Eggs have been a dietary staple for cultures around the world for thousands of years, and for much of that time have been considered nutritional powerhouses. They are a good source of protein, including all the essential amino acids. They are rich in a variety of vitamins and minerals, including vitamin B12, vitamin D, vitamin A, riboflavin, and folate. They are an excellent source of choline, which is an essential nutrient that plays an important role in brain health, nerve function, and metabolism. They contain lutein and zeaxanthin, antioxidants beneficial for eye health. They are also rich in omega-3 fatty acids, which have a variety of important roles.1 In addition to being nutrient-dense, eggs are versatile and affordable. In other healing traditions, eggs are often viewed favorably. In Chinese medicine, for example, eggs help maintain the balance of yin and yang. They support vital energy (qi), nourish the body’s essence (jing), moisten the body, and are relatively easy to digest.

 

Medicine’s relationship with eggs has been a complicated one in recent years, though, with concerns that they may lead to high cholesterol and inflammation. Are eggs healthy? Are they not healthy? How do we know?

 

The answer is—it depends on the egg, and it depends on the person. But with the right egg, they can be an excellent food.

 

When it comes to nutrition, you are what you eat. Not only that, but you are also what you eat, eats. And when it comes to eggs, not all eggs are created equal. I think one of the biggest challenges that we encounter when thinking about eggs is that most eggs that are available in the supermarket are a shadow of what they are supposed to be. Most eggs are “conventional eggs”, which have dramatically different nutritional qualities than the eggs that were likely dietary staples for millennia.

 

Before we talk about the nutritional differences between, say, an organic, pastured egg and a conventional, caged egg, it’s worth clarifying some terms. The egg aisle of grocery stores can be pretty confusing these days, and terms that sound appealing (“cage-free”, for example) don’t actually mean what we might think they should. Some of the terms are regulated by the USDA; some are regulated by other agencies. So what do the marketing terms you’ll encounter actually mean? Here’s a brief list. A committed farmer (like the folks at The Edge Farms, a regenerative farm outside of Philadelphia that inspired this list) could give you a much more thorough rundown.

 

Conventional – This is the standard egg product. These eggs come from chickens that are generally kept in small cages, in very crowded conditions, sometimes called battery cages or Concentrated Animal Feeding Operations (CAFOs). Cages are tightly arranged and stacked such that the floor of one is the ceiling of another, and the wall of one is the wall another. Chickens must have 116 square inches of space in the cage (less than the size of a sheet of paper). They have limited space to move or exhibit natural behaviors. This is generally considered the least humane, and results in eggs of the lowest quality.

 

Cage-Free – This is a term from the United States Department of Agriculture (USDA). Hens are not confined to battery cages but are still typically in crowded indoor spaces (perhaps with thousands of other birds). To use this term, there is no requirement that the birds have outdoor access. The term implies that hens can move freely, but this is not necessarily the case. Overcrowding can lead to stress, aggression, hygiene concerns, and disease.

 

Free-Range – By USDA definition, chickens must have access to the outdoors. However, the quality of conditions can vary widely—it may simply be a ramp leading to a small outdoor area, or an open window. There may be space to engage in natural behaviors, though overcrowding may still be problematic. These products may differ little from cage-free, and birds in practicality may not actually be outdoors at all.

 

Pastured – Pastured hens can graze on pastures or open fields, where they have a varied diet complemented by forage for insects and plants in addition to their feed (chickens naturally are omnivores). This is generally considered a more natural lifestyle and has the potential to result in eggs with higher nutritional quality. This term is not regulated by the USDA. However, if the eggs are also either “Certified Humane” or “Animal Welfare Approved”, they must have at least 108 square feet of outdoor space in addition to indoor space.

 

Regenerative – These eggs come from farms that follow specific agricultural practices, though it is worth noting that this is not a USDA certification term (other certification programs do exist for this). Regenerative agriculture is a farming approach that is designed to restore and improve the health of the land, soil, and ecosystem while producing food. Regenerative farming enhances ecosystem health with practices such as rotational grazing, the use of cover crops, composting, carbon sequestration, biodiversity enhancement, minimal chemical inputs, etc. Regenerative eggs would also be pastured eggs.  

 

Organic – This is a USDA term. Chickens are given food that is free of pesticides, synthetic fertilizers, and antibiotics. However, this designation doesn’t provide any insight into the living conditions of the chickens, which may still be very confined.

 

Vegetarian – This term can be applied to any of the above classifications, though actually implies that the birds are not pastured (as birds are omnivores, they eat a non-vegetarian diet when foraging).

 

Omega-3 enriched: Chickens are fed a diet that is enriched with a product containing omega-3 fatty acids (typically flax seeds or fish oils). This term doesn’t reflect living conditions.  

 

Corn-free, Soy-free – Chickens are fed a diet that is free of corn and soy. Corn and soy are common ingredients in chicken feed. For some individuals with allergies or sensitivities to corn or soy, eating eggs from chickens that were fed these ingredients may cause symptoms. Corn and soy are also often genetically modified products, and their inclusion may lead to increases in the omega-6:omega-3 ratio of eggs (more on that below).  

