They certainly don't seem to alleviate "Type II Diabetes" in Mexicans with huge fat rear ends!
Seriously, though...there are a great many natural foods with "anti-oxidant" properties which are good for you, but there are equally as many, if not more, other sources of cancer risk...such as breathing city air, drinking chlorinated water, etc...
As most cancer specialists will tell you...in the final analysis it's your particular genetic makeup which might prevent you from developing cancer; or result in your having cancer regardless of what foods or other preventative measures you take.
Today, cancer is the #1 childhood killer!
Very few young children have lived long enough to have smoked cigarettes for 20 years, or to have breathed polluted air for 60 years, so....?