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does eating red meat increase risk of stroke

by Alex Boersma

Red-meat consumption linked to increased stroke risk

December 30, 2010 | Medscape

Eating lots of red meat ups women’s stroke risk

Dr. Oz website headline

Eating Lots of Red Meat Increases Women’s Stroke Risk

Foxnews.com

 

 HOLD THE PHONES.  I CAN HEAR THEM RINGING ALREADY:

Alex, you told me it was OK to eat red meat!  Now look what you’ve done!  I think I’m having a stroke!”

Just kidding, actually.  Most of the friends and clients who I give nutritional advice to are a little more media savvy than those for whom these kinds of headlines are designed.  Besides, they rarely follow my “crazy” advice anyway.  Still, it gets under my craw.  I can’t figure out who’s worse;  the journalists who are spreading this nonsense or the scientists who are providing it.

Before I get too hot and bothered, let’s take a look at the abstract from this wonderful study and see what the researchers actually found:

  • In the background and purpose section, the authors state that “Our objective was to examine the association between red meat consumption and stroke incidence in the Swedish Mammography Cohort”.  So, just to be clear, this study is about associations.  Which means, from the outset, that it cannot prove that “Eating lots of red meat ups women’s stroke risk”.  The best it can do is show that there is an association between eating red meat and stroke in women.  Let’s find out it if actually does show such an association.

  • In the methods section, the authors state that they “prospectively” followed about 35,00 women who were free of heart disease and cancer.  They gave them a questionnaire to assess dietary intake as well as a number of other risk factors for heart disease.  They divided them into five groups (called quintiles) according to how much red meat they ate.  Then they sat back and watched.

  •  After about 10 years, there had been roughly 1700 strokes in the group.  About 1,300 of these were cerebral infarctions, the most common type of stroke.  In their words, the researchers found that “. Total red meat and processed meat consumption was associated with a statistically significant increased risk of cerebral infarction” The relative risk of having one of these cerebral infarctions was 22% higher in the women who ate the most “red meat” as compared to the women who ate the least.  Sounds ominous!

  • Then there’s this:  “Fresh (unprocessed) meat consumption was not associated with total stroke or with any stroke subtype.”  What?  Didn’t they just say that red meat was associated?  Does red meat not qualify as fresh meat?  No explanation in the abstract. 

  • Their conclusions:  “Findings from this study suggest that red and processed meat consumption may increase the risk of cerebral infarction in women.”  Fair enough…if it turns out to be true!   Notice the strategic use of the word “may” which indicates the reality of this study…it proves nothing.

The details of the study are not accessible, so we shall have to rely on some of the extra information provided in the stories listed above.

From the Medscape article we learn that “For the study, researchers grouped meats into red meat, fresh meat, and processed meat such as sausage, hot dog, salami, ham, and liver pâté. Red meat was the sum of fresh and processed meat.”  Aha!  So was “red meat” really associated with stroke…NOT SO MUCH!  Red meat, which for this study equals processed meat  plus fresh meat, is only associated with meat as long as it includes processed meat. 

Red meat minus processed meat = fresh meat = NO ASSOCIATION! 

Big news!  Eating a pile of processed meat every day may not be good for you!  Doesn’t sound quite so ominous anymore.

From the original Reuter’s story, “Red meat increased stroke risk in non-smokers, but not smokers, and in women who didn’t have diabetes, but not in women with diabetes.”  Hmmm.  First of all, from this study we cannot say that anything increased the risk of anything.  The best we can say, and this is an important distinction, is that something may increase the risk of something.  In this case, eating processed meat (not red meat) may increase the risk of certain kinds of stroke.  Does this mean that if you are a smoker or a diabetic you can eat all the processed meat you want because being a smoker or a diabetic somehow protects you from the stroke promoting ravages of processed meat consumption?  

I don’t think so. 

