Red meat is bad for you? Burger off!
Medical researchers now churn out scary-sounding studies about steak and bacon faster than McDonald's produces Big Macs.
It’s official, it seems: red meat – particularly processed red meat – will be the death of you. ‘Small quantities of processed meat such as bacon, sausages or salami can increase the likelihood of dying early by a fifth, researchers from Harvard School of Medicine found. Eating steak increases the risk of early death by 12 per cent’, declared the Daily Telegraph yesterday. BBC1 Breakfast’s resident GP, Dr Rosemary Leonard, told millions of viewers the link was ‘very, very clear’.
The study, published in Archives of Internal Medicine, followed two groups of people: 37,000 men enrolled in the Health Professionals Follow-up Study (1986-2008) and 83,644 women from the Nurses’ Health Study (1980-2008). The two groups filled in detailed questionnaires about their health and eating habits at the start of their respective studies and then were followed up every four years.
The topline results were that, after adjustment for major lifestyle and dietary risk factors, there was a 13 per cent increase in the risk of death for each portion of red meat eaten per day and a 20 per cent increase in mortality for each portion of processed meat consumed per day. This is not the first study to suggest that eating meat is bad for you. But that might simply mean that this study shares many of the same problems that all the other studies have had.
However, before we get to the problems, here’s some brighter news. At the end of the study, the members of the two groups studied had, on average, reached the grand old age of 75. How many had died along the way? Less than 20 per cent. Those who started the study were four times more likely than not to reach 75. So, whatever your eating habits when it comes to eating red meat or processed meat, the most important lesson is that most people live a long time these days. ‘Early death’ is very much a relative concept.
The authors claim that 9.3 per cent of deaths in men and 7.6 per cent of deaths in women could be avoided by eating little or no red meat. To put that into some back-of-an-envelope statistical perspective: multiplying that 9.3 per cent by the 20 per cent who actually died shows that about 1.8 per cent of red-meat eaters would die by the time they were 75 because of their meat-eating habit. Even if that claim were absolutely accurate (and even the authors call it an estimate), would you really give up your favourite foods for decades on the slim possibility of an extra year or two of old age?
Secondly, the biggest risk factor in this study wasn’t whether you ate lamb or beef instead of fish or lentils. The thing most likely to determine whether you live or die – apart from old age, of course – is whether you are male or female. One way to illustrate this is to add up the total number of years that people in each group lived and divide it by the number of people who died. The group of women who ate the most processed meat suffered one death for every 124 person-years lived. The group of men who ate the least processed meat suffered one death for every 89 person-years lived. Being a man is much more dangerous than eating bacon, it would seem.
But it is worth digging into the particular problems of this study. A perennial problem for any kind of dietary research is measuring accurately what people eat. Questionnaires require that people try to estimate what they eat and how much. In the case of this study, participants were asked about their consumption of up to 166 different items! Unsurprisingly, when the researchers tested the validity of the questionnaires against dietary records kept by a subset of the subjects, they found they were by no means accurate.
For the analysis, foods were grouped into categories. But a category of food like ‘fruit’ contains a whole range of different kinds of food: bananas are different to apples and pears, which are pretty different to berries. Take grapefruit: it’s now widely recognised to mess with the way you absorb medicines, so many people on long-term medication are advised to avoid it. If we are going to worry about the effect of different kinds of meat, shouldn’t studies also be concerned about the possible effect of different kinds of fruit and vegetables, too?
A serious problem with the present study is that while the researchers excluded anyone who had a heart problem or cancer at the time the study started, there were some pretty important differences between the groups examined. In both the male and female groups, at the start of the study the people who ate the most red meat were also about twice as likely to be diabetic and took much less exercise. The men in the high red-meat group were also three times as likely to be smokers and drank much more, too. (Women who like their red meat also liked booze and fags more than their burger-dodging sisters did, but the differences weren’t as large.)
There was also a clear trend in total calories consumed per day for both men and women. The low red-meat group consumed far fewer calories each day (1,659 for men and 1,202 for women) then the highest red-meat group (2,396 for men and 2,030 for women). These are enormous differences.
Can the researchers really be sure that the differences in meat consumption were to blame for the fairly small difference in health outcomes, rather than all the other differences between the groups? And these are the differences we know about. What other differences between the groups weren’t examined in the research analysis? For example, other researchers have pointed the finger of blame for many chronic diseases at carbohydrates, but there doesn’t appear to be any mention of them here.
The researchers will, of course, have tried to adjust for many of these confounding factors. But the scale of these differences suggests that the two groups who were most different in meat-eating habits were also very different in many other ways, too. Indeed, the study would be more accurately summed up like this: ‘The kind of people who say they eat quite a lot of red meat and processed meat are slightly more likely to die before they reach 75 years of age than those who say they don’t eat very much of those things.’
In short, on the one hand we have groups with different meat-eating habits who are also different in terms of lots of other lifestyle factors; any of these factors could have a significant impact on the results. On the other hand, the additional risk from eating red meat and processed meat would appear to be small. Is it really that hard to believe that the apparent risk is completely illusory?
What is really striking is that the eat-meat-die-young panic keeps rearing its ugly head so regularly, based on study after study with equally feeble risk ratios and numerous confounding factors. This suggests that the constant desire to scare those of a carnivorous bent has little to do with the evidence – which is shakier than a cow with BSE – and more to do with the prejudices of those who want us all to live a less red-blooded lifestyle. The particular desire to promote lentil-munching over hot dogs and burgers rather suggests a general sniffiness towards mass-produced food, too.
The most accurate answer to the question of whether red meat and processed meat are bad for you is this: we just don’t know. My hunch is that the health risks are non-existent – in practical terms, they are pretty much irrelevant – but given the difficulties of conducting this research, it’s hard to believe we could ever know if one particular type of food is especially bad for us. Still, that won’t stop the medics and the researchers from trying to enforce their food rules on us anyway.