Taking care with what you take in

ResearchBlogging.org

Although I sometimes choose The Observer for my Sunday world-catch-up, I have long since decided to skip quickly past Barbara Ellen, who is bizarrely afforded a whole page for her rant-lite banalities and inanities among the news in the front half of the paper, away from the (not always) interesting comment columns towards the rear. (For example, see Carole Cadwalladr’s excoriation of Tesco; and, if you’re feeling a bit mid-winter bluesy, I recommend treating yourself to the last paragraph of Nick Cohen’s latest.) I mean, you can actually get paid for doing this? Golly!

But yesterday, I was stopped in my page-turning tracks, by noting that she had decided to exploit last week’s news of the supposed connection between processed meat and an increased risk of developing pancreatic cancer (Note how I phrase that: not that eating processed meat causes pancreatic cancer; but that eating it regularly is associated with an increased risk of going on to develop the disease) in order to extol her own vegetarian virtuousness (or virtuous vegetarianism – which works better?). I was piqued, not just by my suspicion that sound scientific findings were (again) being alarmingly misappropriated; but out of personal interest: my maternal grandfather succumbed to pancreatic cancer (in his early seventies); as did my all time favourite comedian, Bill Hicks (tragically at just 32 years of age).

Don’t misunderstand me: I’m not criticising vegetarians for their reasoned justifications for their dietary choices: you pays your money and takes them. (Although I might gripe on how come, when you get together to share a take-away selection, meat is off the choice list?; or – admittedly unoriginal joke, this – how come when you invite them around for dinner you have to cater to their limited palette, but never presume to ask them to knock you up a medium-rare steak when you’re invited round to theirs?)

What annoys me is her self-righteous endorsement of her lifestyle: specifically, her vegetarianism – and the not too disguised opinion that omnivores (which we have evolved to be), ie those who do eat meat, are… thick. (She qualifies this, unconvincingly, as ‘brave’.) In fact, because she can ‘read’, she may even have allowed herself a scan of the abstract of the paper in question: ‘Red and processed meat consumption and risk of pancreatic cancer: meta-analysis of prospective studies’, published last week in the British Journal of Cancer, and thus surely could not have missed its final cogent line: ‘Further prospective studies are needed to confirm these findings.’ She could perhaps have gone on to the Discussion, where the limitations of, and uncertainties arising from a study are to be found. (Not too big an ask – the paper’s pithiness entailing only five pages.)

Epidemiology is a powerful tool for pinpointing such associations, from which the public can be more reliably informed on relative risks. Yet, Larsson & Wolk, reporting their meta-analysis, rightly reiterate the problems of drawing on very few available relevant studies; and further, the inability to control for any failure of those studies to control for potential confounders, thus compromising an already limited investigation. Although high consumption of red meat and/or processed meat has been associated with increased risk of some gastrointestinal cancers, Larsson & Wolk found no statistically significant association between red meat consumption and pancreatic cancer, either overall or in women, although a positive association with risk was observed in men.

One potential confounder here could be a misclassification of red and processed meat consumption; this, along with other confounders, may skew an over- or underestimation of the association with pancreatic cancer risk. Nevertheless, a statistically significant positive association between risk of pancreatic cancer and consumption of processed meat is identified. However, statistical power is limited by a dearth of studies, and prevents association between processed meat consumption and pancreatic cancer in the United States and Europe.

BE acknowledges that this is about processed meat; but that doesn’t detract her from a diatribe at meat-eaters in general, and the opportunity to opine thus:

‘… it’s the meat eaters’ duty to take this information on board and take direct personal responsibility for the consequences, just as alcoholics and smokers do.’

I’ll leave you to ponder that line of reasoning, because, you know, I might be a tad biased on account of my dislike for her mal-enunciations in general.

But what I would perhaps find more interesting is just who and why? Which sausage and bacon eaters are more likely to succumb to this particular cancer? Does this affect a particular socio-economic bracket of society more frequently? Would that be because it can’t afford choice fillet cuts (on a regular basis)? And might there be an exacerbating combination with heavy smoking? Carcinogenic N-nitroso compounds are absorbed from cigarette smoke and (the digestion products of) nitrite-preserved processed meats. However, to conclude that pancreatic cancer risk is affected by any modifying relation between processed meat consumption and smoking is again hampered by insufficient studies (so whether this did for Bill Hicks, a ‘committed’ smoker, we can’t say). Hence the author’s important caveat:

‘Large prospective studies with better adjustment for potential confounders are warranted to establish potential associations of red and processed meat consumption with pancreatic cancer risk. Whether the association between processed meat consumption and pancreatic cancer is modified by smoking needs further study.’

Yes, prevention is (usually) better than (expensive) cure. But if _we_’ve known all this for so long, then so have the manufacturers and retailers and advertisers who produce and sell and encourage us to buy their processed wares. In fact, if marketing is the over-emphasis on the positive, and the obfuscation of the negative, then, well, we’re inclined to believe what we want to hear.

Personally, I can’t imagine an evening out with the barely-disguised disgust of BE. Don’t order steak in the restaurant, else she’ll deduce, and remonstrate you, on your stupidity, particularly if you have a drink too many and nip outside for a cigarette. And boringly pontificate on the superiority of eating plants, which produce far more compounds, with unknown biological effects, than we yet know of. Her attitude is manna to all those patronising diet and lifestyle marketeers who rub their hands together at this post-indulgence time of year.

Think I’m gonna have a quick re-read of that last Nick Cohen paragraph.

Larsson, S., & Wolk, A. (2012). Red and processed meat consumption and risk of pancreatic cancer: meta-analysis of prospective studies British Journal of Cancer DOI: 10.1038/bjc.2011.585

2 responses to “Taking care with what you take in

  1. You forgot (?) to mention another big limitation of meta-analysis: publication bias. The authors are right: you do need large prospective studies to confirm these findings. All we have now is an inkling. Might be a coincidence… On top of that, when the presumed association is weak, epidemiological studies have a hard time confirming these kind of associations… (if it is not impossible, all together)
    On to the vegetarianism. Well, I’m a vegetarian. And I really feel annoyed by her self-righteousness as well. And that of many other vegetarians… I too find it odd that if I don’t want to serve meat (which I don’t), that I then have the moral grounds to ask you to serve something vegetarian. That would be claiming that my philosophy has higher moral grounds than yours. I can’t see it another way. It did take me a while to integrate both values in my world view. I just eat what is put in front of me. I either skip the meat, or eat it, depending on the situation. I don’t eat meat, because I don’t want to harm other beings as much as reasonable achievable (plants included, yes). Forcing others to cook something just to suit my philosophy, doesn’t outweigh the harm done to the animal that has already been killed, in my view. I accepted your offer of hospitality, knowing that you are not a vegetarian. So I either don’t go to your dinner or accept whatever is served. In other words: not all vegetarians are self-righteous ;)
    And about this: ‘… it’s the meat eaters’ duty to take this information on board and take direct personal responsibility for the consequences, just as alcoholics and smokers do.’ You might be a tad biased, but it still remains a presumptuous line of reasoning…

  2. Thanks, Tine.
    I’d edited out a comment on publication bias; but the authors do recognise and test for this, and found no evidence of such.

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