|"Not the yellow part of the egg!", is the literal translation of "Nicht das Gelbe vom Ei!", which is German and means "not exactly brilliant" - telling isn't it?|
Recipe for disaster? Take 20 men and women with metabolic syndrome, 5040 whole eggs...
With 40 men and women aged 30–70 years who had been classified with metabolic syndrome the researchers from the University of Connecticut and University of Antioquia in Medellin, Columbia, intentionally picked a representative sample from the ever-increasing number of people with metabolic syndrome for their 12-week dietary intervention trial. I mean, who if not the men and women in this high risk group should suffer from the negative side effects of the cholesterol-laden yellowy, orange-yellow heart killers in disguise?
The assumption that subjects with established metabolic syndrome (for the "official" criteria check out the table on the right) is however one of the very few things the study at hand and studies like the one that triggered such an upheaval in August (see Sciencedaily. 2012) have in common. Instead of relying on total, low density and high density lipoprotein levels in the sera of their study participants, Blesso et al. conducted a differential analysis that included paricle number, size (measured by nuclear magnetic resonance spectroscopy), apolipoproteins (apos), oxidized LDL (oxLDL), cholesteryl ester transfer protein (CETP) and lecithin-cholesterol acyltransferase (LCAT) activities at baseline and after 12-weeks on a carbohydrate-restricted diet (25%–30% energy) that contained either 3 regular whole eggs/day (EGG, n = 20) or the volume equivalent in form of a yolk-free egg substitute (manufactured by Sysco Corporation, Houston, TX).
AHA Definition of Metabolic syndrome
according to Grundy. 2004
|Abdominal obesity (waist)|
|Fasting glucose||≥110 mg/dL|
Accordingly, the subjects in the "real egg group" (EGG) consumed approximately 534 mg cholesterol, 0 g carbohydrate, 16 g protein, 12 g fat per day (186 kcal) from hole eggs, while a single serving of the cholesterol and fat-free substitute (SUB) contained approximately 2 g carbohydrate, 14 g protein, no fat, no cholesterol and only 60 kcal.
To minimize possible confounding factors and allow for "blinding" (you can't tell me you don't taste the difference between egg whites and whole eggs, but alas...), the eggs / egg supplements were prepared in advance.
"Compliance was monitored by use of weekly questionnaires and collection of empty product containers. Participants were asked to maintain their normal physical activity, medications, and dietary supplement usage upon starting the 12-week study." (Blesso. 2012)To be able to track the dietary intake of the subjects, all participants had to fill out 5-day dietary intake records (3 weekdays + 2 weekend days) at baseline, week 6 and week 12 of the study period. Based on the analysis of the respective data, the scientists determined that
- increased relative protein intake from 17.3%± 3.0% to 23.9%± 4.1%
- increased relative fat intake from 38.6%± 6.4% to 45.7%± 7.4%
- reduced total energy intake of -24% for all participants
- reduced relative CHO intake from 40.9 ± 7.4 to 28.3 ± 9.5% of total energy
- reduced absolute CHO intake from 211.9 ± 51.8 to 114.5 ± 55.0 g/d
- Δ cholesterol intake +106% in EGG vs. -38% in SUB
- Δ choline intake +52% in EGG vs. -12% in SUB
"So, the men and women in the egg-group did not die?"
Not exactly, no. Rather than being as bad as cigarettes (as the aforementioned "study" that was published roughly 2 months ago would make us believe; Spence. 2012), the consumption of three eggs per day lead to rather favorable changes in the lipoprofile of the EGG consumers:
|Figure 1: Lipoprotein serum levels (left), particle size and ratio of LDL to HDL count (right) of the 37 participants who completed the 12-week trial (data expressed relative to baseline; calculated based on Blesso. 2012)|
- triglycerides: -29% vs. -18%
- insulin: -21% vs. -14%
- HOMA-IR: -22% vs. -18%
The same goes for the increase in LCAT activity the researchers observed only in the EGG group. Since LCAT is critically important in facilitating HDL particle stability and HDL maturation, its elevation in the EGG group
"[...] could be indicative of an enhanced capacity for HDL maturation and may help explain the shift towards larger HDL particles seen with egg feeding" (Blesso. 2012; my emphasis)and would thus favor enhanced HDL-mediated reverse cholesterol transport from (e.g. the endothelium of your coronary heart arteries) back to the liver.
So what's the verdict? In conjunction with the aforementioned additive effects on glucose management and the slightly more pronounced decrease in oxidized LDL (both are probably rather a result of the -12% reduction in carbohydrate content of the participants' diets than the effect of the eggs), the statistically significant improvements in LCAT activity in the EGG eater group speak in favor of the notion that three whole eggs a day will still help you keep the doctor away. Whether they will suffice to throw his statins away, as well (see "Eat Whole Eggs All Day and Throw Your Statins Away?"), will yet have to be elucidated and appears overall questionable - and this goes regardless of whether you belong or don't belong to the relatively small subgroup of people who actually benefit from taking a statin, or not.
What about the lipid oxidation?If we assume that part of the negative effects that have been ascribed to the consumption of egg(-yolks) are brought about by oxidized fatty acids and respective byproducts, it appears wise not to hard-boil your eggs, because the prolonged heat exposure during hard-boiling increases the oxidation of fatty acids. Aside from temperature and duration of the heat exposure, Cortinas et al. also identified the fatty acid composition of the eggs and their vitamin E content as crucial factors that will influence the formation of oxidized lipids. Since the fatty acid composition of the eggs depends on the diet the hens are fed, you would be particularly ill-advised to hard-boil eggs from hens who were fed a diet enriched in fish oil.
What stands out of question, however, is that the "side effects" of three egg yolks per day are quite distinct from those of cigarettes, the consumption of which the headline of the aforementioned ScienceDaily.com article implicitly equates with "egg yolk consumption". And just like smoking and eating eggs are two very different pairs of shoes, there is a huge difference between this well-controlled trial, on the one hand, and the undifferentiated observational hokum that got Spence et al. so much media attention back in August, when they concluded "Our findings suggest that regular consumption of egg yolk should be avoided by persons at risk of cardiovascular disease." (Spence. 2012), on the other hand.
- Blesso CN, Andersen CJ, Barona J, Volek JS, Fernandez ML. Whole egg consumption improves lipoprotein profiles and insulin sensitivity to a greater extent than yolk-free egg substitute in individuals with metabolic syndrome. Metabolism. 2012 Sep 26.
- Cortinas L, Galobart J, Barroeta AC, Baucells MD, Grashorn MA. Change in α-tocopherol contents, lipid oxidation and fatty acid profile in eggs enriched with linolenic acid or very long-chain ω3 polyunsaturated fatty acids after different processing methods. J. Sci. Food Agric. 2003; 83: 820–829.
- Grundy SM, Brewer HB Jr, Cleeman JI, Smith SC Jr, Lenfant C; American Heart Association; National Heart, Lung, and Blood Institute. Definition of metabolic syndrome: Report of the National Heart, Lung, and Blood Institute/American Heart Association conference on scientific issues related to definition. Circulation. 2004 Jan 27;109(3):433-8.
- ScienceDaily. Egg yolk consumption almost as bad as smoking when it comes to atherosclerosis, study suggests. August 13, 2012 < http://www.sciencedaily.com /releases/2012/08/120813155640.htm > accessed on October 03, 2012.
- Spence JD, Jenkins DJ, Davignon J. Egg yolk consumption and carotid plaque. Atherosclerosis. 2012 Oct;224(2):469-73.