Narrator: This is Science Today. Take antioxidants and prevent cancer -- that's the conventional wisdom.

Broaddus: And there's a lot of evidence that people who eat a lot of fruits and vegetables that contain antioxidants are more resistant to cancer.

Narrator: But in the laboratory, Dr. Courtney Broaddus of the University of California, San Francisco fed antioxidants to lung cells that had been exposed to asbestos, a powerful carcinogen. The cells survived, but in mutated form -- mutations that could lead to cancer. Broaddus says her results help explain several other studies...

Broaddus: In which large numbers of people who were heavy smokers or who had asbestos exposure were given antioxidants on a daily basis to see if it would help prevent their cancers. And to the surprise of almost all physicians, this backfired in the sense that those people who took the antioxidants -- they actually developed more lung cancer than the group that took the placebo.

Narrator: Broaddus says stay away from big doses of antioxidant pills and stick to fruits and vegetables. For Science Today, I'm Steve Tokar.