View source for Eggs as food

{{short description|Edible animal product}}
{{redirect|Chicken egg|the causality dilemma|Chicken or the egg|the definition of the egg in biology|Egg|other uses|Egg (disambiguation)}}
{{about|eggs as food for humans|eggs as food hunted by other animals|Egg predation}}
{{pp-vandalism|small=yes}}
{{Use dmy dates|date=January 2018}}
{{Infobox food
| image    = Huevo frito.jpg
| caption  = An egg being fried
| cookbook = Egg
}}

Humans and other [[Hominidae|hominids]] have consumed [[Egg|eggs]] for millions of years.<ref>Kenneth F. Kiple, ''A Movable Feast: Ten Millennia of Food Globalization'' (2007), p. 22.</ref> The most widely consumed eggs are those of [[fowl]], especially [[chicken]]s. People in Southeast Asia began harvesting chicken eggs for food by 1500 BCE.<ref>{{cite journal |last1=Peters |first1=Joris |last2=Lebrasseur |first2=Ophélie |last3=Irving-Pease |first3=Evan K. |last4=Paxinos |first4=Ptolemaios Dimitrios |last5=Best |first5=Julia |last6=Smallman |first6=Riley |last7=Callou |first7=Cécile |last8=Gardeisen |first8=Armelle |last9=Trixl |first9=Simon |last10=Frantz |first10=Laurent |last11=Sykes |first11=Naomi |last12=Fuller |first12=Dorian Q. |last13=Larson |first13=Greger |display-authors=3 |title=The biocultural origins and dispersal of domestic chickens |journal=Proceedings of the National Academy of Sciences |date=14 June 2022 |volume=119 |issue=24 |article-number=e2121978119 |doi=10.1073/pnas.2121978119 |doi-access=free |pmid=35666876 |pmc=9214543 |bibcode=2022PNAS..11921978P}}</ref> Eggs of other [[bird]]s, such as [[duck]]s and [[ostriches]], are eaten regularly but much less commonly than those of chickens. People may also eat the eggs of [[reptile]]s, [[amphibian]]s, and [[fish]]. Fish eggs consumed as food are known as [[roe]] or [[caviar]].

[[Chicken|Hens]] and other egg-laying creatures are raised throughout the world, and [[mass production]] of chicken eggs is a global industry. In 2009, an estimated 62.1 million [[metric ton]]s of eggs were produced worldwide from a total laying flock of approximately 6.4 billion hens.<ref>[http://www.wattagnet.com/Outlook_for_egg_production.html Outlook for egg production] {{Webarchive |url=https://web.archive.org/web/20150315145439/http://www.wattagnet.com/Outlook_for_egg_production.html |date=15 March 2015 }} WATT Ag Net – Watt Publishing Co</ref> There are issues of regional variation in demand and expectation, as well as current debates concerning methods of mass production. In 2012, the [[European Union]] banned [[Battery cage|battery husbandry]] of chickens.

== History ==
[[File:Maler der Grabkammer des Menna 009.jpg|thumb|Ancient Egyptian depictions of offerings at the [[TT69|tomb of Menna]], including a basket of eggs]]
Bird eggs have been valuable foodstuffs since [[prehistory]], in both hunting societies and more recent cultures where birds were domesticated. The chicken was most likely domesticated for its eggs (from jungle fowl native to tropical and subtropical Southeast Asia and [[Indian subcontinent]]) before 7500 [[Common Era|BCE]]. [[Chicken]]s were brought to Sumer and Egypt by 1500 BCE, and arrived in [[Greece]] around 800 BCE, where the [[quail]] had been the primary source of eggs.<ref name="McGeep70">{{cite book |title=McGee on Food and Cooking |first=Harold |last=McGee |publisher=Hodder and Stoughton |year=2004 |isbn=978-0-340-83149-6 |page=70}}</ref> In [[Thebes, Egypt]], the tomb of Haremhab, dating to approximately 1420 BCE, shows a depiction of a man carrying bowls of [[ostrich egg]]s and other large eggs, presumably those of the [[pelican]], as offerings.<ref name=Brothwell>{{cite book |title=Food in Antiquity: A Survey of the Diet of Early Peoples |first=Don R. |last=Brothwell |author2=Patricia Brothwell |publisher=[[Johns Hopkins University Press]] |pages=54–55 |isbn=978-0-8018-5740-9 |year=1997}}</ref> In [[ancient Rome]], eggs were preserved using a number of methods and meals often started with an egg course.<ref name=Brothwell/> The [[Ancient Rome|Romans]] crushed the shells in their plates to prevent evil spirits from hiding there.<ref name=Larousse/> The [[Babylonian Talmud]], a Jewish work from [[late antiquity]], states, "A soft-boiled egg is better than six logs of [[Farina (food)|farina]]."<ref name=":2">{{Cite book |last=Broshi |first=Magen |title=Bread, Wine, Walls and Scrolls |date=2001 |publisher=Bloomsbury Publishing PLC |isbn=978-1-84127-201-6 |series=The Library of Second Temple Studies |location=London |page=137}}</ref>

In the [[Middle Ages]], eggs were forbidden during [[Lent]] because of their richness,<ref name=Larousse/> although the motivation for forgoing eggs during Lent was not entirely religious. An annual pause in egg consumption allowed farmers to rest their flocks, and also to limit their hens' consumption of feed during a time of year when food stocks were usually scarce.

Eggs scrambled with acidic fruit juices were popular in [[France]] in the seventeenth century; this may have been the origin of [[lemon curd]].<ref name="McGee087"/>

[[File:Scenes at the Samarkand Square, or the Registan, and Its Market Types. Egg Vendors WDL10882.png|thumb|Egg vendors in [[Samarkand]], {{Circa|1870}}]]
The dried egg industry developed in the nineteenth century, before the rise of the frozen egg industry.<ref name=Stadelman221>{{cite book |title=Egg Science and Technology |first=William |last=Stadelman |publisher=Haworth Press |year=1995 |isbn=978-1-56022-854-7 |pages=221–223}}</ref> 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.<ref name=Stadelman221/> The production of [[Powdered eggs|dried eggs]] significantly expanded during [[World War II]], for use by the United States Armed Forces and its allies.<ref name=Stadelman221/>

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.<ref>{{cite news |url=http://www.bcnorth.ca/magazine/pages/Jim/egg/egg1.htm |title=The Coyle Egg-Safety Carton |first=Jim |last=Easterday |publisher=Hiway16 Magazine |date=21 April 2005 |access-date=21 April 2008 |archive-url=https://web.archive.org/web/20080915080915/http://www.bcnorth.ca/magazine/pages/Jim/egg/egg1.htm |archive-date=15 September 2008 }}</ref> [[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 (often made of recycled material) that once again became more widely used.

Whereas the wild Asian fowl from which domesticated chickens are descended typically lay about a dozen eggs each year during the breeding season, several millennia of selective breeding have produced domesticated hens capable of laying more than three hundred eggs each annually, and to lay eggs year round.

