Maintain normal weight Women with a BMI <25 kg/m2 have a reduced risk of breast cancer. This recommendation was not listed out of thin air by the three departments, 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 drink of alcoholic beverages per day, and maintain a body mass index (BMI) of less than 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 following 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, the relative risk of postmenopausal breast cancer increases by 11%, postmenopausal endometrial cancer by 39%, and postmenopausal ovarian cancer by 13%. The key problem is that the weight of adults increases with age, and this cannot be prevented. So you can only manage your health well. Increased physical activity MET=7.5-15 and reduced risk of cancer death. Several observational studies have found that physical activity reduces the risk of breast, colorectal, and endometrial cancers. A study of U.S. and European populations found a 20% lower risk of cancer death among those who exercised at the minimum recommended level of exercise - a metabolic equivalent (MET) of 7.5-15 per week - compared to those who were physically inactive. A recent meta-analysis of breast and colorectal cancer survivors (50,000 patients) also showed that being physically active reduced the mortality rate of breast and colorectal cancer among survivors. Eat more vegetables, less meat? Eating lean meat isn't so bad. A recent meta-analysis study found that eating more fruits and vegetables reduced all-cause mortality and cardiovascular mortality in people, but was 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. This shows that processed meat products are more important to be aware of than lean meats. Drink alcohol in moderation Drink 1 standard glass of alcohol per day, and no more. Heavy alcohol use (more than 5 standard drinks per day) is significantly associated with the development of 10 cancers: oropharyngeal, esophageal squamous, breast, larynx, colorectal, liver, stomach, gallbladder, pancreatic, and lung cancers. In addition, small amounts of alcohol (1 standard glass of alcohol per day) have been found to increase the risk of oropharyngeal, esophageal squamous epithelial, and breast cancers. However, recent studies have reported that moderate alcohol consumption can prevent cancer. In addition, we cannot ignore the fact that abstaining from alcohol is associated with higher overall mortality, as there is a trend toward higher cardiovascular morbidity among non-drinkers, so we cannot just advocate that "abstaining from alcohol is good for your health". Do not take vitamin supplements indiscriminately. Do not take them if you are not deficient. A recent randomized clinical trial investigated whether vitamin supplements could reduce the risk of cancer in healthy people. However, the study produced sobering results: (1) folic acid increased the risk of cancer, especially prostate and colorectal cancers; (2) beta-carotene increased the risk of lung and stomach cancers; (3) selenium increased the risk of non-melanoma skin cancer; and (4) vitamin E increased the risk of prostate cancer. In summary, obesity, lack of exercise, and excessive alcohol intake are risk factors for cancer development and should be given priority attention. However, dietary habits may not be a risk factor for cancer development, at least the current evidence suggests so.