Comfort for meat eaters?
into carcinogens. Red meat is red because of a protein, myoglobin, and the haemoglobin of blood. These contain ‘heme iron’, which, when oxidised by heat, becomes toxic. These have been shown to damage the cells of the digestive tract wall, but it isn’t proved that those cells then become malignant: tumour-forming.
Another issue is heterocyclic amines – toxic substances produced when you cook meat – but these are produced when you cook white meat like chicken, too.
Processed meat is on the danger list because of the compounds that come from the salts that are crucial in the curing process: the nitrates and nitrites. Cooked and passing through the digestive system, these turn into a compound that is certainly cancer-forming – and this is also present in people who eat a lot of red meat. The risk factors for those who eat a lot of processed meat are slightly higher in the surveys than they are for people who eat mainly red meat. But, again, there are worrying holes in the research. The Spanish eat twice as much cured meat as people in Britain, but colorectal cancer rates there are no higher.
So the search for a culprit goes on – with a new idea emerging in the medical press regularly. This year the interest is in carnitine, a harmless substance in meat often added to energy drinks. US researchers announced in April that they believed carnitine was acting as a fuel for microbes that produce a compound that causes a build-up of plaque in the arteries. This throws a new light not on colorectal cancer but the old thesis about meat and its role in heart disease.
For the meat eater, only one happy result has emerged from all these investigations. Researchers in China have been fascinated by the effects of a new meat-heavy diet on people who traditionally ate very little. The average I am a devoted eater of meats – white, red and processed. If I go to Spain, I take an extra-large suitcase, stuffing it with cured meats on the journey home. And I don’t want to stop. So I turned for support to Professor David Colquhoun, a collector of dubious and contradictory research that he exposes on his popular blog, Improbable Science. (He is also an eminent pharmacologist at University College, London.) Colquhoun’s view is that while there are risks exposed by some of the long-term studies of diet and red and processed meat, they are too small to get wound up about.
The biggest study of all, the European Prospective Investigation into Cancer and Nutrition, followed 450,000 people in 10 countries for 12 years. It concluded that there was a “moderate positive association” between processed meat consumption and mortality.
But that risk was about one 20th of the risk of smoking causing cancer and so small that you could not, Colquhoun says, adequately allow for all the other factors that might blur the results – and those results don’t justify the risk warnings. Even if the studies did prove a causal relationship between meat and cancer, they mean that eating a hamburger a day shortens your life expectancy from 80 to 79 years. “Sounds rather small,” comments Colquhoun.
“The problem is that it’s hard being an epidemiologist,” Colquhoun said to me after the carnitine research came out. “Competition for funding is an incentive to exaggerate. People don’t like papers that don’t come to any solid conclusion – and some scientists like to get media attention.”
Colquhoun’s scepticism was comforting. But it did not let me off the hook. There are a host of very good reasons to cut out meat eating, as I found while researching my new book on cheap meat, which was sparked by the UK’s horsemeat scandal in January. Modern livestock farming and demand for ever-cheaper meat is madly expensive on resources. It brings huge threats to the environment and an appalling cost in animal suffering.
But then, as I contemplated a vegetarian future, I was saved by a startling piece of research done in my own kitchen. I charted one week’s meat consumption among our family of four and found that, although we ate some meat every day, in total we ate very little. A spaghetti Bolognese for four of us, with some leftovers, used just 200g of meat, getting us into the Harvard School of Public Health’s safety zone. And, taking that week’s animal protein eating and multiplying by 52, I found we were eating just 25kg of meat a year.
But these are the consolations of a worried, middleclass foodie. My diet is not representative. To get within the parameters that the Harvard School of Public Health study says will reduce the disease risks to levels near those that vegetarians enjoy, we need to reduce our consumption of the risky meats to just 350g a week – just a couple of sausages and one steak. Or go meat-free two days a week. The great meat feast is over. Alex Renton is the author of Planet Carnivore - Why Cheap Meat Costs the Earth, available on Amazon.