Does Vitamin C Help Fight Cancer?

The relationship between vitamin C and cancer is a highly debated subject amongst oncologists. Scientists have been searching for answers regarding high dose Vitamin C for cancer treatment since the 1970’s, and the road has been somewhat controversial. However, the University of Iowa (UI) conducted a new study which was published in Redox Biology. The findings illuminated some of the grey areas and questions surrounding high dose Vitamin C which have garnered mixed results when it comes to treating cancer.

Vitamin C cancer treatment has typically been administered orally. However, when Vitamin C is taken orally, much of it becomes destroyed and degraded in the digestive tract, and the body ends up excreting a large percentage of it. The alternative is intravenous administration, a far more superior method, as the concentration of Vitamin C that reaches the blood system proves to be much higher. In fact, intravenous administration can result in a concentration almost 500 times higher than oral Vitamin C administration. This is because the digestive system and excretion processes are skipped outright, and the Vitamin C is sent directly to the bloodstream.

When asking “can Vitamin C cure cancer?”, it is the level of Vitamin C in the blood that must be looked at, as this is how Vitamin C proponents suggest that it deals with cancer. Vitamin C can be a huge help in fighting and destroying cancer cells when in high concentrations in the blood, which is why oral vitamin C for cancer is not the right approach.

Another method of administering Vitamin C therapy for cancer is via Liposomal Vitamin C. This method also results in a high level of Vitamin C in the bloodstream compared to regular oral administration. What is more, liposomal Vitamin C is far easier, more convenient, and cheaper to provide than intravenous Vitamin C treatment.

The recent study conducted by UI saw scientists propose a possible reason why high Vitamin C levels selectively kill cancer cells without damaging or compromising the health of normal cells. They suggested that it might not be the antioxidant properties of Vitamin C that makes it a viable cancer prevention method [1].

High-Dose Vitamin C Can Selectively Kill Cancer Cells

UI scientists found that Vitamin C quickly degenerates into hydrogen peroxide (H2O2) in the body. Since hydrogen peroxide is a free radical, this can sound contradictory as free radicals are known to cause oxidation and oxidative stress in the body, and as a result, damage DNA and cells. As a fighting mechanism, the body uses Vitamin C (as it is an antioxidant) to combat free radicals and minimize the damage they can cause.

So, how is Vitamin C used for cancer treatment?

  • H2O2 is removed from the body by healthy cells. They reduce the accumulation of free radicals and therefore reduce oxidative damage. One of the keyways they do this is via the enzyme catalase, which is found in healthy tissue and cells
  • Human cancer cells produce very small amounts of catalase, which could mean that most cancer cells don’t have the tools to neutralize H2O2 themselves
  • When high doses of Vitamin C are sent straight to the cancer or tumor cells, the high levels of hydrogen peroxide free radicals prove fatal to cancer cells as they don’t have the ability to destroy and detoxify themselves of the influx of H2O2
The lead researcher, Gary Buettner, is a professor of radiation oncology and member of the Holden Comprehensive Cancer Center at the University of Iowa. He sheds light on how Vitamin C is linked to cancer. Buettner clarifies that cancer cells cannot detoxify themselves of hydrogen peroxide as efficiently as normal, healthy cells. This means that tumor cells are more susceptible to being damaged and killed by free radicals. “This explains how the very, very high levels of vitamin C used in our clinical trials do not affect normal tissue, but can be damaging to tumour tissue,” adds Buettner. [2]

Lower catalase levels equals increased damage to cancer cells

The UI research team found that cells with lower catalase levels were more susceptible to damage via Vitamin C exposure. “Our results suggest that cancers with low levels of catalase are likely to be the most responsive to high-dose vitamin C therapy, whereas cancers with relatively high levels of catalase may be the least responsive,” Buettner explains. This finding is important as it helps to determine the types of cancer cells that could be treated and destroyed by high doses of Vitamin C.

Vitamin C as an Effective Component of Cancer Treatment

Scientists at UI are working on clinical trials to assess the effectiveness of intravenous Vitamin C on pancreatic and lung cancer patients. This is done in conjunction with chemotherapy or radiation therapy. Preliminary trials suggest that this treatment is promising as it improves the outcome in cancer patients. What’s more, Vitamin C administration is safe, does not cause serious side effects, and is well tolerated by patients. This is opposed to conventional cancer treatments which can cause serious side effects and collateral damage by compromising the patient’s immune system and destroying healthy cells as well as cancer cells.

Large-scale trials are now being conducted, aiming to figure out whether Vitamin C therapy could positively influence patient survival.


  1. Garry R. Buettner et al. Tumor cells have decreased ability to metabolize H2O2: Implications for pharmacological ascorbate in cancer therapy. Redox Biol. 2016.
  2. Jennifer Brown. Why high-dose vitamin C kills cancer cells. The University of Iowa. 2017.