Eggs as Bad as Smoking for Your Heart? No Way Jose!!!!

“Eggs are as Bad as Smoking for Heart Health: A Case Study of Bad Science and Media Propoganda”

Today’s post is a bit of a long one, I apologize for the lack of brevity as I know your time is precious; however, this is an area I am extremely passionate about and just want to provide you all with the best possible information and avoid the “trap” of mass media.

 One of the big issues surrounding health, fitness and nutrition is the poor dissemination of information.  A few weeks ago I came across an article online that claimed “egg yolks almost as bad as smoking”1 and nearly fell out of my chair.  So as an exercise science/ physiology nerd I had to do a little digging. Even though it was published in reputable periodicals, there was no way this could be true…. could it?

The article referred to the findings of a recent study comparing egg yolk intake vs. cigarette smoking and its effect on carotid plaque2.  To the lay person, this article is convincing; it contains medical terminology, great looking figures, tables, and the most feared word in American society when it comes to heart disease “cholesterol”.  However, a dissection of the meat and bones of the research: the methodology, results, and analysis, leaves me unconvinced.

Let’s tackle the methodology first, as the methods drive the results and the extent to which the researchers can draw conclusions.  The design of this study is retrospective, meaning it is looking backward in time, it is also an observational study.  These types of designs limit the findings in that they are able to show correlation. Now correlation is not causation.  This is an extremely important point and will be developed further on in the post.  Observational and retrospective studies are also extremely susceptible to confounding variables, meaning it is almost impossible to isolate the individual variables the researchers are looking for; this study is no different, there are a copious confounding variables present.

Before we tackle the confounding variables, I want to address their methods of subject selection and data collection.  The study chose to only select patients with pre-existing cardiovascular disease; thus, there was no control group in which the data could be compared to. Essentially, almost any variable they chose could then be construed as a “risk factor” for heart disease. To collect the data the researchers used recall, this is highly problematic, especially over the span of decades. (I don’t know about you but I can’t remember what I ate 4 days ago, let alone 5 years). Recall bias is highly pervasive and a limitation present in this study.

 This study failed to control for quite a few variables, all of which can have substantial implications for cardiovascular disease. First off, there was no dietary control.  We do not know if the individuals had high carbohydrate diets, diets high in processed foods, what their omega-3 to omega-6 ratio was, or even their alcohol consumption (All of these factors have been shown to be associate with CVD in the literature and can be a topic all in and of themselves).  The researchers also failed to control for exercise. Their last big faux pas was their failure to separate or distinguish whether those who were considered high smokers were also high egg users.

Ok, so methodology was not as sound as you would like a study to be when conducting scientific research you want scrutinized by peers, but hey, their results were pretty profound….. right?  In short, my answer would be “no”. 

Where to start with the results…. I guess we can start with the beautiful little table they put together (Table 2 for those of you who pulled up the article).  The study found absolutely no difference between the amount of egg yolks consumed and the following variables: 1) total cholesterol, 2) triglycerides, 3) HDL cholesterol, and 4) LDL cholesterol.  Their results also revealed no association between cholesterol and plaque growth (wasn’t that the whole impetus behind their hypothesis “dietary cholesterol can lead to plaque buildup”).  The finding that cholesterol was not associate with plaque growth, then the development of the plaque must have been by some other mechanism. However, they did show that plaque increased with age (again see Table 2 if you pulled up the article), which is believed to be a common occurrence in humans.

Now we can return to the issue of correlation and causation*.  It is tempting to think because there is a relationship between two things that one causes the other.  This is a common misconception and one that, more often than not, turns out to be wrong.  Consider the following famous example.

“I tend to carry an umbrella when it rains, so umbrella and rain are correlated. However, it would be unreasonable to say that my carrying the umbrella caused it to rain.”

I am not an expert on cardiovascular disease, in fact, far from it. There may come a time when we have irrefutable proof that eggs do indeed have negative impact on our health, but this study is not that.  

Scientific analysis aside, I would still find it hard to believe that a food as wholesome as the egg (it has high-quality protein, lutein, choline, and is chalk full of essential vitamins and minerals) would be as deleterious to my heart as smoking.  In fact, my breakfast tomorrow is going to consist of fried eggs and roasted squash; however, I don’t think I will be adding a cigarette into the mix.  

Plus, here is a shameless plug for some of my favorite websites.

PaleoOMG Egg Recipes

Health-Bent Egg Recipes

New Paleo Solution Podcast Every Tuesday. Great Content, Great Entertainment (At least for us nerdy people)

*Nowhere in the article did the authors indicate causation, I just wanted to make this point clear because it is a common misconception to many people (including myself prior to a good shellacking by scientists as a young graduate student

1   http://articles.nydailynews.com/2012-08-17/news/33252380_1_yolks-hollandaise-spence

http://www.atherosclerosis-journal.com/article/S0021-9150%2812%2900504-7/fulltext

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