Children exposed to secondhand cigarette smoke have lower levels of antioxidants -- chemicals that protect against biological stresses -- a new study has found.

Researchers from the University of Rochester Medical Center looked at data on antioxidant levels and the level of secondhand-smoke exposure among 6- and 18-years-olds. The study found that kids who had higher levels of the nicotine metabolite cotinine in their bodies had lower levels of antioxidants, which help the body fight against cell damage from free radicals.

"We don't know enough yet to say that this group of children need supplements to make up for the antioxidants they're losing, but it's always wise to feed children an abundance of fruits and vegetables high in antioxidants and other healthy nutrients," said study author Karen Wilson.

However, researchers found that smoke exposure did not reduce vitamin levels in the bodies of study subjects.

The results were presented at the annual Pediatric Academic Society Meeting in Baltimore, Maryland.