Eggs as food: the story on HearLore

Eggs as food

Eggs have been a cornerstone of human survival for millions of years, with hominids consuming them long before the dawn of agriculture. The earliest evidence of this dietary habit dates back to prehistoric times, where bird eggs served as a vital source of protein and fat for hunting societies. By 1500 BCE, people in Southeast Asia had already begun harvesting chicken eggs, marking a significant shift from wild foraging to early domestication. The chicken itself was likely domesticated specifically for its egg production, originating from jungle fowl native to tropical and subtropical regions of Southeast Asia and the Indian subcontinent. This domestication process was so successful that chickens reached Sumer and Egypt by 1500 BCE and arrived in Greece around 800 BCE, where quail had previously been the primary source of eggs. In ancient Egypt, the tomb of Haremhab, dating to approximately 1420 BCE, depicts a man carrying bowls of ostrich eggs and other large eggs, possibly from pelicans, as offerings to the afterlife. These historical artifacts reveal that eggs were not merely food but held deep spiritual and cultural significance, serving as offerings in tombs and religious ceremonies. The Romans, too, valued eggs highly, preserving them using various methods and often starting meals with an egg course. They even crushed eggshells on their plates to prevent evil spirits from hiding within them, a practice that underscores the mystical beliefs surrounding this humble food. In the Middle Ages, eggs were forbidden during Lent, not solely for religious reasons but also to allow farmers to rest their flocks and limit feed consumption during times of scarcity. This annual pause in egg consumption highlights the practical and economic importance of eggs in medieval society, where food stocks were often limited. The dried egg industry emerged in the nineteenth century, with a company in St. Louis, Missouri, transforming egg yolk and white into a light-brown meal-like substance in 1878. This innovation significantly expanded during World War II, providing essential nutrition for the United States Armed Forces and its allies. The invention of the egg carton by Joseph Coyle in Smithers, British Columbia, in 1911 solved a dispute over broken eggs between a farmer and a hotel owner, revolutionizing the way eggs were transported and sold. Early cartons were made of paper, and while polystyrene became popular in the latter half of the twentieth century for its protective qualities, environmental concerns have led to a return to biodegradable paper cartons. Selective breeding over millennia has transformed wild Asian fowl, which laid about a dozen eggs annually, into domesticated hens capable of producing more than three hundred eggs each year, laying them year-round. This dramatic increase in productivity has made eggs one of the most widely consumed animal products globally, with mass production becoming a cornerstone of the modern food industry.

When did people in Southeast Asia begin harvesting chicken eggs?

People in Southeast Asia began harvesting chicken eggs by 1500 BCE. This event marked a significant shift from wild foraging to early domestication of the chicken.

Who invented the egg carton and when was it created?

Joseph Coyle invented the egg carton in 1911 in Smithers, British Columbia. The invention solved a dispute over broken eggs between a farmer and a hotel owner.

What is the air cell in a chicken egg and how does it determine egg grade?

The air cell is a pocket of air located at the larger end of the egg that forms when the contents cool and contract after being laid. Egg grading systems measure the size of this air cell during candling to determine freshness, with a small air cell receiving a grade of AA and larger cells receiving lower grades.

Which countries banned the killing of unwanted male chicks as of June 2023?

Germany, France, Luxembourg, and Italy banned the killing of unwanted male chicks as of June 2023. This practice has been replaced by in-ovo sexing technology in some regions to remove male eggs from incubation before hatching.

How does the European Union regulate egg production standards and cage types?

The European Union banned conventional battery cages for egg-laying hens effective the 1st of January 2012 under EU Directive 1999/74/EC. The EU mandates an egg marking code where 3 indicates caged chicken, 1 indicates free-range eggs, and 0 indicates organic egg production.

