Mice suffering from cancer were found to benefit when vitamin C was given alongside immunotherapy, but the findings should be interpreted with caution.

While vitamin C can provide significant health benefits in some contexts, there are also a lot of myths surrounding it. Vitamin C has a definitive role in preventing and treating scurvy, but beyond that, its efficiency in the prevention and treatment of various diseases is disputed, with reviews often finding conflicting results.

For instance, a 2012 review found no effect of vitamin C supplementation on overall mortality. Even in the case of the common cold, the disease fought traditionally with vitamin C, the results are unclear, with studies finding mild improvements, or no improvements at all. In the case of cancer, the role of vitamin C is also hotly disputed.

Several trials, analyses, and meta-analyses looked at the link between vitamin C intake and the risks of various types of cancers, but links were once again found to be weak or non-existent.

While most of these studies looked at vitamin C on its own, a team of researchers led by Alessandro Magri from the University of Torino looked at vitamin C in conjunction with immunotherapy — and this time they found that the vitamin can really help.

Vitamin C vs cancer

The idea that vitamin C could help against cancer goes back to the 1970s, but after some promising bouts, most researchers gave up on the idea after studies seem to find little benefits to the supplement. However, those studies typically focused on vitamin C that was ingested.

“Vitamin C (VitC) is known to directly impair cancer cell growth in preclinical models, but there is little clinical evidence on its antitumoral efficacy. In addition, whether and how VitC modulates anticancer immune responses is mostly unknown,” the researchers write in the study.

The gut does not absorb vitamin C in high amounts, and the body tends to eliminate the excess vitamin. So patients weren’t actually receiving all that much vitamin C — so in the new effort, the researchers injected vitamin C directly into the veins, as an aid to an immunotherapy regimen.

“Despite some controversy over the years, it is gradually becoming clear that vitamin C has some anticancer effects, albeit only when given intravenously and at sufficiently high doses,” the scientists add.

The study was administered on mice with various types of tumors, and the researchers found that the high doses of vitamin C prevented the growth (or at least slowed down the growth) of melanoma, colorectal, pancreatic and breast cancer tumors. Furthermore, the researchers found that the T cells, a group of cells that protect the body from infection and may help fight cancer, received an extra boost from the treatment as well. In some cases, adding vitamin C to the immunotherapy regimen resulted in some breast cancer tumors disappearing completely, which surpassed their expectations.

Of course, the study comes with a few caveats. For starters, the immune system needed to work properly in order to reap the benefits. Secondly, and perhaps most importantly, the study was carried out on mice — which can mean the findings can carry out on humans but doesn’t guarantee it. We need to replicate the same study on humans before drawing any clear conclusions.

The researchers plan on replicating the study on humans, but there’s a big hurdle: side effects. The doctors gave mice a huge dose of vitamin C for their small body mass, the equivalent of vitamin C found in a single orange. But translated to humans, that’s the equivalent of vitamin C in a few thousand oranges; before this type of study can happen, we need to ensure that there will be no major side effects.

So you shouldn’t barge and take vitamin C supplements, that’s not how this study should be interpreted. What this study does mean is that in niche cases, under medical supervision, vitamin C can be helpful as a part of medical treatment against some types of cancer.

No doubt, more research will help shed new light on how this finding can be best implemented in anti-cancer treatments. Thanks to research, cancer survival rates have more than doubled in the past four decades and show a continuously improving trend, but there is still much more work to be done.

The findings are right in time for National Cancer Prevention Month, a good time to examine what you can do in your life to prevent certain cancers and develop healthy habits, such as using sunscreen, quitting smoking, exercising, getting vaccinated, and attending regular physical exams. 

According to National Cancer Health, about 1.9 million people in the United States will be diagnosed with cancer by 2022 and studies from the American Association for Cancer Research show that more than 40 percent of cancer diagnoses and nearly half of the cancer deaths in the United States can be attributed to preventable causes such as smoking, excess weight, physical inactivity, and overexposure to the sun.

The study “High-dose vitamin C enhances cancer immunotherapy” was published in Science Translational Medicine.