Returning to the Spotlight: High-Dose Vitamin C in Cancer Therapy

Long known as the anti-scurvy substance, vitamin C is an essential dietary supplement commonly found in fruits and vegetables.(1) Although previous research has established its importance in several physiological processes (e.g., collagen production), considerable controversy still surrounds the role of vitamin C in cancer therapy. In the mid-20th century, Toronto physician William McCormick postulated that vitamin C conferred a protective effect against cancer after observing that patients with malignancies were deficient in the key nutrient.(2) Capitalizing on this correlation, Cameron and Pauling conducted a pair of studies whose results decisively validated McCormick’s hypothesis.(3,4) Soon after though, in the 1980s, researchers from the Mayo Clinic failed to replicate such positive findings and published them in the New England Journal of Medicine.(5) The more rigorous design and high-profile publication of the follow-up trials extinguished enthusiasm for vitamin C as a cancer therapy, despite the data from the Cameron-Pauling trials.(2) Interest subsided further as findings from subsequent investigations suggested that vitamin C had little clinical value as an anticancer mono-therapy.(6)

Since the mid-1980s, scientific understanding of vitamin C and its effects in the human body has advanced considerably. With time, researchers have also been able to explain the discordant results collected from 20th century trials of vitamin C in cancer patients. Perhaps the most consequential difference between trials was the route of administration. Scientists understand now that a millimolar concentration of ascorbate is necessary to induce cytotoxicity in cancer cells, but patients can only achieve such levels of vitamin C throug