Mice receiving extra vitamins A and E showed no benefit in either the size or incidence of brain tumors, Salganik said. They also had relatively short lives.
"Interestingly and more importantly, in animals that received antioxidant-depleted diets, brain tumors were significantly reduced in size because of induction of oxidant stress due to what are commonly called free radicals in the brain tumors," Albright said. "Higher levels of cell death was restricted only to the brain tumors, while normal tissues were not affected by depletion of antioxidants in the mouse diets."
In mice getting low levels of vitamins A and E, no negative effects were seen in normal cells, but about 19 percent of tumor cells showed evidence of apoptosis. In those ingesting normal quantities of antioxidant vitamins, only about 3 percent of tumor cells were apototic.
The group's findings may explain two previous clinical studies showing that heavy smokers who ate a diet high in beta-carotene antioxidants had significantly higher rates of lung cancer, Salganik said.
"These new studies raise important issues regarding the advisability of ingesting high levels of antioxidants as a potential anti-cancer benefit," Albright said. "Clearly, more studies are needed at the clinical level in human populations to address the real value of antioxidant supplements or antioxidant depletion in people at risk of developing cancer."
Salganik said he hoped clinical studies would begin within a year or two. Van Dyke is a member of the UNC Lineberger Comprehensive Cancer Center.
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Contact: David Williamson
David_Williamson@unc.edu
919-962-8596
University of North Carolina at Chapel Hill
12-Dec-1999