Question: If I have never had breast cancer, can soy prevent or reduce my risk of getting breast cancer?
Answer: Areas in the world that depend on soy as their major source of protein in their diet have a lower risk of breast cancer; and we're not sure if it's because of the soy, or if it's because their weight tends to be close to their ideal body weight, they tend to exercise more, they're less likely to smoke cigarettes, they have many fruits and vegetables in their diet, there are fewer fried foods, and there are a lot of lifestyle issues that go along with a lower risk of breast cancer.
But there's no clear evidence that soy foods alone, as one thing for you to do, will affect your risk, either increasing it or decreasing it. In general, soy foods are considered healthy; we don't yet know, however, the health and safety of purified concentrated soy products, like soy powders and soy pills. That has not yet been effectively studied. But when it comes to soy foods, those are considered safe and healthy ways to get protein into your diet, instead of other sources, or as a mix with other sources of protein, like fish, chicken, and red meat.