Women with no history of breast cancer and a lifestyle that has included a soy-rich diet over many years (such as Japanese women) may actually have a lower risk of developing breast cancer in their lifetimes. This could be because the plant-derived phytoestrogens found in soy products lower the circulating estrogen levels produced by women's bodies.
The situation may be different, however, for women who have breast cancer, perhaps particularly for women with estrogen-receptor-positive tumors. Women with this type of breast cancer are generally treated with antiestrogen therapies, such as tamoxifen or, in postmenopausal women with invasive breast cancer, one of the aromatase inhibitors. Because the goal of hormone treatment in estrogen-receptor-positive breast cancer is to limit the amount of circulating estrogen in the body, menopausal breast cancer patients are not generally given hormone replacement treatment. The same rationale is behind the general recommendation that women with estrogen-receptor-positive breast cancer not adopt diets that are very high in soy and its phytoestrogens.
This means that although eating some soy is very likely to be fine, a change to a completely soy-based diet is not generally recommended. There are certainly many other balanced, lower-calorie, lower-fat diet plans out there to consider if weight reduction is your goal.
Learn more in the Everyday Health Breast Cancer Center.
Last Updated: 6/9/2008