This phase II trial studies the effects of a soy bread versus a wheat bread in improving immune function in participants who are beginning a course of androgen deprivation therapy for prostate cancer. Components found in soy foods may influence the immune system in a way that may be beneficial for prostate cancer prevention and survivorship.

PRIMARY OBJECTIVES:

I. To precisely define the impact of soy on myeloid derived suppressor cells (MDSC) in a human model clinical trial.

OUTLINE: Participants are randomized to 1 of 2 arms.

ARM I (SOY BREAD): Participants consume 2 slices of soy bread daily for approximately 20 weeks in the absence of unacceptable toxicity. Concurrent with the intervention, participants will be staring androgen deprivation therapy at the direction of their medical oncologist.

ARM II (WHEAT BREAD): Participants consume 2 slices of wheat bread daily for approximately 20 weeks in the absence of unacceptable toxicity. Concurrent with the intervention, participants will be staring androgen deprivation therapy at the direction of their medical oncologist.

Inclusion Criteria:

• Have biopsy proven adenocarcinoma of the prostate (no small cell, sarcomatoid, or other rare subtypes)
• Be planning a course of at least 5 months of androgen deprivation therapy. Patients who have had androgen deprivation therapy in the past as part of salvage therapy or primary therapy, but are initiating a new course will be eligible.
• Have a testosterone concentration within normal limits.
• No neoadjuvant hormonal or chemotherapy (other clinical trials) for their prostate cancer
• Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.
• Have blood, urea, nitrogen (BUN)/creatinine (Cr), liver enzymes, complete blood count (CBC), and prothrombin time (PT)/partial thromboplastin time (PTT)/international normalized ratio (INR) within normal limits
• Voluntarily agree to participate and a sign an informed consent document
• Agree to have prostate biopsy blocks provided to the study for evaluation
• Willing to discontinue all current vitamin/mineral supplements
• Not currently be taking complementary or alternative products (i.e. PC-SPES, Saw Palmetto) that target the prostate or may impact the hormonal environment
• Agree to consume a standardized vitamin and mineral supplement (provided by the study) and avoid other nutrition, dietary, or alternative medications/supplements for the duration of the study

Exclusion Criteria:

• Have an active malignancy other than prostate cancer that requires therapy
• No diagnosed hematologic malignancy
• Not currently taking steroid medications (i.e., chronic lymphocytic leukemia [CLL])
• No chronic infection (i.e., human immunodeficiency virus-positive [HIV+])
• No history of organ transplant requiring immunosuppressive medications
• History of nephrolithiasis (renal stones)
• Renal insufficiency with creatinine > 1.8, including anyone on dialysis regardless of nadir creatinine
• Have certain medical conditions. Have no history of malabsorptive disorders or other metabolic disorders requiring special diet recommendations (for example, Crohn?s disease or gluten enteropathy)