Vitamin C causes cancer: retro health scare

October 31, 2008 at 8:47 pm (Bad Science, Media, Supplements) (, , , , , , , , )

In 1998, Ian Podmore and others had a paper published in Nature. This quote is from the paper:

Vitamin C is marketed as a dietary supplement, partly because of its ‘antioxidant’ properties. However, we report here that vitamin C administered as a dietary supplement to healthy humans exhibits a pro-oxidant, as well as an antioxidant, effect in vivo.

Here’s an idea of what the press ran with

TOO MUCH VITAMIN C CAN GIVE YOU THE BIG C; SCIENTISTS THINK IT HARMS DNA; TOO MUCH VITAMIN C CAN TRIGGER CANCER WARN SCIENTISTS [headline and sub-headlines from the Daily Mirror report; April 9th 1998]; TOO much vitamin C could trigger cancer and other diseases, scientists warned yesterday [from the body of the Mirror story]; LARGE doses of vitamin C may not be such a healthy option, research at Leicester University has suggested. Far from preventing diseases such as cancer and heart disease, vitamin C in large amounts might help trigger them [The Times; April 9th 1998]

Here’s some extracts from the published responses

“Because the reported changes in levels of 8-oxoguanine and 8-oxoadenine occurred in lymphocytes, the relevant vitamin C concentrations are not those in plasma but those in lymphocytes; however, these data were not presented”; “…because 500 mg is a saturating dose of vitamin C, the initial plasma vitamin C concentration was roughly 50 mM (refs 5,6). However, at this concentration lymphocytes are already saturated…”; “The concentrations of 8-oxoguanine reported by Podmore et al are 25–120 times more than those reported by others” [Mark Levine and others]

“Artefactual oxidation ex vivo in their study cannot be excluded and hence their results are difficult to interpret”; “the study design is without randomization or true placebo control”; “Third, Podmore et al. did not mention whether any of their subjects smoked. Fourth, the authors did not reference relevant previous studies.” [Poulsen and others]

Here’s a few bits from the authors’ reply to the above mentioned responses

“The suggestion made above by Poulsen et al. and Levine et al. that artefactual oxidation has occurred during lymphocyte isolation and DNA extraction is based entirely on the measurement of a single marker, 8-oxoguanine. […] we have measured 8-oxoguanine in DNA samples from healthy volunteers by two additional assays […] All three assays show the same decrease in 8-oxoguanine on vitamin C supplementation.”

“We disagree with Poulsen et al. about the need for randomization or a double-blind study, as we were not reporting a clinical trial requiring a subjective interpretation of efficacy.”

“We do not consider the references cited by Poulsen et al. to be relevant to our study on human volunteers (all of whom were non-smokers, as smoking is known to reduce levels of plasma ascorbate).”

“Levine et al. argue that lymphocytes saturate when plasma ascorbate levels reach 50 mM. We do not find their argument compelling as it seems to be based on a depletion–repletion study of seven healthy volunteers”

“we observe highly significant positive and negative correlations between plasma ascorbate concentration and levels of 8-oxoadenine and 8-oxoguanine, respectively, which we believe suggests that vitamin C is influencing levels of both markers in a divergent manner (Cooke, M. S. et al., manuscript in preparation). This differential effect, which cannot be explained as methodological artefact”

This next bit is interesting in light of the media articles: “In conclusion, our results show a definite increase in 8-oxoadenine after supplementation with vitamin C. This lesion is at least ten times less mutagenic than 8-oxoguanine, and hence our study shows an overall profound protective effect of this vitamin.” [my italics]. So, not quite the “Vit C gives you the Big C!” story that appeared in the newspapers then. What a surprise.

Sadly, and I genuinely mean this, I have been unable to find (so far) any record of a response from the food supplements industry – nothing from HSIS, HFMA or the CRN. I’m sure this is due to my piss-poor research skillz rather than any lack of response but the entire comedy value of this post relied upon there being something from a trade body giving us half-truths or red herrings that have no bearing on the study findings or soliciting opinion from such experts on health as Cliff Richard. Who, of course, you will all remember had his say on the Cochrane review of antioxidant supplements. The responses to the article and the replies from the author are great. Levine, Poulsen and their respective colleagues bring up points that are relevant to the study and the authors answer these points. They discuss the methodology, results and interpretation of the study and they look at what factors have and have not been taken into consideration. I actually remember reading a response to the Nature paper from an industry spokesman and am incredibly annoyed that I can’t find it. I’m almost certain that the spokesman made no comment relating to the techincal apsects of the study, no criticism of the methodology… basically said nothing at all that was relevant. The responses to the Cochrane review are even more egregious examples of the inability of the food supplements-nutritionist industrial complex to engage with the evidence and so I have linked to them to shine a bit of light on the willingness of the vast, corporate incarnate, $50bn food supplement industry. No member of which, incidentally, appears to have spoken out yet about Matthias Rath. Never gonna happen.

I like to think I’ve managed to make the points that the newspapers don’t accurately report scientific papers and that nutritionists and the $50bn food supplements industry don’t engage with evidence in the way that academics do. Next up: Pope is Catholic, bears shit in woods [Except during hibernation, when they use a butt plug made of hair and faeces to cork their cornholes. Apparently.] and quite possibly a stunning revelation that Russell Brand can be a bit rude sometimes. That or something on the disgraceful way that the media represents mental health issues.


The Podmore paper: if you’re willing to pay, that is… ; Link to PDF of responses: podmore-et-al-vitamin-c-as-pro-oxidant ;


  1. Healthy life » Apples Reduce Colon Cancer Risk said,

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  2. jdc325 said,

    I have an update: The Daily Mail have been good enough to claim that we are now overdosing on Vitamin C.

