Support for treating cancer with vitamin C has gone back-and-forth over the years. During the 1970s, Nobel Prize-winning chemist Linus Pauling found that large doses of vitamin C, or ascorbate, could possibly reduce tumor growth. But after clinical trials failed to substantiate his claims, many doctors strayed away from the treatment. As more cancer patients are once again looking into vitamin C as treatment, a new study shows that intravenous (IV) administration of vitamin C may be able to reduce the severity of side effects from chemotherapy.

Researchers from the University of Kansas already knew that most of the studies following Pauling’s claims tested vitamin C’s effectiveness against cancer using oral doses of the vitamin. This was important, because some of the earlier, smaller trials used an IV solution. According to the National Cancer Institute, high-dose vitamin C is much more present in the blood of people who are given it through an IV.

“When you swallow a pill or eat an orange, vitamin C is absorbed at a certain rate by the gun and excreted very quickly by the kidneys,” Dr. Jeanne Drisko, co-author of the study and director of integrative medicine at the University of Kansas Medical Center, told The Los Angeles Times. “But when you give it intravenously, you override that. Plasma levels can get very high.” In fact, patients could be getting up to 2,000 oranges’ worth of vitamin C in one IV treatment.

When vitamin C is given through an IV in high doses, it promotes the formation of hydrogen peroxide. The researchers found that hydrogen peroxide was able to kill cancer cells and damage their DNA in cell cultures. When they paired the vitamin C up with chemotherapy in mice with ovarian cancer, they found that the combined therapy slowed tumor growth. To further see if vitamin C could work, they administered vitamin C to 13 of 25 ovarian cancer patients who were undergoing chemotherapy as well, and found that the vitamin C group was less likely to report side effects from chemotherapy. “That was surprising,” Drisko told the L.A. Times. “We did not expect to find that.”

Despite the promising results, the researchers cautioned that vitamin C may not work for every type of cancer. Still, the National Cancer Institute notes that studies have shown it to be effective against tumor growth in cancers like prostate, pancreatic, liver, colon, malignant mesothelioma, neuroblastoma, and more. The researchers called for more research into the effects of vitamin C on cancer, noting that the research should be federally funded because vitamin C can’t be patented, and therefore, pharmaceutical companies won’t look into developing it.

“It’s difficult to tell with such a small trial whether high-dose vitamin C injections had any effect on survival, but it’s interesting that it seemed to reduce the side-effects of chemotherapy,” Dr. Kat Arney, science communications manager for Cancer Research UK, told the BBC. “Any potential treatment for cancer needs to be thoroughly evaluated in large clinical trials to make sure it’s safe and effective, so further studies are needed before we know for sure what benefits high-dose vitamin C may have for patients.”

Source: Ma Y, Chapman J, Levine M ,et al. High-Dose Parenteral Ascorbate Enhanced Chemosensitivity of Ovarian Cancer and Reduced Toxicity of Chemotherapy. Science Translational Medicine. 2014.