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