 

Other descriptors are often used to talk about eggs, like “antibiotic free”, “no added hormones”, and “all natural”. These terms usually don’t mean much. Growth hormones are not approved for poultry production in the US. Antibiotics may be used to reduce risks of infection (which is more common in overcrowded houses). All natural has essentially no meaning—it is not a regulated term.

 

Practically speaking, conventional eggs bear little resemblance to pastured eggs. Physically, they are entirely different specimens. Conventional eggs have brittle shells, weak, thin yolks and watery whites; pastured eggs have strong shells and robust yolks, which are often deep yellow in color (this color comes from carotenoids in the chickens’ diet—color itself is not necessarily a marker of the quality of the egg, though, as colorants can easily be added to feed, and some pastured eggs have lighter colored yolks as a result of dietary variation). You can do this experiment yourself—crack a conventional egg side by side with a pastured egg, and the physical differences will be obvious.

 

From a nutritional standpoint, these two eggs can also be very different. The first study hinting at these differences came in 1989 and was published as letter to the editor in the New England Journal of Medicine. The authors noted that pastured chickens in Greece (which have a diet rich in insects and grass, supplemented with dried figs, barley flour, and small amounts of corn) had high amounts of omega-3 fatty acids—the total content was ten times higher than that in a “US supermarket egg” (100 g of the Greek egg yolk contained nearly 2000 mg of omega-3 fatty acids). Furthermore, the ratio of omega-6 fattys acids to omega-3 fatty acids was 1.3 in the Greek egg, compared to 19.4 in the supermarket egg.2 In general, the lower this ratio, the better—some suggest the optimal ratio should be as low as 1:1, whereas the ratio in the typical Western diet is 15:1 or 16:1.3 Higher ratios are associated with obesity, inflammation, and a variety of chronic diseases.4

 

Several other studies of pastured eggs have yielded similar findings. A 2010 study comparing the eggs of caged hens to pastured hens found that the pastured eggs had more vitamin A, twice as much vitamin E, more than twice as much omega-3 fatty acids, and less than half the ratio of omega-6 to omega-3 fatty acids.5 Another study found that pasture-raised eggs had twice as much carotenoid content, three times as much omega-3 fatty acid, and an omega-6:omega-3 ratio that was 5-10 times lower than cage-free eggs (not even conventional eggs).6 Clearly these are very different products.

 

It’s true that eggs can be a major source of dietary cholesterol, which is one of the main factors often raised when concerns about eggs are voiced. The impact of dietary cholesterol from eggs on blood cholesterol, though, is not always clear. The conversation about dietary cholesterol is beyond the scope of this post, but it’s worth noting that large-scale epidemiologic studies have not reliably found a connection between eggs and cardiovascular health, and several large studies have found that the impact of blood cholesterol from eggs is highly variable—the majority of the population (over 2/3) have minimal response in blood cholesterol from eggs, and those who do typically have increases in both LDL and HDL.7 These differences most likely come down to individual variations in gene expression (an issue that can be understood at the level of the individual with the help of nutrigenomics). And in thinking about other healing traditions, whether they are the best food for an individual would depend on the individual’s constitution and health concerns—in Chinese medicine, for example, someone with a tendency toward dampness or phlegm formation, for example, might want to moderate their consumption of eggs.

 

If you are going to eat eggs, pay attention to what you get. Try to find pastured eggs, ideally from a local farm that is thoughtful about their approach to agriculture. You are what you eat. You are what you eat, eats. This becomes very apparent in the case of eggs. Not all eggs are the same. Better living conditions and more natural diets for the chickens lead to dramatically better eggs. Conventional eggs are barely eggs at all.

 

References 

1.         Herron KL, Fernandez ML. Are the Current Dietary Guidelines Regarding Egg Consumption Appropriate? J Nutr. 2004;134(1):187-190. doi:10.1093/jn/134.1.187

2.         Simopoulos AP, Salem N. n-3 fatty acids in eggs from range-fed Greek chickens. N Engl J Med. 1989;321(20):1412. doi:10.1056/NEJM198911163212013

3.         Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother Biomedecine Pharmacother. 2002;56(8):365-379. doi:10.1016/s0753-3322(02)00253-6

4.         Simopoulos AP, DiNicolantonio JJ. The importance of a balanced ω-6 to ω-3 ratio in the prevention and management of obesity. Open Heart. 2016;3(2):e000385. doi:10.1136/openhrt-2015-000385

5.         Karsten HD, Patterson PH, Stout R, Crews G. Vitamins A, E and fatty acid composition of the eggs of caged hens and pastured hens. Renew Agric Food Syst. 2010;25(1):45-54. doi:10.1017/S1742170509990214

6.         Sergin S, Jambunathan V, Garg E, Rowntree JE, Fenton JI. Fatty Acid and Antioxidant Profile of Eggs from Pasture-Raised Hens Fed a Corn- and Soy-Free Diet and Supplemented with Grass-Fed Beef Suet and Liver. Foods. 2022;11(21):3404. doi:10.3390/foods11213404

7.         Blesso CN, Fernandez ML. Dietary Cholesterol, Serum Lipids, and Heart Disease: Are Eggs Working for or Against You? Nutrients. 2018;10(4):426. doi:10.3390/nu10040426