== Varieties ==
[[File:Vogeleier.jpg|thumb|Quail eggs (upper left), chicken egg (lower left), and [[ostrich]] egg (right)]]
[[File:Eggs in basket 2020 G1.jpg|thumb|Collected chicken eggs and quail eggs in a wicker basket]]
[[Bird]] eggs are a common [[food]] and one of the most versatile [[ingredients]] used in cooking. They are important in many branches of the modern [[food industry]].<ref name=Larousse>{{cite book |title=Larousse Gastronomique |first=Prosper |last=Montagne |isbn=978-0-609-60971-2 |publisher=Clarkson Potter |year=2001 |pages=447–448 |title-link=Larousse Gastronomique}}</ref>

The most commonly used bird eggs are those from the [[chicken]], [[duck]], and [[goose]]. Smaller eggs, such as [[quail egg]]s, are used occasionally as a gourmet ingredient in Western countries. Eggs are a common everyday food in many parts of Asia, such as China and [[Thailand]], with Asian production providing 59 percent of the world total in 2013.<ref>{{cite web |url=http://www.thepoultrysite.com/articles/3446/global-poultry-trends-2014-rapid-growth-in-asias-egg-output/ |title=Global Poultry Trends 2014: Rapid Growth in Asia's Egg Output |website=The Poultry Site |date=6 May 2015 |access-date=12 June 2016 |archive-url=https://web.archive.org/web/20160810232554/http://www.thepoultrysite.com/articles/3446/global-poultry-trends-2014-rapid-growth-in-asias-egg-output/ |archive-date=10 August 2016}}</ref>

The largest bird eggs, from [[ostrich]]es, tend to be used only as special luxury food. [[Gull egg]]s are considered a delicacy in [[England]],<ref name=Roux8>{{cite book |title=Eggs |first=Michel |last=Roux |author2=Martin Brigdale |publisher=Wiley |isbn=978-0-471-76913-2 |year=2006 |page=8}}</ref> 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.<ref name=Stadelman001>{{cite book |title=Egg Science and Technology |first=William |last=Stadelman |publisher=Haworth Press |year=1995 |isbn=978-1-56022-854-7 |page=1}}</ref> [[Pheasant]] eggs and [[emu]] eggs are edible, but less widely available;<ref name=Roux8/> sometimes they are obtainable from farmers, [[wikt:poulterer|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.<ref name=Roux8/>

== Production ==
[[File:World Production Of Hen Eggs.svg|thumb|World production of hen eggs]]
In 2017, world production of chicken eggs was 80.1 million [[tonne]]s. The largest producers were China with 31.3 million of this total, the United States with 6.3 million, India at 4.8 million, Mexico at 2.8 million, Japan at 2.6 million, and Brazil and Russia with 2.5 million each.<ref name="faostat">{{cite web |url=http://faostat3.fao.org/browse/Q/QL/E |title=Eggs, hen, in shell; Production/Livestock Primary for World in 2017 |publisher=[[Food and Agriculture Organization]] of the [[United Nations]], Statistics Division (FAOSTAT) |date=2019 |access-date=3 October 2019 |archive-date=5 March 2016 |archive-url=https://web.archive.org/web/20160305013333/http://faostat3.fao.org/browse/Q/QL/E}}</ref> The largest egg factory in British Columbia, for example, ships 12 million eggs per week.<ref>{{cite news |last1=Quito |first1=Anne |title=Target used 16,000 eggs to decorate a dinner party, in a grand display of design's wastefulness |url=https://qz.com/973820/target-used-16000-eggs-to-decorate-a-dinner-party-then-sent-them-to-a-pig-farm/ |access-date=11 May 2017 |work=[[Quartz (publication)]] |date=11 May 2017 |archive-date=11 May 2017 |archive-url=https://web.archive.org/web/20170511193203/https://qz.com/973820/target-used-16000-eggs-to-decorate-a-dinner-party-then-sent-them-to-a-pig-farm/ |url-status=live}}</ref>

[[File:Egg index.webp|thumb|[[Urner Barry]] index of egg prices in the United States, 2019–2025]]
For the month of January 2019, the United States produced 9.41 billion eggs, with 8.2 billion for table consumption and 1.2 billion for raising chicks.<ref name="carey">{{cite news |last1=Varley |first1=Kevin |last2=Carey |first2=Dominic |url=https://www.bloomberg.com/news/articles/2019-02-27/the-u-s-produced-enough-eggs-in-january-to-reach-the-moon |title=The U.S. produced enough eggs in January to reach the Moon |newspaper=[[Bloomberg News]] |date=27 February 2019 |access-date=28 February 2019 |archive-date=1 March 2019 |archive-url=https://web.archive.org/web/20190301074432/https://www.bloomberg.com/news/articles/2019-02-27/the-u-s-produced-enough-eggs-in-january-to-reach-the-moon |url-status=live}}</ref> Americans are projected to each consume 279 eggs in 2019, the highest since 1973, but less than the 405 eggs eaten per person in 1945.<ref name=carey/>

During production, eggs can be [[candling|candled]] to check their quality.<ref name="ui">{{cite web |url=http://urbanext.illinois.edu/eggs/res26-candling.html |title=Candling eggs |publisher=[[University of Illinois system|University of Illinois Extension]] |quote=Eggs are candled to determine the condition of the air cell, yolk, and white. Candling detects bloody whites, blood spots, or meat spots, and enables observation of germ development. Candling is done in a darkened room with the egg held before a light. The light penetrates the egg and makes it possible to observe the inside of the egg. Incubated eggs are candled to determine whether they are fertile and, if fertile, to check the growth and development of the embryo |date=2019 |access-date=6 June 2012 |archive-date=3 May 2015 |archive-url=https://web.archive.org/web/20150503172110/http://urbanext.illinois.edu/eggs/res26-candling.html |url-status=live}}</ref> The size of an egg's air cell is determined, and if fertilization took place three to six days or earlier prior to the candling, blood vessels can typically be seen as evidence that the egg contains an embryo.<ref name=ui/> Contrary to [[List of common misconceptions|common misconception]], this is not conclusive evidence of fertilization, as blood vessels can just denote an ordinary rupture on the egg yolk surface while the egg was forming.<ref>{{Cite news |last=Wolke |first=Robert L |date=April 16, 2002 |title=Egged On |url=https://www.washingtonpost.com/archive/lifestyle/food/2002/04/17/egged-on/9b6a738c-42f2-4e9b-9ab1-029687406320/ |access-date=June 25, 2024 |newspaper=[[The Washington Post]]}}</ref> Depending on local regulations, eggs may be washed before being placed in [[egg box]]es, although washing may shorten their length of freshness.

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== Anatomy and characteristics ==
{{See also|Egg (biology)}}
[[File:Chicken Egg without Eggshell 5859.jpg|thumb|A raw chicken egg within its membrane, with the shell removed by soaking in [[vinegar]]]]
[[File:Anatomy of an egg.svg|thumb|Schematic of a chicken egg: {{olist
 | [[Eggshell]]
 | Outer membrane
 | Inner membrane
 | [[Chalaza]]
 | Exterior [[albumen]]
 | Middle [[albumen]]
 | [[Vitelline membrane]]
 | [[Nucleus of Pander]]
 | [[Germinal disc]] (nucleus)
 | Yellow [[yolk]]
 | White [[yolk]]
 | Internal [[albumen]]
 | [[Chalaza]]
 | Air cell
 | [[Cuticula]]
}}]]

Bird and reptile eggs consist of a protective [[eggshell]], albumen ([[egg white]]), and vitellus ([[yolk|egg yolk]]), contained within various [[eggshell membrane|thin membranes]]. The egg yolk is suspended in the egg white by one or two spiral bands of tissue called the [[chalaza]]e (from the Greek word [[wikt:χάλαζα|χάλαζα]], meaning 'hailstone' or 'hard lump'). The shape of a chicken egg resembles a [[prolate spheroid]] with one end larger than the other and has cylindrical symmetry along the long axis.