 I think (and this is just my humble opinion) that being a smoker or a diabetic shows that you are not a particularly healthy person.  Having established that you are not a healthy person, it doesn’t matter at all how much or what kind of meat you eat because you are much more likely to be living an unhealthy lifestyle.  It is this unhealthy lifestyle which is causing you to have a high risk of stroke…not the type or amount of meat you eat.  If you are not a smoker or a diabetic, it is much more likely that you are leading a healthy lifestyle, and it is this healthy lifestyle which is protecting you from a stroke. 

However, if you belong to the non-smoker, non-diabetic club but do not maintain a healthy lifestyle, your chances of having a stroke are probably higher.  Shall we say 22% higher?  If you belong to this “I don’t smoke, I’m not diabetic, but I couldn’t give a rat’s ass about my health” club, you are much more likely to eat Sausage McMuffins for breakfast, bologna sandwiches for lunch and Quarter Pounders for dinner.  Is it the sausage, bologna and mystery meat which increases your risk of stroke?  Or is it the wonderbuns, the trans fattened fries, the rancid cooking oils, the ketchup or any of the myriad other factors associated with not giving a rat’s ass?

It is quite likely that the consumption of processed meat is simply a marker of having a less than stellar lifestyle, not a cause of stroke.

Again from the Medscape article:  “Commenting on this research, Dr Thomas W Wolever (University of Toronto, ON) agreed that the high heme iron content of red meat could be a factor in the association between this type of meat and some types of stroke.”  Dr. Wolever, you must be OK because you are from Toronto, but you should have read the study…red meat (the kind with high heme iron content) was not a factor in stroke risk!  If there was anything worth further investigation here, it was processed meat, not red meat.  And even if it was a factor, the heme iron theory of vascular disease has pretty much been put to pasture

(Dr Wolever does go on to talk about high sodium content in processed meat being a possible mechanism of action.  And, to his credit, he gets the final line in the article, in which he cautions “that the associations uncovered by the study do not prove causality”.  The problem, however, is that millions of people read the misleading Medscape headline while only a small percentage ever get to Dr Wolever’s words of caution.)

  

SO WHAT DOES IT ALL MEAN?

Let’s do a little math.  35,00 women were followed for 10 years.  In that 10 years, 1,300 had strokes that might somehow have been associated with some sort of meat consumption.  That works out to about a 4% chance of having a “meat related” stroke over 10 years.  The relative risk of having one of these strokes was 22% higher if you ate a bunch of processed meat every day (actually, from the Medscape article, you only had to eat an average of 1.3 oz of processed meat a day to be in this “high stroke risk” group) than if you ate very little processed meat. 

But just what does a 22% relative risk mean?

It means that if you take 100 women between the age of 49 and 83 (these numbers also from the medscape article) who don’t frequent deli counters or fast food restaurants, just under 4 of them are likely to have a stroke in the next 10 years.  If you take another 100 who couldn’t be bothered paying attention to the quality of their meat intake, just over 4 of them may keel over with a stroke during that same  decade.  That impressive sounding relative risk of 22% turns into an increased risk of  less than 1 in 100 over 10 years!  And this in a relatively older population amongst whom the death rate is about 4 or 5% per year anyway.  Maybe the headlines should read:

Eating processed meat is associated with a 1 in 100 chance of dying from stroke in the next 10 years …in a bunch of elderly women who have a 5 in 100 chance of dying from something anyway in any given year.

 

Such a headline would be unlikely to captivate many readers.  Which is exactly my point.  This study is not worth publishing.  It proves nothing and even the weak associations it does find are not news.  Unless you’ve been living under a rock for the last decade or two, you already know that eating a lot of processed meat is probably not a great idea.  If there is anything of interest here, it is the fact that red meat may not be associated with stroke. 

Too bad the study authors didn’t point that out in their conclusions!

AND TOO BAD THE JOURNALISTS DIDN’T TAKE A LITTLE CLOSER LOOK AT THE STUDY BEFORE MISLEADING THE PUBLIC YET AGAIN!

 

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