One more credible article on the yoke about egg yokes - Kock

The 2012 Atherosclerosis egg study: Plaque decreased as LDL increased with consumption of 2.3 eggs per week or more

 August 20, 2012 Ned Kock Health Correlator

A new study by David Spence and colleagues, published online in July 2012 in the journal Atherosclerosis ( 1), has been gaining increasing media attention (e.g., 2). The article is titled: “Egg yolk consumption and carotid plaque”. As the title implies, the study focuses on egg yolk consumption and its association with carotid artery plaque buildup.

The study argues that “regular consumption of egg yolk should be avoided by persons at risk of cardiovascular disease”. It hints at egg yolks being unhealthy in general, possibly even more so than cigarettes. Solid critiques have already been posted on blogs by Mark Sisson, Chris Masterjohn, and Zoe Harcombe ( 3, 4, 5), among others.

These critiques present valid arguments for why the key findings of the study cannot be accepted, especially the finding that eggs are more dangerous to one’s health than cigarettes. This post is a bit different. It uses the data reported in the study to show that it (the data) suggests that egg consumption is actually health-promoting.

I used the numbers in Table 2 of the article to conduct a test that is rarely if ever conducted in health studies – a moderating effect test. I left out the “egg-yolk years” variable used by the authors, and focused on weekly egg consumption (see Chris’s critique). My analysis, using WarpPLS ( 6), had to be done only visually, because using values from Table 2 meant that I had access only to data on a few variables organized in quintiles. That is, my analysis here using aggregate data is an N=5 analysis; a small sample indeed. The full-text article is not available publicly; Zoe was kind enough to include the data from Table 2 in her critique post.

Below is the model that I used for the moderating effect test. It allowed me to look into the effect that the variable EggsWk (number of eggs consumed per week) had on the association between LDL (LDL cholesterol) and Plaque (carotid plaque). This type of effect, namely a moderating effect, is confusing to many people, because it is essentially the effect that a variable has on the effect of another variable on a third. Still, being confusing does not mean being less important. I should note that this type of effect is similar to a type of conditional association tested via Bayesian statistics – if one eats more eggs, what is the association between having a high LDL cholesterol and plaque buildup?

You can see what is happening visually on the graph below. The plot on the left side is for low weekly egg consumption. In it, the association between LDL cholesterol and plaque is positive – eating fewer eggs, plaque and LDL increase together. The plot on the right side is for high weekly egg consumption. In this second plot, the association between LDL cholesterol and plaque is negative – eating more eggs, plaque decreases as LDL increases. And what is the inflection point? It is about 2.3 eggs per week.

So the “evil” particle, the LDL, is playing tricks with us; but thankfully the wonderful eggs come to the rescue, right? Well, it looks a bit like it, but maybe other foods would have a similar effect. In part because of the moderating effect discussed above, the multivariate association between LDL cholesterol and plaque was overall negative. This multivariate association was estimated controlling for the moderating effect of weekly egg consumption. You can see this on the plot below.

The highest amount of plaque is at the far left of the plot. It is associated with the lowest LDL cholesterol quintile. (So much for eggs causing plaque via LDL cholesterol eh!?) What is happening here? Maybe egg consumption above a certain level shifts the size of the LDL particles from small to large, making them harmless. (Saturated fat consumption, in the context of a nutritious diet in lean individuals, seems to have a similar effect.) Maybe eggs contain nutrients that promote overall health, leading LDL particles to "behave" and do what they are supposed to do. Maybe it is a combination of these and other effects.

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Reade the complete article here.

Are Eggs Really As Bad For Your Arteries as Cigarettes?

This past weekend, amidst all the Ancestral Health Symposium madness, I caught the headline while flicking through my phone for a few brief seconds. Didn’t open it up, though. Just cruised on past. I’d hoped to just forget about it, to ignore it, to banish it to the back of my mind where half truths and junk studies go to die. And truth be told, I pretty much had forgotten about it until I checked my email to find a ton of frantic emails from readers wondering if their beloved and dependable egg yolk breakfasts were killing them faster than the cigarettes they don’t smoke. What? You didn’t hear?

STUDY: EGG YOLKS ALMOST AS BAD AS SMOKING
Followed by (with less hysterical capitalization) “May increase carotid plaque build-up.”
So what are we looking at here?