=== Air cell ===
The larger end of the egg contains an air cell that forms when the contents of the egg cool down and contract after it is laid. Chicken eggs are graded according to the size of this air cell, measured during [[candling]]. A very fresh egg has a small air cell and receives a grade of AA. As the size of the air cell increases and the quality of the egg decreases, the grade moves from AA to A to B. This provides a way of testing the age of an egg: as the air cell increases in size due to air being drawn through pores in the shell as water is lost, the egg becomes less dense and the larger end of the egg will rise to increasingly shallower depths when the egg is placed in a bowl of water. A very old egg will float in the water and should not be eaten,<ref name="McGee">{{cite book |last=McGee |first=H. |title=On Food and Cooking: The Science and Lore of the Kitchen |location=New York |publisher=Scribners |year=2004 |isbn=978-0-684-80001-1}}</ref> especially if a foul odor can be detected if the egg is cracked open.<ref>{{Cite web |url=https://ask.usda.gov/s/article/What-does-it-mean-when-an-egg-floats-in-water |title=AskUSDA |website=ask.usda.gov |access-date=1 December 2022 |archive-date=1 December 2022 |archive-url=https://web.archive.org/web/20221201125357/https://ask.usda.gov/s/article/What-does-it-mean-when-an-egg-floats-in-water |url-status=live}}</ref>

=== Shell ===
{{Main|Eggshell}}
Eggshell color is caused by [[pigment]] deposition during egg formation in the [[oviduct]] and may vary according to [[species]] and [[breed]], from the more common white or brown to pink or speckled blue-green. The brown pigment is [[protoporphyrin IX]], a precursor of [[heme]], and the blue pigment is [[biliverdin]], a product of the breakdown of heme.<ref name="Sachar" >{{cite journal |title=Protoporphyrin IX: The Good, the Bad, and the Ugly |year=2016 |last1=Sachar |first1=M. |last2=Anderson |first2=K. E. |last3=Ma |first3=X. |journal=Journal of Pharmacology and Experimental Therapeutics |volume=356 |issue=2 |pages=267–275 |doi=10.1124/jpet.115.228130 |doi-access=free |pmid=26588930 |pmc=4727154}}</ref><ref>{{cite journal |volume=94 |issue=10 |title=Isolation of Biliverdin IXα, as its Dimethyl Ester, from Emu Eggshells |year=2017 |journal=Journal of Chemical Education |pages=1533–1537 |last1=Halepas |first1=Steven |last2=Hamchand |first2=Randy |last3=Lindeyer |first3=Samuel E. D. |last4=Brückner |first4=Christian |doi=10.1021/acs.jchemed.7b00449 |bibcode=2017JChEd..94.1533H}}</ref> Generally, [[List of chicken breeds|chicken breeds]] with white ear lobes lay white eggs, whereas chickens with red ear lobes lay brown eggs.<ref>{{cite web |url=http://www.ces.purdue.edu/extmedia/AS/AS-518.pdf |title=Information on chicken breeds |access-date=10 January 2010 |archive-url=https://web.archive.org/web/20100216212628/http://www.ces.purdue.edu/extmedia/AS/AS-518.pdf |archive-date=16 February 2010 }}</ref> Although there is no significant link between shell color and nutritional value, often there is a cultural preference for one color over another (see {{section link||Color of eggshell}} below). As candling is less effective with brown eggs, they have a significantly higher incidence of blood spots.<ref>{{cite web |url=https://qz.com/431136/heres-why-your-brown-eggs-have-more-blood-spots-than-white-ones/ |title=Here's why your brown eggs have more blood spots than white ones |first=Deena |last=Shanker |date=19 June 2015 |access-date=22 January 2018 |archive-date=17 November 2017 |archive-url=https://web.archive.org/web/20171117192319/https://qz.com/431136/heres-why-your-brown-eggs-have-more-blood-spots-than-white-ones/ |url-status=live}}</ref>

=== Membrane ===
{{Main|Eggshell membrane}}

The [[eggshell membrane]] is a clear film lining the eggshell, visible when one peels a boiled egg. Primarily, it is composed of fibrous [[proteins]] such as [[collagen]] [[Type I collagen|type I]].<ref>{{cite journal |last1=Wong |first1=M. |last2=Hendrix |first2=M.J. |last3=van der Mark |first3=K. |last4=Little |first4=C. |last5=Stern |first5=R. |title=Collagen in the egg shell membranes of the hen |journal=Dev Biol |date=July 1984 |volume=104 |issue=1 |pages=28–36 |pmid=6203793 |doi=10.1016/0012-1606(84)90033-2}}</ref> These membranes may be used commercially as a dietary supplement.

=== White ===
{{Main|Egg white}}

"White" is the common name for the clear liquid (also called the albumen or the glair/glaire) contained within an egg. Colorless and transparent initially, upon cooking it turns white and opaque. In chickens, it is formed from the layers of secretions of the anterior section of the hen [[oviduct]] during the passage of the egg.<ref>Ornithology, Volume 1994 By Frank B. Gill p. 361</ref> It forms around both [[Fertilisation#Fertilisation in animals|fertilized]] and unfertilized yolks. The primary natural purpose of egg white is to protect the yolk and provide additional nutrition during the growth of the [[embryo]].

Egg white consists primarily of approximately 90 percent water into which is dissolved 10 percent [[protein]]s (including [[albumin]]s, [[mucoprotein]]s, and [[globulin]]s). Unlike the yolk, which is high in [[lipid]]s (fats), egg white contains almost no fat and the [[carbohydrate]] content is less than one percent. Egg white has many uses in food and many other applications, including the preparation of [[vaccine]]s, such as [[Influenza vaccine|those for influenza]].<ref>{{cite web |title=How Influenza (Flu) Vaccines Are Made |url=https://www.cdc.gov/flu/protect/vaccine/how-fluvaccine-made.htm |publisher=Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases, US Department of Health and Human Services |access-date=30 April 2017 |date=7 November 2016 |archive-url=https://web.archive.org/web/20141121200238/http://www.cdc.gov/flu/protect/vaccine/how-fluvaccine-made.htm |archive-date=21 November 2014}}</ref>

=== Yolk ===
{{Main|Egg yolk}}
[[File:An egg with two yols.jpg|thumb|A single egg with two yolks]] The [[Egg yolk|yolk]] in a newly laid egg is round and firm. As the yolk ages, it absorbs water from the albumen, which increases its size and causes it to stretch and weaken the [[vitelline membrane]] (the clear casing enclosing the yolk). The resulting effect is a flattened and enlarged yolk shape.

Yolk color is dependent on the diet of the hen. If the diet contains yellow or orange plant [[pigments]] known as [[xanthophyll]]s, then they are deposited in the yolk, coloring it. [[Lutein]] is the most abundant pigment in egg yolk.<ref>F. Karadas et al., Effects of carotenoids from lucerne, marigold and tomato on egg yolk pigmentation and carotenoid composition. Br Poult Sci. 2006 Oct;47(5):561-6. {{Cite journal |doi=10.1080/00071660600962976 |title=Effects of carotenoids from lucerne, marigold and tomato on egg yolk pigmentation and carotenoid composition |pmid=17050099 |year=2006 |last1=Karadas |first1=F. |last2=Grammenidis |first2=E. |last3=Surai |first3=P. F. |last4=Acamovic |first4=T. |last5=Sparks |first5=N. H. C. |journal=British Poultry Science |volume=47 |issue=5 |pages=561–566 |s2cid=20868953}}</ref> A diet without such colorful foods may result in an almost colorless yolk. Yolk color is, for example, enhanced if the diet includes foods such as yellow [[maize]] and [[tagetes|marigold]] petals.<ref name="usda-eggs">[https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/eggs/shell-eggs-farm-table Shell eggs from farm to table]. USDA Food Safety and Inspection Service, (2019).</ref> In the US, the use of artificial color additives is forbidden.<ref name="usda-eggs"/>

