Dr. David Spence of Western University, Canada, and his team surveyed more than 1200 patients and found that regular consumption of egg yolks is about two-thirds as bad as smoking when it comes to increased build-up of carotid plaque, a risk factor for stroke and heart attack.

Atherosclerosis is a disorder of the arteries where plaques, aggravated by cholesterol, form on the inner arterial wall. Plaque rupture is the usual cause of most heart attacks and many strokes.

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.

The researchers found carotid plaque area increased linearly with age after age 40, but increased exponentially with pack-years of smoking and egg yolk-years. In other words, compared to age, both tobacco smoking and egg yolk consumption accelerate atherosclerosis. The study also found those eating three or more yolks a week had significantly more plaque area than those who ate two or fewer yolks per week.

"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. In diabetics, an egg a day increases coronary risk by two to five-fold," said Dr. Spence, a Professor of Neurology at Western's Schulich School of Medicine and Dentistry and the Director of its Stroke Prevention and Atherosclerosis Research Centre (SPARC) at the Robarts Research Institute.

"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," he stated.

Dr. Spence added the effect of egg yolk consumption over time on increasing the amount of plaque in the arteries was independent of sex, cholesterol, blood pressure, smoking, body mass index and diabetes.

And while he said more research should be done to take in possible confounders such as exercise and waist circumference, he stresses that regular consumption of egg yolk should be avoided by persons at risk of cardiovascular disease.