We’re looking at a study in which a trio of researchers (two of whom with extensive ties to the statin industry) quizzed a group of middle-aged and elderly stroke patients about their lifelong egg intake and smoking history, making sure to stress the importance of accuracy and honesty in their answers. Yes, you heard me right: they expected people to remember every last egg they ever ate. Still, everyone in the study was assumed to have supernatural memory, so I guess it evens out.

Those who ate the most eggs were the oldest – almost 70 years old on average, compared to the relatively sprightly 55 year-old egg avoiders. It’s pretty well accepted that with age comes the progression of atherosclerosis, a process that takes, well, time to occur. Plaque doesn’t just snap into existence; it develops. All else being equal, the older you get, the more plaque you’ll have.

Those who ate the most eggs also smoked the most and were the most diabetic. To their credit, the authors tried to control for those factors, plus several others. Although they tried to control for sex, blood lipids, blood pressure, smoking, body weight index, and presence of diabetes, the study’s authors didn’t – couldn’t – account for all potentially confounding variables. In their own words, “more research should be done to take in possible confounders such as exercise and waist circumference.” Hmm. “Possible” confounders, eh?

Exercise reduces inflammatory markers of atherosclerosis.
Exercise even reduces markers of atherosclerosis in pre-pubertal obese children!
Exercise reduces thickness of the carotid arterial wall. It doesn’t get much clearer than that. Exercise is a massively confounding variable that the authors failed to take into account.

What about waist circumference?
A high waist circumference predicts atherosclerosis of the carotid artery.
Or how about stress, which also wasn’t considered?

Perceived daily psychological demands – the amount of crap you perceive to be heaped on your plate – are associated with progression of carotid arterial plaque.

Yeah, it’s not like the size of a person’s waist, whether or not they move of their own volition or sit in an easy chair all day, and how much stress they endure have any impact on their risk of developing atherosclerosis. Those things may be linked, and I’m sure the authors would have loved to include them in their analysis, but there just wasn’t enough space on the questionnaire. Besides, it’s not like a little physical activity and mediation could even undo the damage wrought by 4.68 sinful egg yolks per week. Why, that’s nearly a half dozen!

Seriously, though, the subjects were all stroke patients who’d lived to tell the tale. They’d been in contact with the medical community (you generally don’t just shake off a stroke without medical attention), who no doubt gave them the standard required advice to prevent another event, which includes “a reduction in saturated fat and cholesterol intake…and a boost in physical activity.” Since the egg-eaters obviously didn’t listen to their doctors’ recommendations to cut back on cholesterol intake, I’d wager they treated the exercise recommendations with similar levels of disdain. What do you think?

Here’s what I think: this is an observational study whose already limited worth depends entirely on the memory of an inherently fallible creature being infallible. As such, it cannot assign causality, contrary to what the media (“Egg Yolks Can Quicken Hardening of the Arteries“) and authors (“It has been known for a long time that a high cholesterol intake increases the risk of cardiovascular events”) say. Furthermore, why single out egg yolks? I mean, I get it – the authors sort of have a vendetta against eggs – but what about other foods? Were those even analyzed or asked about? What about the stuff that people generally eat with eggs, like pancakes and vegetable oils, or the foods that contain egg yolks, like baked goods and mayonnaise? For all we know, egg yolk intake could have been a marker for eating garbage; most people aren’t tossing raw yolks into post-workout shakes, gently poaching eggs with coconut vinegar, or horrifying co-workers with a bag full of hard-boiled eggs like we Primals are wont to do. They’re getting Grand Slams at Denny’s, eating bologna sandwiches with mayo on white bread, and overcooking scrambled eggs in canola oil until they’re rubber.

For fun, though, let’s look at what some other studies have found with regards to the artery-clogging capabilities of whole eggs:
Egg consumption and endothelial function: a randomized controlled crossover trial. Two eggs daily did not impair endothelial function (the flow of blood through the arteries), nor did it increase total or LDL cholesterol. Overall, eating two eggs a day elicited no change in cardiovascular health when compared to eating oatmeal (a cardiologist’s pride and joy).

Daily egg consumption in hyperlipidemic adults – effects on endothelial function and cardiovascular risk. In patients with high cholesterol, eating several hard-boiled eggs a day had no effect on endothelial function.