=== Abnormalities ===

Abnormalities that have been found in eggs purchased for human consumption include:
* '''[[Yolk#Double-yolk eggs|Double-yolk eggs]]''', when an egg contains two or more yolks, occurs when ovulation occurs too rapidly, or when one yolk becomes joined with another yolk.<ref>{{cite web |url=http://www.abc.net.au/science/k2/moments/s409538.htm |title=Double-yolked eggs and chicken development |first=Karl S. |last=Kruszelnicki |year=2003 |publisher=[[Australian Broadcasting Corporation]] |access-date=9 December 2007 |archive-date=14 July 2008 |archive-url=https://web.archive.org/web/20080714061959/http://www.abc.net.au/science/k2/moments/s409538.htm |url-status=live}}</ref>
* '''[[Yolkless egg|Yolkless eggs]]''', which contain whites but no yolk, usually occurs during a pullet's first effort, produced before her laying mechanism is fully ready.<ref name="Dwarf Eggs and the Timing of Ovulation in the Domestic Fowl">{{cite journal |title=Dwarf Eggs and the Timing of Ovulation in the Domestic Fowl |date=25 June 1996 |volume=210 |issue=5043 |doi=10.1038/2101371a0 |journal=Nature |page=1371 |last1=Rookledge |first1=K. A |last2=Heald |first2=P. J |s2cid=4280287 |doi-access=free}}</ref>
* '''Double-shelled eggs''', where an egg may have two or more outer shells, is caused by a counter-peristalsis contraction and occurs when a second oocyte is released by the ovary before the first egg has completely traveled through the oviduct and been laid.<ref name="The Case of the Double-Shelled Egg">{{cite journal |url=https://academic.oup.com/ps/article-abstract/48/1/349/1597808?redirectedFrom=PDF |title=The Case of the Double-Shelled Egg |date=1 January 1969 |access-date=4 September 2019 |volume=48 |issue=1 |doi=10.3382/ps.0480349 |pmid=5389851 |journal=Poultry Science |pages=349–350 |last1=Blaine |first1=E. M |last2=Munroe |first2=S. S |doi-access=free |archive-date=23 December 2019 |archive-url=https://web.archive.org/web/20191223174541/https://academic.oup.com/ps/article-abstract/48/1/349/1597808?redirectedFrom=PDF |url-status=live}}</ref>
* '''Shell-less''' or '''thin-shelled eggs''' may be caused by [[egg drop syndrome]].<ref>{{Cite web |url=http://www.cfsph.iastate.edu/Factsheets/pdfs/egg_drop_syndrome.pdf |title=Egg Drop Syndrome 1976 |vauthors=Spickler, Rovid A |date=2017 |access-date=20 February 2019 |archive-date=23 November 2018 |archive-url=https://web.archive.org/web/20181123133358/http://www.cfsph.iastate.edu/Factsheets/pdfs/egg_drop_syndrome.pdf |url-status=live}}</ref>

== Culinary properties ==
=== Types of dish ===
{{See also|List of egg dishes}}
[[File:Fried Egg 2.jpg|thumb|A fried chicken egg, [[wikt:sunny side up|sunny side up]]]]
[[File:Rührei.jpg|thumb|[[Scrambled eggs]] served with ham and toast]]
Chicken eggs are widely used in many types of dish, both sweet and savory, including many [[baking|baked goods]]. Some of the most common preparation methods include [[scrambled egg|scrambled]], [[fried egg|fried]], [[poached egg|poached]], [[boiled egg|hard-boiled]], soft-boiled, [[omelettes]], and [[pickled egg|pickled]]. They also may be eaten raw, although this is not recommended for people who may be especially susceptible to [[salmonellosis]], such as the elderly, the infirm, or pregnant women. In addition, 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.<ref>{{cite journal |last1=Evenepoel |first1=P. |last2=Geypens |first2=B. |last3=Luypaerts |first3=A. |last4=Hiele |first4=M. |last5=Ghoos |first5=Y. |last6=Rutgeerts |first6=P. |display-authors=3 |year=1998 |title=Digestibility of Cooked and Raw Egg Protein in Humans as Assessed by Stable Isotope Techniques |url=http://jn.nutrition.org/content/128/10/1716.abstract |journal=The Journal of Nutrition |volume=128 |issue=10 |pages=1716–1722 |doi=10.1093/jn/128.10.1716 |pmid=9772141 |doi-access=free |access-date=18 April 2011 |archive-date=18 June 2011 |archive-url=https://web.archive.org/web/20110618184528/http://jn.nutrition.org/content/128/10/1716.abstract |url-status=live}}</ref>

As a cooking ingredient, egg yolks are an important [[emulsifier]] in the kitchen, and are also used as a thickener, as in [[custard]]s.

The [[albumen]] (egg white) 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. Egg whites may be aerated or whipped to a light, fluffy consistency, and often are used in desserts such as [[meringue]]s and [[mousse]].

Ground eggshells sometimes are used as a [[food additive]] to deliver [[calcium]].<ref>{{cite journal |author1=Anne Schaafsma |author2=Gerard M Beelen |title=Eggshell powder, a comparable or better source of calcium than purified calcium carbonate: piglet studies |journal=Journal of the Science of Food and Agriculture |volume=79 |issue=12 |pages=1596–1600 |year=1999 |url=http://www3.interscience.wiley.com/cgi-bin/abstract/63003036/ABSTRACT |archive-url=https://archive.today/20121216134419/http://www3.interscience.wiley.com/cgi-bin/abstract/63003036/ABSTRACT |archive-date=16 December 2012 |doi=10.1002/(SICI)1097-0010(199909)79:12<1596::AID-JSFA406>3.0.CO;2-A|bibcode=1999JSFA...79.1596S |url-access=subscription }}</ref> 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.<ref>Marian Burros, [https://www.nytimes.com/2007/02/07/dining/07eggs.html?_r=0 "What the Egg Was First"] {{Webarchive |url=https://web.archive.org/web/20161224091430/http://www.nytimes.com/2007/02/07/dining/07eggs.html?_r=0 |date=24 December 2016 }}, ''The New York Times'', 7 February 2007</ref>

=== Cooking ===
[[File:Potato galettes with quail eggs.jpg|thumb|Soft-boiled [[quail eggs]] with potato [[galette]]s. The yolk of the eggs have not yet fully solidified.]]
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]], or solidifies, between {{convert|61|and|70|C|F}}. Egg white gels at different temperatures: {{convert|60|to|73|C|F}}. The white contains exterior albumen which sets at the highest temperature. In practice, in many cooking processes the white gels first because it is exposed to higher temperatures for longer.<ref>{{cite journal |last1=Vega |first1=César |last2=Mercadé-Prieto |first2=Ruben |year=2011 |title=Culinary Biophysics: On the Nature of the 6X°C Egg |journal=Food Biophysics |volume=6 |issue=1 |pages=152–9 |doi=10.1007/s11483-010-9200-1 |s2cid=97933856}}</ref>

Salmonella is killed instantly at {{convert|160|F|C|order=flip}}, but also is killed from {{convert|54.5|C|F}}, if held at that temperature for sufficiently long time periods. To avoid the issue of salmonella, [[Pasteurized eggs|eggs may be pasteurized]] in-shell at {{convert|57|C|F}} for an hour and 15 minutes. Although the white then is slightly milkier, the eggs may be used in normal ways. Whipping for meringue takes significantly longer, but the final volume is virtually the same.<ref>{{cite journal |vauthors=Schuman JD, Sheldon BW, Vandepopuliere JM, Ball HR |title=Immersion heat treatments for inactivation of Salmonella enteritidis with intact eggs |journal=Journal of Applied Microbiology |volume=83 |issue=4 |pages=438–44 |date=October 1997 |pmid=9351225 |doi=10.1046/j.1365-2672.1997.00253.x |s2cid=22582907}}</ref>

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.<ref>{{Cite journal |last1=Tinkler |first1=Charles Kenneth |last2=Soar |first2=Marion Crossland |date=1 April 1920 |title=The Formation of Ferrous Sulphide in Eggs during Cooking |journal=Biochemical Journal |volume=14 |issue=2 |pages=114–119 |doi=10.1042/bj0140114 |issn=0006-2936 |pmc=1258902 |pmid=16742889}}</ref> It also may occur with an abundance of iron in the cooking water.<ref>{{Cite web |date=22 March 2023 |title=What causes a green ring around the yolk of a hard-cooked egg? |url=https://ask.usda.gov/s/article/What-causes-a-green-ring-around-the-yolk-of-a-hard-cooked-egg |archive-url=https://web.archive.org/web/20231027145750/https://ask.usda.gov/s/article/What-causes-a-green-ring-around-the-yolk-of-a-hard-cooked-egg |archive-date=27 October 2023 |website=AskUSDA}}</ref> Overcooking harms the quality of the protein.<ref>{{Cite news |url=https://timesofindia.indiatimes.com/life-style/health-fitness/health-news/what-happens-when-you-overcook-eggs/articleshow/70191466.cms |title=overcooked eggs |website=Times of india |date=12 July 2019 |access-date=13 February 2020 |archive-date=27 July 2019 |archive-url=https://web.archive.org/web/20190727004604/https://timesofindia.indiatimes.com/life-style/health-fitness/health-news/what-happens-when-you-overcook-eggs/articleshow/70191466.cms |url-status=live}}</ref> Chilling an overcooked egg for a few minutes in cold water until it is completely cooled may prevent the greenish ring from forming on the surface of the yolk.<ref>{{Cite web |date=28 March 2018 |title=How To Make Perfect Hard-Boiled Eggs With No Green Ring |url=https://patch.com/maryland/annapolis/how-make-perfect-hard-boiled-eggs-no-green-ring |access-date=8 January 2022 |website=Annapolis, MD Patch |language=en |archive-date=8 January 2022 |archive-url=https://web.archive.org/web/20220108034205/https://patch.com/maryland/annapolis/how-make-perfect-hard-boiled-eggs-no-green-ring |url-status=live}}</ref>

