Washington, Aug 5 (IANS) High-dose injections of vitamin C reduced tumour weight and growth rate by nearly 50 percent in mouse models of brain, ovarian, and pancreatic cancers, according to a new study. Researchers traced the vitamin’s anti-cancer effect to the formation of hydrogen peroxide in the extra-cellular fluid surrounding the tumours. Normal cells were unaffected.

Natural physiologic controls precisely regulate the amount of ascorbate or vitamin C absorbed by the body when it is taken orally.

“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,” said Mark Levine, co-author of the study and chief of the Molecular and Clinical Nutrition Section of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

To bypass these normal controls, NIH scientists injected ascorbate into the veins or abdominal cavities of rodents with aggressive brain, ovarian, and pancreatic tumours.

They were able to deliver high doses of ascorbate, up to four grams per kilogram of body weight daily. “At these high injected doses, we hoped to see drug-like activity that might be useful in cancer treatment,” said Levine.

Vitamin C plays a critical role in health, and a prolonged deficiency leads to scurvy and eventually to death. Some proteins known as enzymes, which have vital biochemical functions, require the vitamin to work properly.

Vitamin C may also act as an antioxidant, protecting cells from the damaging effects of free radicals. The NIH researchers, however, tested the idea that ascorbate, when injected at high doses, may have pro-oxidant instead of antioxidant activity.

Pro-oxidants would generate free radicals and the formation of hydrogen peroxide, which, the scientists hypothesized, might kill tumour cells.

In their lab experiments on 43 cancer and five normal cell lines, the researchers discovered that high concentrations of ascorbate had anticancer effects in 75 percent of cancer cell lines tested, while sparing normal cells.

These findings were published in Tuesday’s issue of the Proceedings of the National Academy of Sciences.