This was posted at sciencedaily the other day. Thoughts?
http://www.sciencedaily.com/releases/2012/08/120813155640.htm ScienceDaily (Aug. 13, 2012) — Newly published research led by Western's Dr. David Spence shows that eating egg yolks accelerates atherosclerosis in a manner similar to smoking cigarettes.
Surveying more than 1200 patients, Spence found regular consumption of egg yolks is about two-thirds as bad as smoking when it comes to increased build-up of carotid plaque, a risk factor for stroke and heart attack. The research is published online in the journal Atherosclerosis.
Atherosclerosis, also called coronary artery disease, is a disorder of the arteries where plaques, aggravated by cholesterol, form on the inner arterial wall. Plaque rupture is the usual cause of most heart attacks and many strokes.
The study looked at data from 1,231 men and women, with a mean age of 61.5, who were patients attending vascular prevention clinics at London Health Sciences Centre's University Hospital. Ultrasound was used to establish a measurement of total plaque area and questionnaires were filled out regarding their lifestyle and medications including pack-years of smoking (number of packs per day of cigarettes times the number of years), and the number of egg yolks consumed per week times the number of years consumed (egg yolk-years).
The researchers found carotid plaque area increased linearly with age after age 40, but increased exponentially with pack-years of smoking and egg yolk-years. In other words, compared to age, both tobacco smoking and egg yolk consumption accelerate atherosclerosis. The study also found those eating three or more yolks a week had significantly more plaque area than those who ate two or fewer yolks per week.
"The mantra 'eggs can be part of a healthy diet for healthy people' has confused the issue. It has been known for a long time that a high cholesterol intake increases the risk of cardiovascular events, and egg yolks have a very high cholesterol content. In diabetics, an egg a day increases coronary risk by two to five-fold," said Spence, a professor of Neurology at Western's Schulich School of Medicine & Dentistry and the director of its Stroke Prevention and Atherosclerosis Research Centre at the Robarts Research Institute.
"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. In the long haul, egg yolks are not okay for most Canadians."
Spence added the effect of egg yolk consumption over time on increasing the amount of plaque in the arteries was independent of sex, cholesterol, blood pressure, smoking, body mass index and diabetes. And while he says more research should be done to take in possible confounders such as exercise and waist circumference, he stresses that regular consumption of egg yolk should be avoided by persons at risk of cardiovascular disease.
Egg yolk consumption and carotid plaque
Background Increasingly the potential harm from high cholesterol intake, and specifically from egg yolks, is considered insignificant. We therefore assessed total plaque area (TPA) in patients attending Canadian vascular prevention clinics to determine if the atherosclerosis burden, as a marker of arterial damage, was related to egg intake. To provide perspective on the magnitude of the effect, we also analysed the effect of smoking (pack-years).
Methods Consecutive patients attending vascular prevention clinics at University Hospital had baseline measurement of TPA by duplex ultrasound, and filled out questionnaires regarding their lifestyle and medications, including pack-years of smoking, and the number of egg yolks consumed per week times the number of years consumed (egg-yolk years).
Results Data were available in 1262 patients; mean (SD) age was 61.5 (14.8) years; 47% were women. Carotid plaque area increased linearly with age after age 40, but increased exponentially with pack-years of smoking and with egg-yolk years. Plaque area in patients consuming <2 eggs per week (n = 388) was 125 ± 129 mm2, versus 132 ± 142 mm2 in those consuming 3 or more eggs per week (n = 603); (p < 0.0001 after adjustment for age). In multiple regression, egg-yolk years remained significant after adjusting for coronary risk factors.
Interpretation Our findings suggest that regular consumption of egg yolk should be avoided by persons at risk of cardiovascular disease. This hypothesis should be tested in a prospective study with more detailed information about diet, and other possible confounders such as exercise and waist circumference.
"It has been known for a long time that a high cholesterol intake increases the risk of cardiovascular events"
I'm a PhD student at NC State studying diet and genetics.
I just broke down this study and exposed it's shortcomings. Check it out on my blog: http://understandnutrition.blogspot.com/
Epidemiology. Food frequency questionaires. Need I say more? Yes, this is a biased crap study.
We live in a society that thinks eggs are bad for you - especially the yolks. Are people who eat a lot of egg yolks the type of people to be concerned about health? Possibly not. Maybe they are the type of people to eat a lot of other crap as well. I can pretty much guarantee that nobody in that study was eating anywhere near paleo.
Chris Masterjohn knows a crapload about cholesterol and heart disease. For anyone who hasn't crawled out from under a internet rock, he is getting a PhD in cholesterol biochemistry. Chris says eggs are good eatin'. Especially the yolks. That's good enough for me.