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.<ref>This was shown experimentally and documented in the book ''[[The Food Lab]]: Better Home Cooking Through Science'' by J. Kenji López-Alt; published 21 September 2015 by W. W. Norton & Company, {{ISBN|978-0-393-08108-4}}</ref>

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.<ref>{{Cite news |last=Nazaryan |first=Alexander |date=2025-02-06 |title=How to Boil an Egg? Scientists Claim to Have Cracked the Recipe. |url=https://www.nytimes.com/2025/02/06/science/boiled-egg-science-recipe.html |access-date=2025-02-11 |work=The New York Times |language=en-US |issn=0362-4331}}</ref> The method requires alternating between boiling and lukewarm water: two minutes in {{convert|100|C}} water, two minutes at {{convert|30|C}}, repeated eight times.<ref>{{Cite journal |last1=Di Lorenzo |first1=Emilia |last2=Romano |first2=Francesca |last3=Ciriaco |first3=Lidia |last4=Iaccarino |first4=Nunzia |last5=Izzo |first5=Luana |last6=Randazzo |first6=Antonio |last7=Musto |first7=Pellegrino |last8=Di Maio |first8=Ernesto |date=2025-02-06 |title=Periodic cooking of eggs |journal=Communications Engineering |language=en |volume=4 |issue=1 |pages=1–10 |article-number=5 |doi=10.1038/s44172-024-00334-w |pmid=39915675 |issn=2731-3395|pmc=11802719 }}</ref>

=== Flavor variations ===
[[File:HK Sai Ying Pun Des Voeux Road West Tea Eggs Snack Shop.JPG|thumb|A batch of [[tea egg]]s with shell intact soaking in a brew of spices and tea]]
Although the age of the egg and the conditions of its storage have a greater influence, the bird's diet affects the flavor of the egg.<ref name="McGee087">{{cite book |last=McGee |first=Harold |author-link=Harold McGee |title=On Food and Cooking: The Science and Lore of the Kitchen |publisher=Scribner |year=2004 |isbn=978-0-684-80001-1 |page=87}}</ref> For example, when a brown-egg chicken breed eats [[rapeseed]] (canola) or soy meals, its intestinal microbes metabolize them into fishy-smelling [[triethylamine]], which ends up in the egg.<ref name="McGee087"/> The unpredictable diet of free-range hens will produce likewise, unpredictable egg flavors.<ref name="McGee087"/> Duck eggs tend to have a flavor distinct from, but still resembling, chicken eggs.

Eggs may be soaked in mixtures to absorb flavor. [[Tea egg]]s, a common snack sold from street-side carts in China, 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.<ref>{{Cite web |last=Zhu |first=Maggie |date=2018-06-01 |title=Chinese Tea Eggs (w/ Soft and Hard Boiled Eggs, 茶叶蛋) |url=https://omnivorescookbook.com/chinese-tea-eggs/ |access-date=2024-10-07 |website=Omnivore's Cookbook |language=en-US}}</ref>

=== Storage ===
Careful storage of edible eggs is extremely important, as an improperly handled egg may contain elevated levels of ''[[Salmonella]]'' [[bacteria]] that may cause severe [[food poisoning]]. In the US, eggs are washed. This cleans the shell, but erodes its [[wikt:cuticle|cuticle]].<ref name="Anatomy">{{cite web |title=Anatomy of an Egg |url=https://www.exploratorium.edu/cooking/eggs/eggcomposition.html |website=Science of Cooking |publisher=Exploratorium |access-date=30 October 2017 |archive-date=14 November 2017 |archive-url=https://web.archive.org/web/20171114004330/http://www.exploratorium.edu/cooking/eggs/eggcomposition.html |url-status=live}}</ref><ref name="Forbes">{{cite news |last1=Arumugam |first1=Nadia |title=Why American Eggs Would Be Illegal In A British Supermarket, And Vice Versa |url=https://www.forbes.com/sites/nadiaarumugam/2012/10/25/why-american-eggs-would-be-illegal-in-a-british-supermarket-and-vice-versa/3/#368c25d752cf |access-date=30 October 2017 |work=Forbes |date=25 October 2012 |archive-date=24 October 2017 |archive-url=https://web.archive.org/web/20171024210821/https://www.forbes.com/sites/nadiaarumugam/2012/10/25/why-american-eggs-would-be-illegal-in-a-british-supermarket-and-vice-versa/3/#368c25d752cf |url-status=live}}</ref> The USDA thus recommends refrigerating eggs to prevent the growth of ''Salmonella''.<ref name="usda-eggs"/>

Refrigeration also preserves the taste and texture.<ref>{{cite web |url=http://www.motherearthnews.com/Sustainable-Farming/1977-11-01/Fresh-Eggs.aspx |title=How to Store Fresh Eggs |archive-url=https://web.archive.org/web/20111127071159/http://www.motherearthnews.com/Sustainable-Farming/1977-11-01/Fresh-Eggs.aspx |archive-date=27 November 2011 |work=Mother Earth News |date=1 November 1977 }}</ref>{{Unreliable source?|date=May 2024}} In Europe, eggs are not usually washed, and the shells are dirtier, however the cuticle is undamaged, and they do not require refrigeration.<ref>{{cite web |url=https://www.npr.org/sections/thesalt/2014/09/11/336330502/why-the-u-s-chills-its-eggs-and-most-of-the-world-doesnt |website=[[NPR]] |title=Why The U.S. Chills Its Eggs And Most Of The World Doesn't |date=September 11, 2014 |first=Rae Ellen |last=Bichell |access-date=4 February 2025 }}</ref><ref name=Forbes/>{{Unreliable source?|date=May 2024}} In the UK in particular, hens are immunized against salmonella and generally, their eggs are safe for 21 days.<ref name=Forbes/>

=== Preservation ===
[[File:Salty egg.JPG|thumb|upright|220px|Salted duck egg]]
The simplest method to preserve an egg is to treat it with [[salt]]. Salt draws water out of [[bacteria]] and [[Mold (fungus)|mold]]s, which prevents their growth.<ref name="McGee116">{{cite book |last=McGee |first=Harold |author-link=Harold McGee |title=On Food and Cooking: The Science and Lore of the Kitchen |publisher=Scribner |year=2004 |isbn=978-0-684-80001-1 |page=116}}</ref> The Chinese [[salted duck egg]] is made by immersing duck eggs in [[brine]], or coating them individually with a paste of salt and [[mud]] or [[clay]]. The eggs stop absorbing salt after approximately a month, having reached [[osmotic equilibrium]].<ref name="McGee116"/> Their yolks take on an orange-red color and solidify, but the white remains somewhat liquid. These often are boiled before consumption and are served with rice [[congee]]; the yolks are also used in [[mooncake]]s and other pastries.

