Saturday, February 4, 2012

Eat Whole Eggs All Day and Throw Your Statins Away? 375x Increased Dietary Cholesterol Intake From Eggs Reduces Visceral Fat & Promotes Healthy Cholesterol Metabolism

Image 1: You better make sure you don't miss out on these delicious heart- and brain-healthy cholesterol bombs.
Most of you will probably be familiar with the good old saying "An apple a day, keeps the doctor away!", right? And if you are an otherwise healthy individual the micronutrients from the apple will probably really help you maintain this status. But what if the doctor was already there to put you on the healthy low fat diet, the negative health consequences of which I have addressed in yesterday's blogpost? In that case, whole eggs probably provide a more promising escape route from that low-fat, high-carb trap - at least this is what the the results of a soon to be published study from the Huazhong Agricultural University in Wuhan, China would suggest (Yang. 2012).

Surprising(?) -9% belly-fat reduction on whole egg diet

In their 60 to 90 day experiment, the Chinese researchers put a group of 8-week old Sprague-Dawley rats (n=18 for each group) on dietary regimen which differed in either cholesterol content (control vs. experimental groups) or the source of dietary cholesterol, i.e. 17.5% lard + synthetic cholesterol, 31.25% freeze dried egg yolk or 55.56% whole egg powder.
Figure 1: Composition of the control and the three experimental diets (adapted from Yang. 2012)
If you take a closer look at the exact composition of the diets in figure 1 the you will probably notice that macronutrient-wise the three standard-chow + lard/yolk/whole egg "high cholesterol" diets are miles-apart from what the average "low carber" would consider a healthy high fat diet. Still, the idea of choosing whole eggs as a major constituent (>55%) of one's diet should ring a bell for everyone who is familiar with the practical realization of the so-called "induction phase" of the purportedly (from the perspective of the same people who recommend the purportedly "heart-healthy low-fat diet") artery-clogging Atkins diet.
Figure 2: Body weight gain, food intake, food efficiency (food intake / weight gain) and relative visceral fat weight (per body weight) in Sprague Dawley rats after 60 and 90 days on experimental diets; data expressed relative to control group on standard rodent chow (data calculated based on Yang. 2012)
Interestingly, the data in figure 2 shows that even this version of "Atkins gone wrong", with a 40% carbohydrate content in the whole egg group (cf. figure 1) lead to significant reductions in weight gain and food efficiency (weight gain per gram of chow) and, more importantly, produced statistically significant reductions in the visceral fat / total body weight ratio at the end of the 90day study period (at 60 days there were no statistical significant inter-group differences).

55.56% whole egg diet kickstarts healthy cholesterol metabolism

In view of the fact that it has never been the notion that eggs would make you fat, but rather their purported negative effect on cholesterol levels due to which eggs, in general, and yolks, in particular, have gotten a bad rep over the last years, I guess that the visceral fat argument, alone, won't suffice to convince the egg-white consumer that they are missing out on the best part of the egg. After all, it was and unfortunately still is their purported negative effect on cholesterol that is literally at the heart of the egg(yolk)-scare.
Figure 3: Triglyceride, total, low density (LDL) and high desnity (HDL) cholesterol in Sprague Dawley rats after 60 and 90 days on experimental diets; data expressed relative to control group on standard rodent chow (data calculated based on Yang. 2012)
If you do yet take a look at the actual effects the natural cholesterol from the egg-containing diets had on the blood lipids of the rodents (cf figure 3), you will notice that those were statistically non-existent. In other words, only the lard + synthetic cholesterol diet had a statistically significant negative impact on the plasma lipids of the rats.
Figure 4: mRNA expression of hydroxymethylglutaryl CoA reductase (HMG-CoA R), LDL receptor (LDL-r), cholesterol 7a -hydroxylase (CYP71A), acyl-CoA:cholesterol acyltransferase (ACAT) lecithin cholesterol acyltransferase (LCAT) expressed relative to control (data adapted from Yang. 2012)
The 375x higher dietary cholesterol intake in the egg-groups, on the other hand, did not only shut down the endogenous cholesterol synthesis, as evidenced by the reduction in hydroxymethylglutaryl CoA reductase expression (HMG-CoA R, cf. figure 4) and increase its metabolization into bile acid via cholesterol 7a -hydroxylase (CYP71A), it also increased the LDL receptor expression in the liver (lack of LDL-r expression in the brain is associated with increased plaque formation in Alzheimer's, cf. Katsouri. 2011), lowered the formation and storage of cholesterol esterified cholesterol in the tissue by reducing acyl-CoA:cholesterol acyltransferase (ACAT) and increased the maturation of HDL and peripheral tissue cholesterol efflux via increased lecithin cholesterol acyltransferase (LCAT) expression.
In case you doubt that this rodent data has any significance for human beings, I just want to remind you that a 2008 study by Mayurasakorn et al., which found that "[i]n the majority of healthy adults" the addition of one egg per day to a "normal fat diet" lead to increases in HDL-c and decreases of the total cholesterol to HDL ratio (Mayurasakorn. 2008). Their conclusion that "egg consumption might benefit blood cholesterol" was however similarly ignored as the absence of scientific data to support the "eggs = increased risk of heart disease"-myth.
It is thusly not surprising that the Chinese scientists conclude that contrary to the "conventional approach to weight reduction", of which the scientists state that it is "a high-carbohydrate, low-fat, energy-deficient diet" that "has not proven to be very effective for many obese and over-weight individuals [I am not making that up, it is the exact wording from the study ;-]", an "egg diet", which "theoretically [...] would be more likely to cause obesity", could not only help those individuals finally shed unhealthy visceral fat, it could also lead to significant improvements in their lipid metabolism. If it were not for the statement that
[...] the mechanisms by which an egg diet lowers plasma cholesterol need to be further characterized and the special functional factors in egg need to be identified
one could be led to believe that Yang et al. had finally grasped the notion that just eating the right (whole) foods could solve the problem... the term "functional factors" does yet tell me that they are probably just trying to developing an "egg in a pill" that will soon be patented and sold as an adjunct to the standard statin therapy,