Effect of a high-saturated fat and no-starch diet on serum lipid subfractions in patients with documented atherosclerotic cardiovascular disease. Obese patients with heart disease ate lots of saturated fat, zero starch (including zero grains – sound familiar?), and tons of vegetables, and saw massive weight loss without any negative effects on their blood lipids. Once upon a time, I had access to the full study (it was freely available at the website for the Mayo Clinic, who’s since taken it down…wonder why), and I remember seeing that they ate three or four eggs a day. If egg yolks were bad for all heart disease patients, these guys would have felt the effects.

Okay, despite all those confounders and other egg studies that support yolks as harmless and the fact that this was merely an observational study without the power to assign causation and whose authors failed to even propose a potential mechanism of action, let’s entertain the notion that something was going on with this population of egg eaters. What if the egg yolks did have something to do with the atherosclerosis?

In a previous post on “Human Interference Factor,” I highlighted a study showing hens given an unnatural industry-standard diet high in omega-6 containing grains (soy and corn) produce less healthful eggs than hens on a more natural diet of grains lower in omega-6 with supplementary antioxidants. When subjects ate two of the soy/corn-fed eggs a day, which were high in omega-6 fats, their oxidized LDL levels were increased by 40%. Subjects who ate two of the other eggs each day, which were low in omega-6 fats, had normal levels of oxidized LDL (comparable to subjects in the control group, who consumed between two and four eggs a week). Since the oxidation of LDL particles is strongly hypothesized to be a crucial causative factor in atherosclerosis, it’s conceivable that eating normal, industrial eggs could have a negative effect on carotid plaque.

Anyway, what are the takeaways here?

Exercise, practice stress reduction, and get your waist circumference checked.

Don’t smoke.

Don’t age.

Don’t pay too much attention to ridiculous observational studies (this is part of stress reduction).

Oh, yeah – eat egg yolks, and lots of them.

Doubly so if you’re low-carb (remember the starch/grain-free high-egg diet referenced above). Make ‘em pastured, if possible, or at least from hens that ate something besides soy and corn. They’re more nutritious and probably “safer” than industrial eggs.

(In retrospect, that mention of the authors’ ties to the pharmaceutical industry was a low blow. After all, I myself am a direct benefactor of my local pastured egg industry; they pay me in delicious golden yolks.)


Read more: http://www.marksdailyapple.com/are-eggs-really-as-bad-for-your-arteries-as-cigarettes/#ixzz23d2RYCJv
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Read the complete article here.

Eggs and Atherosclerosis

Eggs and Atherosclerosis

Published by Steven Novella             Science-Based Medicine

The headline of a recent Los Angeles Times article is, “No yolk: eating the whole egg as dangerous as smoking?” The question mark is meant to convey uncertainty or surprise, or perhaps both. The article represents much of what is wrong with science and health reporting by mainstream media.
The news report is based upon an article published in Atherosclerosis – Egg yolk consumption and carotid plaque. The study is highly problematic in ways not explored at all in the LA Times article.
The researchers surveyed 1262 patients seen in a vascular prevention clinic, asking them about their egg consumption, smoking history, and other lifestyle factors. They created a measure known as “egg yolk years” – the number of egg yolks consumed on average per week times the number of years of consumption. They compared this to pack years of smoking – packs per day times number of years, a routing method of reporting smoking history.
Their conclusion:

“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.”

The LA times times used this as their money quote:

“We believe our study makes it imperative to reassess the role of egg yolks, and dietary cholesterol in general, as a risk factor for coronary heart disease,” the study authors write.

The authors feel the role of dietary cholesterol needs to be reassessed because current evidence does not support a significant role for dietary cholesterol in heart disease, but more on that below.
The weaknesses of this study include the fact that it is retrospective and based on survey data, which is notoriously inaccurate. Further, it is an observational study and therefore there are many confounding factors that are not controlled for. Perhaps people who eat more egg yolks also eat more bacon, or have a generally poorer diet, or don’t exercise as much. The authors acknowledge this in their last line about needed a prospective study that controls for possible confounding factors.
But the data in the study is even more problematic, in my opinion. The article itself is behind a paywall, but here is table two containing the key data.