[[File:Pickled egg.jpg|thumb|left|upright|220px|Pickled egg, colored with beetroot juice]]
Another method is to make [[pickled egg]]s, by boiling them first and immersing them in a mixture of [[vinegar]], salt, and spices, such as [[ginger]] or [[allspice]]. Frequently, [[beetroot]] juice is added to impart a red color to the eggs.<ref name=Stadelman479/> If the eggs are immersed in it for a few hours, the distinct red, white, and yellow colors may be seen when the eggs are sliced.<ref name=Stadelman479/> If marinated for several days or more, the red color will reach the yolk.<ref name=Stadelman479>{{cite book |title=Egg Science and Technology |first=William |last=Stadelman |publisher=Haworth Press |year=1995 |isbn=978-1-56022-854-7 |pages=479–480}}</ref> If the eggs are marinated in the mixture for several weeks or more, the vinegar will dissolve much of the shell's [[calcium carbonate]] and penetrate the egg, making it [[acidity|acidic]] enough to inhibit the growth of bacteria and molds.<ref name="McGee116"/> Pickled eggs made this way generally keep for a year or more without refrigeration.<ref name="McGee116"/>

[[File:Century egg.jpg|thumb|upright|220px|[[Century egg]]]]
A [[century egg]] or hundred-year-old egg is preserved by coating an egg in a mixture of [[clay]], [[wood ash]], salt, [[Calcium oxide|lime]], and [[rice]] straw for several weeks to several months, depending on the method of processing. After the process is completed, the yolk becomes a dark green, cream-like substance with a strong odor of sulfur and ammonia, while the white becomes a dark brown, transparent jelly with a comparatively mild, distinct flavor. The transforming agent in a century egg is its [[alkaline]] material, which gradually raises the [[pH]] of the egg from approximately 9 to 12 or more.<ref name="McGee117">{{cite book |last=McGee |first=Harold |author-link=Harold McGee |title=On Food and Cooking: The Science and Lore of the Kitchen |publisher=Scribner |year=2004 |isbn=978-0-684-80001-1 |page=117}}</ref> This chemical process breaks down some of the complex, flavorless proteins and fats of the yolk into simpler, flavorful ones, which in some way may be thought of as an "inorganic" version of [[fermentation (food)|fermentation]].

== Nutrition and health effects ==
{{Infobox nutritional value
| name           = Chicken egg<br />whole, hard-boiled
| kJ             = 647
| water          = 75 g
| protein        = 12.6 g
| fat            = 10.6 g
| carbs          = 1.12 g
| iron_mg        = 1.2
| calcium_mg     = 50
| magnesium_mg   = 10
| phosphorus_mg  = 172
| potassium_mg   = 126
| sodium_mg      = 126
| zinc_mg        = 1.0
| vitA_ug        = 149
| pantothenic_mg = 1.4
| folate_ug      = 44
| thiamin_mg     = 0.066
| riboflavin_mg  = 0.5
| niacin_mg      = 0.064
| vitB6_mg       = 0.121
| vitB12_ug      = 1.11
| vitK_ug        = 0.3
| tryptophan     = 0.153 g
| threonine      = 0.604 g
| isoleucine     = 0.686 g
| leucine        = 1.075 g
| lysine         = 0.904 g
| methionine     = 0.392 g
| cystine        = 0.292 g
| phenylalanine  = 0.668 g
| tyrosine       = 0.513 g
| valine         = 0.767 g
| arginine       = 0.755 g
| histidine      = 0.298 g
| alanine        = 0.700 g
| aspartic acid  = 1.264 g
| glutamic acid  = 1.644 g
| glycine        = 0.423 g
| proline        = 0.501 g
| serine         = 0.936 g
| vitD_iu        = 87
| vitE_mg        = 1.03
| choline_mg     = 294
| opt2n          = [[Cholesterol]]
| opt2v          = 373 mg
| source_usda    = 1
| note           = For edible portion only.<br />Refuse: 12% (shell).<br />An egg just large enough to be classified as "large" in the U.S. yields 50 grams of egg without shell. This size egg is classified as "medium" in Europe and "standard" in New Zealand.<br />[https://fdc.nal.usda.gov/food-details/173424/nutrients Link to USDA Database entry]
}}

Egg yolks and whole eggs store significant amounts of [[protein]] and [[choline]].<ref name="USDA_Home_and_Garden_no_264"/><ref name="USDA_Food_Choline_Chart">{{Cite web |title=USDA Database for the Choline Content of Common Foods |url=http://www.nal.usda.gov/fnic/foodcomp/Data/Choline/Choline.pdf |date=March 2004 |last1=Howe |first1=Juliette C. |last2=Williams |first2=Juhi R. |last3=Holden |first3=Joanne M. |publisher=United States Department of Agriculture ([[USDA]]) |page=10 |archive-url=https://web.archive.org/web/20101205060719/http://www.nal.usda.gov/fnic/foodcomp/Data/Choline/Choline.pdf |archive-date=5 December 2010 }}</ref> Due to their protein content, the [[United States Department of Agriculture]] formerly categorized eggs as ''Meat'' within the [[Food Guide Pyramid]] (now [[MyPlate]]).<ref name="USDA_Home_and_Garden_no_264">{{Cite journal |title=How to Buy Eggs |publisher=United States Department of Agriculture ([[USDA]]) |author=Agricultural Marketing Service |journal=Home and Garden Bulletin |page=1 |issue=264 |url=https://books.google.com/books?id=vAwUAAAAYAAJ |year=1995 |access-date=28 February 2019 |archive-date=5 April 2023 |archive-url=https://web.archive.org/web/20230405025950/https://books.google.com/books?id=vAwUAAAAYAAJ |url-status=live}}</ref> Under the [[Protein digestibility corrected amino acid score|Protein Digestibility Corrected Amino Acid Score]] (PDCAAS) system, they score the maximum value of 1.0, and under the [[Digestible Indispensable Amino Acid Score]] (DIAAS) system, they are also classified as an excellent-quality protein source.<ref>{{Cite journal |last=Fanelli |first=Natalia S. |last2=Martins |first2=Juliana C. F. R. |last3=Stein |first3=Hans H. |date=2024 |title=The digestible indispensable amino acid score (DIAAS) in eggs and egg-containing breakfast meals is greater than in toast breads or hash browns served without eggs |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC11658930/ |journal=Journal of Nutritional Science |volume=13 |pages=e68 |doi=10.1017/jns.2024.71 |issn=2048-6790 |pmc=11658930 |pmid=39703894}}</ref>

A {{convert|50|g|oz|adj=on}} [[Chicken egg sizes|medium/large]] chicken egg provides approximately 70&nbsp;kilocalories (290&nbsp;kJ) of food energy and 6&nbsp;grams of [[protein]].<ref name=USDAboiledeggs>[https://ndb.nal.usda.gov/ndb/foods/show/01129?n1=%7BQv%3D1%7D&fgcd=&man=&lfacet=&count=&max=25&sort=default&qlookup=egg%2C+whole%2C+boiled&offset=&format=Full&new=&measureby=&Qv=1&ds=&qt=&qp=&qa=&qn=&q=&ing= "Full Report (All Nutrients): 01129, Egg, whole, cooked, hard-boiled"]{{dead link|date=June 2025|bot=medic}}{{cbignore|bot=medic}}, USDA Branded Food Products Database</ref><ref name=USDAeggs>[https://ndb.nal.usda.gov/ndb/foods/show/45174951?fgcd=&manu=&format=&count=&max=25&offset=&sort=default&order=asc&qlookup=45174951&ds=&qt=&qp=&qa=&qn=&q=&ing= "Full Report (All Nutrients): 45174951, EGGS"]{{dead link|date=June 2025|bot=medic}}{{cbignore|bot=medic}}, USDA Branded Food Products Database</ref>

