Vitamin C is a nutrient found in food and dietary supplements. It is an antioxidant and also plays a key role in making collagen. High-dose vitamin C is given by an intravenous (IV) infusion (through a vein into the bloodstream so it can reach higher levels in the blood than when the same amount is taken by mouth. Some studies of IV high-dose vitamin C in patients with cancer have shown improved quality of life, as well as fewer side effects. In general, high-dose vitamin C given by IV has caused very few side effects in clinical trials.
The mechanism that might explain the potential efficacy of vitamin C in treating cancer relates to the cancer cells’ metabolism. As a consequence of the faulty metabolism that occurs inside the cancer cells’ mitochondria, these cells produce abnormally high levels of so-called redox active iron molecules. These molecules react with vitamin C and form hydrogen peroxide and hydrogen peroxide-derived free radicals. Scientists think that these free radicals drive cancer cell death by damaging the cells’ DNA. The free radicals are also thought to weaken the cancer cells and make them more vulnerable to radiation therapy and chemotherapy.