Egg Yolks a Strong Risk Factor for Atherosclerosis
By on August 13th, 2012

Eggs are rarely found in ‘unhealthy food’ lists, but a new study suggests that their regular consumption is not as beneficial to our health in the long run. A strong link has been found between the consumption of 3 or more egg yolks a week and atherosclerosis—the thickening of the blood vessels which is associated with cardiac disease and stroke.

Eggs are Cholesterol-rich

The yolk of eggs contains a little less than the total protein in the egg, and virtually all its fat and vitamins. A single egg yolk contains more than two-thirds the daily recommended amount of cholesterol. However, despite widespread measures to reduce cholesterol intake, eggs have not come under the scanner, because there has been no consensus on their effects on serum cholesterol. There has been prior research saying that eating up to one egg a day does not have any effect on heart disease, though eating even moderate quantities of eggs (6 a week) can increase chances of cardiovascular disease in diabetic patients.

A cross-section of a blood vessel (called the artery) showing fatty deposits leading to atherosclerosis. [Image Credit: fitnessavenue.net]

Fatty Deposits on Blood Vessels

Researchers at the University of Western Ontario studied Canadian participants who had been admitted to vascular prevention clinics and measured the area of the carotid plaque—the layer of fats and cholesterol deposits—using ultrasound. The higher the plaque area, the more blocked your blood vessels get. It’s akin to a cylindrical pipe with moss on its walls, slowly blocking water flow as the moss grows larger. They had data on long-term egg-consumption and smoking for 1231 patients. While no link was seen between cholesterol levels and egg yolk consumption, they did find that the carotid plaque area increased with increasing levels of yolk consumption.

The increase in carotid plaque area increases exponentially with both smoking and egg yolk consumption, as opposed to just linearly with age. “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.” said Dr. David Spence, who headed this study.

Further study has to be conducted taking into account factors like exercise and waist size which could also be significant factors that could affect the results. For instance, if a majority of the 1231 participants fell into the low-exercise category, then perhaps egg yolk consumption is harmful only in the absence of exercise. Moreover, this research was only conducted on people who already suffered from cardiovascular disease. We do not know if the same effects will be seen in a similar cohort of unaffected individuals. Cardiovascular disease is caused by a host of factors, and it is difficult to say how much of an effect one factor, like egg yolk,  alone can have. Until more conclusive evidence is found, however, you might want to think about r-egg-ulating the amount of eggs in your diet.

You can read about this research here.

 

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Author: Shweta Ramdas
Beginning life as a grad student studying human genetics.

Shweta Ramdas has written and can be contacted at shweta@techie-buzz.com.
  • S Young

    I was astounded that your author could read this study and reach the conclusions she has – or indeed that the authors of the study would wish us to accept. The study failed to demonstrate a causal link between the consumption of egg yolk and atherosclerosis. Your author makes the point that egg yolk is cholesterol rich and that high levels of cholesterol are directly related to the development of cartoid plaque which in simple terms leads to blocked arteries – one assumes that she is therefore postulating that it is the cholesterol in eggs that leads to an increased risk of atherosclerosis. Yet the data from the study actually indicated that cholesterol levels in participants, and in particular LDL, did not increase with increased egg consumption – in fact LDL levels were lower in participants with higher egg yolk consumption. So what is the causal factor – what is it in egg yolk that is causing increased cartoid plaque because it clearly isn’t the cholesterol. You could carry out a survey which indicated a statistical relationship between a persons height and their likelihood of being promoted to a managerial position but that doesn’t actually mean that the taller you are the more intelligent or competent you will be – otherwise the Harlem Globetrotters would control the world.

    There are so many flaws in this study, or should I say survey, it is frightening. This shouldn’t be surprising when you read the Conflict of Interest disclosures – “Dr Spence and Dr Davignon have received honoraria and speaker’s fees
    from several pharmaceutical companies manufacturing lipid-lowering
    drugs, and Dr Davignon has received support from Pfizer Canada for an
    annual atherosclerosis symposium; his research has been funded in part
    by Pfizer Canada, AstraZeneca Canada Inc and Merck Frosst Canada Ltd.“. The authors receive funding from pharmaceutical companies which sell cholesterol reducing drugs – they have a vested interest.

    • shweta

      Hi S.Young. I agree about the lack of a complete mechanistic link. All that has been found is a correlation. It is pertinent, however, that even a correlation is to be taken notice of, and used as a starting point for more thorough research. I did have a look at the data in this research- the sample size is decent, and the statistics quite clear. Going back to your example, if I did find that 80% of executive positions are held by tall people, I wouldn’t conclude that taller people are more intelligent, but I would question it being a random event. I would look for indirect connections, for instance, perceptions of tallness leading to a societal bias. It is, however, true that this study used no controls, and testing for egg yolks in such a population would be more conclusive. I have added that as an update to this article. Thanks for the comment.

  • J Elmore

    I agree with S Young; yet another flawed study on eggs. There are enough good studies on egg consumption to say that there are minimal effects on cardiovascular health. Indeed, eggs are one of the best things to eat and I am not talking about just one a day!

 
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