By now, many of you have seen the headlines or read the articles.
– Egg yolks almost as bad for your heart as smoking cigarettes, says study – NY Daily News
– No yolk: eating the whole egg as dangerous as smoking? – LA Times
– Egg yolks almost as bad as smoking, researcher says – Vancouver Sun
It was also all over the internet:
– Egg Yolk Consumption Almost as Bad as Smoking When It Comes to Atherosclerosis, Study Suggests AND
Eating egg yolks accelerates atherosclerosis in a manner similar to smoking cigarettes, new research shows.- Science Daily
– Egg Yolks Just as Bad as Smoking for Your Heart – Eating egg yolks can be as bad for your health as smoking, a new study says.- Medical Daily
– Eating egg yolks as ‘bad as smoking’ – Nursing Times
And of course it was also all over the TV and radio news. Just when you thought it was safe to eat eggs, we find out that eggs are bad. Well, not so fast!
This morning, just as I do approximately three times a week, I enjoyed two eggs for breakfast. I didn’t take out the yolks either. Am I crazy? Do I have a death wish? Should I just take up smoking and get it over with? I may be crazy, but I don’t have a death wish, nor will I start smoking. I am also sure that eating eggs is not nearly as bad for your heart and arteries as smoking. The scientific study that these headlines are referring to is a peer-reviewed article by three Canadian researchers to be published in the journal Atherosclerosis. The researchers analyzed plaque buildup in carotid arteries of 1262 people referred to Canadian vascular prevention clinics. They compared plaque buildup of smokers with that of self reported consumers of more than two whole eggs per week. Despite all of these headlines, at no point in this article did the authors state that eggs or egg yolks are nearly as bad for you as smoking. They did state that their results suggested a relationship between egg consumption and build-up of arterial plaque within the population they studied. They concluded that their results suggest that egg consumption should be avoided by individuals at risk of cardiovascular disease. They go on to acknowledge the limitations of their study, most importantly that they did not consider, nor control for other nutritional and lifestyle factors that may have accompanied egg consumption, and therefore may also have an influence on the buildup of plaque in arteries. Some of these factors include dietary habits known to correlate with plaque buildup, physical activity level, and waist circumference.
The disconnect between the headlines and the actual conclusions of the researchers leads me to question whether the people writing these news articles actually read the study. While it is clear that the researchers acknowledged the limitations of their study, these limitations diminish the studies usefulness as part of the overall body of evidence regarding the influence of egg consumption on cardiovascular health. There are many problems with using the information in this study to conclude that eggs or egg yolks are nearly as bad for you as cigarettes.
First, the authors don’t make this claim. In fact, scientific research rarely leads to such broad, sweeping, and generalized conclusions. Most scientific studies, like this one, are limited to the population being observed, and the variables being investigated. The subjects of this study have all been identified as high risk for developing cardiovascular disease. The average age of the participants in this study was 62 years. The results of this study cannot be applied to the general population, especially young people and/or those not at high risk of cardiovascular disease. Drawing conclusions from this is further complicated by the authors’ admitted lack of control over other variables that may have influenced the buildup of plaque including other components of subjects’ diets, level of exercise, and stress.
Correlation between egg yolk consumption and buildup of arterial plaque does not mean that egg yolk consumption causes arterial plaque. In order to make the jump from correlation to causation, a mechanism for how egg yolk consumption causes buildup of arterial plaque must be identified. We know how cigarette smoke constricts arteries and contributes to favorable conditions for plaque buildup. The current body of research, however, mostly contradicts the idea that egg yolk consumption causes buildup of plaque in arteries. Correlation studies are more useful toward drawing conclusions when there is a correlation between two changes. For instance, if a study showed that the frequency of cardiovascular disease increased at the same time that egg yolk consumption increased, then maybe there would be more to investigate. From 1970-1995, egg consumption in the US decreased by 24 percent. During this time, hospital discharges for cardiovascular disease increased by nearly 3 million. We see that decreased egg consumption did not correlate with a decrease in incidence of cardiovascular disease. In fact, the opposite was true.
One medium egg yolk contains approximately two-thirds of the recommended daily amount of cholesterol. Presumably, it would be the cholesterol in the egg yolk that would be the cause of increased plaque formation. Studies have consistently shown that dietary cholesterol consumption has little impact on blood cholesterol levels, including the “bad cholesterol” that is associated with cardiovascular disease. In fact, any rise in “bad cholesterol” found to be associated with egg consumption is matched by a similar or greater rise in “good cholesterol.” Therefore the ratio of bad to good cholesterol remains unchanged. It is this ratio that has been found to be a greater indicator of cardiovascular risk than the actual blood cholesterol level.
The manner in which dietary cholesterol is absorbed also contradicts the concept that cholesterol consumption raises blood cholesterol and therefore increases plaque in arteries. It is questionable whether much of the cholesterol in egg yolk is even absorbed by the body. On average, approximately half of cholesterol present in the digestive system is absorbed. Cholesterol absorption is highly influenced by the level of consumption. As consumption increases, percentage of absorption decreases. Egg yolks are also high in lecithin, which is known to significantly interfere with the absorption of cholesterol by the body.
The evidence to dispute causation between egg consumption and cardiovascular disease is exhaustive. That is not to say that egg overindulgence will not increase risk of cardiovascular disease in certain individuals. Current recommendations are that individuals with high risk of cardiovascular disease limit egg yolk consumption. This includes those genetically predisposed to cardiovascular disease, and those with other concurrent high risk factors such as Diabetes.
Eggs are a nutrient dense food. They contain the most digestible and complete protein sources available. Egg yolks are one of the few foods that naturally contain vitamin D. They also contain many other important vitamins and minerals and are a great source of choline, an important substance for brain development. Eggs are relatively low in saturated fat, while high in monounsaturated fats and contain omega – 3 fatty acids. Eggs consumed in moderation can be part of a healthful, balanced diet. So there is no need to swear off that omelet. Just make it a two egg instead of three.
Fred's Food For Thought 