Injected vitamin C cuts cancer growth
Injections of high doses of vitamin C have almost halved the rate of tumour growth in mice, leading US researchers to believe it may be useful in the treatment of cancer in humans.
Researchers at the National Institutes of Health noted the phenomenon in brain, ovarian and pancreatic cancers, according to findings published today in the Proceedings of the National Academy of Sciences.
The idea that vitamin C, also known as ascorbic acid, could be used to treat cancer was advanced in the 1970s by American scientist Linus Pauling, who was awarded the Nobel Prize in chemistry in 1954.
The notion was controversial and studies failed to show a benefit. But those studies involved vitamin C given orally.
In the latest study researchers injected the vitamin C to enable greater concentrations of it to get into the system.
Injections were necessary because the body regulates vitamin C when ingested, so that higher doses cannot be attained.
"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," says Dr Mark Levine, the study's lead author and chief of the Molecular and Clinical Nutrition Section of the National Institute of Diabetes and Digestive and Kidney Diseases.
Scientists "injected ascorbate into the veins or abdominal cavities of rodents with aggressive brain, ovarian, and pancreatic tumours", the report says, delivering "up to four grams per kilogram of body weight daily".
By injecting mice with 43 cancer and five normal cell lines, "the researchers discovered that high concentrations of ascorbate had anticancer effects in 75% of cancer cell lines tested, while sparing normal cells".
"The key finding here is that this is ascorbic acid used as a drug and it appears to have some promise in treating some cancers," says Levine.
The researchers believe the elevated amounts of ascorbic acid generate hydrogen peroxide in the body that acts against the cancer cells.
'Leads to cancer cell deaths'
"That hydrogen peroxide leads to death of some cancer cells and does not seem to kill normal cells. Why that is, we don't know," Levine says.
Scientists involved with the study also point to evidence that "these high ascorbate concentrations could be achieved in people".
"In immune-deficient mice with rapidly spreading ovarian, pancreatic, and glioblastoma (brain) tumours ... the ascorbate injections reduced tumour growth and weight by 41% to 53%."
The researchers say the findings "provide the first firm basis for advancing pharmacologic ascorbate in cancer treatment in humans".
A reasonable next step would be to begin studies testing whether this works in people, Levine says.
"I think we're pretty close to being ready to do that," he adds.