The Global Industry

In 2017, world production of chicken eggs reached 80.1 million tonnes, with China leading at 31.3 million tonnes, followed by the United States with 6.3 million, India at 4.8 million, and Mexico at 2.8 million. Japan produced 2.6 million, while Brazil and Russia each contributed 2.5 million. The largest egg factory in British Columbia ships 12 million eggs per week, illustrating the scale of modern egg production. For January 2019, the United States produced 9.41 billion eggs, with 8.2 billion for table consumption and 1.2 billion for raising chicks. Americans were projected to consume 279 eggs in 2019, the highest since 1973, though this figure remains below the 405 eggs eaten per person in 1945. During production, eggs can be candled to check their quality, with the size of the air cell determining the grade. If fertilization occurred three to six days prior to candling, blood vessels may be visible, though this is not conclusive evidence of fertilization. Depending on local regulations, eggs may be washed before being placed in boxes, although washing can shorten their freshness. In the United States, eggs are washed, which cleans the shell but erodes its cuticle, leading the USDA to recommend refrigeration to prevent Salmonella growth. In Europe, eggs are not usually washed, and the shells remain dirtier, but the cuticle is undamaged, allowing them to be stored without refrigeration. In the UK, hens are immunized against Salmonella, and their eggs are generally safe for 21 days. The largest egg factory in British Columbia ships 12 million eggs per week, demonstrating the massive scale of industrial production. Regional variations in demand and expectation have led to debates about mass production methods, with the European Union banning battery husbandry of chickens in 2012. The production of eggs has become a global industry, with mass production raising concerns about animal welfare and environmental impact. The United Egg Producers program includes guidelines regarding housing, food, water, air, living space, beak trimming, molting, handling, and transportation, though opponents argue that certification is misleading and allows unchecked animal cruelty. Effective the 1st of January 2012, the European Union banned conventional battery cages for egg-laying hens, as outlined in EU Directive 1999/74/EC. The EU permits the use of enriched furnished cages that must meet certain space and amenity requirements, though egg producers in many member states have objected to the new quality standards. In all methods of egg production, unwanted male chicks are killed at birth during the process of securing a further generation of egg-laying hens. As of June 2023, this practice has been banned in Germany, France, Luxembourg, and Italy. Some egg producers have begun using in-ovo sexing to analyze the sex of a chick before it hatches, allowing them to remove male eggs from incubation and avoid chick culling. As of April 2025, five companies offer commercially available in-ovo sexing technology, which is used for 28 percent of the European layer population.

The Kitchen Alchemist

Eggs are one of the most versatile ingredients in the kitchen, used in a wide variety of dishes, both sweet and savory. Common preparation methods include scrambled, fried, poached, hard-boiled, soft-boiled, omelettes, and pickled. They may also be eaten raw, though this is not recommended for people who may be especially susceptible to salmonellosis, such as the elderly, the infirm, or pregnant women. The protein in raw eggs is only 51 percent bioavailable, whereas that of a cooked egg is nearer 91 percent bioavailable, meaning the protein of cooked eggs is nearly twice as absorbable as the protein from raw eggs. As a cooking ingredient, egg yolks are an important emulsifier in the kitchen and are also used as a thickener, as in custards. The albumen contains protein but little or no fat and may be used in cooking separately from the yolk. The proteins in egg white allow it to form foams and aerated dishes, often used in desserts such as meringues and mousse. Ground eggshells are sometimes used as a food additive to deliver calcium, and every part of an egg is edible, although the eggshell is generally discarded. Some recipes call for immature or unlaid eggs, which are harvested after the hen is slaughtered or cooked while still inside the chicken. Eggs contain multiple proteins that gel at different temperatures within the yolk and the white, and the temperature determines the gelling time. Egg yolk becomes a gel between 65 and 70 degrees Celsius, while egg white gels at different temperatures, with the exterior albumen setting at the highest temperature. Salmonella is killed instantly at 71 degrees Celsius but also is killed from 63 degrees Celsius if held at that temperature for sufficiently long time periods. To avoid the issue of salmonella, eggs may be pasteurized in-shell at 60 degrees Celsius for an hour and 15 minutes. If a boiled egg is overcooked, a greenish ring sometimes appears around the egg yolk due to changes to the iron and sulfur compounds in the egg. It also may occur with an abundance of iron in the cooking water. Overcooking harms the quality of the protein, and chilling an overcooked egg for a few minutes in cold water until it is completely cooled may prevent the greenish ring from forming. Peeling a cooked egg is easiest when the egg was put into boiling water as opposed to slowly heating the egg from a start in cold water. In February 2025, scientists published research confirming that periodic cooking of an egg is the best way to preserve the distinct textures of each part of an egg as well as its nutritional value. The method requires alternating between boiling and lukewarm water: two minutes in 100 degrees Celsius, two minutes at 40 degrees Celsius, repeated eight times. The bird's diet affects the flavor of the egg, and when a brown-egg chicken breed eats rapeseed or soy meals, its intestinal microbes metabolize them into fishy-smelling triethylamine, which ends up in the egg. The unpredictable diet of free-range hens will produce likewise, unpredictable egg flavors. Duck eggs tend to have a flavor distinct from, but still resembling, chicken eggs. Eggs may be soaked in mixtures to absorb flavor, such as tea eggs, a common snack sold from street-side carts in China, which are steeped in a brew from a mixture of various spices, soy sauce, and black tea leaves to give flavor. Hard boiled eggs are cracked slightly before being simmered in the marinade for more flavor, also giving them their marble pattern.