Mark Sisson just did a robust takedown of this study. Thought I should add the link:
My thoughts are study = correlation.
You know what else is a correlation. Rain dances. Dance + rain = dancing causes rain. In psychology we refer to that as superstition. When people dont understand things, or cant control them, they tend to rely on it, instead of reason.
I thought had already been established that dietary cholesterol doesnt turn into blood cholesterol, tho? (Am I right?)
Either way, there needs to be some proposed mechanism via which the LDL becomes oxidised, produces plaque etc. Without a mechanistic explaination, all the mainstream heart disease talk is hot air. Just having lots of LDL, when normal LDL itself doesnt cause artery plaque, isnt a satifactory glossing over of the facts.
When the mainstream view delivers a satifactory mechanistic explaination for all these assertions about the dangers of high LDL, and the "protective effects" of HDL regarding the still not well understood phenomena of heart disease, I might start listening to their ramblings. Once they have a full and total explaination ie "a hypothesis" they can test it in animal studies.
Until then its a bit like alchemy, or brain drilling, or measuring the width of your skull etc...
I would really love to "prove" a stastical link between umbrellas and lung cancer or something weird, just to freak people out :P
Its reasonably , sorta clear heart disease has some strong association with small dense LDL, which as an explaination makes some sense. If you add to that picture the clear and obvious factor of inflammation, which increase with stress, and you have yourself a semi-decent sounding theory - IMO.
Ie - high carbs & sugars + low fat + lots a stress etc = small dense LDL pinging thru your artery wall ie heart disease (Add in lots o-6 oils because they are inflammatory, and a lack of o-3 from salmon and grassfed meats)
People do seem to get heart attacks when they are stressed. And theres no doubt that people are getting them more now people eat less fat, more sugar, more carbs and more vegetable oil just like these stupid people told them to.
Not that I eat alot of eggs these days, I am currently restricting iodine. Egg yolks are pretty high in iodine.
And men who shave live longer. (But shaving has nothing to do with it -- it's the kind of person who shaves versus the kind of person who doesn't)
And women who took hormone replacement therapy in the 80s had 40% fewer heart attacks, controlling for age, smoking, etc. (But in double-blind experiments in the 90s, hormone replacement therapy lead to an increase in heart attacks. Apparently the kind of woman who got therapy was the kind of woman who otherwise took care of herself, and so the net result was greater health, even though the therapy itself was harmful to cardiovascular health.)
And your odds of drowning are much higher if you've eaten ice cream in the last 24 hours. (Summertime!)
Correlation is not causation. I'm not saying eggs aren't bad for you, just that this study doesn't prove it. It could well be that people who eat eggs are people who otherwise tend to ignore doctor's advice and participate in unhealthful activities. Or maybe eggs tend to be cooked in unhealthful oils. Or maybe eggs are unhealthful. Now that this intriguing question has been raised, hopefully these researchers will follow up with a study that can give more definitive results.
I think you could add this study to these other very convincing examples of correlation and causation:
"Is this Mountain Range Affecting the Murder Rate?"
I guarantee people who eat egg whites instead of whole eggs aren't sitting on the couch all Sunday downing wings, bread, beer, and watching football...
people eat egg whites because they think they're more healthy. These people are much more likely to get their asses off the couch. Same with whole grains...If you eat whole grains instead of white bread chances are you give a shit and have an overall healthy lifestyle.
This should become an FAQ about reading reportage of studies of food and disease: if the report doesn't tell us What did they eat?, we cannot even draw correlations, never mind infering causation. When I say What did they eat?, I mean everything. just saying someone ate 3 egg yolks tells us almost nothing meaningful. And there is more to health than diet. They tell us some people smoked, but what else do they know about the health and habits of the respondents?
So, what about all the other foods they ate besides the eggs? Most people eating a standard American diet eat eggs as part of breakfast. American breakfast usually or often includes bread, biscuits, pancakes, waffles, pastries, or other cereals. Did the study separate those who ate eggs without the cereals from those who ate both? What about vegetable oils?
Another thing about these studies is that they rely on questionnaires. Can you remember what you ate (including portion size) a week ago? How about a month? A year ago? Do you remember with enough detail and accuracy that you would make important decisions based on those data? Yeah--me either. Unless people could a) be trusted not to fib; b) to log all their food during the study; and c) the researchers accounted for all confounders, including the other foods, then we cannot derive conclusions from this.
Also, the researcher quoted who said "What we have shown...." is full of shit and should go back to school to re-learn how studies work. At the very least, he should read the Wikipedia entry on epidemiological studies.