age, and this cannot be prevented. Therefore, we can only do a good job in health management. 2.Enhance physical exercise MET=7.5-15, reduce the risk of cancer death Several observational studies have found that physical exercise can reduce the risk of breast cancer, colorectal cancer and endometrial cancer. A study of U.S. and European populations found that those who exercised at the minimum recommended level of exercise - a metabolic equivalent (MET) of 7.5-15 per week - had a 20 percent lower risk of cancer death compared to those who were physically inactive. At this year's ASCO Annual Meeting, Professor Abrams of the University of California noted that exercise can improve the prognosis for treatment of patients with diagnosed cancer. A recent meta-analysis of breast and colorectal cancer survivors (50,000 patients) also showed that active exercise can reduce the mortality rate of breast and colorectal cancers among survivors. 3.Eating more vegetables and less meat? A recent meta-analysis found that eating more vegetables and fruits can reduce all-cause mortality and cardiovascular mortality, but is not associated with cancer-related mortality. In addition, the study also found that lean meat is not as bad as we think, at least from a cancer risk perspective. The European Prospective Investigation into Cancer and Nutrition showed that the most important concern was whether processed meat products (e.g., canned meat, sausage) increased the risk of cancer. The study found that eating an additional 50g of processed meat products per day was associated with an 11% increased risk of cancer. However, lean meat was not associated with cancer risk. Therefore, compared with lean meat, processed meat products should be paid more attention. 4. Moderate alcohol consumption 1 standard glass of alcohol per day and no more Heavy alcohol consumption (more than 5 standard glasses of alcohol per day) is significantly associated with the development of 10 types of cancer: oropharyngeal cancer, esophageal squamous cancer, breast cancer, laryngeal cancer, colorectal cancer, liver cancer, stomach cancer, gallbladder cancer, pancreatic cancer, and lung cancer. In addition, some studies have found that small amounts of alcohol consumption (1 standard glass of alcohol per day) may also increase the risk of oropharyngeal, esophageal squamous epithelial, and breast cancers. However, recent studies have reported that moderate alcohol consumption may prevent cancer. In addition, we cannot ignore the fact that not drinking alcohol is associated with overall mortality, as there is a trend of increased cardiovascular incidence in patients who do not drink alcohol, so we cannot just advocate "abstinence from alcohol is good for health". 5. Don't take vitamin supplements indiscriminately Don't take vitamin supplements if you are not deficient A recent randomized clinical trial studied whether vitamin supplements could reduce the risk of cancer in healthy people. However, the study brought thought-provoking results: (1) folic acid can increase the risk of cancer, especially prostate cancer and colorectal cancer; (2) beta-carotene can increase the risk of lung cancer and stomach cancer; (3) selenium can increase the risk of non-melanoma skin cancer; (4) vitamin E can increase the risk of prostate cancer. In summary, obesity, lack of exercise, and excessive alcohol intake are risk factors for cancer development, and we should pay attention to them. However, dietary habits may not be a risk factor for cancer development, at least the current evidence suggests so.