Credit: Schoenfeld, et al.
The 11 evaluable patients enrolled in the brain cancer safety trial received three infusions of vitamin C a week for 2 months followed by two infusions per week for 7 months while receiving standard care radiation and chemotherapy. The goal of each infusion was to raise the concentration of vitamin C in a patient's blood to 20,000 μM, as compared to a blood level of about 70 μM found in most adults. The high dose is necessary because vitamin C has a half-life of about two hours in the circulation of humans. The treatment was generally well tolerated; with modest side effects including frequent trips to the bathroom and dry mouth. Rarely, some patients developed high blood pressure that subsided quickly following infusion.
Why is this approach safe? Vitamin C, even at high levels, isn't toxic to normal cells. The research group at Iowa found, however, that tumor tissue's abnormally high levels of redox active iron molecules (a by-product of abnormal mitochondrial metabolism) react with vitamin C to form hydrogen peroxide and free radicals derived from hydrogen peroxide. These free radicals are believed to cause DNA damage selectively in cancer cells (versus normal cells) leading to enhanced cancer cell death as well as sensitization to radiation and chemotherapy in cancer cells.