Could injections of vitamin C help treat cancer? That’s the suggestion from a new study in mice – and trials are already under way to test similar injections in people.

But some cancer specialists are sceptical, and fear that desperate patients will be prompted to start taking large doses of the vitamin. That may be dangerous, because antioxidants such as vitamin C could undermine the effectiveness of standard cancer drugs and radiation therapy.

Excitement over the idea of treating cancer with vitamin C grew in the 1970s after the Nobel prize-winning chemist Linus Pauling suggested that it helped terminally ill patients survive for longer.

However, in 1985, two placebo-controlled trials found no effect of taking vitamin C pills.


In the current study, researchers led by Mark Levine of the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Maryland, gave vitamin C to mice intravenously.

Oxidation boost

The researchers injected immune-deficient mice with cells from three aggressive human cancers – ovarian and pancreatic tumours, plus a form of brain cancer called glioblastoma – and found that vitamin C injections slowed tumour growth by up to 53%.

By injecting into the bloodstream, Levine explains, it is possible to get much larger amounts of the vitamin to a tumour than is possible with oral supplements. While vitamin C is usually an antioxidant, under these circumstances it causes the formation of hydrogen peroxide, a powerful oxidising agent that kills cancer cells.

Levine suggests that intravenous vitamin C could be a useful addition to conventional cancer therapy. His team has also found that women in a preliminary clinical trial are getting similar doses of vitamin C to those seen in the experimental mice. “It’s pharmacologically achievable,” Levine says.

That trial, led by Jeanne Drisko of the University of Kansas in Kansas City, aims to recruit 50 women to test the safety of giving intravenous vitamin C, plus other antioxidants given orally, on top of existing therapies for ovarian, cervical or uterine cancer.

Although there is little evidence that it works in humans, Drisko’s clinic also offers intravenous vitamin C to paying patients.

Self-medication risks

Meanwhile, the Cancer Treatment Centers of America (CTCA) in Zion, Illinois, is testing the safety of intravenous vitamin C in late-stage cancer patients for whom there is no other treatment option. So far, 10 out of a planned 18 patients have been enrolled into the trial.

Definitive answers on the effectiveness of intravenous vitamin C will only come from subsequent larger trials. But given recent experiences with a drug called DCA, which some patients began taking without medical supervision after reading about promising results on cancer cells, there are concerns that patients may take matters into their own hands by injecting themselves with vitamin C or taking large doses of vitamin C pills.

Many cancer patients take antioxidant vitamins, often without telling their doctors. While Drisko and other backers of complementary approaches suggest that antioxidants can aid therapy and reduce side-effects, conventional chemotherapy and radiotherapy are thought to work in part by generating free radicals which kill cancer cells.

Because antioxidant vitamins can mop up these radicals, they may interfere with cancer therapy, other researchers warn. “You want to make sure you’re not taking supplemental vitamins,” says David Agus, an oncologist at the Cedars-Sinai Medical Center in Los Angeles.

Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0804226105)

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