High Levels of Vitamin C Inhibit Tumor Growth

Cancer researchers have found that treatment with high-dose injections of vitamin C (ascorbate or ascorbic acid) reduced tumor weight and growth rate by about 50% in mouse models of brain, ovarian, and pancreatic cancers.

In humans, vitamin C is a highly effective antioxidant, acting to lessen oxidative stress, a substrate for ascorbate peroxidase, and an enzyme cofactor for the biosynthesis of many important biochemicals. Vitamin C acts as an electron donor for eight different enzymes. Attempts to study the therapeutic benefits of high doses of vitamin C have not given clear-cut results. This is due to the body's tight control of blood levels of vitamin C following oral administration.

In the current study, investigators at the [U.S.] National Institutes of Health (Bethesda, MD, USA) treated mice with various types of tumors with injections of vitamin C. This route avoided oral control and allowed blood levels of the vitamin to reach up to four grams per kilogram of body weight.

Results published in the August 4, 2008, online edition of the Proceedings of the [U.S.] National Academy of Sciences (PNAS) revealed that ascorbate injections reduced tumor growth and weight by 41 to 53% in immune-deficient mice with rapidly spreading ovarian, pancreatic, and glioblastoma tumors. These high levels of vitamin C, which could be readily achieved in humans given ascorbate intravenously, did not damage normal tissues.

Treatment of cells growing in tissue culture further demonstrated the anticancer properties of vitamin C. Exposure of 43 cancer and five normal cell lines to high concentrations of ascorbate produced anticancer effects in 75% of the cancer cell lines while the normal cell lines were not effected. The anticancer activity was presumed to be due to vitamin C acting as a prooxidant that caused the hydrogen-peroxide-dependent cytotoxicity of the rapidly growing cancer cells while not harming normal cells.

"When you eat foods containing more than 200 milligrams of vitamin C a day--for example, two oranges and a serving of broccoli--your body prevents blood levels of ascorbate from exceeding a narrow range,” explained senior author Dr. Mark Levine, chief of the molecular and clinical nutrition section of the National Institutes of Health. "Clinical and pharmacokinetic studies conducted in the past 12 years showed that oral ascorbate levels in plasma and tissue are tightly controlled. In the case series, ascorbate was given orally and intravenously, but in the trials, ascorbate was just given orally. It was not realized at the time that only injected ascorbate might deliver the concentrations needed to see an anti-tumor effect.”

New clinical trials of injected ascorbate as a cancer treatment in humans are in the planning stages.

Related Links:
National Institutes of Health