Breast cancer is the most common malignant tumor among women in the world, and the incidence rate of breast cancer in China is increasing by 4% every year. The incidence rate of breast cancer in Shanghai, the largest city with the highest incidence rate in China, has increased by 37% in the past 10 years, and the age of incidence is getting younger and younger, and breast cancer patients between 30 and 35 years old are very common, which has attracted close attention. Recent medical studies have shown that the occurrence of breast cancer is closely related to the level of estrogen that accompanies women throughout their life. Estrogen is a physiological hormone, and an appropriate amount of estrogen can reduce menopausal symptoms and osteoporosis, but it does not mean that estrogen is an “anti-aging drug”. If estrogen levels increase, it will prolong the stimulation of the breast epithelium by estrogen and change the endocrine environment in the body, leading to cellular malignancy and triggering the occurrence of breast cancer. Epidemiological surveys have found that the incidence of breast cancer can be significantly increased by both sustained increases in endogenous estrogen levels and exogenous estrogen supplementation. Studies have shown that estrogen metabolism causes DNA damage, and estrogen promotes the transformation of breast cells and the proliferation and invasion of estrogen receptor-positive breast tumor cells, which is the basis for the use of anti-estrogen therapy in some breast cancer patients. In modern society, women are under a lot of pressure due to fierce competition, which often affects estrogen levels; they use a lot of beauty products with estrogen to achieve skin rejuvenation; they eat hormone-fed chicken, fish and other meat; and they suffer from serious environmental pollution. In addition to the part of estrogen secreted by the ovaries, obese women can also produce a considerable amount of estrogen from adipose tissue, which increases the risk of breast cancer. Repeated abortions can increase the likelihood of breast cancer in women. This is because after each abortion, the pregnancy is suddenly interrupted and the hormone levels in the body change significantly, which can be a trigger for breast cancer. Alcohol can increase the level of estrogen in women’s bodies, and this may be the reason why alcohol consumption increases the recurrence rate of breast cancer. Therefore, when it is necessary for these women to use estrogen, they should use it in a reasonable and appropriate amount under the guidance of a doctor. Of course, estrogen should not be considered as a beast, because different doses of estrogen have opposite effects in the process of breast morphogenesis: physiological levels of estrogen can induce tumor regression, which is caused by the two-way effect of estrogen. Studies have found that the benefits of estrogen use in patients on hormone replacement therapy still outweigh the harms, but standardized use with good follow-up and monitoring is recommended. Therefore, to prevent breast cancer, women must pay special attention to their dietary habits. A diet rich in soy can reduce the risk of breast cancer by altering the effects of estrogen and other hormones. In addition, you should attend regular annual health check-ups, preferably within a week after each period, to check your breasts for lumps and detect precancerous lesions early.