WASHINGTON (Reuters) - Vitamin C can impede the growth of some types of tumors although not in the way some scientists had suspected, researchers reported on Monday.

A shopper walks past oranges for sale in the Municipal Market in Asuncion August 10, 2007. Vitamin C can impede the growth of some types of tumors although not in the way some scientists had suspected, researchers reported on Monday. REUTERS/Jorge Adorno

The new research, published in the journal Cancer Cell, supported the general notion that vitamin C and other so-called antioxidants can slow tumor growth, but pointed to a mechanism different from the one many experts had suspected.

The researchers generated encouraging results when giving vitamin C to mice that had been implanted with human cancer cells -- either the blood cancer lymphoma or prostate cancer. Another antioxidant, N-acetylcysteine, also limited tumor growth in the mice, the researchers said.

Antioxidants are nutrients that prevent some of the damage from unstable molecules known as free radicals, created when the body turns food into energy. Vitamin C, vitamin E and beta-carotene are among well-known antioxidants.

Previous research had suggested that vitamin C may stifle tumor growth by preventing DNA damage from free radicals.

But researchers led by Dr. Chi Dang, a professor of medicine and oncology at Johns Hopkins University in Baltimore, found that antioxidants appear to be working in a different way -- undermining a tumor’s ability to grow under certain conditions.

Figuring out how antioxidants impede tumors should help scientists figure out how they might be harnessed to fight cancer, Dang said. In addition to the cancer types involved in this study, others that might be vulnerable to vitamin C include colon cancer and cervical cancer, he said.

Dang said more research is needed and cautioned against taking high doses of vitamin C based on these findings.

“Certainly we would very much discourage people with untreated cancer to go out and take buckets full of vitamin C,” Dang said in a telephone interview.

Linus Pauling argued in the 1970s that vitamin C, also called ascorbic acid, could ward off cancer, but the notion has proved contentious.

Pauling, who won the Nobel Prize in chemistry as well as the Nobel Peace Prize, died in 1994.

“Pauling actually had some good evidence that under certain situations vitamin C can prevent tumor formation. It’s just the mechanism was really not that clear then,” Dang said.

“Now that, I think, we provide relatively compelling evidence of how this works, maybe Pauling is partly right. We shouldn’t dismiss him so quickly.” Dang added.