I was doing some research the other day and I came across some secret military research on the DARPA site (thats where the pentagon leaks stuff on their reseach).
They have been looking into this compound quercitin which is a natural extract as a counter to free radical builup in soldiers under combat stress.

Quercitin is a bioflavonid (a type of nutrient that is found in some fruits and green, leafy vegetables, amongst other things such as teas and beans).

Quote:
“After testing at the Mayo clinic, quercitin was also shown to be useful in helping to treat or prevent prostate cancer. In the findings of the Mayo Clinic study about quercitin, Mayo Clinic researcher Nianzeng Xing, Ph.D stated that “Our laboratory results showed quercitin blocks the androgen activity in androgen-responsive human prostate cancer cell lines.” He then followed this statement by asserting that “By blocking the androgen activity, the growth of prostate cancer cells can be prevented or stopped.” While this research doesnt prove quercitin will actually truly benefit men with prostate cancer or those at risk, it definitely shows promise as a preliminary study.”

Quercitin has been found to be the most active bioflavonid. Quercitin is a naturally occurring flavonoid that can be found in food sources such as fruits and vegetables. It is most commonly found in apples, onions, cherries, certain citrus fruits, leafy vegetables, broccoli, raspberries, black tea, green tea, red wine and red grapes.

You can buy it as a supplement too of course.