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Old 08-04-2008, 09:05 PM
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Default Vitamin C and Cancer (Positive and Negative News)

First, the positive:

ScienceDaily (Aug. 4, 2008) — High-dose injections of vitamin C, also known as ascorbate or ascorbic acid, reduced tumor weight and growth rate by about 50 percent in mouse models of brain, ovarian, and pancreatic cancers, researchers from the National Institutes of Health (NIH) report in the August 5, 2008, issue of the Proceedings of the National Academy of Sciences.

The researchers traced ascorbate's anti-cancer effect to the formation of hydrogen peroxide in the extracellular fluid surrounding the tumors. Normal cells were unaffected.

Natural physiologic controls precisely regulate the amount of ascorbate 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, 2 oranges and a serving of broccoli--your body prevents blood levels of ascorbate from exceeding a narrow range," says 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 (NIDDK), part of the NIH.

To bypass these normal controls, NIH scientists injected ascorbate into the veins or abdominal cavities of rodents with aggressive brain, ovarian, and pancreatic tumors. By doing so, they were able to deliver 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," 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 prooxidant instead of antioxidant activity.

Prooxidants would generate free radicals and the formation of hydrogen peroxide, which, the scientists hypothesized, might kill tumor cells. In their laboratory experiments on 43 cancer and 5 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. In their paper, the researchers also showed that these high ascorbate concentrations could be achieved in people.

The team then tested ascorbate injections in immune-deficient mice with rapidly spreading ovarian, pancreatic, and glioblastoma (brain) tumors. The ascorbate 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 had no signs of disseminated cancer.

"These pre-clinical data provide the first firm basis for advancing pharmacologic ascorbate in cancer treatment in humans," the researchers conclude.

Now, the negative report:

BACKGROUND: Ascorbic acid is a widely used and controversial alternative cancer treatment. In millimolar concentrations, it is selectively cytotoxic to many cancer cell lines and has in vivo anticancer activity when administered alone or together with other agents. We carried out a dose-finding phase I and pharmacokinetic study of i.v. ascorbic acid in patients with advanced malignancies.

Patients with advanced cancer or hematologic malignancy were assigned to sequential cohorts infused with 0.4, 0.6, 0.9 and 1.5 g ascorbic acid/kg body weight three times weekly.

RESULTS: Adverse events and toxicity were minimal at all dose levels. No patient had an objective anticancer response.

High-dose i.v. ascorbic acid was well tolerated but failed to demonstrate anticancer activity when administered to patients with previously treated advanced malignancies. The promise of this approach may lie in combination with cytotoxic or other redox-active molecules.

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Old 08-05-2008, 06:47 AM
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The following points strike me regarding the two conflicting reports:

The dosage in the successful study was 4g/kg body weight as against much lower dosages in the McGill study, which had a maximum of 1.5g/kg.

The patients in the McGill study had advanced malignancies which meant they were probably treating larger tumours with a lower dosage of Vitamin C. The mice study tumours were described as 'aggressive' but its fair to assume that the researchers wanted to judge the effects of Vitamin C before the mice died from cancer so it is fair to assume they were not as advanced as tumours in the McGill study .

The patients with the advanced tumours would no doubt have had by this time large amounts of chemotherapy. In the succesful study the mice had only Vitamin C and no chemotherapy.

I am not sure how much chemotherapy would have interfered with the Vitamin C action,but it would probably have knocked out the immune system altogether, as against the mice described as merely 'immune compromised'. How much this immune system difference made on the study results difference would be would be hard to estimate.

Last edited by liverock; 08-05-2008 at 07:06 AM.
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Old 08-05-2008, 09:54 AM
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I think that you make some valid points. The studies clearly weren't comparable.

From my perspective, even the latter study isn't a clear-cut failure. It simply provides additional information that can be used to determine when and how IV vitamin C may be used successfully and when it's unlikely to.
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