A new study suggests that eating three whole eggs a week can thicken the arteries as much as smoking. Some heart experts say not so fast

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Is your breakfast omelet harming your heart? A recent study by researchers at Western University in Canada found that the more egg yolks people ate, the thicker their artery walls became — an indicator of heart disease risk — and that the effect was almost as bad as from smoking cigarettes.

In the study, the researchers measured carotid plaque build-up in the arteries of 1,231 men and women, average age 62, who were seeking care at cardiovascular-health clinics. Participants filled out questionnaires detailing lifestyle habits including medication use, cigarette smoking and egg-yolk consumption. The researchers gauged how much people smoked and how many egg yolks they ate over time, by calculating their “pack-years” (the number of packs of cigarettes people smoked per day multiplied by the number of years they spent smoking) and “egg-yolk years” (how many egg yolks they ate per week for how many years).

After about age 40, participants’ plaque began building up steadily, but among the participants who ate the most eggs — three or more yolks per week — that build-up increased “exponentially,” the study found. As people’s egg-yolk years went up, so did their plaque accumulation — an association that was independent of factors like gender, cholesterol levels, blood pressure, smoking, body mass index and diabetes.

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Among the 20% of participants who ate the most eggs, the carotid plaque build-up was about two-thirds that of the study’s heaviest smokers. The researchers concluded that the plaque increase from eating eggs “follows a similar pattern to that of cigarette smoking.”

Arterial accumulation of plaque is a key risk factor for heart attack and stroke. As plaque builds up, it thickens artery walls and narrows the space through which blood can flow, forcing the heart to pump harder. If plaques become unstable, they can break off and form clots, which can halt blood flow to either the brain or the heart, causing stroke or heart attack.

The authors argue that their findings should quell doubts over the link between high dietary cholesterol and heart disease. “The prevailing tendency to ignore dietary cholesterol as a risk factor for coronary heart disease requires reassessment, including the consumption of cholesterol from eggs,” the authors wrote.

The government’s dietary guidelines recommend that adults consume no more than 300 mg of cholesterol a day. One whole egg contains about 180 mg of cholesterol, nearly two-thirds of your daily recommended ma.

“The mantra ‘eggs can be part of a healthy diet for healthy people’ has confused the issue. It has been known for a long time that a high cholesterol intake increases the risk of cardiovascular events, and egg yolks have a very high cholesterol content,” study author Dr. David Spence, a professor of neurology at western’s Schulich School of Medicine & Dentistry, said in a statement. “In diabetics, an egg a day increases coronary risk by two- to five-fold.

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However, the study’s findings raised brows among other health experts, ABC News reports:

[C]ardiologists say the study shouldn’t be taken so seriously because the research is flawed. “This is very poor quality research that should not influence patient’s dietary choices,” said Dr. Steven Nissen, who chairs the department of Cardiovascular Medicine at the Cleveland Clinic Foundation, in an email. “It is extremely important to understand the differences between ‘association’ and ‘causation’.” Nissen said the researchers relied on patients to recall how many eggs they consumed, but asked them once and assumed it remained constant, which isn’t reliable. He said the way researchers measured patients’ plaque has come under “considerable criticism,” and that researchers failed to adjust for other dietary factors.

Indeed, it’s possible that the people who ate a lot of eggs also tended to eat a lot of other high-fat, high-salt or high-cholesterol foods. Or maybe they also tended to exercise less.

The researchers say that while further studies are needed to flesh out the association, people at risk for heart disease should still refrain from eating egg yolks on a regular basis.

The study is published in the journal Atherosclerosis.

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