The overall objective of this study is to test the effect of walnuts added to a usual diet on prostate cancer progression as measured by Ki67 expression in the prostate tissues. Subjects will be randomized 1:1 to usual diet or usual diet with the addition of 2 ounces of walnuts daily. The baseline visit will occur in conjunction with a standard of care visit post-biopsy, the intervention period will range from 4-10 weeks dependent upon the scheduled date of the standard of care radical prostatectomy (RP), and the final visit will occur in conjunction with a standard of care visit prior to RP.