Oranges aren’t enough

The interest in these studies seems to have partly come from the fact that vitamin C is considered ‘natural’ and found in lots of foods, from oranges to broccoli. It can also be consumed in high doses via supplements.

But a closer look at the research reveals that neither study used food or supplements as the source of vitamin C being tested to treat cancer. Instead, the researchers were injecting patients or mice with very high doses of vitamin C – much higher than you could get from food or supplements directly.

A mixed basket of results

In the most recent studies, results tentatively support the idea that high-dose vitamin C has potential as a cancer treatment.

The first study tested vitamin C as a treatment in mice with blood cancer, and found that injecting high doses of vitamin C slowed down the progression of the disease.

But as mice are very different to people, this has some way to go before we can say that vitamin C will help treat cancer patients.

The other study was testing the safety of high dose vitamin C injections in people with either non-small cell lung cancer or glioblastoma, an aggressive type of brain tumour, not if it’s an effective treatment. These tests would follow only if the injections are safe.

This early work showed that doctors could safely inject high doses of vitamin C into patients, but as they only tested it in a small number of people it’s hard to say if this would be the same for everyone.

This is far from the clear-cut answer some headlines would have you believe. Especially considering neither study looked at long term effects of a vitamin C jab in people, and to date there’s no evidence that vitamin C improves cancer survival.

Some studies have suggested that vitamin C may help alleviate some of the side effects of cancer treatment. But other clinical trials had to be stopped early due to severe side effects caused by vitamin C itself.

Some studies have even suggested vitamin C could interfere with some anti-cancer drugs, with one study showing it may even protect breast cancer cells from the drug tamoxifen.

Together, the research paints a confused picture, and perhaps it’s unsurprising that headlines around vitamin C can often be misleading. But as there’s no evidence a vitamin C jab cures cancer, and may even cause harm, this is unlikely to become a treatment any time soon.

High dose injections of vitamin C aren’t routinely available for cancer patients. And research testing these jabs is in its earliest stages. But when headlines draw connections between this research and what we eat, cancer patients may be left asking: ‘Is it worthwhile taking vitamin supplements?’ Martin Ledwick, Cancer Research UK’s head information nurse, says cancer patients shouldn’t take them without first talking to their doctor.

“The key thing is we just don’t know if it is safe to take them alongside conventional treatment that is known to work. It is possible that in some situations they may interfere with the way chemotherapy works, which might make treatment less effective.”

This doesn’t mean to say vitamin C won’t be of benefit to some patients one day. But there’s certainly no evidence yet from any clinical trial that vitamin C improves cancer survival.

Either way, given the mixed results so far, media reports around vitamin C could be doing more harm than good. And as for vitamin C as the next big wonder drug? The signs aren’t pointing that way just yet.