• This study will be conducted in postmenopausal women who have increased risk of breast cancer and high BMI \>= 30 kg/m\^2

• The study population will consist of women with a relative risk of developing breast cancer that is at least \> 2 x that of the general population for their age group based on any of the following:

‣ Have a known genetic mutation associated with hereditary breast cancer (including BRCA1, BRCA2, p53, etc.)

⁃ One or more first degree relatives with breast cancer, with at least one under the age of 60

⁃ Two or more second degree relatives with breast cancer, with at least one under the age of 50

⁃ Prior biopsy diagnosing atypical lobular hyperplasia, atypical ductal hyperplasia, lobular carcinoma in situ, or ductal carcinoma in situ in the last 10 years

⁃ Have a Gail Risk Assessment (which is based on age, race, age of menarche, age of first live birth, number of first degree relatives with breast cancer, number of breast biopsies, and presence of high risk histology on any biopsies) that is considered high risk compared to the general population i.e. 5 year Gail \>= 1.7

⁃ Prior diagnosis of T1 or T2 breast cancer \>= 5 years, without antiestrogen therapy for \> six months when applicable

• ELIGIBILITY CRITERIA FOR HIGH RISK PATIENTS FOR THE CLINICAL TRIAL

• Body mass index (BMI) \>= 30 (Asian BMI \>= 25 kg/m\^2)

• Postmenopausal, defined as continuous absence of menstruation for 12+ months, status post bilateral oophorectomy, or status post hysterectomy with follicle stimulating hormone (FSH) in menopausal range

• Bilateral mammogram within the 12 months prior to study enrollment that is read as not suspicious for breast cancer (American College of Radiology \[ACR\] class I-III). Subjects with a class IV mammogram may be entered once they have had a negative biopsy. In cases of bilateral mastectomy, documentation that the patient has been continuously without evidence of disease for 5 years will suffice

• Serum creatinine of 1.5 X upper limit of institutional norm or less

• Total bilirubin of 1.5 X upper limit of institutional norm or less

• ALT and aspartate aminotransferase (AST) of less than 2 X upper limit of institutional norm or less

• Hemoglobin of 9.0 gm/dL or more

• Platelets of 100,000/mm\^3 or more

• Total white blood cell (WBC) of 3500/mm\^3

• Absolute neutrophil count (ANC) of 1500/mm\^3 or more

• Must be willing to have about 40-50 ml of blood (approximately 8-10 teaspoons) drawn at 0 and 3 months

• Must be able to swallow pills

• This study will assess WBM powder in postmenopausal women of 21 years of age or older. Younger women are unlikely to be postmenopausal

• Participants will have Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1

• The effects of WBM on the developing fetus are unknown. Pregnant and women with childbearing potential are not eligible to participate in this study of postmenopausal women at high risk of breast cancer

• All subjects must have the ability to understand and the willingness to sign a written informed consent. Participants must be aware of their increased breast cancer risk and willingly consent after being informed of the investigational nature of the intervention, alternatives, potential benefits, side-effects, risks, and discomforts

• Prior therapies, including chemoprevention or adjuvant therapies, must have been completed for 6 or more months prior to study entry. Prior use of mushroom or mushroom chemical-containing supplements must have been completed within 3 months of study entry