Eggs: The Nutritional Microcosm
Eggs: The Nutritional Microcosm
Delve into the wholesome world of eggs' nutrients and nourishment
Eggs seem to occupy a fascinating spot in the cultural imagination of people worldwide. While decorating eggs is often associated with Easter in the West, it is, in fact, a truly global tradition. Archaeologists discovered the oldest decorated eggs in present-day South Africa, dated as far back as 65,000 years ago.
This enormous historical span of decorating eggs owes their featured role in our minds across cultures and geography as symbols of life, creation, and renewal. The concept that eggs are a microcosm, containing a universe of promise and possibility, is mirrored in their nutritional profile, arguably making them the single most complete food on the planet.
Eggs are laid by birds, reptiles, fish, amphibians, and even a few mammals. But generally, 'eggs' and 'chicken eggs' are virtually synonymous. Humans have kept chickens for their egg production for 7,000 years, at a minimum.
Two Foods in One
While there may be regional preferences for one or the other, there is no difference in nutrition between white and brown eggs. However, the yolk of an egg and its white are as different in their nutrient profile as in hue; each eggshell essentially contains two entirely different but complementary foods.
The Eggwhite
The white of the egg is the protein component. It's essentially protein and water with very little of anything else. Egg whites feature less than one per cent carbohydrates and virtually zero fat, hence the arrival of the egg white omelet trend.
The concentrated protein in egg whites establishes them as great food for reducing appetite, supporting immunity, balancing hormones and blood sugar, tissue repair, and neurotransmitter optimization. But what makes egg protein so unique is its quality.
The most recent widely accepted framework for evaluating protein quality is the DIAAS or Digestible Indispensable Amino Acid Score. This scoring system evaluates different foods for how much protein, which amino acids they contain, and how effectively those nutrients are absorbed in the small intestine based on direct measurement.
Even before using the DIAAS, eggs were seen as the gold standard for protein because of their perfectly balanced amino acid composition, meaning they have an ideal ratio of the essential amino acids our body can't make. Since adopting this new scoring system, however, we can also see that eggs top the list of all food protein sources for absorption. Each egg contains six or seven grams of protein, but it's likely to be much more potently effective than the same amount from any other food source.
The Yolk
The yolk is akin to the nucleus of the egg. Where the white is relatively simple chemically, the yolk is intricate and chock full of information. And where the white is the protein component, the yolk is its fatty counterpart.
All the cholesterol, omega-3s, vitamins, minerals and other exciting micronutrients reside in this golden orb. Egg yolks are among the few foods that contain significant sources of vitamin D and other fat-soluble nutrients like vitamin K and vitamin A in their preferred active form. They also contain various B vitamins, including B2, B5, and biotin. The biotin in yolks is bound to a protein called avidin until heat breaks this bond and makes it available. So, drinking raw eggs will not be a source of biotin.
Yolks are also rich in minerals, including molybdenum, potassium, zinc, iron, magnesium, iodine and loads of selenium to support thyroid and immune function.
Choline
Eggs are a significant source of another fat-soluble B vitamin called choline. Cell membranes, healthy nerves, and optimal brain function all require choline. Choline requirements increase during lactation and pregnancy as developing babies need it for healthy brain formation. For this reason, infant formulas must contain it. Pregnant mothers supplementing it tend to have babies with better cognitive function, and deficiency has been linked to several neurological disorders.
Egg choline is significantly more absorbable than any other sources, including supplements. This is because it is connected to special fats called phospholipids in a complex known as phosphatidylcholine.
In addition to helping build healthy cells, brains, and brain cells, the phosphatidylcholine complex found in eggs also helps reduce markers of systemic inflammation. So, as long as there is no food sensitivity in the picture, eggs can be an excellent protein source in a healthy anti-inflammatory diet.
DHA
Perhaps the most impressive superstar egg yolk nutrient is the super-unsaturated fat docosahexaenoic acid, also known as DHA. This remarkable omega-3 has not changed in hundreds of millions of years of evolution! And since it makes up 20 per cent of the human brain, it may be the most critical fat in our diet.
Like choline, DHA intake during pregnancy correlates with higher cognitive ability, intelligence and language processing. And like choline, it is a strict requirement for baby formulas as an indispensable requirement of the developing brain.
Even for adults, DHA has been shown to raise brain-derived neurotrophic factor (BDNF), which is often referred to casually by medical experts as "Miracle-Gro for the brain" because it stimulates the generation of new neurons. This type of neuroplasticity was thought impossible until recently.
DHA is generally known as one of the distinctive fatty acids that make fish oil unique and beneficial to health. A very delicate and elegant molecule, DHA never appears in nature unaccompanied. Fortunately, the precious DHA in eggs is also protectively bound to the phospholipids mentioned above.
Nevertheless, the DHA alone is a great reason to put hard-boiled eggs in cold water as soon as they finish cooking and not overcook the yolks. You've gone too far if you see the green ring around the yolk (formed by the interaction of iron and sulphide).
