Large doses of vitamin C shrink tumors by about 50 percent in mice with brain, ovarian and pancreatic cancers, according to a new report in the Proceedings of the National Academy of Sciences.
Although vitamin C — also known as ascorbate — has many health benefits, and deficiencies in vitamin C levels can lead to scurvy or even death, the body precisely regulates the amount it absorbs when 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, M.D., 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.
The researchers were able to bypass these normal controls by injecting ascorbate directly into the veins or abdominal cavities of rodents with aggressive brain, ovarian and pancreatic tumors, delivering high doses of ascorbate up to 4 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," Levine said.
And they did. In their experiments on 43 cancer and five normal cell lines, the researchers discovered that high concentrations of ascorbate had cancer-fighting effects in 75 percent of cancer cell lines tested, while normal cells were unaffected. In their paper, the researchers also demonstrated that these high ascorbate concentrations could be achieved in humans.
The team also tested ascorbate injections in immune-deficient mice with rapidly spreading ovarian, pancreatic and glioblastoma (brain) tumors. The injections reduced tumor growth and weight by 41 to 53 percent. In 30 percent of glioblastoma controls, the cancer had spread to other organs, but the ascorbate-treated animals showed no signs of the cancer spreading. "These pre-clinical data provide the first firm basis for advancing pharmacologic ascorbate in cancer treatment in humans," the researchers wrote.
Vitamin C has been heralded as a potential cancer therapy for 30 years, but studies in 1979 and 1985 reported no benefit for cancer patients taking high oral doses in two double-blind, placebo-controlled clinical trials. But clinical studies conducted in the past 12 years have revealed the body’s tight control of oral ascorbate levels in plasma and tissue, leading to the theory that only injected ascorbate might deliver the concentrations needed to see an anti-tumor effect.
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