An injection of a high dose of vitamin C could reduce the size of cancerous tumors in people, new research with mice suggests.

A cancer therapy with intravenous doses of vitamin C that proved effective in treating several mice with cancer disease will be tested on humans.

The key element of the therapy is an injection with a high dose of vitamin C which can halve the growth rate of tumors in mice. High concentrations of ascorbate (vitamin C) generate hydrogen peroxide, which is known to slow tumors in mice, researchers wrote in a paper published this week in the Proceedings of the National Academy of Sciences.

Qi Chen, of the National Institutes of Health and colleagues implanted three types of aggressive cancer cells – which developed into brain, ovarian and pancreatic tumors– into laboratory mice.

After testing high-concentrations of vitamin C injections that were injected into the abdominal cavity of mice, researchers found that injections reduced tumour growth by 43 percent to 51 percent, while in untreated mice the disease spread rapidly and involved other parts of the body. The vitamin C produces hydrogen peroxide which kills the cancerous cells, while leaving healthy cells unharmed. Preventing the spread of tumors is one of the main goals of cancer research. It’s not clear why some tumors are immune to the treatment and others are not, Levine said, but the hydrogen peroxide does not seem to kill normal cells.

Levine said a recent clinical study in Canada showed that similar high doses of vitamin C can be injected into people with very minimal side effects. He said the body’s “tight control” over vitamin C levels can be modified by giving the nutrient intravenously and bypassing the digestive system. The technique involves “short-circuiting” the body’s normal control mechanisms and “finding there’s an unexpected surprise that may be beneficial.”

One in three people will be diagnosed with cancer in their lifetime and the movement of cancer cells from the main tumor to other parts of the body is one of the main reasons why the disease is so lethal: each new tumor means a fresh course of treatment is needed.

“These pre-clinical data provide the first firm basis for advancing pharmacologic ascorbate in cancer treatment in humans,” the researchers wrote.

But researchers cautioned that the treatment isn’t ready for use: “Should patients with any kind of tumor go out and get IV ascorbate [vitamin C]? That's not the message here,” Levine said.

The interesting thing is the research shows an unexpected use of vitamin C, which has previously been thought of as a nutrient, not a drug, Levine said. But there appears to be a long way to go from the theory in the lab to the practical application in the clinic, researchers said.

Vitamin D also proved efficient in the treatment of cancer. Another study suggested that high blood levels of vitamin D correlated with a reduced risk of death from colon cancer. There was also some evidence that vitamin D may help prevent colon cancer.

However, the study shows the need for more research.