WALNUTS for POWER: Polyphenols, Omega-3 Fatty Acids, Weight Loss, and EneRgy

Inclusion Criteria: * Pathologically confirmed prostate adenocarcinoma. * Diagnostic biopsy cores with ≥10 cores with each core examined separately to determine exact tumor location. * Biopsy grade group 2 or higher (Gleason ≥7). * Planning to undergo RP. * Willing to adhere to a usual diet with the possible addition of 2 oz of walnuts per day. * Reads, writes, and understands English. * Age 18 or older Exclusion Criteria: * Allergy to nuts. * History of receiving hormone therapy or antiandrogen therapy. * Use of 5-alpha reductase inhibitors in the past 6 months. * Prior prostate radiotherapy (external beam or brachytherapy) or prior prostate cryotherapy. * Currently enrolled in a modified diet/weight loss program and/or taking dietary supplements that contain omega-3s (e.g., fish oil). * Other active malignancy, excluding basal cell carcinoma or squamous cell carcinoma * Significant co-morbidities (e.g., cardiac, pulmonary, liver disease, alcohol/drug addiction, malabsorption syndromes), that in the opinion of the study physician make the patient ineligible. * Individuals with psychological/mental conditions which can affect the consent process and/or their adherence to the protocol.