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http://sciencenow.sciencemag.org/cgi/content/full/2008/805/2?etoc

New Life for a Discredited Treatment?

By Rachel Zelkowitz
*Science*NOW Daily News
5 August 2008
The long-dormant debate over vitamin C's usefulness for cancer therapy may
be about to reignite. Researchers have found that injecting mice with high
doses of the vitamin staved off tumor growth. The findings could upend the
established view that vitamin C is useless as a cancer treatment.

The idea that high doses of vitamin C, or ascorbic acid, might help cancer
patients first surfaced in the late 1970s. It sparked a heated debate within
the research community until studies in 1979 and 1985 by scientists at the
Mayo Clinic in Rochester, Minnesota, seemed to demonstrate 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
reinvestigate once he realized that patients in the Mayo study had ingested
the vitamin. The intestine absorbs only a limited amount of ascorbic acid,
so those patients did not get a full dose, he says.

Levine and his colleagues tested high doses of vitamin C delivered directly
to tumors. They grew 43 types of cancer cells and five strains of normal
cells on a medium with vitamin C. For 75% of the tumor types, less than 10
millimoles of the vitamin killed about half of the cells while sparing
normal cells. Next, the researchers implanted mice with pancreatic, breast,
and brain cancer cells. They injected half of the rodents with enough
vitamin C so that the concentration in the fluid around their cells would
reach at least 10 millimoles. Tumors in the mice that received the shots
grew by 41% to 50% less than growths in mice that did not receive the
treatment.

In humans, the concentration of ascorbic acid in the extracellular fluid
normally doesn't climb higher than 0.2 millimoles. But in other studies,
researchers have injected humans with the same solution they gave the mice
and increased vitamin C in the blood to more than 10 millimoles. Those
recipients showed few adverse effects, the team notes.

The results show that high doses of injected vitamin C could be another
weapon against cancer, the researchers conclude in this week's issue of the
*Proceedings of the National Academy of Sciences*. Levine speculates that a
massive dose of ascorbic acid triggers a chemical reaction that produces
high levels of hydrogen peroxide. Normal cells have enzymes and other
mechanisms that prevent hydrogen peroxide from damaging them. But some
cancer cells seem to lack those controls and die when concentrations of
hydrogen peroxide are too high. Levine says potential to help treat cancer
with minimal side effects makes vitamin C worth pursuing, in spite of the
historical controversy surrounding the treatment.

Other researchers are encouraged by the results. Chi Dang, a cancer
biologist who has performed similar work with vitamin C at Johns Hopkins
University in Baltimore, Maryland, says the data are sound and deserve
further exploration. "I hope people will look at this more objectively
without the baggage from history," he says. But Stephen Barrett, who runs
the anti-fraud Web site Quackwatch and has long opposed the use of high
doses of vitamin C, remains skeptical that this will lead to practical
applications in humans: "I hope this will not touch off a rash of people to
offbeat practitioners to get intravenous vitamin C."


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Michael Balter
Contributing Correspondent, Science
Adjunct Professor of Journalism,
Boston University

Email: [log in to unmask]

Website: michaelbalter.com
Balter's Blog: michael-balter.blogspot.com
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