Introduction to Vitamin C and Cancer Clinical Studies
The use of vitamin C as an adjunctive cancer therapy has a long and controversial history. Although high-dose vitamin C had been used sporadically to treat cancer in the 1940s and 1950s, the largest and most careful studies were conducted in the 1970s by Linus Pauling and his clinical collaborator in Scotland, Ewan Cameron, who proposed that vitamin C would increase “host resistance” to cancer. Most of the treated patients responded favorably to vitamin C given orally and intravenously, although the studies were not formally randomized. Other clinical studies by Pauling's colleagues in Japan confirmed the therapeutic value of high-dose vitamin C. The Mayo Clinic conducted two randomized controlled trials to check these results, but there was no difference in outcomes between controls and patients treated with vitamin C. The Mayo Clinic trials were criticized for various methodological flaws; based on recent pharmacokinetic studies and research on the putative anticancer mechanisms of vitamin C, the trials likely failed because the vitamin C was given only orally, not intravenously, which results in limited plasma concentrations. This chapter provides a historical perspective on the clinical research that has stimulated a resurgence of interest in the use of vitamin C in cancer.