Vitamin C in Cancer Therapy – Another False Dawn?

When suffering from a cold, you probably reach for the orange juice and a dose of vitamin C. The enduring popularity of vitamin C as a cure-all is in no small part down to respected chemist and two-time Nobel Laureate Linus Pauling, who advocated large doses against many diseases –so-called megavitamin therapy – late in his life. Despite the complete lack of evidence of any beneficial effect, the connection endures to this day. Pauling also promoted vitamin C as a cure for cancer, although his study of terminally ill patients was found to be badly flawed and actually suggested negative effects of vitamin C as a treatment. Yet alternative practitioners still promote this “all-natural” medicine, and a recent study has been widely publicised with headlines such as “Vitamin C can help ‘keep cancer at bay’”. The media is full of conflicting reports around vitamin C – a cursory search on the Daily Mail website throws up all manner of positive and negative contradictory coverage – so was Pauling right all along?

The research

The study, published in Science Translational Medicine, found high doses of Vitamin C in damaged cancer cells grown in cultures.  Further studies looked at vitamin C as a co-drug, administered intravenously alongside established anticancer treatments paclitaxel and carboplatin, both in mouse models of ovarian cancer and in human patients suffering from ovarian cancer. In the mouse model studies, a synergistic effect was observed, which suggests that the combination of vitamin C and the anticancer drug together worked more effectively in killing the ovarian tumour cells than either did individually.

The human trials, conducted over five years on only 22 participants, suggested a potential slight benefit in a synergistic treatment, but this was not statistically significant. The trial participants did, however, report a perceived decrease in the notorious side-effects of chemotherapy when vitamin C was administered. It should be noted that the patients were aware of the use of vitamin C, so the study was not “blind” and placebo effects may come into play. Additionally, the sample size was too small to make any significant conclusions, and the researchers called for larger clinical trials.

The Coverage

Unsurprisingly, the study received a lot of coverage, thanks in part to the researcher’s enthusiastic press release.  The BBC came under criticism from the NHS for its original headline “Vitamin C keeps cancer at bay”, which was later changed to “Vitamin C ‘gives chemotherapy a boost’”. The initial studies on ovarian cancer cell cultures, where cell death was observed, were discussed in the context of vitamin C being a cancer cure, although these types of encouraging results can be found with many different compounds which rarely make effective drugs. The remainder of the studies were reported quite well, despite the misleading headlines. Most reports included quotes from the researchers, and the BBC did redeem themselves somewhat by including an expert statement discussing the small sample size:

“It’s difficult to tell with such a small trial – just 22 patients – whether high-dose vitamin C injections had any effect on survival, but it’s interesting that it seemed to reduce the side-effects of chemotherapy.  Any potential treatment for cancer needs to be thoroughly evaluated in large clinical trials to make sure it’s safe and effective, so further studies are needed before we know for sure what benefits high dose vitamin C may have for patients.”

Disappointingly, most of the reports perpetuated the trope that pharmaceutical companies are unlikely to fund further studies as vitamin C cannot be patented. This is not a helpful statement, often used as “evidence” for the supposed efficacy of useless treatments hawked by unscrupulous snake-oil salespeople to desperate and unwitting cancer sufferers.  This reasoning was put forward by the researchers themselves – a cheeky public plea for funding perhaps?

Outlook

Whilst the sample size in the study is too small to draw conclusions, there is a suggestion of potential benefits of administering vitamin C during established chemotherapy programmes.  Even if further studies show it only helps to mitigate side-effects, this will be a useful and welcome step forward. So should patients reading these headlines start chomping down vitamin pills, just as Pauling did, in case the benefits turn out to be real? They’re vitamins, they must be harmless, right? Well, the study reported intravenous (direct injection) administration of vitamin C – it is well known that oral ingestion results in fairly rapid excretion of the compound. Also, despite being vital to our well-being, vitamin C is just like any other chemical, and massive doses could well be bad for us, although it’s estimated that you would need to eat around 2 lb, or 900 g of the stuff, to kill an average adult. A quote from an expert contribution in a balanced news article in Nature sums it up well:

“If it works, then great. And if it’s doing more harm than good, then that’s something we need to know, too.”

When thinking about medical treatments, especially for serious diseases like cancer, always consult medical experts, not headlines.

Y. Ma, J. Chapman, M. Levine, K. Polireddy, J. Drisko and Q. Chen (2014). “High-Dose Parenteral Ascorbate Enhanced Chemosensitivity of Ovarian Cancer and Reduced Toxicity of Chemotherapy”. Science Translational Medicine vol 6, 222ra18 doi: 10.1126/scitranslmed.3007154.