Low levels of catalase enzyme make cancer cells vulnerable to high-dose vitamin C University of Iowa, January 9, 2022 Vitamin C has a patchy history as a cancer therapy, but researchers at the University of Iowa believe that is because it has often been used in a way that guarantees failure. Most vitamin C therapies involve taking the substance orally. However, the UI scientists have shown that giving vitamin C intravenously–and bypassing normal gut metabolism and excretion pathways–creates blood levels that are 100 – 500 times higher than levels seen with oral ingestion. It is this super-high concentration in the blood that is crucial to vitamin C’s ability to attack cancer cells. Earlier work by UI redox biology expert Garry Buettner found that at these extremely high levels (in the millimolar range), vitamin C selectively kills cancer cells but not normal cells in the test tube and in mice. Physicians at UI Hospitals and Clinics are now testing the approach in clinical trials for pancreatic cancer and lung cancer that combine high-dose, intravenous vitamin C with standard chemotherapy or radiation. Earlier phase 1 trials indicated this treatment is safe and well-tolerated and hinted that the therapy improves patient outcomes. The current, larger trials aim to determine if the treatment improves survival. In a new study, published recently in the December issue of the journal Redox Biology, Buettner and his colleagues have homed in on the biological details of how high-dose vitamin C (also known as ascorbate) kills cancer cells.