The Health Debate

Egg yolks and whole eggs store significant amounts of protein and choline, and due to their protein content, the United States Department of Agriculture formerly categorized eggs as Meat within the Food Guide Pyramid. A medium/large chicken egg provides approximately 70 kilocalories of food energy and 6 grams of protein. Eggs supply several vitamins and minerals as significant amounts of the Daily Value, including vitamin A, riboflavin, pantothenic acid, vitamin B12, choline, phosphorus, zinc, and vitamin D. The diet of laying hens also may affect the nutritional quality of eggs, with chicken eggs that are especially high in omega-3 fatty acids produced by feeding hens a diet containing polyunsaturated fats from sources such as fish oil, chia seeds, or flaxseeds. Pasture-raised free-range hens, which forage for their own food, also produce eggs that are relatively enriched in omega-3 fatty acids when compared to those of cage-raised chickens. A 2010 USDA study determined there were no significant differences of macronutrients in various chicken eggs. Cooked eggs are easier to digest than raw eggs, as well as having a lower risk of salmonellosis. More than half the calories found in eggs come from the fat in the yolk, with 50 grams of chicken egg containing approximately five grams of fat. Saturated fat makes up 27 percent of the fat in an egg, while the egg white consists primarily of water and protein, with no cholesterol and 0.2 percent fat. There is debate over whether egg yolk presents a health risk, with some research suggesting dietary cholesterol increases the ratio of total to HDL cholesterol and adversely affects the body's cholesterol profile, whereas other studies show that moderate consumption of eggs, up to one a day, does not appear to increase heart disease risk in healthy individuals. Harold McGee argues that the cholesterol in the egg yolk is not what causes a problem, because fat, particularly saturated fat, is much more likely to raise cholesterol levels than the consumption of cholesterol. Studies have shown conflicting results about a possible connection between egg consumption and type 2 diabetes, with a 2013 meta-analysis finding that eating four eggs per week was associated with a 29 percent increase in the relative risk of developing diabetes. Another 2013 meta-analysis also supported the idea that egg consumption may lead to an increased incidence of type two diabetes, though a 2016 meta-analysis suggested that the association may be restricted to cohort studies from the United States. A 2020 meta-analysis found that there was no overall association between moderate egg consumption and risk of type 2 diabetes and that the risk found in US studies was not found in European or Asian studies. Research has also explored the link between egg consumption and cancer, with a 2015 meta-analysis finding an association between higher egg consumption and increased risk of breast cancer, and another meta-analysis finding that egg consumption may increase ovarian cancer risk. A 2019 meta-analysis found an association between high egg consumption and risk of upper aero-digestive tract cancers in hospital-based case-control studies, though a 2021 review did not find a significant association between egg consumption and breast cancer. Cardiovascular health has also been a subject of study, with one systematic review and meta-analysis of egg consumption finding that higher consumption of eggs was associated with a significant reduction in risk of coronary artery disease, while another found that egg consumption was associated with an increased all-cause mortality and CVD mortality. These contrary results may be due to somewhat different methods of study selection and the use primarily of observational studies, where confounding factors are not controlled. A 2018 meta-analysis of randomized clinical trials found that consumption of eggs increases total cholesterol, LDL-C, and HDL-C compared to no egg-consumption but not to low-egg control diets. In 2020, two meta-analyses found that moderate egg consumption is not associated with an increased cardiovascular disease risk, and an umbrella review concluded that increased egg consumption is not associated with cardiovascular disease risk in the general population. Another umbrella review found no association between egg consumption and cardiovascular disorders, and a 2013 meta-analysis found no association between egg consumption and heart disease or stroke. However, a 2013 systematic review and meta-analysis found no association between egg consumption and cardiovascular disease or cardiovascular disease mortality, but did find egg consumption of more than once daily increased cardiovascular disease risk 1.69-fold in those with type 2 diabetes mellitus when compared to type 2 diabetics who ate less than one egg per week. Another 2013 meta-analysis found that eating four eggs per week increased the risk of cardiovascular disease by six percent. Eggs are one of the largest sources of phosphatidylcholine in the human diet, and a study published in the scientific journal Nature showed that dietary phosphatidylcholine is digested by bacteria in the gut and eventually converted into the compound TMAO, a compound linked with increased heart disease. Another study found that type 2 diabetes mellitus and kidney disease also increase TMAO levels and that evidence for a link between TMAO and cardiovascular diseases may be due to confounding or reverse causality. Egg consumption does not increase hypertension risk, and a 2016 meta-analysis found that consumption of up to one egg a day may contribute to a decreased risk of total stroke. Two recent meta-analyses found no association between egg intake and risk of stroke, and a 2019 meta-analysis revealed that egg consumption has no significant effect on serum biomarkers of inflammation. A 2021 review of clinical trials found that egg consumption has beneficial effects on macular pigment optical density and serum lutein.

