Last week saw the emergence of some news reports (example here) regarding research which linked the eating of processed meat. The study looked at the relationship between dietary habits and risk of death from a variety of causes in a group of people pooled from 10 European countries [1]. Analysis occurred over an average of about 13 years.
After adjustments making adjustments for factors which can bias results (including so-called ‘confounding factors’ such as body weight, exercise and smoking), red meat was not found to be associated with an increased risk of death, but processed meat was. Here’s a summary of their findings:
[box style=”rounded” border=”full”]After correction for measurement error, higher all-cause mortality remained significant only for processed meat (HR = 1.18, 95% CI 1.11 to 1.25, per 50 g/d). We estimated that 3.3% (95% CI 1.5% to 5.0%) of deaths could be prevented if all participants had a processed meat consumption of less than 20 g/day. Significant associations with processed meat intake were observed for cardiovascular diseases, cancer, and ‘other causes of death’. [/box]
These findings show that for each 50 g portion of processed meat eaten each day, overall risk of death was 18 per cent higher. The researchers went from here to make their prediction regarding restricted processed meat consumption and the lives this would save.
This study, however, has the same fundamental weakness that all studies of this type (epidemiological studies) have: that they can only tell us about associations between things. Even if two things are associated with each other, that does not mean that one is causing the other. It doesn’t matter how many statistical adjustments one makes, this inherent weakness in such studies does not go away.
As it happens, I am suspicious of processed meats myself. It’s not so much the meat that bothers me, but the usual presence in them of preservative chemicals (specifically nitrites) that appear to have the capacity to harm (they’ve been implicated cancer, for instance). My instinct and first principles tell me that it’s probably not a good idea to be ramming myself full of bacon, sausage and salami.
However, I do eat these foods. But I eat them in the context of a diet in which the vast majority of what I eat is ‘natural’ and unprocessed. Meat (including red meat), fish, seafood, vegetables, nuts and seeds make up the bulk of my diet. The presence of occasional processed meat in it is not, in my view, likely to jeopardise my health too much, particularly if I am also looking after other key lifestyle factors such as activity and sleep.
As it happens, since this study was published, another study emerged which suggests that the presence of processed meat in a diet may indeed not ring the ring knell for us.
This study concentrated on a large group of men and women in the US [2]. The data was extracted from what is known as the NHANES III (National Health and Nutrition Examination Survey III). After adjusting for confounding factors, here’s what the researchers found:
[box style=”rounded” border=”full”]…neither red and processed meat, nor white meat consumption were consistently associated with all-cause or cause-specific mortality.[/box]
In other words, eating more red and processed meat was not associated with an elevated risk of death. Incidentally, this newest study was performed by the same group of researchers in Switzerland that produced the earlier one which got the lion’s share of the press.
We have other evidence that supports the idea that some processed meat in the diet is not deadly in the form of studies which show that meat-eaters are at no heightened risk of death compared to vegetarians. It’s a fair assumption, I think, that the vast majority of meat-eaters consume some processed meat in addition to fresh meat.
This evidence, along with the most recent study from the US, suggest that the eating of red meat (including processed meat) is not associated with a greater risk of death. If that’s the case, then how bad can it be?
References:
1. Rohrmann S, et al. Meat consumption and mortality – results from the European Prospective Investigation into Cancer and Nutrition. BMC Medicine 2013, 11:63 (7 March 2013)
2. Kappeler R, et al. Meat consumption and diet quality and mortality in NHANES III. Eur J Clin Nutr. 2013 Mar 13. [Epub ahead of print][hr]
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