Came across this study on Reuters and would be interested to hear thoughts/opinions on it. I don't have access to the full study, so I'm not clear on what exactly how they define "red meat." I'm also confused by the statement that "Fresh (unprocessed) meat consumption was not associated with total stroke or with any stroke subtype." What is the difference between "red" meat and "fresh" meat?
Red Meat Consumption and Risk of Stroke in Swedish Women
Susanna C. Larsson, PhD; Jarmo Virtamo, MD; Alicja Wolk, DMSc From the Division of Nutritional Epidemiology (S.C.L., A.W.), National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; and Department of Chronic Disease Prevention (J.V.), National Institute for Health and Welfare, Helsinki, Finland.
Correspondence to Susanna C. Larsson, PhD, Division of Nutritional Epidemiology, National Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-17177 Stockholm, Sweden. E-mail email@example.com
Background and Purpose—High red meat consumption has been associated with increased risk of some cancers and may also be a risk factor for cardiovascular diseases. However, epidemiological studies of red meat consumption in relation to risk of stroke are very limited. Our objective was to examine the association between red meat consumption and stroke incidence in the Swedish Mammography Cohort.
Methods—We prospectively followed 34 670 women without cardiovascular disease and cancer at baseline. Participants completed a self-administered questionnaire on diet and other risk factors for cardiovascular diseases in 1997. Cox proportional hazards models were used to estimate multivariable-adjusted relative risks (RR) and 95% CI.
Results—During a mean follow-up of 10.4 years, we ascertained 1680 incident cases of stroke, comprising 1310 cerebral infarction, 154 intracerebral hemorrhage, 79 subarachnoid hemorrhage, and 137 unspecified stroke. Total red meat and processed meat consumption was associated with a statistically significant increased risk of cerebral infarction, but not of total stroke, intracerebral hemorrhage, or subarachnoid hemorrhage. The multivariable RR of cerebral infarction for the highest versus the lowest quintile of consumption were 1.22 (95% CI, 1.01–1.46) for red meat and 1.24 (95% CI, 1.04–1.49) for processed meat. Fresh (unprocessed) meat consumption was not associated with total stroke or with any stroke subtype.
Conclusion—Findings from this study suggest that red and processed meat consumption may increase the risk of cerebral infarction in women.
Don over at Primal Wisdom recently posted a nice takedown:
To clarify, if 4 of every 100 people had a stroke (as in this study), the absolute risk for stroke was 4%. If in one of the subgroups 5 of every 100 people had a stroke, their absolute risk was 5%. But if you compare the two groups, the subgroup had a 25% greater risk than the other, because 5% is 25% greater than 4%. Yet in the one group, 96% of people did not have a stroke, and in the other, 95% did not have a stroke.
That's why the math comes out to reflect a "significant" (22%) increase in stroke risk. Don calls it "creative accounting."
take a close look at the last sentence of the abstract of the journal article:
"Fresh (unprocessed) meat consumption was not associated with total stroke or with any stroke subtype."
What? In the immediately previous sentence, they stated that red meat was associated with a 22% relative risk in cerebral infarction type stroke, but the last sentence says that fresh meat was not associated with total stroke or any subtype, which would include cerebral infarction.
I feel confused. How can "high" red meat consumption be associated with a 22% greater risk of stroke, and yet not associated at all with total stroke or any stroke subtype? It seems that the trick must be in combining both fresh and processed red meat to get the positive association.
As you can see from the title of the Reuters report, the first claim got plastered on the headlines, but the last was ignored. What's up with that?
My only request is that we do the same kind of takedown when a Paleo-friendly paper comes out, if it's as poorly done as this one is. And by "we," I mean people who are smarter than I am. Masterjohn, for example, did a good one on his most recent blog post.
I don't consider the factory-farmed "meat" that the average person eats to be food, so any reference to "meat" as a monolithic thing must be taken with a grain of salt.
Edit: Perhaps meat quality is better in Scandinavia? I'm not sure. I get the feeling that they are referring to cured vs, fresh, and we all know that sodium nitrite/nitrates are carcinogenic as it is and could conceivably cause other problems.
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