{{clarify span|Cooking methods affect the nutritional values of eggs.|date=June 2022}} For example, a large whole chicken egg contains approximately 0.45 - 0.5 μg of vitamin B12, which is concentrated in the yolk. Different cooking methods retain varying amounts of this vitamin; [[scrambled eggs]] lose about 5%, [[Fried egg|lightly fried eggs]] 5 - 15%,  and hard-boiled up to 20%.<ref>{{Cite journal |last=Moravcová |first=Monika |last2=Siatka |first2=Tomáš |last3=Krčmová |first3=Lenka Kujovská |last4=Matoušová |first4=Kateřina |last5=Mladěnka |first5=Přemysl |date=2025-06-01 |title=Biological properties of vitamin B12 |url=https://www.cambridge.org/core/journals/nutrition-research-reviews/article/biological-properties-of-vitamin-b12/58C586B5D6B9960C421D92A41D7D0691 |journal=Nutrition Research Reviews |language=en |volume=38 |issue=1 |pages=338–370 |doi=10.1017/S0954422424000210 |issn=0954-4224|doi-access=free }}</ref> Studies have also found that the average absorption of vitamin B12 from fried or boiled eggs is more than twice that from scrambled eggs.<ref>{{Cite journal |last=Doscherholmen |first=A. |last2=McMahon |first2=J. |last3=Ripley |first3=D. |date=1975-09-01 |title=Vitamin B12 absorption from eggs |journal=Proceedings of the Society for Experimental Biology and Medicine |volume=149 |issue=4 |pages=987–990 |doi=10.3181/00379727-149-38940 |issn=0037-9727 |pmid=1172618}}</ref> Eggs (boiled) supply several vitamins and minerals as significant amounts of the [[Daily Value]] (DV), including (per 100g) [[vitamin A]] (19% DV), [[riboflavin]] (42% DV), [[pantothenic acid]] (28% DV), [[vitamin B12|vitamin B<sub>12</sub>]] (46% DV), [[choline]] (60% DV), [[phosphorus]] (25% DV), [[zinc]] (11% DV) and [[vitamin D]] (15% DV).

The diet of laying hens also may affect the nutritional quality of eggs. For instance, chicken eggs that are especially high in [[omega-3]] [[fatty acid]]s are produced by feeding hens a diet containing [[polyunsaturated]] fats from sources such as [[fish oil]], [[chia seeds]], or [[flaxseeds]].<ref>{{cite journal |title=Omega-3 fatty acid profile of eggs from laying hens fed diets supplemented with chia, fish oil, and flaxseed |vauthors=Coorey R, Novinda A, Williams H, Jayasena V |journal=J Food Sci |year=2015 |volume=80 |issue=1 |pages=S180–7 |doi=10.1111/1750-3841.12735 |pmid=25557903}}</ref> [[Pastured poultry|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.<ref>{{cite journal |journal=Poultry Science |year=2011 |volume=90 |issue=7 |pages=1600–1608 |doi=10.3382/ps.2010-01289 |title=Comparison of fatty acid, cholesterol, and vitamin A and E composition in eggs from hens housed in conventional cage and range production facilities |author=Anderson KE |pmid=21673178 |doi-access=free}}</ref><ref>{{cite journal |journal=Renewable Agriculture and Food Systems |year=2010 |volume=25 |pages=45–54 |doi=10.1017/S1742170509990214 |title=Vitamins A, E and fatty acid composition of the eggs of caged hens and pastured hens |author=Karsten HD |s2cid=33668490 |display-authors=etal}}</ref>

A 2010 USDA study determined there were no significant differences of [[macronutrients]] in various chicken eggs.<ref>{{Cite journal |title=Physical quality and composition of retail shell eggs |last1=Jones |first1=Deana |last2=Musgrove |first2=Michael |journal=Poultry Science |year=2010 |pages=582–587 |doi=10.3382/ps.2009-00315 |last3=Anderson |first3=K. E. |last4=Thesmar |first4=H. S. |volume=89 |issue=3 |pmid=20181877 |doi-access=free}}</ref>

Cooked eggs are easier to digest than raw eggs,<ref>{{cite journal |last=Evenepoel |first=P |author2=Geypens B |author3=Luypaerts A |title=Digestibility of cooked and raw egg protein in humans as assessed by stable isotope techniques |journal=The Journal of Nutrition |volume=128 |issue=10 |pages=1716–1722 |date=October 1998 |pmid=9772141 |display-authors=etal |doi=10.1093/jn/128.10.1716 |doi-access=free}}</ref> as well as having a lower risk of [[salmonellosis]].<ref name="cspinet"/>

=== Cholesterol and fat ===
More than half the calories found in eggs come from the fat in the yolk; 50&nbsp;grams of chicken egg (the contents of an egg just large enough to be classified as "large" in the US, but "medium" in Europe) contains approximately five grams of fat.<!-- Please do not change the amount of fat without a source; the USDA table contained in this article is the source of fat in an egg in this section. --> [[Saturated fat]] ([[palmitic acid|palmitic]], [[stearic acid|stearic]], and [[myristic acid]]s) makes up 27 percent of the fat in an egg.<ref name="eggwhole">{{cite web |publisher=FoodData Central, US Department of Agriculture |title=Egg, whole, raw, fresh per 100 g |url=https://fdc.nal.usda.gov/food-details/171287/nutrients |date=1 April 2019 |access-date=8 July 2023}}</ref> The [[egg white]] consists primarily of water (88 percent) and protein (11 percent), with no cholesterol and 0.2 percent fat.<ref name="eggwhite">{{cite web |publisher=FoodData Central, US Department of Agriculture |title=Egg, white, raw, fresh per 100 g |url=https://fdc.nal.usda.gov/food-details/172183/nutrients |date=1 April 2019 |access-date=8 July 2023}}</ref>

There is debate over whether egg yolk presents a health risk. Some research suggests dietary [[cholesterol]] increases the ratio of total to [[High-density lipoprotein|HDL cholesterol]] and, therefore, adversely affects the body's cholesterol profile;<ref>{{cite journal |vauthors=Weggemans RM, Zock PL, Katan MB |title=Dietary cholesterol from eggs increases the ratio of total cholesterol to high-density lipoprotein cholesterol in humans: a meta-analysis |journal=Am. J. Clin. Nutr. |volume=73 |issue=5 |pages=885–91 |year=2001 |pmid=11333841 |doi=10.1093/ajcn/73.5.885 |doi-access=free}}</ref> 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.<ref name=Hu>{{cite journal |vauthors=Hu FB, Stampfer MJ, Rimm EB |title=A prospective study of egg consumption and risk of cardiovascular disease in men and women |journal=JAMA |volume=281 |issue=15 |pages=1387–94 |year=1999 |pmid=10217054 |doi=10.1001/jama.281.15.1387 |display-authors=etal |doi-access=free |bibcode=1999JAMA..281.1387H }}</ref> [[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.<ref name="McGee"/>

=== Type 2 diabetes ===

Studies have shown conflicting results about a possible connection between egg consumption and [[type 2 diabetes]].

A meta-analysis from 2013 found that eating four eggs per week was associated with a 29 percent increase in the relative risk of developing diabetes.<ref name="ReferenceA">{{cite journal |title=Egg consumption and risk of cardiovascular diseases and diabetes: a meta-analysis |year=2013 |volume=229 |issue=2 |pmid=23643053 |last1=Li |first1=Y |last2=Zhou |first2=C |last3=Zhou |first3=X |last4=Li |first4=L |pages=524–530 |doi=10.1016/j.atherosclerosis.2013.04.003 |journal=Atherosclerosis}}</ref> Another meta-analysis from 2013 also supported the idea that egg consumption may lead to an increased incidence of type two diabetes.<ref name="Shin2013">{{cite journal |vauthors=Shin JY, Xun P, Nakamura Y, He K |date=July 2013 |title=Egg consumption in relation to risk of cardiovascular disease and diabetes: a systematic review and meta-analysis |journal=Am J Clin Nutr |volume=98 |issue=1 |pages=146–59 |doi=10.3945/ajcn.112.051318 |pmc=3683816 |pmid=23676423}}</ref> A 2016 meta-analysis suggested that association of egg consumption with increased risk of incident type 2 diabetes may be restricted to cohort studies from the [[United States]].<ref>{{cite journal |vauthors=Tamez M, Virtanen J, Lajous M |year=2016 |title=Egg consumption and risk of incident type 2 diabetes: a dose–response meta-analysis of prospective cohort studies |journal=British Journal of Nutrition |volume=15 |issue=12 |pages=2212–2218 |doi=10.1017/S000711451600146X |pmid=27108219 |doi-access=free}}</ref>

