March 25, 2009
How the red meat story was undercooked
“Killer Meat” – headlined an LA Times online column.
“Want to Live Longer? Cut Back on Red Meat” – pronounced CNN.com.
“Daily Red Meat Raises Chances Of Dying Early” warned washingtonpost.com.
It all sounds so certain.
But this was an observational study – not an experiment. It was based on responses to a questionnaire.
Such a study CAN NOT – simply CAN NOT – establish cause-and-effect and therefore CAN NOT establish risk.
So any story that said “higher risk” or “chances of dying” was simply wrong.
Stories on such studies are obliged to point out the potential weaknesses in such studies.
Journalists and consumers should read a column we published on HealthNewsReview.org, entitled “Does Your Language Fit the Evidence?”
And stories that gave these kinds of percentage (as the Washington Post did) are obliged to give you more:
Among women, those who ate the most red meat were 36 percent more likely to die for any reason, 20 percent more likely to die of cancer and 50 percent more likely to die of heart disease. Men who ate the most meat were 31 percent more likely to die for any reason, 22 percent more likely to die of cancer and 27 percent more likely to die of heart disease.
35% of what? 20% of what? 50% of what?
That’s like having a 50% off coupon and not knowing if it applies to the purchase of a Lexus or the purchase of a lollipop. Give the absolute risk reduction figures.
I gave my undergrad health journalism students about 5 minutes to analyze one such story yesterday. They easily came up with the above flaws and more.
Come on, folks. We have to get smarter about evaluating studies – and news coverage of studies.
Comments
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Beryl Rosenberg
March 25, 2009 at 10:34 amWhat if the subject was eating more red meat in 3 oz portions on a weekly basis instead of fish, chicken or dairy. Had a low intake of simplex carbs and junk food, didn’t smoke, exercised daily and had a moderate to high fiber and fresh vegetable intake? Was that type of candidate included in the study?
The Publisher
March 25, 2009 at 11:18 amYou can read the specifics yourself at:
http://archinte.ama-assn.org/cgi/content/full/169/6/562
Ill and Uninsured in Illinois
March 25, 2009 at 3:01 pmPart of the trouble is that too many journalists need a course in remedial math. Anybody who waves statistics at them — especially hard stuff like percentages — intimidates them, so they just parrot back whatever the source said instead of adding up the figures themselves. You see that over and over again in science stories, in financial stories, in stories about taxes and government spending.
The reporters probably didn’t check that the percentages were accurate, or they’d have figured out part of the equation was missing.
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