Summary of foods that may be prostate protective – Colorful eats cut risk of some cancer
The same foods that prevent prostate cancer probably slow cancer down.
The problem is that there have not been good studies yet that show exactly which foods or vitamins help.

The nice thing about this article is it tells which foods have substances that may help:

The food with the highest lycopene concentration is watermelon.
Other foods: tomatoes, guava, red grapefruit, papaya.
Speaking of fat, the same fats that protect the heart seem to protect the prostate. Fatty fish such as salmon, tuna, sardines and herring contain healthy omega-3 fats called EPA and DHA.

In contrast, fats from animal products such as meat and the whole-fat dairy products seem to increase risk of both prostate cancer and heart disease.
Broccoli, cabbage, cauliflower, collard greens, mustard greens, turnip greens, kale, bok choy and Brussels sprouts are all members of the crucifer family. This family’s weapon against cancer is a natural chemical called sulforaphane.

Vitamins E and D and selenium also seem to reduce cancer risk in some men, depending on family history and PSA levels. To get them from a supplement, take a regular multivitamin, not a mega dose.

Natural chemicals in green tea and pomegranate juice also may reduce the risk of cancer.