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Death by Meat PDF Print E-mail
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Written by Dr. Steven Novella   

A recent study which is getting a lot of press finds a correlation between the consumption of processed meat (bacon, hot dogs, sausage), and all-cause mortality. Like many such studies, however, the exact implications are tricky to work out.

This is an observational study, meaning that it is able to detect correlation only, and not establish causation. However, it should be pointed out that when correlations hold up over numerous types of observation they can be used as a legitimate way to infer probable causation. In other words, I do not dismiss correlational data out of hand. It is one type of evidence, and has to be put into context.

In this case, however, it is very problematic. The study found that people who eat large amounts of red meat and processed meat has a significantly higher rate of death (all cause mortality). However, the correlation with red meat did not hold up when corrected for measurement error, while the correlation with processed meats did. For completely, they also found no association with eating chicken.

The study also found, however, that people who ate large amounts of processed meats were also more likely to smoke and be overweight. The correlation with increased risk of death was still present even when these other factors were controlled for.

However - here is the big weakness of this kind of data. What these correlations show is that people who eat large amounts of processed meat also engaged in other unhealthy behaviors. They can control for such behaviors that they know about and which were reported, but not for all possible unhealthy behaviors. The study reports, for examle:

"Men and women in the top categories of red or processed meat intake in general consumed fewer fruits and vegetables than those with low intake. They were more likely to be current smokers and less likely to have a university degree (Table 1). Men with high red meat consumption consumed more alcohol than men with a low consumption, which was not seen in women."

It seems likely, therefore, that processed meat eaters were subject to other health risks not accounted for in this study. There is no way to know how much of the apparent risk from eating processed meat is actually due to these other health risks.

The association was also only significant for the 160+grams per day category, when compared to the lowest category. Bacon is about 5-10g per slice (depending on brand and cooking). That about a package of cooked bacon every single day (at least - remember, this is 160+ grams per day).

It is not difficult to believe that if you eat a package of bacon a day you are going to be unhealthy. This doesn't tell us much, however, about those who eat the occasional few slices of bacon, maybe a hot dog or sausage every couple of weeks.

These results are similar to other studies looking at red meat, which found increased mortality only for the highest consumption groups, those eating red meat every day.

Given the totality of research, it does seem likely that there is a small but real health risk from eating red and especially processed red meats. It is unclear if this risk is due to other associated behavior, or directly to the red meat. It may, for example, have more to do with eating fewer vegetables.

If we take this data at face value, a reasonable recommendation, for those interested in staying healthy, is to limit red and especially processed meats to moderate levels. Having a few servings of red meat a week does not seem to carry any significant health risk. Lean meats - poultry and fish - are fine. Also, eat plenty of vegetables, don't smoke, get enough sleep, and exercise regularly.

Steven Novella, M.D. is the JREF's Senior Fellow and Director of the JREF’s Science-Based Medicine project.

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written by SheldonHelms, March 09, 2013
I keep hearing this word "processed" thrown around as if it has scientific value. No one seems to be able to define it, though. Is meat "processing" adding some harmful chemical to our food? All the term seems to do is serve as a spooky placeholder for "evil" food producers.
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written by Lucas, March 10, 2013
@SheldonHelms The term "processed" usually means it has been enriched with more additives than "unprocessed" meat. The additional additives may or may not have health impacts over time.
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written by OPa, March 11, 2013
A pound is 454 grams, according to my bacon package. Regular slice bacon runs about 16 pieces per package.
So that comes out to about 29 grams per slice, not just 5-10. 160 grams would be just more than a third of a package, not a whole package. Or is my math messed up?
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written by powerfulmojo, March 11, 2013
Quoth OPa: "Or is my math messed up?"

I took the context "Bacon is about 5-10g per slice (depending on brand and cooking)" to mean that they measured weight after cooking. Now... you'd have to like your bacon pretty crispy if you're in the habit of cooking off 2/3 of its weight, but it's at least believable that you'd sizzle off some water and leave some fat in the pan.
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written by OPa, March 11, 2013
I guess my main point was the study was not talking about a whole package of bacon a day, but only about a third of a package; 4-5 slices. This is an amount more likely to be ingested by most people. I know I have no trouble with that amount!
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written by lytrigian, March 11, 2013
You don't eat all the fat that cooks off, though, so 160g is *still* rather more than 4-5 slices.

Well. You eat the fat if you save it and use it for cooking something else, as earlier generations tended to, but I suspect most don't do that anymore.
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written by xxi_centuryboy, March 12, 2013
"The term "processed" usually means it has been enriched with more additives than "unprocessed" meat. The additional additives may or may not have health impacts over time."

This is partially true and is probably what the author or study refers too. All commercial food is processed to some degree, which is why they call them food processing plants. Plant and animal foods have to be picked, sorted, killed and or butchered to get to a market and this is called processing. It would be more accurate to use specific preservative than to use the blanket term "processed", which is just fear mongering. Beer is a processed food for example. It has been altered and preserved from its original form, and is still quite tasty and enjoyable.
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Meat not an issue
written by tlsimpson, March 12, 2013
The most important statement, in this group looking at half a million people was this: After correction for measurement error, red meat intake was no longer associated with mortality, and there was no association with the consumption of poultry." --- the other was that while smoking was pointed out as a bad behavior with eating processed meat- the relative risk of eating that quantity of processed meat was low, while the relative risk of smoking is high. They cannot separate them out, and cannot account for smoking in that. More about this on my blog here: http://budurl.com/redmeatlive
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"Processed"
written by Matt_D, March 12, 2013
Processed meat does usually mean something a bit more specific than the "processed food" catch-all. It refers to cold cuts, ham, bacon, sausages, hot dogs, and other servings of meat that have been cured or preserved / flavoured with salts and chemicals.
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written by Rrose Selavy, March 20, 2013
Beer is a processed food for example. It has been altered and preserved from its original form, and is still quite tasty and enjoyable.


Beer is a food? Enjoyable it maybe for some but it's mostly calories with hardy any nutritional value.
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