Why Do Experts Keep Changing Their Minds About Eggs???

 

 

           Whenever someone tries to discredit mainstream nutrition recommendations, a common tactic is to tackle the apparent fickleness of the science behind them. Every dietitian is intimately familiar with one argumentative example in particular: eggs. “First they say eggs are good for you, then they said they were bad for you, and then they said they were good for you again.” I hear these words echoing around the aching void between my ears on those nights that I cannot sleep. Just typing them spikes my blood pressure in a way no amount of salt on my over-medium breakfast ever could. However, at the risk of my own emotional stability, I’ll try once and for all to tackle the dreaded Egg Question^TM.

 Who is they?

               First and foremost, we need to address the pronoun. “They say eggs are good for you.” “They say not to eat eggs.” “They are always changing their mind.” This is one of those examples in human nature of a subconscious strategic ambiguity used to defend an argument from specific criticism. To address it, the first question we need to ask is “who is they?” I would boldly venture to say-though I have no data to support it-that most people aren’t regularly consulting experts in nutrition to stay up to date on changing recommendations. Despite this, all of us are constantly inundated with health recommendations daily. Morning news shows, social media personalities, your cousin with undiagnosed orthorexia, and the tabloid shelf leading to the only open register at your local grocery chain are all shouting at you about what “experts” have to say. For most people, what “research shows” is disseminated via a cynical game of telephone through three or four voices-all with a different agenda-before they even reach a point of visibility. When most people use “they” in this context, they believe themselves to refer to the experts, when that “they” is a medium of media that profits from attention rather than accuracy.

                To better explain this point, let me use a different controversial example: red wine. Red wine can be a very rich source of antioxidants, which can reduce inflammation, neutralize free radicals, and have a myriad of other health benefits (1). The polyphenols in red wine have demonstrated anti-cancer properties (2). Red wine also contains several carcinogenic compounds, as well as ethanol, which is heavily carcinogenic even at moderate intake levels (3). None of these statements contradict one another; all of them can be true at the same time. Therefore, a magazine could publish an article titled “Experts Say Red Wine Fights Cancer!” while another could publish an article titled “Experts Say Red Wine Causes Cancer!” and both would be telling the truth. While neither of these realities would alter expert or government agency recommendations, a person reading these two headlines could very reasonably assume that the aforementioned experts were hopelessly fickle in their recommendations.

 A magazine could publish an article titled “Experts Say Red Wine Fights Cancer!” while another could publish an article titled “Experts Say Red Wine Causes Cancer!” and both would be telling the truth.

                Now what does this have to do with eggs? For decades, the reporting on eggs has followed a similar pattern. For at least the duration of my lifetime, eggs have always been recognized as an incredible source of nutrients. Eggs are rich in the B vitamins as well as vitamins A, D, and E, as well as calcium, zinc, phosphorous, potassium, and trace amounts of other minerals as well (4). Additionally, eggs are considered the pinnacle of protein sources, the literal gold standard. There are numerous rating systems used in research to rate food protein quality based on amino acid content and bioavailability, and most of these scales measure food sources against an egg as the perfect score. None of these have been recent developments, and for decades nutrition scientists have endorsed these benefits consistently.

 

The Protein Digestibility-Corrected Amino Acid Score is one of the most popular ways of measuring protein quality and assigns egg a perfect score of 1.00 (5).

 

                The controversy arises around the fat and cholesterol content of eggs. While there is some variation based on chicken feed and environment, egg fat content is generally 33-35.5% saturated fat (6). Saturated fat intake has long been associated with cardiovascular disease. Egg yolks are also very high in cholesterol, which has long been associated with elevated circulating cholesterol and poor cardiovascular outcomes. (If you’re yelling at your screen after this paragraph, give me time, I’m getting there).

 

Confusing conflicting information on eggs comes from everywhere, from small social media pages to headlines from major news outlets. Many of these headlines refer to "studies" or "research" that do not at all corroborate the reporting. 

