The “milk is bad” theory has subsided, but the “soy milk is carcinogenic” theory has become the focus of people’s attention. Every week, there are different patients in the breast clinic asking “Can I drink soy milk and will it cause breast cancer?” There are many different opinions and opinions. Soybeans and their products contain soy isoflavones, which mainly include soy glucosinogen and goldfinch isoflavones. Goldfinch isoflavones are similar in structure to estrogen and can bind to estrogen receptors in breast cells to exert the effects of estrogen, so they are called phytoestrogens. Phytoestrogens are different from estrogens derived from animals or chemically synthesized estrogens. Although this phytoestrogen has the effect of estrogen, its pro-mammary gland hyperplasia effect is only one thousandth of that of estrogen, and it can not only improve the symptoms of menopausal syndrome, but also has good anti-cancer effects. Therefore, in recent years, soy isoflavones have been widely used in the treatment of menopausal syndrome. The latest research by breast disease experts at Harvard Medical School confirmed that soy milk and soy products can significantly inhibit the growth of breast tumor cells, leading to increased apoptosis of breast tumor cells. Instead of promoting the growth of breast tumor cells, it has a significant anti-cancer effect. Epidemiological data show that in addition to breast cancer, soy isoflavones also have a risk-reducing effect on stomach, prostate, colon and ovarian cancers. Therefore, the idea that phytoestrogens can increase the risk of breast cancer in the same way as estrogen is a familiar misconception. The real reason for the high incidence of breast cancer may be excessive fat intake, which is positively correlated with breast cancer incidence. Moreover, vegetable oils are high in polyunsaturated fatty acids, and the intake of polyunsaturated fatty acids is positively correlated with the risk of breast cancer. It is a great loss to be afraid to drink soy milk and eat soy products because of misunderstanding the role of phytoestrogens. May women get out of this misunderstanding and go enjoy delicious soy milk and soy products.