History Magazine

Cancer and Vitamin C: The Mayo Clinic Trial

By Scarc
Cancer and Vitamin C: The Mayo Clinic TrialLinus Pauling, 1979

[Part 7 of 9]

In their 1979 book, Cancer and Vitamin C, Ewan Cameron and Linus Pauling sought to explore the potential for vitamin C to treat or even cure a disease that claimed the lives of millions per year. The two understood that many would raise an eyebrow at the notion that something as simple as vitamin C could treat cancer more effectively than other chemotherapeutics, and to defray this skepticism the duo knew that their point of view needed be independently verified.

After a period of reluctance, Pauling and Cameron found scientists at the Mayo Clinic who were willing to conduct a vitamin C trial on some of their cancer patients. But as we will see, instead of validating Pauling and Cameron’s findings, the Mayo Clinic’s results indicated that vitamin C did not help fight cancer, and in some instances, actually made patients’ outcomes worse. These findings were not at all expected by Pauling and Cameron, and afterward they devoted significant energy to unraveling what had gone wrong with the trials. But before they were able to do so, word had already spread that vitamin C did not work, and little that Pauling and Cameron did could change people’s minds from there.


Ewan Cameron was a physician at Vale of Leven Hospital in Scotland who, after reading up on the subject, and believing that he had nothing to lose, began to treat some of his most severe cancer patients with vitamin C. The results were quite dramatic, with some patients who were near death making positive progress that bordered on miraculous. Even though many of the treated patients’ cancer was so progressed as to rule out a complete recovery, nearly all those given vitamin C experienced a marked improvement of their quality of life. Cameron was convinced and soon almost all of his cancer patients were being given vitamin C.

Shortly after Cameron began vitamin C treatments in earnest, he began his collaboration with Pauling. The two knew that their results had the potential to change medicine and they were eager to let the scientific world know about the work. The problem, however, was that no clinical trial or scientific study had been conducted, and the team knew that claims based on anecdotal data would not hold up in the eyes of many. One solution would be for Cameron and Pauling to conduct their own trial, but Cameron objected to this on moral grounds, believing it wrong to treat a portion of the trial group with a placebo instead of life-saving vitamin C. As such, Cameron was unwilling to conduct a clinical trial on his own patients. Pauling supported his partner’s stance but still understood the need for someone to validate their results.

Cameron and Pauling were also aware of the difficulties inherent to convincing a research group to undertake such a task, particularly given the unorthodox nature of their claim. For many, vitamin C also seemed too simple and too easy a solution. Notably, Cameron and Pauling were likewise not able to readily explain how vitamin C worked. They knew that the treatment did work because they had seen it do so in patient after patient, but the actual underlying biological mechanism remained elusive.

Another problem that Cameron and Pauling faced was the fact that ideal vitamin C dosing had not been formally determined. In other words, there was no standard dose of vitamin C for Cameron’s cancer patients. Instead, Pauling and Cameron let individual patients’ bodies “decide” their own specific optimal dose. They did so by increasing individual dosages up to bowel tolerance — once a patient began experiencing diarrhea, they had reached their maximum dose. This lack of uniformity was atypical and looked down upon by many.


Though Pauling and Cameron were in need of their own study, clinical trials that examined vitamin C and cancer had actually predated their work. The earliest study that Cameron and Pauling were able to find took place in Germany in 1940, several decades before Cameron began dosing his patients with vitamin C. In the German study, researchers confirmed that cancer patients tended to have lower levels of vitamin C in their blood than was the case with healthy subjects. Much later, in 1979, a Japanese team found that cancer patients who were given vitamin C tended to enjoy better five-year prognoses compared to those who did not add supplemental vitamin C to their diets.

These data, while helpful, mostly left Pauling and Cameron wanting more. What they needed was research that mirrored their own approaches to treatment and that would help support their ideas. Through some advocating by Pauling, scientists at the Mayo Clinic in Minnesota agreed to conduct a study that intended – but ultimately failed – to mimic Cameron and Pauling’s work. Carried out in 1978-1979, the study was double-blind, meaning that patients and practitioners alike could not determine if a given participant was in the treatment group or the placebo group.

At the conclusion of the study the Mayo researchers published their results, and they were not what Pauling and Cameron had hoped for, nor expected. Instead of finding that vitamin C helped fight cancer, the Mayo study concluded the polar opposite, going so far as to advocate that vitamin C not be used in conjunction with a cancer patient’s therapy.


Pauling and Cameron were both scientists at their core and would have been willing to accept the Mayo results if they thought that the trials had been rigorous. But in fact, Pauling and Cameron believed that the Mayo Clinic’s study was too dissimilar to their own protocol to be considered a valid test. Notably, the duo objected strongly to the fact that patients in the Mayo study were given vitamin C after receiving chemotherapy, whereas Cameron and Pauling always gave vitamin C before chemotherapy. This was important because Pauling and Cameron believed that chemotherapy degraded the effectiveness of vitamin C and, as such, dosing afterwards was bound to yield poor results. Indeed, in their own work, Cameron and Pauling had developed similar conclusions to the Mayo team for patients given vitamin C after chemotherapy. Fundamentally, Cameron and Pauling were not trying to prove the effectiveness of vitamin C when used after chemotherapy, but before.

Cameron and Pauling also balked at the trial’s method for administering vitamin C. Importantly, in the Mayo study, patients were given vitamin C orally, whereas Cameron and Pauling delivered their doses as intravenous drips. Even though Cameron and Pauling did not, at the time, know for sure why the mechanism of delivery should make a difference, they clearly understood that it did. The Mayo group disagreed and argued that their testing protocols were similar enough that the results should be deemed as valid.

In the end, the Mayo Clinic’s prestige and name recognition won out, and most observers aligned themselves with the study’s results. And while this clearly affected physicians and their prescribing behavior, it did not diminish Cameron and Pauling’s belief in the efficacy of vitamin C to treat cancer, and they continued to advocate for its use.


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