Eating egg yolks can be as bad for your health as smoking, a new study says.

According to researchers from Western University, eating three or more egg yolks per week increases chances of atherosclerosis and that eating egg yolk is about two thirds as bad as smoking.

Atherosclerosis occurs when fat, cholesterol and other substances build up on the walls of arteries and form hard structures called plaque. The plaque can then blocks the arteries, restrict blood flow that can result in damage or tissue death. Sometimes the plaque breaks into smaller bits and blocks other smaller blood vessels or get in the lungs.

“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 very high cholesterol content. In diabetics, an egg a day increases coronary risk by two to five-folds,” said David Spence, a professor of Neurology at Western University.

For the study, researchers analyzed data from more than 1,200 men and women who were around 60 years old. All the participants were patients attending vascular prevention clinics at London Health Sciences Centre’s University Hospital. These participants were then given questionnaires asking them about their lifestyles like smoking habits and how many eggs they ate per week. The participants also underwent an ultrasound test to determine plaque area in their arteries.

Researchers found that the area of plaque increased with age but people who smoked or ate more than three egg yolks per week had higher plaque area.

“What we have shown is that with aging, plaque builds up gradually in the arteries of Canadians, and egg yolks make it build up faster - about two-thirds as much as smoking. In the long haul, egg yolks are not okay for most Canadians," Spence said.

Spence advises that people who are at a high risk for heart disease must avoid regular consumption of egg yolk.

The study was published in the journal Atherosclerosis.