Vitamin C has been studied extensively as a potential treatment for cancer. Lab testing shows that in high concentrations, it can have toxic effects on cancer cells while remaining harmless to healthy cells. Definitive human research (i.e. a large randomized trial) has not been done because there is little financial motivation for anyone to conduct such a trial. There is research which shows that taking vitamin C by mouth does not produce the high blood levels needed to induce the death of cancer cells (i.v. dosing is required). In addition, there are some published case reports showing clear cancer remission from vitamin C.