A	B	C	D	E
Egg yolk years	<50 td="td">	50-110	110-150	150-200	>200
Age at first visit	55.70	57.97	56.82	64.55	69.77
Eggs per week	0.41	1.37	2.30	2.76	4.68
Total cholesterol	4.93	4.94	5.00	4.90	4.81
Triglycerides	1.88	1.84	1.96	1.94	1.85
HDL	1.34	1.33	1.33	1.29	1.35
LDL	2.76	2.75	2.81	2.73	2.67
BMI	27.62	27.42	28.71	27.00	26.31
Smoking (pack years)	14.14	14.37	16.57	13.88	17.00
Female	48.60%	51.70%	44.80%	45.00%	46.70%
Diabetic	11.80%	14.50%	11.80%	13.40%	14.60%
Plaque area (mm2)	101.45	110.35	113.58	135.76	175.77

The table does indeed show a significant increase in carotid plague, the build up of cholesterol on the inner lining of the main arteries that feed the brain, with increase in egg yolk years. There are significant confounders and contradictions in the data as well, however. The most glaring to me is that total cholesterol, triglycerides, HDL and LDL do not vary significantly across the egg yolk years columns. Apparently what the authors have shown (which is consistent with previous data) is that eating lots of eggs does not increase total cholesterol or bad cholesterol (LDL) nor does it decrease good cholesterol (HDL). In my mind this leaves the authors completely without a mechanism to explain a causal relationship between egg consumption and carotid plaque. This strongly suggests the association is not causal but is incidental or spurious – unless an alternate mechanism can be proposed and supported by evidence.

Further, egg yolk consumption was associated with increased age at first presentation (a known significant risk factor) and pack years of smoking (although inconsistently). The authors say that the association between egg yolks and carotid plaques remained significant even after adjusting for risk factors and for age. However, these associations suggest the probable existence of other factors not controlled for.

Overall the data are not very compelling. The lack of correlation with cholesterol is most damning, in my opinion.
The story of eggs, cholesterol, and vascular disease is actually a bit complex. Recent studies are all over the place in terms of correlations. This recent study, for example, shows that eating eggs increases HDL and improves the cholesterol profile. A recent review also concludes:
Egg intake has been shown to promote the formation of large LDL and HDL subclasses in addition to shifting individuals from the LDL pattern B to pattern A, which is less atherogenic. For these reasons, dietary recommendations aimed at restricting egg consumption should be taken with caution and not include all individuals. We need to acknowledge that diverse healthy populations experience no risk in developing coronary heart disease by increasing their intake of cholesterol but in contrast, they may have multiple beneficial effects by the inclusion of eggs in their regular diet.
Another study found no association between egg consumption and cholesterol or mortality in men but did find an increase for women. And yet another study finds an increased risk for vascular disease from high cholesterol and lipid diets in the older population, especially diabetics.
A 2001 BMJ systematic review of fat and cardiovascular disease concluded:

There is a small but potentially important reduction in cardiovascular risk with reduction or modification of dietary fat intake, seen particularly in trials of longer duration.

A 2012 review concluded:

The findings are suggestive of a small but potentially important reduction in cardiovascular risk on modification of dietary fat, but not reduction of total fat, in longer trials. Lifestyle advice to all those at risk of cardiovascular disease and to lower risk population groups, should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturates. The ideal type of unsaturated fat is unclear.

My conclusion is that the topic is very complicated and the current data is a bit unclear. There does seem to be a consistent signal in the research data that high LDL and triglycerides and low HDL are risk factors for vascular disease, especially when combined with other risk factors. Improving the lipid profile through diet, exercise, and medication are beneficial to vascular risk.

The dietary recommendations are a bit complex, though. Reducing total fat 1980s style is probably not a good idea, as the reduction in good cholesterol probably more than outweighs the reduction in bad cholesterol. Further, the dietary contribution to lipid profile for most people is probable mild (unless you have an extreme diet).

Overall, if you have a balanced diet and avoid extremes and exercise regularly you are probably OK. Further tweaking your diet is unlikely to produce large health benefits. If you are in a high risk group, such as diabetics, you need to be more specific about your eating habits, and should consult with your physician.

With respect to eggs specifically, it seems that moderate consumption of eggs are not a health risk and may even be beneficial. It is reasonable, based on the data, to avoid extreme high egg consumption – but you can probably say that about most things.

When it comes to diet the rule of thumb, everything in moderation, seems to be a good first approximation of the scientific data.
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Read the complete article here.