Monday, December 29, 2014

Is the Egg Industry Fooling Us Into Thinking Eggs Are Healthy? A Review of a Study On Eggs and Cholesterol Levels and Weight

Some scientific studies have shown eggs aren't harmful for your heart.  But is that the truth, or are these studies fundamentally flawed?  Here's a brief look at today's research review.

  • The study under review today claims that eating eggs does not affect cholesterol levels in the body, but the researchers tested cholesterol levels after a 10-hour fast.
  • Participants who ate eggs in the study for just three months showed modest rises in fasted cholesterol levels, though not enough of a change to be considered statistically significant.
  • The researchers had almost no control over the subjects' diets, making it practically impossible to draw conclusions from the data collected.
  • This study uses other poorly designed scientific experiments as citations for its hypothesis, building further upon already flawed research.  
  • Unsurprisingly, this study was funded by the American Egg Board.

For a long time, I thought eggs were a nutritious food.  They have lots of choline, a decent amount of protein, and a moderate amount of calories.  Eggs are generally cheap, filling and tasty to boot, which made them a main stay in my breakfast meal for most of my life.

But are they really that nutritious?  I've changed my mind about eggs being healthy, due to a large variety of research I've been reading over the past few weeks.

A lot of the evidence against eggs has been revealed to me by the fantastic work of Dr. Michael Greger, the creator of  I don't want to plagarize his work, so I will post a few links to my favorite egg "debunking" videos here so you can check out his research for yourself:

There are more videos on that go into further detail about the science behind food and health, with tons of scientific literature to support his claims.  If you haven't yet visited his site, I strongly urge you to check it out.  Dr. Greger really knows his nutrition.

But today, I am going to do my own review on recent scientific study investigating the effects of a breakfast with eggs on the weight and cholesterol levels of freshman college students.  Just like Dr. Greger does in his video about misleading studies on eggs, I will show you that the data does not line up with the researcher's conclusions.

The Study Under Scrutiny

The specific study I am reviewing today is titled "Impact of Breakfasts (with or without Eggs) on Body Weight Regulation and Blood Lipids Over a 14-Week Semester" which was conducted by Janice M. Rueda and Pramod Khosla at Wayne State University in Detroit, Michigan.  The researchers attempted to discern the health effects of adding eggs to college students' breakfast meals for a little over three months.

One objective of this study was to find out if including eggs at breakfast would lead to greater satiety and reduced caloric intake versus not eating eggs, based off of results of a different study that claims "subjects lost 65% more weight by eating breakfast with eggs instead of a bagel."  Sounds good, but they neglected to mention that, in that particular study, both egg- and bagel-eaters only lost a tiny amount of weight (about 5 lbs and 2 lbs, respectively) despite the 1000-calorie deficit diet they were "suggested" to follow.  Because the researchers only suggested, and did not strictly enforce, this diet protocol, we cannot conclude that eating eggs was the principle cause of greater weight loss in that group.  Additionally, a three pound difference in weight loss between two groups of overweight/obese subjects is hardly worth mentioning, despite the impressive-sounding "65% more weight loss" figure mentioned in the study results.  See the graphs below:

Did overweight egg eaters really lose that much more weight than overweight bagel eaters?  "65% more weight loss" amounts to about 2.5 lbs in this study.  The 65% figure just sounds so much better...

So this study is being partly-based on the results of another study that is of questionable design and quality.

The researchers also wanted to determine what effect, if any, eggs would have on cholesterol levels.  They cite a prospective study on eggs and cardiovascular risk (concluded increase CVD risk in egg-eating diabetics, but not in healthy individuals), a six week study comparing eggs vs. oatmeal on cholesterol levels (concluded that oatmeal, but not eggs, lowered high cholesterol levels), and a study that claims high cholesterol levels may increase a "subclass" of LDL particles which are less damaging to the heart.

The authors of the study currently under review use these papers as evidence that eggs do not adversely affect cholesterol levels, but if one actually looks at those cited studies more closely, it appears that they are actually refuting what they are supposed to be supporting.

In the first study mentioned, the researchers looked at data from several observational studies and concluded that up to one egg per day does not significantly increase risk of CVD in healthy people, but it may increase the risk for diabetics.  So as long as you are not a diabetic, you can eat at least an egg per week, right?  Not exactly.  Several other studies have looked at the relationship between egg consumption and the risk of developing diabetes, and they all conclude that eating eggs may increase risk for that disease, too!  
Some of the scientific literature like these studies suggest that eating eggs will lead to diabetes, which in turn, will lead to cardiovascular disease.  Not the best citation to start off with.  

If you are trying to lower your cholesterol, eat oatmeal... not eggs.