    “The current recommended daily allowance of Vitamin C is only 40mg.” Wrong. The EU RDA is 60mg. The DM might wish we weren’t in Europe, but I’m afraid we are and I’m afraid the RDA is 60, not 40mg.

    “Despite Dr Pauling’s faith, the evidence in support of his theories on Vitamin C has been mixed.” True. Bit surprised the DM are pointing this out, but nevermind.

    “High doses won’t do any harm as Vitamin C is water-soluble and can’t be stored in the body.” Fair enough, but if high doses won’t do any harm then WTF was the point of that overdose headline?

    From the comments: “I smoke and take a 1000mg per day of Vit C, slow release. I don’t get colds, and I look younger than my age.
    Have been taking it for years. It is essential for smokers.” It is a vitamin – I think you’ll find it is essential for non-smokers too. I too am free from colds and look younger than my years. I don’t take Vitamin C tablets. What is keeping me so fresh-faced and healthy Carrie from London? I’d love to hear your opinion…

    Another glorious comment: “Giving cancer patients intravenous injections of vitamin C is a good way to cure them. Do not tell the Pharmaceutical drug companies about this as they will want to make the sale of vitamin C illegal. On average every cancer patient makes £25,000 of profit for the drug companies (from selling toxic chemotherapy drugs). This adds up to total profits world wide of 400 billion dollars. This is why natural treatments, like vitamin C, are not promoted by the medical establishment as it would mean the loss of all those billion dollar profits.” Brilliant comment there from Michael Haymar of Oxford. Michael obviously does not realise that Big Pharma owns half the supplement industry anyway – the more vitamin pills we buy, the bigger the profit for Big Pharma.

    “Whole food supplements are the only way to go – isolated pharmaceutical grade micro nutrients are not recognized or easily assimilated by the body” D’ya reckon Andy from London knows where we can get these whole food supplements? Maybe, just maybe, he sells them. That or he gets his info from people who do…

    “The Cochrane people are at it again!
    There is a big difference between natural vitamin c and synthetic versions; there are supplements available such as Acerola Cherry that provide vitamin c as it is found in nature; I would hazard a guess that they didnt include supplements of these kinds in the study!”
    Excellent work, Rachel from Launceston. Linus Pauling, like pretty much every other scientist with an interest in vitamins, used to claim that natural and synthetic vitamins are to all intents and purposes the same. Rachel knows better. And “the Cochrane people are at it again” comment? Clearly, Cliff Richard has got to Rachel… Although she hasn’t actually read the Cochrane review, she can just ‘hazard a guess’ at what they did and how. See? It’s easy when you know how.

    “Linus Pauling was the guru of Vitamin C. He took very high doses every day, up to 12 g I think. He was often criticised for it. But he died at 93. So it seems to help to live longer. I take around 1 g a day.” Oh, it must be true then. Because academics who don’t wolf down Vit C are famous for dying young aren’t they?

    “I whole heartedly agree that fresh foods are important. So too is keeping warm – wearing a hat in the cold weather – 30% of our body heat goes through the top of our head. If you left your front door open when the central heating was on you would think twice. Yours body is your central heating.”
    Meri Jenkins knows nothing about Vit C, but she does like to get her name in the Daily Mail.

    “Thats about a pound each per year!” Andy knows the approximate population of GB and can spot a coincidence when he sees one. Handily, he’s let everyone else know about it too. [Well, 60m, 75m – what’s 15million between friends?]

    “Most mass produced food is devoid of nutrition due to top soil depletion and processing
    Eating more it’s the the body’s way of trying to tell you it’s deficient in certain micro nutrients” David of London has evidence to back up his assertion about mass-produced food. No, I’m sure he does. Really.

  3. jdc325 said,

    Off-topic, but more fun Daily Mail reader comments under this story about the below-label claim results of some assays of food supplements: here.

    After a couple of people have pointed out that synthetic and natural vitamin C are identical, we get this insightful comment from Jacqui in Malaga (it looks very much like the kind of thing Gus the Fuss would post on JABS) –
    “Are you crazy – “synthetic chemicals are exactly the same as natural ones” – yes, right !!!! Next you’ll tell me that synthetic hormones are exactly the same as natural ones – PLEASE – dont be ridiculous ! Do some research !
    There are companies that strive to produce good quality supplements – but Big Pharma makes their lives miserable – look it up – google natural health and see.
    Good Luck and lets hope some of you people actually use the supplements and stop making negative comments without knowing.”
    Actually, that last bit also looks like the kind of thing the trolls who occasionally blight the Holford Watch blog might write.

  4. Journey through a Burning Mind » Stuff from the Science Blogosphere said,

    […] persists in the New Age and CAM circles though… If anything, Vitamin C has been recently shown to have pro-oxidant effects and increase the risk of developing cancer in in-vivo studies (as opposed to in-vitro studies that […]

  5. Media Reporting of Research: Consistently Poor « jdc325’s Weblog said,

    […] supplement, but high beam has a copy of the Mirror’s fail and I wrote about them here in October last […]

  6. vitamin+health said,

    Very interesting information about vitamin+health

  7. Roger Langford said,

    Here is another use for vitamin C, in this case as a treatment for a person who is Comatose. Here is a quote from the article I read.

    “What the article had actually stated was that 50,000 IU indictable vitamin C was given to a boy in India who had been comatose for over a month following a head injury. The boy awoke on the third day of injections.”

    ADMIN NOTE: I have removed the link to what seems to be a commercial AltMed website.

  8. jorg said,

    God – Do not give in to the devil, for eat the light of the bible, and you shall live many years.

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