Lutein and Zeaxanthin
Why are egg yolks yellow? There are at least two legitimate answers to this question. The first is that the colour of the yolk will vary depending on what the chickens are fed. There can be no better example of this principle than Chef Dan Barber's famous bright red egg yolks from hens fed on red peppers.
The second explanation of why egg yolks are the colour they are (yellow, almost always) is a brightly pigmented carotenoid called lutein. Associated heavily with the eyes, dietary lutein prevents macular degeneration and keeps our vision sharp into old age.
As if this wasn't enough, another bright carotenoid in eggs called zeaxanthin works synergistically with lutein to make egg yolks a true superfood for the eyes. And just like with choline and DHA, eating eggs is more efficient at raising blood levels of lutein and zeaxanthin than taking supplements.
Caveats
Salmonella contamination, cholesterol, and allergy or sensitivity are the three most common concerns about eating eggs.
Salmonella
Due to tightening industry standards, salmonella contamination may only affect one in 30,000 North American eggs, so poisoning by egg yolks is extremely rare. Nevertheless, avoiding raw or undercooked eggs for the immunocompromised or during pregnancy is still a reasonable and harmless recommendation.
Critics of this logic might say that overcooking egg yolks will compromise their nutrient composition and that trace amounts of salmonella bacteria are no match for solid stomach acid and a healthy microbiome.
Cholesterol
As for cholesterol from eggs and concerns about cardiac health, extensive studies have shown that including eggs in the diet does not increase the risk of developing heart disease. They can even help raise HDL, the so-called good cholesterol. On the other hand, someone struggling with balancing cholesterol or diabetes may want to limit the number of egg yolks in their diet. For more information on dietary cholesterol and health debate, check out Rily feature, Our Friend Cholesterol.
Allergies & Sensitivities
It seems that the most well-founded concern about including eggs in a healthy diet is that immune reactions to them are relatively common. Eating eggs frequently, especially during infancy and childhood, can develop or worsen egg sensitivity. You might consider ruling out responses with a sensitivity panel or an elimination diet if this concerns you. In general, rotating foods throughout the month instead of eating the same ones every day is a good rule of thumb to prevent allergies or sensitivities from developing.
Get Cracking
Despite all their history, the science on eggs and their health benefits is still unfolding. For example, the eggshell membrane (between the shell and the white) has recently been established as a potent anti-inflammatory pain reliever. It has its own dedicated supplements in health food stores.
It's no coincidence they are associated with breakfast: eggs provide an excellent source of protein, healthy fats, and sophisticated micronutrients, helping to support clear thinking and balanced blood sugar. The humble egg is, in truth, a multivitamin, a multimineral, a nutritional microcosm and a true superfood, and it has been eaten for thousands of years for excellent reason.
Alexander, D. D., Miller, P. E., Vargas, A. J., Weed, D. L., & Cohen, S. S. (2016). Meta-analysis of egg consumption and risk of coronary heart disease and stroke. Journal of the American College of Nutrition, 35(8), 704–716. https://doi.org/10.1080/07315724.2016.1152928
Anderson, L. V. (2014, March 6). I’ve consumed hundreds of raw eggs and have never gotten salmonella poisoning. here’s why. Slate Magazine. https://slate.com/technology/2014/03/salmonella-and-raw-eggs-how-ive-eaten-tons-of-cookie-dough-and-never-gotten-sick.html
Bailey, H. M., & Stein, H. H. (2019). Can the digestible indispensable amino acid score methodology decrease protein malnutrition. Animal frontiers : the review magazine of animal agriculture, 9(4), 18–23. https://doi.org/10.1093/af/vfz038
Bechthold, A., Boeing, H., Schwedhelm, C., Hoffmann, G., Knüppel, S., Iqbal, K., De Henauw, S., Michels, N., Devleesschauwer, B., Schlesinger, S., & Schwingshackl, L. (2017). Food Groups and risk of coronary heart disease, stroke and heart failure: A systematic review and dose-response meta-analysis of prospective studies. Critical Reviews in Food Science and Nutrition, 59(7), 1071–1090. https://doi.org/10.1080/10408398.2017.1392288
Boesch, S. (2023, March 31). Are eggs good for you? 10 science-backed effects of eating them every day. Eat This Not That. https://www.eatthis.com/are-eggs-good-for-you/
Cloete, S. (2022, February 17). The top 10 healthiest foods as identified by 10 nutritionists. Medium. https://medium.com/in-fitness-and-in-health/the-top-10-healthy-foods-as-identified-by-10-nutritionists-36281e0fba93
Ede, G. (2019, March 31). The brain needs animal fat. Psychology Today. https://www.psychologytoday.com/ca/blog/diagnosis-diet/201903/the-brain-needs-animal-fat
Egg Allergy. Cleveland Clinic. (n.d.). https://my.clevelandclinic.org/health/diseases/25086-egg-allergy Eggs. The Nutrition Source. (2023, February 2). https://www.hsph.harvard.edu/nutritionsource/food-features/eggs/ Geiker, N. R. W., Larsen, M. L., Dyerberg, J., Stender, S., & Astrup, A. (2017). Ugeskrift for laeger, 179(20), V11160792.
