Narrator: This is Science Today. It's a good idea to take antioxidants to prevent cancer, right? Not necessarily, says Dr. Courtney Broaddus of the University of California, San Francisco. In the lab, she found that giving high doses of antioxidants to lung cells helps the cells survive -- but they develop strange mutations and may get cancer later on.

Broaddus: What everyone would have thought made perfect sense turned out to reveal an unexpected and harmful side of something that seemed so good for us.

Narrator: Her work supports the findings of other researchers, who say that the thing to do is not take lots of high-dose antioxidant pills...

Broaddus: ...but rely on the tried and true source of antioxidants, which are vegetables and fruits. Because they contain either the right combination of antioxidants or the right concentrations of fiber together with antioxidants, whatever combination they have, they are the beneficial entity -- and not something that we purify from them and think that we've got the answer.

Narrator: For Science Today, I'm Steve Tokar.