Applying the Spam Filter
Nigel Williams, 7 March 2013
Studies like the massive investigation into processed meat consumption published by BMC Medicine are undeniably valuable. Nearly half a million volunteers took part in the study, revealing details of their diets and medical history for years so that we could have a better idea of the link. They deserve our gratitude. There were plenty of authors too. The paper lists 47, from 37 different institutions, including the School of Public Health at Imperial College, London, the Medical Research Council Epidemiology unit at Cambridge and the Cancer Epidemiology Unit at Oxford. This is heavyweight research. The value goes beyond providing newspapers with headlines for a day, but we need to think a bit about how to use the information.
The study found an association between regular consumption of processed meat and an increased risk of early death. Two possible but misguided reactions are to vow instantly never to eat processed meat again and to dismiss all such research as confusing and contradictory.
The first trick is not to think of any study as representing the entire state of human knowledge. It provides information that can adjust what we already know from other sources. Bigger studies count for more than smaller ones, especially if the study group concerns people more like us. If our family and friends typically live healthily into our nineties then there is little need to change our habits. If on the other hand we are regularly mourning close relatives and witnessing health scares among people with whom we share a lifestyle, then it is helpful to know what may be contributing.
The next trick is to assess the scale of the risk in absolute terms. This study estimates that somewhere between 1.5 per cent and 5 per cent of deaths in the age group 35 to 69 were attributable to eating more than 20g of processed meat per day. Those deaths were mostly because of heart disease but also because of cancer. In 2011, 72,000 men and women died in England and Wales from all causes at ages from 35 to 64. There were 560,000 living 65-year olds. If the goal is to survive to 65, then eating less processed meat will make little difference to 249 out of 250 people. Most of us like the idea of surviving that long and people with commitments to partners and children have greater concern to be there for them. But if a large part of the attraction of a long life is the chance to enjoy eating sausages, we may not worry so much about the risk. That is the value of making an informed choice.
The third trick is to remember that some risks stack up. Being male is bad news regarding heart disease. Smoking multiplies that risk. The fact that processed meat affects the chances of heart disease means that it needs to be taken seriously. Sedentary lifestyles don’t help. A bacon sandwich as a Saturday-morning reward for walking the dog is less risky than eating a fry-up in front of the television. The ‘3 per cent of early deaths’ headline from this study comes after careful adjustments for other factors but it will matter more for people already exposed to related risks.
How then to respond to the news that more people die young among eaters of processed meat? First, don’t rush. The effects are gradual, so one more day won’t kill you and an instant cessation won’t save you. Then think about whether your diet moves you and those close to you into a more dangerous category. The NHS Atlas of Risk is well worth a look to get a sense of perspective. Consider what it is about the processing that makes this food less healthy. Is it the salt or the other additives? Is it the manner of cooking? That may take more studies to establish conclusively but there is some evidence already. As often as papers report studies about meat they carry stories about cooked tomatoes or a sip of red wine. If you want a quick suggestion while you weigh up the other risks, try varying the recipe a bit. Even wholemeal bread can be palatable if it is fresh enough and granary still has twice the fibre of white. And as you grill the bacon for your sandwich, grill some big tomato slices at the same time. There are healthier diets available but I trust you will still enjoy your treat and you will be a step closer to the ‘balanced diet’ that has been the ideal of studies and received wisdom for generations.