This week’s study published in the journal Atherosclerosis comparing eggs yolks to smoking was disturbing and I received a plethora of emails and calls from patients afraid to eat their morning breakfast.
I had to carefully read the study to see how the researchers came up with this information. The study looked at the size of plaque build-up in arteries of 1200 men and women (mean age 61.5 years) visiting cardiovascular clinics in Canada. The researchers claim they found that participants who consumed more than three egg yolks a week and were heavy smokers had significantly more total plaque than those consuming less than two egg yolks per week.
Looking closely at the study shows there were some major methodological flaws
1. The researchers did not adjust for intake of cholesterol from other sources, saturated fat intake, alcohol intake, smoking patterns, exercise, HDL/LDL cholesterol, triglycerides or waist circumference
What does that mean? They did not look at any other patterns of the participants besides smoking and egg yolks. So we have no clue what they were eating, drinking or smoking, whether they were normal or overweight, what were their sleep habits like, etc.? It is irresponsible to take two variables and connect them without more information.
And this study was an epidemiological one, meaning it is just an observation or association (not cause and effect). This study does not prove that eating egg yolks is equal to smoking.
2. The researchers' use of a metric called "egg yolk years" (age mulitplied by the number of eggs the subjects reported to consume per week throughout their lives) to assess total egg intake was beyond troubling. They asked people to remember how many egg yolks per week they had eaten on a regular basis. Research shows that when you have patients "recall" what they ate, especially over many years like this study did, the accuracy is quite questionable.
So what’s the bottom line?
Should you change you morning breakfast based on this study? Absolutely not. Eggs are an excellent source of protein, and most of the fat contained in the egg is polyunsaturated and monounsaturated fat. Eggs are an also a great source of the antioxidant lutein, and the nutrient choline which both lower certain inflammatory responses in the body.
By eating eggs you’ll be getting a great source of protein to provide energy and satiation for the day as well as keeping your metabolic rate in high gear. Including the yolks gives you the extra benefit of lutein and choline.
Quoting Bruce Griffin, a researcher from the University of Surrey:
“The link between egg consumption and raised cholesterol levels was based on out-of-date information. The egg is a nutrient-dense food, a valuable source of high quality protein and essential nutrients….and it is high time we dispelled the mythology surrounding eggs and heart disease and restored them to their rightful place on our menus where they can make a valuable contribution to healthy balanced diets.”