The Contamination Crisis

A health issue associated with eggs is contamination by pathogenic bacteria, such as Salmonella enteritidis. Contamination of eggs with other members of the genus Salmonella while exiting a female bird via the cloaca may occur, so care must be taken to prevent the egg shell from becoming contaminated with fecal matter. In commercial practice in the US, eggs are quickly washed with a sanitizing solution within minutes of being laid. The risk of infection from raw or undercooked eggs is dependent in part upon the sanitary conditions under which the hens are kept. Health experts advise people to refrigerate washed eggs, use them within two weeks, cook them thoroughly, and never consume raw eggs. As with meat, containers and surfaces that have been used to process raw eggs should not come into contact with ready-to-eat food. A study by the U.S. Department of Agriculture in 2002 suggests the problem is not so prevalent in the U.S. as once thought, showing that of the 69 billion eggs produced annually, only 2.3 million are contaminated with Salmonella, equivalent to just one in every 30,000 eggs, thus showing Salmonella infection is quite rarely induced by eggs. This has not been the case in other countries, however, where Salmonella enteritidis and Salmonella typhimurium infections due to egg consumption are major concerns. Egg shells act as hermetic seals that guard against bacteria entering, but this seal can be broken through improper handling or if laid by unhealthy chickens. Most forms of contamination enter through such weaknesses in the shell. In the UK, the British Egg Industry Council awards the lions stamp to eggs that, among other things, come from hens that have been vaccinated against Salmonella. In 2017, authorities blocked millions of eggs from sale in the Netherlands, Belgium, and Germany because of contamination with the insecticide fipronil. One of the most common food allergies in infants is eggs, and infants usually have the opportunity to grow out of this allergy during childhood if exposure is minimized. Allergic reactions against egg white are more common than reactions against egg yolks, and in addition to true allergic reactions, some people experience a food intolerance to egg whites. Food labeling practices in most developed countries now include eggs, egg products, and the processing of foods on equipment that also process foods containing eggs in a special allergen alert section of the ingredients on the labels. The risk of infection from raw or undercooked eggs is dependent in part upon the sanitary conditions under which the hens are kept, and health experts advise people to refrigerate washed eggs, use them within two weeks, cook them thoroughly, and never consume raw eggs. As with meat, containers and surfaces that have been used to process raw eggs should not come into contact with ready-to-eat food. A study by the U.S. Department of Agriculture in 2002 suggests the problem is not so prevalent in the U.S. as once thought, showing that of the 69 billion eggs produced annually, only 2.3 million are contaminated with Salmonella, equivalent to just one in every 30,000 eggs, thus showing Salmonella infection is quite rarely induced by eggs. This has not been the case in other countries, however, where Salmonella enteritidis and Salmonella typhimurium infections due to egg consumption are major concerns. Egg shells act as hermetic seals that guard against bacteria entering, but this seal can be broken through improper handling or if laid by unhealthy chickens. Most forms of contamination enter through such weaknesses in the shell. In the UK, the British Egg Industry Council awards the lions stamp to eggs that, among other things, come from hens that have been vaccinated against Salmonella. In 2017, authorities blocked millions of eggs from sale in the Netherlands, Belgium, and Germany because of contamination with the insecticide fipronil. One of the most common food allergies in infants is eggs, and infants usually have the opportunity to grow out of this allergy during childhood if exposure is minimized. Allergic reactions against egg white are more common than reactions against egg yolks, and in addition to true allergic reactions, some people experience a food intolerance to egg whites. Food labeling practices in most developed countries now include eggs, egg products, and the processing of foods on equipment that also process foods containing eggs in a special allergen alert section of the ingredients on the labels.

