The positive effects of vitamin C in the treatment of cancer were first observed by Linus Pauling and Ewan Cameron. They published two studies in 1976 and 1978 claiming that giving high doses of vitamin C to patients in the terminal stages of cancer had a beneficial effect on their survival. However, these studies were criticised because no control subjects were included in the experiments. A few years later, two more studies were published that refuted Pauling and Cameron's findings, claiming that such high doses of vitamin C in tablet form would be absorbed by the intestine and only low doses of this vitamin would reach the blood and tissues. However, in 2008, a study was published in which authors observed a reduction in the weight of mouse tumours (brain, pancreatic and ovarian) after injecting high doses of vitamin C directly into these tumours. The study authors even suggested a mechanism for how this reduction occurred. They believed that vitamin C interacts with the unique chemistry of tumour cells, resulting in increased production of hydrogen peroxide. This is toxic to the tumour cells and subsequently the tumour itself is eliminated. This mechanism was confirmed with a second experiment by injecting catalase, an enzyme that breaks down hydrogen peroxide into water and oxygen, into the tumours in addition to vitamin C. In this case, they did not see any reduction in the weight of the tumours, suggesting that the production of hydrogen peroxide is critical to the elimination of the tumours.
So, the question arises, how is it possible that injecting high doses of vitamin C has not yet been used to treat human tumours? The answer is simple: there is no evidence that vitamin C is also effective in reducing the weight of human tumours. To date, neither the effects of high doses of vitamin C on patients' tumours nor the long-term side effects of this potential treatment have been studied. Furthermore, it is not known whether vitamin C can interact with other substances used in cancer treatment.
Based on these facts, it can be argued that vitamin C cannot yet be considered a cure for cancer. Moreover, there are up to 200 different types of cancer, and it is highly unlikely that vitamin C could be a panacea for all these diseases in the future.