Vitamin C shows promise as an anti-cancer agent

The idea that vitamin C might offer potential in the treatment of cancer has been around for some decades. Perhaps the person whose name is most linked with this concept is the late Linus Pauling. With his death, it seemed that interest in his ideas died a bit of a death too. However, some scientists have continued to be interested in the area. For example, The National Institute of Diabetes and Digestive and Kidney Diseases (part of the National Institutes of Health in the USA) has continued to research this topic. In fact, this organization published a paper this week that found that injecting vitamin C in the abdomens of mice led to a decrease in the size of tumours that had been induced in them [1].

This paper was accompanied by a commentary articles from two scientists from the Linus Pauling Institute in Oregon, USA [2]. The authors of the commentary (Balz Frie and Stephen Lawson) highlight the fact that the work from the National Institute of Diabetes and Digestive and Kidney Diseases shows that vitamin C at high dose has been shown to be toxic to cancer cells, but leaves normal cells alone. This quality is, obviously highly desirable if we’re seeking to combat cancer but at the same time wish to leave the rest of the body unscathed. Frie and Lawson discuss how high doses of vitamin C can increase production of hydrogen peroxide, which is thought to be the principle substance that accounts of vitamin C’s anti-cancer properties.

Frie and Lawon go on, however, to highlight some of the other evidence in the area. They refer to a study published in 1974 in which 50 patients with advanced cancer were treated with intravenous infusions of vitamin C (at a dose of 5–45 grams per day) and/or oral doses (at a dose of 5–20 grams per day) [3]. In 19 of these patients there was retardation, stabilization or regression of their tumour. They also cite another study, this time one in which the outcomes of 100 individuals treated with vitamin C (intravenous and oral vitamin C at a dose of about 10 grams per day) were compared with a control group (who did not receive vitamin C) [4]. Patients
treated with vitamin C survived approximately four times longer than controls,

A follow-up study reported that patients given vitamin C had an average survival time almost 1 year longer than controls (5). Overall, per cent of the vitamin C-treated group surived for more than a year, compared to only 0.4 per cent of non-treated controls.

Frei and Lawson also refer to two randomized, placebo-controlled, double-blind trials of vitamin C and advanced cancer sponsored by the National Cancer Institute in the USA. Neither of these trials showed a positive effect from vitamin C in terms of survial. However, these trials used oral vitamin C alone and, as Frei and Lawson point out, it is unlikely that sufficient levels of vitamin C would have been achieved for benefit to have been possible.

The authors go on to point to the fact that two recent studies have tested the safety of high doses of vitamin C in humans. Once certain conditions have been screened for, it seems humans have enormous tolerance for vitamin C. They end by saying that now the scientists who produced the recent work in mice are now poised to explore the potential value of high dose vitamin C for the treatment of cancer in humans. Let’s hope that its cheap price and non-patentable status does not hold back interest in this nutrient as an anti-cancer agent.

References:

1. Chen Q, et al. Pharmacologic doses of ascorbate act as a pro-oxidant and decrease growth of aggressive tumor xenografts in mice. PNAS USA 2008;105:11105–11109

2. Frei B, et al. Vitamin C and cancer revisited. PNAS 2008;105(32):11037-11038

3. Cameron E, et al. The orthomolecular treatment of cancer. II. Clinical trial of high-dose ascorbic acid supplements in advanced human cancer. Chem-Biol Interact 1974;9:285–315.

4. Cameron E, et al. Supplemental ascorbate in the supportive treatment of cancer: Prolongation of survival times in terminal human cancer. Proc Natl Acad Sci USA 1976;73:3685–3689.

5. Cameron E, et al. Supplemental ascorbate in the supportive treatment of cancer: Reevaluation of prolongation of survival times in terminal huma n cancer. 1978;Proc Natl Acad Sci USA 75:4538 – 4542.

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