               Because of these benefits and negatives, dietary recommendations have long followed a weighted approach to eggs. While there have been minor tweaks, recommendations have generally followed 2-3 egg yolks per week, without a limit on egg whites. Again, for decades following the first concerns about cholesterol in the 1960s, these recommendations have remained fairly consistent. So why then does it seem like recommendations are always changing? Much like the wine example, reported half truths have confused the public. Focus can also change depending on the field. For example, a cardiologist might give warnings to avoid eggs for the cholesterol, while someone in the fitness realm might endorse them for their protein content. Neither of these people altered the actual recommendations, but it can certainly feel that way.

  So... we did change our mind...

              Ok, so let’s address the elephant in the room. We did change our mind. You got me. To explain why, I need to dig into the concerns about cardiovascular risk. First, the concerns about saturated fats in eggs have been demonstrated to be slightly overblown. This is a hotly debated topic and one that warrants a separate article, but for the sake of brevity, response to saturated fat is strongly associated with genetic variation, but reduction in saturated fat does correlate to lower cardiovascular risk (7).  However, one large egg contains about 1.6 grams of saturated fat, meaning that a person on a 2000 calorie diet would have to eat about 14 eggs to exceed their daily recommended saturated fat intake. Not quite as hotly debated is the effect of cholesterol. From the publishing of Ancel Keys’ famous 7 Country Studies in 1964 until only a few years ago, cholesterol intake has been considered a major risk factor for cardiovascular disease. Modern research, however, indicates that population-based research on cholesterol intake has long been confounded by the fact that most high-cholesterol foods are also high in saturated fats (8). Further, when this variable is removed, there is not sufficient evidence to conclude that dietary cholesterol impacts circulating cholesterol whatsoever. These caveats have combined to justify removing any recommendations for restrictions on egg intake.

Just eat them

                So where does all that leave us? Well first, it means that you can eat eggs with abandon. But more importantly, I want to drive home the fact that while the recommendations have changed, the egg conversation has not been the wild flip flop between extreme positions that some critics make it out to be. That perception is an unfortunate side effect of sensationalist reporting on food science. The egg conversation, like most nutrition discourse, is a very slow and painstaking evolution as researchers grind out new data over the course of decades.

 

 

Citations:

1.      Lopez-Velez, M., Martinez-Martinez, F., & Valle-Ribes, C. D. (2003). The study of phenolic compounds as natural antioxidants in wine.

2.      He, S., Sun, C., & Pan, Y. (2008). Red wine polyphenols for cancer prevention. International journal of molecular sciences, 9(5), 842-853.

3.      Pflaum, T., Hausler, T., Baumung, C., Ackermann, S., Kuballa, T., Rehm, J., & Lachenmeier, D. W. (2016). Carcinogenic compounds in alcoholic beverages: an update. Archives of toxicology, 90, 2349-2367.

4.      Réhault-Godbert, S., Guyot, N., & Nys, Y. (2019). The golden egg: nutritional value, bioactivities, and emerging benefits for human health. Nutrients, 11(3), 684.

5.     Van Vliet, Stephan & Burd, Nicholas & van Loon, Luc. (2015). The Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption. The Journal of nutrition. 145. 10.3945/jn.114.204305.

6.     Cherian, G., Holsonbake, T. B., & Goeger, M. P. (2002). Fatty acid composition and egg components of specialty eggs. Poultry science, 81(1), 30-33.

7.     Johnson, S. A., Kirkpatrick, C. F., Miller, N. H., Carson, J. A. S., Handu, D., & Moloney, L. (2023). Saturated Fat Intake and the Prevention and Management of Cardiovascular Disease in Adults: An Academy of Nutrition and Dietetics Evidence-Based Nutrition Practice Guideline. Journal of the Academy of Nutrition and Dietetics, 123(12), 1808-1830.

8.     Soliman, G. A. (2018). Dietary cholesterol and the lack of evidence in cardiovascular disease. Nutrients, 10(6), 780.