Godos, J., Micek, A., Brzostek, T., Toledo, E., Iacoviello, L., Astrup, A., Franco, O. H., Galvano, F., Martinez-Gonzalez, M. A., & Grosso, G. (2021). Egg consumption and cardiovascular risk: a dose-response meta-analysis of prospective cohort studies. European journal of nutrition, 60(4), 1833–1862. https://doi.org/10.1007/s00394-020-02345-7
Hall, S. (2017, April 6). The ancient art of decorating eggs: Folklife Today. The Library of Congress. https://blogs.loc.gov/folklife/2017/04/decorating-eggs/#:~:text=In%20some%20regions%20solid-color,a%20symbol%20of%20Christ%27s%20blood
Handelman, G. J., Nightingale, Z. D., Lichtenstein, A. H., Schaefer, E. J., & Blumberg, J. B. (1999). Lutein and zeaxanthin concentrations in plasma after dietary supplementation with egg yolk. The American journal of clinical nutrition, 70(2), 247–251. https://doi.org/10.1093/ajcn.70.2.247
Hu, F. B., Stampfer, M. J., & Rimm, E. B. (1999). A prospective study of egg consumption and risk of cardiovascular disease in men and women. JAMA, 281(15), 1387. https://doi.org/10.1001/jama.281.15.1387
Jia, H., Hanate, M., Aw, W., Itoh, H., Saito, K., Kobayashi, S., Hachimura, S., Fukuda, S., Tomita, M., Hasebe, Y., & Kato, H. (2017). Eggshell membrane powder ameliorates intestinal inflammation by facilitating the restitution of epithelial injury and alleviating microbial dysbiosis. Scientific Reports, 7(1). https://doi.org/10.1038/srep43993
Kolahdouz-Mohammadi, R., Malekahmadi, M., Clayton, Z. S., Sadat, S. Z., Pahlavani, N., Sikaroudi, M. K., & Soltani, S. (2020). Effect of Egg Consumption on Blood Pressure: a Systematic Review and Meta-analysis of Randomized Clinical Trials. Current hypertension reports, 22(3), 24. https://doi.org/10.1007/s11906-020-1029-5
Mah, E., Chen, C., & Liska, D. (2020). The effect of egg consumption on cardiometabolic health outcomes: An umbrella review. Public Health Nutrition, 23(5), 935-955. doi:10.1017/S1368980019002441
Mahmoudi, M., Ebrahimzadeh, M. A., Pourmorad, F., Rezaie, N., & Mahmoudi, M. A. (2013). Anti-inflammatory and analgesic effects of egg yolk: a comparison between organic and machine made. European review for medical and pharmacological sciences, 17(4), 472–476.
Marventano, S., Godos, J., Tieri, M., Ghelfi, F., Titta, L., Lafranconi, A., Gambera, A., Alonzo, E., Sciacca, S., Buscemi, S., Ray, S., Del Rio, D., Galvano, F., & Grosso, G. (2019). Egg consumption and human health: An Umbrella Review of Observational Studies. International Journal of Food Sciences and Nutrition, 71(3), 325–331. https://doi.org/10.1080/09637486.2019.1648388
Schnohr, P., Thomsen, O. O., Riis Hansen, P., Boberg-Ans, G., Lawaetz, H., & Weeke, T. (1994). Egg consumption and high-density-lipoprotein cholesterol. Journal of internal medicine, 235(3), 249–251. https://doi.org/10.1111/j.1365-2796.1994.tb01068.x
Smolders, L., de Wit, N. J. W., Balvers, M. G. J., Obeid, R., Vissers, M. M. M., & Esser, D. (2019). Natural Choline from Egg Yolk Phospholipids Is More Efficiently Absorbed Compared with Choline Bitartrate; Outcomes of A Randomized Trial in Healthy Adults. Nutrients, 11(11), 2758. https://doi.org/10.3390/nu11112758
TOI. (n.d.). What happens when you overcook eggs?. The Times of India. https://timesofindia.indiatimes.com/life-style/health-fitness/health-news/what-happens-when-you-overcook-eggs/articleshow/70191466.cms
Wu, A., Ying, Z., & Gomez-Pinilla, F. (2008). Docosahexaenoic acid dietary supplementation enhances the effects of exercise on synaptic plasticity and cognition. Neuroscience, 155(3), 751–759. https://doi.org/10.1016/j.neuroscience.2008.05.061
Zeisel, S. H., & da Costa, K. A. (2009). Choline: an essential nutrient for public health. Nutrition reviews, 67(11), 615–623. https://doi.org/10.1111/j.1753-4887.2009.00246.x
Zhang, Y., & Zhang, D. (2018). Red Meat, poultry, and egg consumption with the risk of hypertension: A meta-analysis of prospective cohort studies. Journal of Human Hypertension, 32(7), 507–517. https://doi.org/10.1038/s41371-018-0068-8