The Cultural Canvas

A popular Easter tradition in some parts of the world is a decoration of hard-boiled eggs, usually by dyeing, but often by spray-painting. A similar tradition of egg painting exists in areas of the world influenced by the culture of Persia. Before the spring equinox in the Persian New Year tradition, called Norouz, each family member decorates a hard-boiled egg and they set them together in a bowl. In Northern Europe and North America, Easter eggs may be hidden by adults for children to find in an Easter egg hunt. They may be rolled in some traditions, and in Eastern and Central Europe, and parts of England, easter eggs may be tapped against each other to see whose egg breaks first. Since the sixteenth century, the tradition of a dancing egg is held during the feast of Corpus Christi in Barcelona and other Catalan cities. It consists of a hollow eggshell, positioned over the water jet from a fountain, which causes the eggshell to revolve without falling. Fraud in the form of fake chicken eggs made from resin, starch, and pigments has been reported on several occasions in China, for both domestic consumption and exports. The color of eggshells is a largely cosmetic issue, with no effect on egg quality or taste, but it is a major issue in production due to regional and national preferences for specific colors. For example, in most regions of the United States, chicken eggs generally are white, but brown eggs are more common in some parts of the Northeastern United States, particularly New England, where a television jingle for years proclaimed brown eggs are local eggs, and local eggs are fresh. Local chicken breeds, including the Rhode Island Red, lay brown eggs. Brown eggs are preferred in China, Costa Rica, Ireland, France, and the United Kingdom. In Brazil and Poland, white chicken eggs are generally regarded as industrial, and brown or reddish ones are preferred. Small farms and smallholdings, particularly in economically advanced nations, may sell eggs of widely varying colors and sizes, with combinations of white, brown, speckled, green, and blue eggs in the same box or carton, while the supermarkets at the same time sell mostly eggs from the larger producers, of the color preferred in that nation or region. These cultural trends have been observed for many years, with the New York Times reporting during the Second World War that housewives in Boston preferred brown eggs and those in New York preferred white eggs. In February 1976, the New Scientist magazine stated that housewives are particularly fussy about the color of their eggs, preferring even to pay more for brown eggs although white eggs are just as good. As a result of these trends, brown eggs are usually more expensive to purchase in regions where white eggs are considered normal, due to lower production. In France and the United Kingdom, it is very difficult to buy white eggs, with most supermarkets supplying only the more popular brown eggs. By contrast, in Egypt it is very hard to source brown eggs, as demand is almost entirely for white ones, with the country's largest supplier describing white eggs as table eggs and packaging brown eggs for export. Research conducted by a French institute in the 1970s demonstrated that blue chicken eggs from the Chilean araucana fowl may be stronger and more resilient to breakage. Research at Nihon University, Japan, in 1990 revealed that when Japanese housewives were deciding which eggs to buy, color was a distinct factor, with most Japanese housewives preferring the white color. Egg producers carefully consider cultural issues, as well as commercial ones, when selecting the breed or breeds of chickens used for production, as egg color varies between breeds. Among producers and breeders, brown eggs often are referred to as tinted, while the speckled eggs preferred by some consumers often are referred to as being red in color. The largest bird eggs, from ostriches, tend to be used only as special luxury food. Gull eggs are considered a delicacy in England, as well as in some Scandinavian countries, particularly in Norway. In some African countries, guineafowl eggs often are seen in marketplaces, especially in the spring of each year. Pheasant eggs and emu eggs are edible, but less widely available, sometimes obtainable from farmers, poulterers, or luxury grocery stores. In many countries, wild bird eggs are protected by laws which prohibit the collecting or selling of them, or permit collection only during specific periods of the year. The largest bird eggs, from ostriches, tend to be used only as special luxury food, and gull eggs are considered a delicacy in England, as well as in some Scandinavian countries, particularly in Norway. In some African countries, guineafowl eggs often are seen in marketplaces, especially in the spring of each year. Pheasant eggs and emu eggs are edible, but less widely available, sometimes obtainable from farmers, poulterers, or luxury grocery stores. In many countries, wild bird eggs are protected by laws which prohibit the collecting or selling of them, or permit collection only during specific periods of the year.

