Acid test. Tumors in mice treated with vitamin C ( right ) increased much less than the tumors in controls.
Qi Chen and Michael Espey, National Institute of Diabetes and Digestive and Kidney Diseases
The long sleep debate on the usefulness of vitamin C to treat cancer perhaps about to revive. The researchers found that mice injected with high doses of vitamin prevented tumor growth. The findings could overturn the vision established that vitamin C is useless as a cancer treatment.
The idea that high doses of vitamin C or ascorbic acid, could help cancer patients first appeared in the late 1970s sparked a heated debate within the research community up that studies in 1979 and 1985 by researchers at the Mayo Clinic in Rochester, Minnesota, seemed to show no benefit. But Mark Levine, a physician and cell biologist at the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Maryland, decided to reopen the investigation as soon as he found that patients in the study had the Mayo ingested vitamin. The intestine absorbs only a limited amount of ascorbic acid, so these patients do not receive a full dose, he said.
high doses Levine and his colleagues tested vitamin C delivered directly to tumors. They increased by 43 types of cancer cells and normal cells of the five strains on a medium with vitamin C. For 75% of tumor types, less than 10 millimoles of vitamin killed about half of the cells, while sparing normal cells. Next, the researchers implanted mice with cells of the pancreas, breast and brain cancer. They injected half rodents with enough vitamin C, so that the concentration in the fluid around their cells is at least 10 millimoles. The tumors in the mice that received the shots increased 41% to 50% less than the growth in mice that did not receive the treatment.
In humans, the concentration of ascorbic acid in the extracellular fluid normally does not climb higher than 0.2 millimoles. But in other studies, researchers injected humans with the same solution, they gave mice and increased vitamin C in the blood to over 10 millimoles. These recipients have shown few side effects, notes the team.
The results show that high doses of injected vitamin C could be another weapon against cancer, researchers conclude in this week's issue of Proceedings of the National Academy of Sciences . Levine hypothesizes a massive dose of ascorbic acid triggers a chemical reaction which produces high levels of hydrogen peroxide. Normal cells have enzymes and other mechanisms that prevent the hydrogen peroxide from damage. But some cancer cells seem to lack the checks and die when hydrogen peroxide concentrations are too high. Levine said potential to help treat cancer with minimal side effects makes vitamin C worth pursuing, despite the historical controversy surrounding the treatment.
Other researchers are encouraged by the results. Chi Dang, a cancer biologist who has done similar work with vitamin C at Johns Hopkins University in Baltimore, Maryland, says the data are strong and deserve further exploration. "I hope people will look at it more objectively without the baggage of history," he said. But Stephen Barrett, who runs the fight against fraud Quackwatch website and has long opposed the use of high doses vitamin C, is skeptical that this will lead to practical applications in humans: "I hope it will not trigger a rash of people eccentric practitioners to get vitamin C intravenously"
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