Vitamin C again under scrutiny as an aid to the treatment of cancer
Could pumping about 2,000 oranges' worth of vitamin C into a patient's bloodstream boost the effectiveness of anti-cancer drugs and mitigate the awful side effects of chemotherapy?
In research published on Wednesday in the journal Science Translational Medicine, scientists found that high doses of vitamin C administered intravenously increased the cancer-killing effects of chemotherapy drugs in mice, and blunted toxic side effects in humans.
But while the research seemed to offer effectiveness for a new method of treatment, vitamin C, or ascorbate, was unlikely to inspire the vigorous, and expensive, research necessary to become an approved tumour remedy, experts said.
Due to a decades-long history of discredited health claims, as well as the inability of pharmaceutical companies to patent an essential nutrient, vitamin C is among the unlikeliest compounds to attract funding for cancer research.
"There has been a bias since the late 1970s that vitamin C cancer treatment is worthless and a waste of time," said Dr Jeanne Drisko, a study co-author and the director of integrative medicine at the University of Kansas Medical Centre. "We're overcoming that old bias."
The furore surrounding vitamin C began with Nobel Prize-winning chemist Linus Pauling, who proposed that heavy doses of ascorbate could prevent and treat most cancers. Although Pauling's broad claims could not be supported in clinical trials, large doses of vitamin C are still used as an alternative form of cancer treatment for thousands of patients, outside mainstream medicine.
Drisko and colleagues argue that vitamin C is worth re-examination, and say the US government should fund further research. One of the problems with earlier studies, they say, is that ascorbate was taken orally, not intravenously.
"When you swallow a pill or eat an orange, vitamin C is absorbed at a certain rate by the gut and excreted very quickly by the kidneys," Drisko said. "But when you give it intravenously, you override that. Plasma levels can get very high."
Researchers examined the effects of vitamin C on a variety of cancer cells in laboratories, and in ovarian cancer cells in mice. When high concentrations of ascorbate entered the space between cells, they said, it formed hydrogen peroxide.
Senior author Qi Chen, an assistant professor of pharmacology, toxicology and therapeutics at the University of Kansas, said the hydrogen peroxide attacked cancerous cells, damaging their DNA, stressing their metabolism and inhibiting their growth.
A third part of the research involved a small trial study with 27 cancer patients, a portion of which were given vitamin C with chemotherapy, provided they did not have kidney problems.
The trial was to see if the vitamin C sickened patients, not whether it was more effective than standard treatment. Many more patients would be required to make that determination.
Not only did the patients who were given vitamin C do well, they tolerated chemotherapy better than those who did not receive it, the authors said. They had more energy, and experienced less nausea.