A new study suggests giving some cancer patients high doses of vitamin C intravenously - as opposed to orally - alongside conventional chemotherapy, may help kill cancer cells and also reduce some of its toxic side effects.
Reporting their findings in Science Translational Medicine, researchers from the University of Kansas (KU) Medical Center describe how they tested the approach in cells, animals and humans.
They found giving infused vitamin C together with carboplatin and paclitaxel - two conventional chemotherapy drugs - stopped ovarian cancer in the lab and also reduced toxic side effects of chemotherapy in ovarian cancer patients.
Since the 1970s, ascorbate - or vitamin C - has been used as an alternative therapy for cancer. It has an "outstanding safety profile," write the researchers, who also note there were anecdotal reports that it was effective if given intravenously.
However, although complementary and alternative therapy doctors continued to use it to combat cancer, conventional oncologists abandoned its use after clinical trials of orally administered vitamin C found it was ineffective against cancer.
Now, more recent studies have resurrected the possibility that intravenous vitamin C may be worth looking at again as a possible anti-cancer therapy, so the KU researchers decided to investigate.
Given intravenously, vitamin C has anti-cancer effects
And indeed, what they found was that vitamin C can be effective against cancer when given intravenously, as senior author Qi Chen, assistant professor in the Department of Pharmacology, Toxicology and Therapeutics at the KU Medical Center, explains:
"What we've discovered is that, because of its pharmacokinetic differences, intravenous vitamin C, as opposed to oral vitamin C, kills some cancer cells without harming normal tissues."
For their clinical trial, the researchers recruited 27 patients who had just been diagnosed with stage 3 or stage 4 ovarian cancer.
They all underwent conventional chemotherapy with paclitaxel or carboplatin, but some also received high doses of vitamin C intravenously. They were then followed for 5 years.
The researchers found that, compared with the patients who did not receive vitamin C in addition to conventional chemotherapy, the toxic effects of the therapy tended to be less in the patients given vitamin C.
In another experiment, the researchers found vitamin C killed cancer cells in mice with ovarian cancer, but only at concentrations that can be achieved if given intravenously. They noticed no toxic effects or changes due to chemotherapy in the animals' livers, kidneys and spleens.
When they looked at what was happening at the molecular level, they found vitamin C in the fluid surrounding tumor cells acts as a "pro-oxidant," spurring formation of hydrogen peroxide, which kills cancer cells.
On further investigation of this path, the researchers found a number of mechanisms through which, acting as a pro-oxidant, vitamin C induced cell death in ovarian cancer cells, including promoting damage to their DNA, without affecting healthy tissue.
Researchers call for large clinical trials
Co-researcher Dr. Jeanne Drisko, who specializes in integrative medicine at KU, says:
"We now have a better understanding of vitamin C's anti-cancer action, plus a clear safety profile, and biological and clinical plausibility with a firm foundation to proceed. Taken together, our data provide strong evidence to justify larger and robust clinical trials to definitively examine the benefit of adding vitamin C to conventional chemotherapy."
However, it may not be easy to find funding for large clinical trials of intravenous vitamin C. Pharmaceutical companies, for example, are unlikely to be interested because with vitamin C being a natural substance, they would not be able to patent it.
Meanwhile, Medical News Today reported a study that suggests athletes should avoid supplementing with vitamin C and vitamin E as it may hamper their endurance training.
Written by Catharine Paddock PhD