Just as you were ready to tuck into a nice three-egg omelet again, comforted by the reassuring news that eggs are not so bad for you, here comes a study warning that for those over 40, the number of egg yolks consumed per week accelerates the thickening of arteries almost as severely as does cigarette smoking.
Server, can you make that an egg-white omelet instead, please?
The study, published Tuesday in the journal Atherosclerosis, measured the carotid wall thickness -- a key indicator of heart disease risk -- of 1,231 patients referred to a vascular prevention clinic, and asked each to detail a wide range of their health habits, from smoking and exercise to their consumption of egg yolks. Just as smoking is often tallied as "pack-years" (the number of cigarette packs smoked per day for how many years), egg-yolk consumption was tallied as "egg yolk years" (the number of egg yolks consumed per week times the number of years they were eaten).
The study subjects were typically referred to the clinic after having suffered a clot-induced stroke or a transient ischemic attack -- a "mini-stroke" in which symptoms may disappear quickly but which often presage a more serious stroke to come.
Smoking tobacco and eating egg yolks increased carotid wall thickness in similar fashion -- which is to say, the rate of increase accelerated with each stair-step up in cigarette smoking or yolk consumption. By contrast, for those who did not smoke, or who rarely consumed egg yolks, carotid wall thickness increased after 40, but at a slow-steady rate.
For those whose consumption of whole eggs was in the highest 20%, the narrowing of the carotid artery was on average about two-thirds that of the study's heaviest smokers.
"We believe our study makes it imperative to reassess the role of egg yolks, and dietary cholesterol in general, as a risk factor for coronary heart disease," the study authors write.
In recent years, nutritionists have begun to agree with egg purveyors that chicken eggs -- cheap and packed with protein -- have gotten a bad rap as a dangerous source of cholesterol. Some studies have suggested that eggs may increase HDL, or "good cholesterol" that protects against heart disease, even as it contributes to the artery-clogging LDL cholesterol, making egg consumption something of a wash. And regular egg-eaters may form larger lipoprotein particles that help clear the blood of fat particles and are not as likely to settle in artery walls.
Still, the National Heart Blood and Lung Institute recommends that to limit their risk of developing heart disease, Americans limit their cholesterol intake to no more than 300 mg per day (an egg yolk has just over 200 mg), and eat no more than four whole eggs weekly, including those in baked goods or processed foods. Those who already have heart disease, diabetes or high LDL-cholesterol, or who have had a stroke, should limit their cholesterol to less than 200 mg per day.