A new study suggests that vitamin C, when used as a supplement to cancer treatments, may increase the efficacy of cancer drugs while lessening the side effects of chemotherapy treatments in some cancer patients. Researchers at the University of Kansas Medical Center reported their findings in Science Translational Medicine in February. According to the study, their research yielded positive results in the lab and in a small trial of ovarian cancer patients.

The researchers tested the effects of vitamin C (also known as ascorbate) when combined with the traditional cancer drugs carboplatin or paclitaxel. They experimented with this combination on a variety of cancer cells in the lab as well as in ovarian cancer cells in mice. They found that high concentrations of vitamin C formed hydrogen peroxide when it entered the spaces between cells. The reaction that followed affected the cancerous cells by damaging their DNA, stressing their metabolism, and inhibiting their growth, thereby weakening the cells and increasing cancer drug efficacy, according to University of Kansas biochemist Qi Chen, a research team member and senior study author.

The research team was surprised to discover that the hydrogen peroxide did not adversely affect the non-cancerous cells. Although the reason for this is unclear at the moment, the researchers say they believe it is connected to how cancer cells inefficiently convert glucose to energy.

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Another element of their research involved experimenting on 27 ovarian cancer patients over the course of 5 years. Some patients underwent standard chemotherapy treatments with paclitaxel or carboplatin, while another group of patients underwent the same treatment with the addition of a vitamin C regimen. According to their research, the patients in the second group reacted positively to this combination, experiencing fewer side effects associated with chemotherapy; in general, they were less nauseated and had more energy.

Whereas previous research into the efficacy of vitamin C in cancer treatments had involved administering the dosage in pill form, the University of Kansas team administered the vitamin dosage intravenously. The researchers believe this key change made all the difference in the effectiveness.

“In the 1970s, ascorbate, or vitamin C, was an unorthodox therapy for cancer. It was safe, and there were anecdotal reports of its clinical effectiveness when given intravenously. But after oral doses proved ineffective in two cancer clinical trials, conventional oncologists abandoned the idea. Physicians practicing complementary and alternative medicine continued to use it, so we felt further study was in order,” Chen 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.”

Despite these findings, other research in this area shows that vitamin C may reduce the efficacy of cancer drugs. Chemotherapy and radiation therapy rely on the production of oxidizing agents to be effective; vitamin C is an antioxidant, and could interfere with the actions of these treatments.

However, studies such as the one conducted at the University of Kansas suggest that this negative interaction specifically does not occur with paclitaxel and carboplatin.

“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,” says Dr. Jeanne Drisko, director of integrative medicine at the University of Kansas Medical Center. “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.”


  1. Benefits of high-dose vitamin C for ovarian cancer patients. Science Daily website. February 10, 2014. http://www.sciencedaily.com/releases/2014/02/140210135908.htm.
  2. Morin M. Promising cancer therapy treatment: vitamin C. Los Angeles Times website. February 5, 2014. http://articles.latimes.com/2014/feb/05/science/la-sci-vitamin-c-cancer-20140206.
  3. Researchers establish benefits of high-dose vitamin C for ovarian cancer patients. University of Kansas website. February 6, 2014. http://www.kucancercenter.org/about-us/news/research-establishes-benefits-of-high-dosh-vitamin-c-for-ovarian-cancer-patients.
  4. Vitamin C may boost chemotherapy. Medical News Today website. February 10, 2014. http://www.medicalnewstoday.com/articles/272408.php.