Wednesday 18 January 2012

Meat causes cancer. It’s been said so many times that you’d have to be an idiot not to believe it, right?


 The latest confirmation of this apparent common sense was a report published last week in the British Journal of Cancer Research. The authors, from the Karolinska Institute in Sweden, brought together 11 studies - published between 1993 and 2011 - that assessed the risk of pancreatic cancer from eating red meat and ‘processed’ meat. From this meta-analysis, the authors found that red meat increased the risk of pancreatic cancer for men, but not for women, and that the risk of pancreatic cancer rose by 19 per cent for every 50 grams of processed meat consumed. The simple claim that ‘processed meat causes cancer’ was widely reported after the study was published. However, it would be wrong to assume that such claims about risk are all they are cracked up to be. First, there is the question of whether the association claimed is real. Epidemiological studies like the ones brought together by the Swedish researchers will typically find out what participants ate for a day or a week using a questionnaire or a food diary. Then, the participants will be checked some years later to see who has succumbed to the disease in question. Did people correctly remember what they ate? And did they accurately recall how much they consumed? It would be unusual for anyone to have weighed the food, so the amounts could be inaccurate, too. What else did the participants eat? Did they change their eating habits in subsequent months or years? And what the hell is ‘processed’ meat, anyway? Unless you slaughter your own animals, your meat will have been processed to one degree or another. At what point does meat that has been processed become ‘processed meat’? There are so many ways in which the crude tools of epidemiology could screw up the result of studies like this that it is normal for fairly small risks - like the 19 per cent increase in this case - to be treated with a massive pinch of salt. The authors of this study even note: ‘All studies controlled for age and smoking, but only a few studies adjusted for other potential confounders such as body mass index and history of diabetes.’ Secondly, even if the association is not simply a product of the way in which the study was designed, we still don’t know if correlation equals causation. The best we could say is that the kind of people who like to eat processed meat are a bit more likely to get pancreatic cancer than the kind of people who don’t eat meat at all. You don’t need to be a rocket scientist - or a professor of epidemiology - to realise that vegetarians live, on average, quite different lifestyles from people who tuck into burgers and kebabs. Thirdly, even if this study has somehow managed to be supremely accurate and found a real risk, we have to ask if such an increase is of any practical significance in the real world. Cancer Research UK gives the following statistics on pancreatic cancer: for the UK, the age-standardised rate is 9.3 cases per 100,000 people per year - roughly one person in every 10,000. So even those people who really like processed meat and eat 150g per day would have about a 50 per cent increased risk - or about 15 cases per 100,000. To express that in terms of odds, instead of it being 10,000-to-one that these kebab-and-burger lovers develop pancreatic cancer in any particular year, it would be 6,667-to-one. So, to sum up: the association between processed meat and pancreatic cancer is so weak it might well be a mirage; the increased risk might not be caused by the processed meat itself; and even if it is, the risk is so low that it’s really not worth bothering about. Yet still we are advised to consider cutting down on our red meat and processed meat consumption. Life is, frankly, too short to miss out on such tasty foods on the slim chance that we might lose a few years of life in old age. Still, that won’t stop people being harangued anyway. A particularly unsavoury example of this appeared in Sunday’s Observer. Illiberal Liberal of the Week contender, columnist Barbara Ellen, declared that the bovine attitude of recent governments towards smokers and drinkers should apply to meat-eaters, too. Now that a precedent has been set - that people should be harangued for doing things that are legal but disapproved of by Those Who Know Better - Ellen is simply following through this logic by attacking those who like sausages, bacon and pies. Here’s the argument: people (like smokers and drinkers) who deliberately do things that are bad for them, despite being told time and again that they should not, are now lectured, restricted and even have their basic rights taken away; eating meat - and particularly ‘processed’ meat - increases your risk of getting cancer and is bad for you; therefore, people who eat meat should now be lectured, restricted and even have their basic rights taken away. This is a shocking but perfectly logical argument, if you accept the petty-authoritarian mindset that flourished under New Labour and is still going strong under the Lib-Con coalition (and, indeed, around the world). Given the tone of Ellen’s piece, you might hope that she would end by saying: ‘Of course, telling people not to eat meat is stupid - every bit as stupid as telling them not to drink or smoke or telling them not to be fat. The government should just butt out.’ Sadly, there is no note of irony anywhere. She really does want to stick it to meat-eaters. So, of the supposed risks of eating meat, Ellen declares: ‘This information has popped up regularly for years in all forms of popular media. Indeed, in this era of info overload, if you’ve never come across the “burgers and kebabs are unhealthy” revelation, one would have to presume you’ve been lying in a coma. With this in mind, isn’t it time to ask, exactly how thick, how hard to educate, are meat-eaters and why aren’t they held accountable in the same way everyone else is?’ She continues: ‘Sympathy is in short supply these days. You can’t move for people being blamed for their own miserable situations: smokers who “burden” the NHS; alcoholics who don’t “deserve” liver transplants; obese people who “should” pay more for flights. Even those poor terrified women with the faulty breast implants are said to have “brought it on themselves”. By this logic, people who’ve been regularly informed of the dangers of meat, particularly the cheap processed variety, but who continue to wolf it down should be held just as accountable.’ Now that the precedent has been set for the government to lambast those who engage in unapproved habits, it’s open season on any habit that a campaigner or columnist disapproves of. Ban it! Tax it! Make them get a prescription for it! Deny them medical care! Ellen’s article is objectionable but it only follows the remorseless logic of so many others. There is another lesson from the meat-and-cancer story: at a time when all sorts of dubious claims are made based on junk science and dodgy statistics, only some panics get wide publicity; others just pop up and disappear again in a matter of hours. The difference is that some play to an existing political or media agenda and some do not. The idea that meat causes cancer appeals to health busybodies, politicians scrabbling around for a sense of purpose, vegetarians who can’t win a moral argument about animal rights, and environmentalists who have failed to convince us that increasing the ‘human footprint’ - by wanting to eat more meat, for example - is killing the planet. It’s not quite possessed of the same force as religious fervour - do the ‘right thing’ or live in agony for eternity - but the idea that if you do something naughty like enjoy bacon then you might die in agony before your time, is the best that many such claims-makers have got going for them right now. The only proper response to this junkscience-based illiberalism is to be extremely sceptical of any such claims and to defend everyone’s right to indulge in these petty vices.