Study sheds light on how high-dose vitamin C kills cancer cells

IOWA CITY, Iowa, Jan. 9 (UPI) -- Researchers at the University of Iowa have determined that the delivery method plays a vital role in how high-dose vitamin C kills cancer cells.

Standard vitamin C therapies involve the patient taking the vitamin orally. However, researchers have found that when vitamin C is given intravenously, blood levels are 100 to 500 times higher than levels seen with oral ingestion.

This super-high concentration of vitamin C in the blood is vital to its ability to kill cancer cells, according to the new study.

Researchers have found that vitamin C breaks down easily, generating hydrogen peroxide, a reactive oxygen species that can damage tissue and DNA.

"In this paper we demonstrate that cancer cells are much less efficient in removing hydrogen peroxide than normal cells," Garry Buettner, professor of radiation oncology and a member of the Holden Comprehensive Cancer Center at the University of Iowa, said in a press release. "Thus, cancer cells are much more prone to damage and death from a high amount of hydrogen peroxide. This explains how the very, very high levels of vitamin C used in our clinical trials do not affect normal tissue, but can be damaging to tumor tissue."

The study showed that the enzyme catalase is the central pathway for removing hydrogen peroxide produced by decomposing vitamin C. Cells with lower amounts of catalase activity were more prone to damage and death when they were exposed to high amounts of vitamin C.

"Our results suggest that cancers with low levels of catalase are likely to be the most responsive to high-dose vitamin C therapy, whereas cancers with relatively high levels of catalase may be the least responsive," Buettner said.

The study was published in Redox Biology.