The Future of Eggs

The future of egg production is shaped by evolving consumer preferences, technological advancements, and ethical considerations. As of April 2025, five companies offer commercially available in-ovo sexing technology, which is used for 28 percent of the European layer population, allowing producers to remove male eggs from incubation and avoid chick culling. This innovation addresses one of the most contentious aspects of egg production, the killing of unwanted male chicks at birth. The practice has been banned in Germany, France, Luxembourg, and Italy as of June 2023, reflecting a growing global awareness of animal welfare issues. Free-range eggs are considered by some advocates to be an acceptable substitute to factory-farmed eggs, with laying hens given outdoor access instead of being contained in crowded cages. However, questions regarding the living conditions of free-range hens have been raised in the United States, as there is no legal definition or regulations for eggs labeled as free-range in that country. The United Egg Producers program includes guidelines regarding housing, food, water, air, living space, beak trimming, molting, handling, and transportation, though opponents argue that certification is misleading and allows a significant amount of unchecked animal cruelty. Other standards include Cage Free, Natural, Certified Humane, and Certified Organic, with Certified Humane and Certified Organic being the most stringent. Effective the 1st of January 2012, the European Union banned conventional battery cages for egg-laying hens, as outlined in EU Directive 1999/74/EC. The EU permits the use of enriched furnished cages that must meet certain space and amenity requirements, though egg producers in many member states have objected to the new quality standards. The production standard of the eggs is visible on a mandatory egg marking categorization where the EU egg code begins with 3 for caged chicken to 1 for free-range eggs and 0 for organic egg production. The dried egg industry developed in the nineteenth century, before the rise of the frozen egg industry, and in 1878, a company in St. Louis, Missouri started to transform egg yolk and egg white into a light-brown, meal-like substance by using a drying process. The production of dried eggs significantly expanded during World War II, for use by the United States Armed Forces and its allies. In 1911, the egg carton was invented by Joseph Coyle in Smithers, British Columbia, to solve a dispute about broken eggs between a farmer in Bulkley Valley and the owner of the Aldermere Hotel. Early egg cartons were made of paper, and polystyrene egg cartons became popular in the latter half of the twentieth century as they were perceived to offer better protection especially against heat and breakage, however, by the twenty-first century environmental considerations have led to the return of more biodegradable paper cartons that once again became more widely used. The future of eggs also involves addressing health concerns, with ongoing research into the nutritional benefits and risks of egg consumption. Studies have shown conflicting results about the connection between egg consumption and type 2 diabetes, cancer, and cardiovascular disease, with some meta-analyses finding associations and others finding no significant links. The diet of laying hens affects the nutritional quality of eggs, with pasture-raised free-range hens producing eggs enriched in omega-3 fatty acids. The egg industry continues to evolve, balancing the demands of a growing global population with ethical and environmental considerations. As of 2025, the industry is exploring new technologies and standards to improve animal welfare, reduce contamination risks, and meet consumer expectations for sustainable and healthy food options. The future of eggs will depend on how these challenges are addressed, with innovations in in-ovo sexing, free-range practices, and organic certification playing key roles in shaping the industry's trajectory.