Antioxidants may help cancers thrive

Antioxidant vitamins have become darlings of the nutritional world. By disarming biologically damaging molecular fragments known as free radicals, antioxidants can fight the ravages of aging and many chronic diseases. Free radicals also offer benefits, however, such as ridding the body of germs and damaged cells. By curbing these activities, a new animal study finds, antioxidants can aid cancer growth.

Several earlier studies had hinted that antioxidants might foster malignancies. Recent work, for instance, showed that cancer cells are more likely than healthy ones to hoard antioxidants (SN: 10/2/99, p. 221)—presumably as ammunition against free radicals unleashed by the body or cancer therapies. Another study found that the more aggressive a woman’s breast cancer, the more vitamin E her blood contains and the lower the free-radical activity in her body (SN: 4/29/95, p. 271).

To further probe the role of dietary antioxidants in cancer, Rudolph I. Salganik and his colleagues at the University of North Carolina in Chapel Hill used genetically modified mice. The scientists started feeding experimental diets to the animals at 2 months of age, a time when the mice invariably begin developing an unusual brain cancer. Seventeen got normal chow; 14 received the same food minus roughly 90 percent of its antioxidants—vitamins A and C.

Four months later, Salganik’s team compared the animals. In mice getting food virtually devoid of antioxidants, tumors were just half the size of those in the brains of animals that had downed normal chow. Moreover, 20 percent of the tumor cells in the antioxidant-deprived mice were undergoing a type of cell death called apoptosis, which is driven by free radicals.

The body ordinarily uses this programmed suicide to rid itself of old or wounded cells. In mice on the normal diet, just 3 percent of cancer cells were undergoing apoptosis. “We were astonished [by this difference],” Salganik told Science News. However, a follow-up study confirmed the findings, he reported last month at the American Society for Cell Biology annual meeting in Washington, D.C.

Salganik, who plans soon to begin trials of antioxidant-depleted diets in cancer patients, emphasizes that antioxidants’ suppression of apoptosis appears to have been restricted to tumors. For cancerfree individuals, he says, antioxidants should produce no deleterious effects.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.