The second study cited compared oatmeal to eggs on cholesterol levels and concluded that eggs did not have an effect on cholesterol levels.  What they left out of the conclusion is that once oats were substituted for eggs, the participants actually lowered their total cholesterol, as well as LDL cholesterol (the undesirable cholesterol particle).  Well, so what?  Maybe oats are just better for us than eggs, but that doesn't make eggs necessarily bad, right?  This is where the egg studies can be quite misleading.  Going back to the excellent work by Dr. Greger, he points out in his video Eggs and Arterial Function that studies on eggs and cholesterol levels sometimes use participants with higher-than-average cholesterol levels to begin with.  This makes the final results seem less dramatic compared to baseline.  Dr Greger puts it best:

"If you threw a lit match into a flaming pool of gasoline and saw no real difference in the height of the flames, you can’t conclude that throwing lit matches into gasoline is not a fire hazard, but that’s what the egg board study concluded. When the addition of eggs didn’t make the arterial function worse than it already was, they concluded that short-term egg consumption does not adversely affect endothelial function in healthy adults."

And in this particular study, the participants started with a borderline high total cholesterol (203 mg/dL).  After just six weeks of eating two eggs per day, the egg group's total and LDL cholesterol actually got worse (203 to 205 and 124 to 129 mg/dL, respectively).  The researchers downplayed these results by saying that the increase was not statistically significant.  This is not to mention they conveniently left out that once the participants switched to eating oats, their cholesterol levels declined into "ideal" levels (according to the Mayo Clinic's website on cholesterol levels).  That's how they made this cited source appear like eggs are not detrimental to heart health.  Delving deeper into the research shows a very different picture from their published conclusions.

Finally, we have the last cited study which reports that higher intakes of dietary cholesterol increase the so-called good "large subparticle LDL," which is supposedly protective against CVD compared to the small subparticle LDL.  In reality, BOTH of the LDL subparticles are bad... one is just worse than the other.  This study published in Circulation in 2009 concluded that it would be pointless to recommend one type of LDL subparticle over another, since "essentially... no improvement was found [compared] to a model that already included the total/HDL cholesterol ratio."

The researchers of the paper under review here today seem determined to challenge the idea that eggs may not be good for heart health, due to the high cholesterol content.  They cherry-pick bits of their cited literature, leaving out important details of the studies, or they just neglect to mention other studies that refute the ones they use as reference.  Just a little bit of research on my part shows that literature that the authors of this paper cite only loosely supports their hypothesis, if it even supports it at all.

Careful examination of the research can sometimes refute (or debunk) the author's conclusions.
 So enough picking apart the literature they cited... let's move on to the study's design and results.

The Experiment

Basically, the researchers recruited 73 college freshman to either eat a breakfast with eggs, or a breakfast with no eggs, at the campus cafeteria.  Either group was instructed to eat breakfast at least five days out of the week, for a little over three months.  The egg group was required to consume at least two whole eggs when they ate breakfast, while the non-egg group obviously avoided eggs.  Other than that, the test subjects could eat whatever they wanted, in any amount they wanted.

The researchers did not attempt to control any other aspect of the diet after breakfast, so the participants just ate whatever they normally would throughout the rest of the day.  This is my first, and probably biggest, gripe with this study.  They had no level of control over the subjects' egg consumption, or overall food consumption, past breakfast.  If the non-egg breakfast eating group consumed eggs later in the day, doesn't that kind of negate the whole point of excluding them at breakfast?

Furthermore, there is no mention of caloric intake control for either of the groups... after breakfast, either group just ate whatever they wanted.  It's pretty commonly accepted that weight gain is a risk factor for heart disease.  That is a huge confounder in this study, as it makes it impossible to determine if any changes in cholesterol levels were due to egg exclusion or change in weight.  Just in case you were wondering, over half of the study's participants gained weight at the end of it.

So they only controlled egg consumption at breakfast, and they had no control over caloric intake at any point.  Are there any other badly designed elements of this study?  Well, they attempted to at least figure out how many calories each subject was consuming by having them complete food diaries.  While this might seem better than doing nothing at all, about 2/3 of the subjects neglected to complete said food diaries!  How can you extrapolate information when you are missing 66% of the data that needed to be collected?

A badly designed study is not the final word on eggs and health.

Just to throw another wrench in the gears, the researchers decided to check the cholesterol levels of the subjects after having fasted for 8+ hours.  If you watched Dr. Greger's video that I linked at the top of this article (How the Egg Board Designs Misleading Studies), you'll know that testing fasted plasma lipids is a somewhat pointless practice in regards testing to the effects of dietary cholesterol.  The subjects spent most of their waking hours in a fed state, regardless of egg intake, so why did the researchers only test the plasma lipids levels after instructing the subjects to stop eating after 10 PM?  It's how they kept cholesterol levels from looking too much worse from one end point to the next, before the participants were subjected to any dietary cholesterol influence from food.

