We've all heard about foods so super in their powers they can fight off disease. This past week, broccoli made headlines for its ability to protect men from prostate cancer.

How exactly is this possible?

Researchers believe a chemical in broccoli sparks hundreds of genetic changes, activating some genes that do battle with cancer and turning off others that fuel tumors. This study is more than just evidence backing the notion that a diet rich in fruits and vegetables reduces cancer risk. It's the first human trial that looks at the potential biological mechanism at work. We know it's good to eat fruits and veggies. Now we know why.

Specifically, the broccoli eaters in this study showed 400 to 500 positive genetic changes. Men carrying a gene called GSTM1 enjoyed the most benefit. About half the population have this gene.

While this British study focused on prostate cancer, it's likely broccoli protects people against a whole range of cancers. And it's not all that hard to protect yourself -- all it takes is a few more portions a week to make a difference.

Prostate cancer is the second-leading cancer killer of men after lung cancer. Each year, about 680,000 men worldwide are diagnosed with the disease. About 220,000 will die from it.