Soy Isoflavones Supplementation in Treating Women at High Risk For or With Breast Cancer

Inclusion Criteria:

* Women at high risk for breast cancer, defined as any of the following groups:
* Five year Gail risk \> 1.7%
* Known BRCA1/BRCA2 mutation carrier
* Family history consistent with hereditary breast cancer
* Prior biopsy exhibiting atypical hyperplasia or lobular carcinoma in situ (LCIS)
* History of invasive breast cancer or ductal carcinoma in situ (DCIS) and have completed standard therapy including tamoxifen/aromatase inhibitor or will not be treated with tamoxifen/aromatase inhibitor
* Signed Informed Consent

Exclusion Criteria:

* Metastatic breast cancer
* Undergoing treatment (chemotherapy, radiation, or SERMs)
* Pregnancy or breast-feeding, or planning to become pregnant within one year prior to study entry
* Regular soy consumers (i.e., \< once per week of soy food, soy supplements or other products)
* Known food allergies such as to soy or nuts
* Not willing to avoid soy foods/supplements during study period
* Current users of exogenous hormones or oral contraceptive or planning to use exogenous hormones during the duration of the study
* Cannot stop taking aspirin or NSAIDs within a week of breast biopsy
* Active participant in other ongoing trials