According to the well known and one of the best United States' John Hopkins Hospital, to keep your prostate healthy, vegetables including greens are essential. Vitamin D from the exposure to sunshine (in moderation) reduces risk of prostate cancer.
Next, prostate screening such as digital rectal exam and PSA testis should be done. Men who might be at higher risk should start getting screened sooner than normal risk men of age 55.
Men with increased risk prostate cancer are African-Americans, men of Scandinavian descent and anyone who's family member had prostate cancer.
Tips for Keeping a Healthy Prostate, John Hopkins Medicine,