Such mutations can be repaired, however, and lead author Ian Blair of the Center for Cancer Pharmacology, at the University of Pennsylvania, cautioned that the study shouldn't be interpreted as a claim that vitamin C causes cancer. Nor does it question the wisdom of eating a balanced diet rich in fruits, vegetables, and whole grains, he said.

The findings, which come from test-tube experiments (in vitro), may help explain why vitamin C has thus far shown little effectiveness at preventing cancer in clinical trials, according to the Science authors.

"It's possible that vitamin C isn't working in cancer prevention studies because it's causing as much damage as it's preventing, but that's really speculation at this point. What we can say is that vitamin C clearly doesn't work when you expect it to, and now we're in a position to see if that's what's happening in vivo, [or, in living cells]" Blair said.

Some scientists have long recommended dietary supplements of vitamin C, particularly for treating and preventing cancer. But the supplements' effectiveness has been hotly debated, with critics saying they either have no effect or that they may be harmful.

"The logic being used [for vitamin C supplements] is that 'fruits, vegetables, etc. contain vitamin C; these foods prevent cancer; thus vitamin C prevents cancer," Blair said. "But our message is that it's the total diet that's important, not just one antioxidant in isolation."

Vitamin C is known to do beneficial work in the body, including acting as an antioxidant that "disarms" free radicals. These highly reactive ions are produc
'"/>

Contact: Cherita Gonzales
cgonzale@aaas.org
202-326-6414
American Association for the Advancement of Science
14-Jun-2001