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A recent study, published in the journal Atherosclerosis July 31, made big headlines comparing the unhealthiness of cholesterol in eggs to the impact of smoking.For example:
- “Study: Eggs Are Nearly as Bad for Your Arteries as Cigarettes” from The Atlantic.
- “Your Breakfast Is Trying to Murder You: Eggs Are Almost as Bad for You as Cigarettes” from Jezebel.
- “No yolk: eating the whole egg as dangerous as smoking?” from The Los Angeles Times.
- “What do egg yolks and cigarettes have in common?” from the Washington Post.
The problem with these punny headlines? Giving the study those titles doesn’t stand up to scientific scrutiny, and because none of these outlets asked outside researchers, they didn’t know.
The study was hyped in a press release from the University of Western Ontario released August 13. Here’s how the release describes the study:
The study looked at data from 1231 men and women, with a mean age of 61.5, who were patients attending vascular prevention clinics at London Health Sciences Centre’s University Hospital. Ultrasound was used to establish a measurement of total plaque area and questionnaires were filled out regarding their lifestyle and medications including pack-years of smoking (number of packs per day of cigarettes times the number of years), and the number of egg yolks consumed per week times the number of years consumed (egg yolk-years).
What the study actually found was that people who eat a ton of eggs — more than 4.5 per week — have about two thirds as much plaque in their arteries as heavy smokers. The problem being that this link can’t be called causation and could be completely unrelated to the egg intake.
First, every scientist will tell you that correlation does not equal causation. This study doesn’t prove that eating egg yolks caused the fatty deposits, it simply shows that people who said they ate more eggs had more fatty deposits than people who said they ate fewer eggs.
Second, this study doesn’t account for other foods that might cause artery-hardening plaque. Think of the typical egg breakfast. Maybe it includes sausage, bacon, cheese, hash browns, biscuits . . . maybe even gravy? Isn’t it possible that the people who ate the most eggs in this study had really sh**ty diets?
Other confounding factors, like the person’s level of physical activity, weren’t accounted for in the study.
The other problem with the study? It didn’t actually track these patients over time. They were just asked how many eggs or cigarettes they smoked during their lifetime — and seriously, who would accurately remember those stats decades later?
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