Why high doses of vitamin C kill cancer cells

Most vitamin C treatments involve oral administration of the drug. However, UI scientists have shown that intravenous administration of vitamin C - bypassing normal intestinal metabolism - creates blood levels that are 100 to 500 times higher than those provided by ingestion of vitamins. It is this ultra-high concentration in the blood that is critical to the ability of vitamin C to attack cancer cells.

Previous work by Iowa State University biologists has shown that at very high levels (in the millimolar range), vitamin C selectively destroys cancer cells without affecting normal cells in vitro or in mice. Doctors at the university hospital are currently conducting clinical trials of treatments for pancreatic and lung cancer that combine high doses of intravenous vitamin C with standard chemotherapy or radiation. The first trial results showed that this treatment is safe, well tolerated and improves the condition of patients. Currently, the main task of trials is to determine how much the survival rate of patients with such treatment improves.

In a new study recently published in the December issue of the journal Redox Biology, scientists have uncovered a mechanism by which high doses of vitamin C (also known as ascorbic acid) kill cancer cells.

It turned out that in the body, vitamin C is easily destroyed, creating hydrogen peroxide, which can damage tissues and DNA. But tumor cells are much less able to resist the effects of hydrogen peroxide than normal cells.

Normal cells have the ability to keep hydrogen peroxide levels low so that it cannot cause damage. The study shows that the enzyme catalase is central to reducing the level of hydrogen peroxide produced during the breakdown of vitamin C, and cells with less catalase activity were more susceptible to damage and death.

This important information can help determine which types of cancer and which treatments can be improved with high doses of ascorbic acid.

Thus, cancers with low catalase levels will be more responsive to high doses of vitamin C, while cancers with relatively high catalase levels may be the least responsive. The aim of new research is to develop methods for measuring the level of catalase in tumors.