After using such terrible methodology and design, it seems like the results of this study would be pretty arbitrary and meaningless.  Nevertheless, let's take a look at what the researchers discovered from the data.

The Results

Out of the 73 subjects who began the study, only 57 completed it to the end.  The researchers found no significant difference between groups other than BMI and body weight.  Average weight gain of all the subjects in the study was about 1.5 lbs.  The researchers go on to say that adding breakfast, either with or without eggs, didn't seem to affect weight changes or BMI.  But given that the participants were allowed to eat whatever they wanted in any amount, how can they be certain of this conclusion?  Their claim is particularly dubious, given that 2/3 of the subjects didn't turn in food diaries.  I'm not trying to argue for or against eating breakfast; I just think that given the huge lack of data and no control over anything, the authors of this paper can't really make any claims.

Let's take a look at some of the data they DID manage to collect.  First up, let's look at the cholesterol levels of both groups at the beginning and end of this study.

The researchers state that there were no significant difference on plasma lipid levels at any point between either group. Take a closer look at the EB columns in the chart, though.  There is a clear trend of increasing total cholesterol, LDL cholesterol, and triglycerides in the egg-eating group over the course of the study.  Their HDL cholesterol also went up slightly, but probably not enough to warrant a rise in all the other risk factors.

By the end of the study, every subject's cholesterol had worsened, regardless of egg consumption.

In the non-egg eating group, whose participants seemed to have started off with slightly worse baseline risks for CVD than the egg group, appeared to keep their cholesterol levels relatively stable, until right around the end of the study.  At that point, their cholesterol levels are almost comparable to egg group!  If eggs seemed to worsen the egg-eating group's cholesterol levels, but this group did not eat eggs, why did their cholesterol levels shoot up?  Again, back to the issue of having no control over food intake. It could have been that the non-egg group was actually consuming eggs (or some other food with higher dietary cholesterol) later in the day, especially near the end of study.  At week 3, the non-egg eaters were only consuming about 154 mg of dietary cholesterol per day.  By week 14, they were consuming 254 mg per day.

As far as the weight control effect supposedly attributed to eating eggs, the researchers themselves state that "There was no significant interaction effect seen for time and breakfast intervention type on either weight or percentage body fat."  Well, there goes that theory.  I mean, it's still possible that eggs could help control weight.... but to find that out, we would have to have a study where the researchers actually controlled egg consumption between groups.

Conclusion, Acknowledgements and Conflicts of Interest

At the end of the day, the authors of this paper claim that "cholesterol content of eggs does not adversely affect plasma lipids in this free-living population of young, healthy adults."

Bullshit.  Just look at the data... it clearly shows an increase in cholesterol levels.  I'm not really sure how they can conclude this, given that even I can see an obvious increase in total cholesterol, LDL, and triglycerides in the egg-eating group over the course of three months.  And that is taking FASTED plasma lipid levels.

This study is clearly trying deceive people on the effects of dietary cholesterol in eggs.  To make such a bold claim when the study only controlled a single variable out of several critical confounders is borderline fraud.

But there's still one very important detail that is easy to miss in their acknowledgements section:

"The study was supported in part by a grant from the American Egg Board."

Funded by the egg board... the most influential group of people for the promotion and consumption of eggs.  I kinda doubt they are going to shell out money for a study that is damning to eggs.  Not when their profits are on the line and egg sales have been steadily declining over the last few decades.

The very last section comically states that the authors declare no conflict of interest.  Yeah, right.

Eggs have no where near the amount of nutrition found fruits and vegetables.

Final Thoughts

Personally, I think this was a just another study facilitated  by the American Egg Board to mislead more consumers into thinking eggs are a health food, when they are actually quite detrimental to health.  Frankly, I'm a little surprised at how badly this study was designed, and yet still made the bold claims in regards to weight and cholesterol management.

I want to be clear that I am not trying shun anyone for eating eggs.  I was eating two dozen eggs or more per week until two weeks ago.  I understand why egg consumption is so popular... cheap, easy to make, versatile and filling.

I want to be a proponent of the truth, though... and my research on the topic thus far has led me to conclude that eggs just aren't good for health.  Some scientific studies may disagree with that conclusion, but most of the time, it's the studies that are funded by the egg industry and designed very poorly.

My goal for this article was to show that information on nutrition is not always as clear as reading a headline of a study.  Deception is rife in the food industry, and one way to get people to consume more goods is using scientific literature to put their mind at ease about a potentially harmful products.  That's one of the reasons scientific research is not always clear cut... different groups of researchers can produce different results using similar studies, depending on their objectives and motivation.

How do you feel about eggs?  Do you think this (and many other) studies are just deceptive enough to make eggs appear harmless?  Or is it simply a matter of poor research design and control?  Let me know in the comments!

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