I have received a tremendous amount of inquiry this week regarding a recently released report that splashed dire and perhaps somewhat eggs-aggerated warnings throughout the media. This Canadian study was published in the journal, Atherosclerosis. In this observational trial, over 1250 men and women with average age of 61.5 years attended a university vascular prevention clinic, “filled out questionnaires regarding their lifestyle and medications, including pack-years of smoking, and the number of egg yolks consumed.” The eggs consumed per week were then converted over a longer time course to represent a measurement called “egg-yolk years.” The study participants also had “baseline measurement of TPA by duplex ultrasound.”[i] This refers to a measurement of the total plaque area (TPA) of any blockages found in the carotid arteries as assessed by ultrasound testing. The researchers found that the “plaque area increased linearly with age after age 40, but increased exponentially with pack-years of smoking and with egg-yolk years.” Their conclusion was that the “size of egg yolks appears to be approximately 2/3 that of smoking…Our findings suggest that regular consumption of egg yolk should be avoided by persons at risk of cardiovascular disease.”[ii]

Let’s now examine the study. The hypothesis upon which the study was based, as noted by the authors was that increasingly “the potential harm from high cholesterol intake, and specifically from egg yolks, is considered insignificant.”[iii] Since eggs and other high cholesterol foods were first demonized when the cholesterol hypothesis was put forth, much as been learned. At the time of the initial concern over dietary cholesterol intake, it was thought that if one consumed foods high in cholesterol that would raise your cholesterol and thus translate into more heart attacks, strokes, etc. Since that time we have learned a lot. Firstly, it is not just the cholesterol level that matters, what really matters is the level of oxidized cholesterol in the lining of the arteries as this is what initiates an inflammatory response. This level depends upon amounts and types of lipoproteins (structures composed both of proteins and fat compounds that transport fats like cholesterol in the mostly aqueous and saline blood-remember oil (fat) and water do not mix). There is a highly genetic variable component in this equation. When it comes to cholesterol and intake, the end result is much more dependent upon certain types of saturated fat intake and genetics than actual ingested cholesterol. For example, a study looked at serum cholesterol levels of men and women 5 hours to 54 days after receiving a food load of 465mg (US daily recommendation is 300mg/day) cholesterol or 54 days of 2 eggs every day. The result; the “serum cholesterol level of some subjects increased and others decreased.”[iv] That is why after the initial fright, foods like eggs and shrimp have been placed back on the menu of a healthful, balanced diet. Foods, unless excessively outrageous in cholesterol content, are best evaluated in terms of certain saturated fat contents, processing and other additives rather than absolute cholesterol content. It is interesting to note, that a reassessment of the blood cholesterol levels of 912 participants of The Framingham Study (from which some of the original cholesterol caveats were derived) showed that within “this population differences in egg consumption were unrelated to blood cholesterol level or to coronary heart disease incidence.”[v] Studies have even shown that in general, there is little correlation between saturated fat intake and cardiovascular disease.[vi] The prepackaged snack food chips loaded with artificial flavors, sodium and processed ingredients that boast “zero cholesterol” are not a more healthful food than some lovely fresh shrimp or a poached egg. It appears that the entire study may be biased as the result of an a priori argument.

Beyond a bias in the hypothesis, the study itself begs several questions. Dietary recall, while often the only option, is notoriously flawed as a mechanism by which to accurately reflect food product intake. Secondly, while most folks can remember eating a steak and labeling it as such, a steak is not usually an ingredient in other food products. Eggs are ubiquitous. It is not clear whether, for example, someone who frequently ate pasta (made with an egg containing pasta dough) had the egg content contained in that food accounted for in their “egg-yolk years”. Thus the true amount of egg consumption in the groups may be inaccurate. There was no mention of correlating highly processed meats such as sausage and bacon that are commonly purchased in the mega-markets. Several studies have correlated regular consumption of these products (as opposed to fresh, less processed red meat) with the development of cardiovascular disease and diabetes. If the persons eating eggs more often also more often consumed bacon and sausage (common egg accompaniments), these items may provide an alternative source to the findings. Additionally, this was a correlative study with no morbidity or mortality endpoints.

Moreover, the findings themselves are a bit questionable. While TPA has proven a better measure then simply examining the carotid intimal medial thickness, it is still fraught with limitations.  The ultrasound assessment is technically demanding and sensitive to operator acquisition. The researchers did not use more objective measures like CT or MRI quantitative analysis which would be less susceptible to operator variability. The addition of femoral arterial measurement can supply further data and increase sensitivity and specificity versus carotid artery measurements alone. While the negative predictive value of these tests is high, there is still debate as to its positive predictive value. This means that if the test says you have no plaque, it is unlikely you will have a cardiovascular event. A negative result (no plaque) predicts no disease. However, if it finds there is disease it is not necessarily a great predictor that you will have a cardiovascular event in the future.[vii] No commentary was provided on the lesion characteristics, like a measure of echogenicity, which in some studies identifies higher risk lesions irrespective of TPA. Finally, and perhaps most importantly, while these patients were being seen in a vascular prevention clinic, no data regarding actual vascular events for any patients are identified. In other words-so what? We have no idea if the measurements, if they even proved true amongst all the aforementioned issues, mean anything at all. Do these findings translate into meaningful clinical events? We have no idea. The study did not even consider known risk factors and influencing variables like exercise and waist circumference before drawing the conclusion that “egg yolks should be avoided by persons at risk of vascular disease.”[viii]

The media release following the study bought into the hype and immediately started recommending that you “make that an egg-white omelet instead.” It is an erroneous conclusion based on the study data because the study could not tell you if it was the egg whites that caused the increased TPA! This promulgation and fear mongering of tired and unproven hypotheses and suppositions continues to keep us bound in a maelstrom of ignorance eating a highly processed, adulterated diet that results in an increasingly large and ill population. Wholesome foods like eggs are currently accepted as part of a balanced, healthful diet. With the current fad to decrease carbohydrates, eggs may be even more important. A study looking at overweight men put on a carbohydrate restricted diet (CRD), markers of inflammation (which are elevated in conditions like diabetes associated with obesity) were measured. It was found that “eggs make a significant contribution to the anti-inflammatory effects of CRD, possibly due to the presence of cholesterol, which increases HDL-C and to the antioxidant lutein which modulates certain inflammatory responses.”[ix]

I watched the Julia Child marathon on PBS the other day, reliving my childhood. She lived a wonderfully iconic and incomparable life until the end of her very productive 92 years adhering to a simple maxim:“Learn how to cook — try new recipes, learn from your mistakes, be fearless and above all have fun.”…small helpings, no seconds, no snacking, and a little bit of everything.” And she loved eggs.

For further discussion on topics like this and others, see “Eating Well Living Better”, available at amazon.com: Eating Well, Living Better (the book)