How do you prevent cell damage that causes cancer?

Antioxidants, especially abundant in fruits and vegetables, are powerful compounds that cancel out cancer-causing free radicals before they damage cells.

"Antioxidants begin working almost immediately upon absorption—as soon as they find a free radical to interact with," Hellmann says.

But don't think you're set for the week after eating a big salad. Antioxidants remain active for only a few hours and need to be continually replenished. "Plus, they are a diverse group and don't all have the same functions," says Hellmann. "The key is always having plenty in your body to take on anything that comes along." That means eating as much produce as possible and mixing up the types as often as you can.