Flaxseed, Aromatase Inhibitors and Breast Tumor Characteristics

Inclusion Criteria:

* Age ≥ 18 and ≤ 85 years
* Postmenopausal status defined as: no menstrual cycle in the past 12 months hysterectomy with bilateral oophorectomy hysterectomy with intact ovaries if age \> 55 years
* Newly diagnosed with incident, primary, invasive, estrogen receptor positive clinical stage II or lower breast cancer
* ECOG performance status of 1 or less
* Willingness to comply with study guidelines and procedures
* Willingness and ability to provide informed consent
* Usual consumption of soy no more than 1 time per week and willingness to avoid whole soy foods or concentrated soy sources (soy milk, tofu, substitute meat products, meal replacement bars) during the intervention period
* Willingness to avoid herbal and dietary supplements (not including vitamins), aspirin, and ibuprofen during the intervention period
* No competing neoadjuvant or chemotherapy treatment
* Time between pre-surgical visit and surgery must be at least 2 weeks
* No chemotherapy in the past 12 months

Exclusion Criteria:

* Inability to read and write English
* Previous invasive breast cancer
* Insulin dependent Type I or II diabetes diagnosed by physician
* History of coagulopathy, thrombocytopenia, or bleeding disorder
* Current (past 30 days) regular (at least once per week) use of reproductive hormone therapy, Tamoxifen, aromatase inhibitors, or other estrogen inhibitors, flaxseed, or antibiotics
* Current chemotherapy or neoadjuvant chemotherapy
* Allergies to flaxseed, nuts, or other seeds
* Renal dysfunction defined as creatinine \> 1.5 mg/dl
* History of Crohns' disease, ulcerative colitis, irritable bowel syndrome, celiac sprue, or other malabsorption syndrome, diverticulitis, diverticulosis, or other bowel diagnosis which, in the opinion of the breast surgeon, would contraindicate large doses of dietary fiber or would impair nutrient absorption
* Current, regular (more than once weekly) use of prescription blood-thinning agents including coumadin, heparin and heparin related drugs, clopidogrel bisulfate