I am not a medical professional, and there is some doubt as to my sanity.
That disclaimer aside, following the B diet (preferably with organic foods), lowering exposure to environmental toxins, and developing a positive spiritual life are the best preventions against all forms of cancer, including prostate.
The problem with identifying particular compounds as being 'anti-cancerous' is that:
a) The tests are often performed in vitro, meaning in a test tube, or in mice, who do not have identical biologies to humans
b) Any in vivo tests, or tests done on living humans, are performed on standard Americans, who by and large [emphasis added], have very high risk factors for these diseases.
The best defense is a good offense. Evaluate where you are today. Start to learn and educate yourself about your body. Start to become proactive in disease prevention, from a wholistic point of view. Supplement when necessary, but most of all:
1) Stay away from avoids for your blood type. Read ingredient labels scrupulously.
2) Drink purified water
3) Reduce your exposure to toxins, especially household cleaners, solvents and commercial personal grooming products.
4) Be happy. Today is a new day, Now is a new time