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.<ref>{{cite journal |vauthors=Drouin-Chartier JP, Schwab AL, Chen S, Li Y, Sacks FM, Rosner B, Manson JE, Willett WC, Stampfer MJ, Hu FB, Bhupathiraju SN |display-authors=3 |year=2020 |title=Egg consumption and risk of type 2 diabetes: findings from 3 large US cohort studies of men and women and a systematic review and meta-analysis of prospective cohort studies |journal=The American Journal of Clinical Nutrition |url= |volume=112 |issue=3 |pages=619–630 |doi=10.1093/ajcn/nqaa115 |pmid=32453379 |pmc=7458776}}</ref>

===Cancer===
A 2015 meta-analysis found an association between higher egg consumption (five a week) with increased risk of [[breast cancer]] compared to no egg consumption.<ref>{{cite journal |vauthors=Keum N, Lee DH, Marchand N, Oh H, Liu H, Aune D, Greenwood DC, Giovannucci EL |year=2015 |title=Egg intake and cancers of the breast, ovary and prostate: a dose-response meta-analysis of prospective observational studies |journal=British Journal of Nutrition |volume=114 |issue=7 |pages=1099–107 |doi=10.1017/S0007114515002135 |pmid=26293984 |s2cid=31168561 |doi-access=free |hdl=10044/1/48759 |hdl-access=free}}</ref> Another meta-analysis found that egg consumption may increase [[ovarian cancer]] risk.<ref>{{cite journal |vauthors=Zeng ST, Guo L, Liu SK, Wang DH, Xi J, Huang P, Liu DT, Gao JF, Feng J, Zhang L |display-authors=3 |year=2015 |title=Egg consumption is associated with increased risk of ovarian cancer: Evidence from a meta-analysis of observational studies |journal=Clinical Nutrition |volume=34 |issue=4 |pages=635–641 |doi=10.1016/j.clnu.2014.07.009 |pmid=25108572}}</ref>

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.<ref>{{cite journal |vauthors=Aminianfar A, Fallah-Moshkani R, Salari-Moghaddam A, Saneei P, Larijani B, Esmaillzadeh A |display-authors=3 |year=2019 |title=Egg Consumption and Risk of Upper Aero-Digestive Tract Cancers: A Systematic Review and Meta-Analysis of Observational Studies |journal=Advances in Nutrition |volume=10 |issue=4 |pages=660–672 |doi=10.1093/advances/nmz010 |pmid=31041448 |pmc=6628841}}</ref>

A 2021 review did not find a significant association between egg consumption and breast cancer.<ref>{{cite journal |vauthors=Kazemi A, Barati-Boldaji R, Soltani S, Mohammadipoor N, Esmaeilinezhad Z, Clark CC, Babajafari S, Akbarzadeh M |display-authors=3 |year=2021 |title=Intake of Various Food Groups and Risk of Breast Cancer: A Systematic Review and Dose-Response Meta-Analysis of Prospective Studies |journal=Advances in Nutrition |volume=12 |issue=3 |pages=809–849 |doi=10.1093/advances/nmaa147 |pmid=33271590 |pmc=8166564}}</ref> A 2021 [[umbrella review]] found that egg consumption significantly increases the risk of ovarian cancer.<ref>{{cite journal |vauthors=Tanha K, Mottaghi A, Nojomi M, Moradi M, Rajabzadeh R, Lotfi S, Janani L |year=2021 |title=Investigation on factors associated with ovarian cancer: an umbrella review of systematic review and meta-analyses |journal=Journal of Ovarian Research |volume=14 |issue=1 |article-number=153 |doi=10.1186/s13048-021-00911-z |pmid=34758846 |pmc=8582179 |doi-access=free}}</ref>

=== Cardiovascular health ===
One systematic review and meta-analysis of egg consumption found that higher consumption of eggs (more than 1 egg/day) was associated with a significant reduction in risk of coronary artery disease.<ref>{{cite journal |display-authors=3 |last1=Krittanawong |first1=Chayakrit |last2=Narasimhan |first2=Bharat |last3=Wang |first3=Zhen |last4=Virk |first4=Hafeez Ul Hassan |last5=Farrell |first5=Ann M. |last6=Zhang |first6=HongJu |last7=Tang |first7=W.H. Wilson |date=January 2021 |title=Association Between Egg Consumption and Risk of Cardiovascular Outcomes: A Systematic Review and Meta-Analysis |journal=The American Journal of Medicine |volume=134 |issue=1 |pages=76–83.e2 |doi=10.1016/j.amjmed.2020.05.046 |pmid=32653422 |s2cid=220499217}}</ref> Another systematic review and meta-analysis of dietary cholesterol and egg consumption found that egg consumption was associated with an increased all-cause mortality and CVD mortality.<ref>{{Cite journal |last1=Zhao |first1=Bin |last2=Gan |first2=Lu |last3=Graubard |first3=Barry I. |last4=Männistö |first4=Satu |last5=Albanes |first5=Demetrius |last6=Huang |first6=Jiaqi |year=2022 |title=Associations of Dietary Cholesterol, Serum Cholesterol, and Egg Consumption With Overall and Cause-Specific Mortality, and Systematic Review and Updated Meta-Analysis |journal=Circulation |volume=145 |issue=20 |pages=1506–1520 |doi=10.1161/CIRCULATIONAHA.121.057642 |pmc=9134263 |pmid=35360933 |s2cid=247853807}}</ref> These contrary results may be due to somewhat different methods of study selection and the use primarily of [[Observational study|observational studies]], where [[confounding]] factors are not controlled.<ref>{{cite journal |vauthors=Zhang X, Lv M, Luo X |year=2020 |title=Egg consumption and health outcomes: a global evidence mapping based on an overview of systematic reviews |journal=Annals of Translational Medicine |volume=8 |issue=21 |page=1343 |doi=10.21037/atm-20-4243 |pmc=7723562 |pmid=33313088 |doi-access=free}}</ref>

A 2018 meta-analysis of randomized clinical trials found that consumption of eggs increases total cholesterol (TC), [[LDL-C]] and [[HDL-C]] compared to no egg-consumption but not to low-egg control diets.<ref>{{cite journal |vauthors=Rouhani MH, Rashidi-Pourfard N, Salehi-Abargouei A, Karimi M, Haghighatdoost F |display-authors=3 |title=Effects of Egg Consumption on Blood Lipids: A Systematic Review and Meta-Analysis of Randomized Clinical Trials |journal=Journal of the American College of Nutrition |date=2018 |volume=37 |issue=2 |pages=99–110 |pmid=29111915 |doi=10.1080/07315724.2017.1366878 |s2cid=33208171}}</ref> In 2020, two meta-analyses found that moderate egg consumption (up to one egg a day) is not associated with an increased cardiovascular disease risk.<ref>{{cite journal |vauthors=Drouin-Chartier JP, Chen S, Li Y |year=2020 |title=Egg consumption and risk of cardiovascular disease: three large prospective US cohort studies, systematic review, and updated meta-analysis |journal=The BMJ |url= |volume=368 |pages=m513 |doi=10.1136/bmj.m513 |pmid=32132002 |pmc=7190072}}</ref><ref>{{cite journal |vauthors=Godos J, Micek A, Brzostek T, Toledo E, Iacoviello L, Astrup A, Franco OH, Galvano F, Martinez-Gonzalez MA, Grosso G |display-authors=3 |year=2020 |title=Egg consumption and cardiovascular risk: a dose-response meta-analysis of prospective cohort studies |journal=European Journal of Nutrition |volume=60 |issue=4 |pages=1833–1862 |doi=10.1007/s00394-020-02345-7 |issn=1436-6207 |url=https://www.researchgate.net/publication/343997269 |pmid=32865658 |pmc=8137614 |s2cid=221372891 |doi-access=free}}</ref> A 2020 umbrella review concluded that increased egg consumption is not associated with cardiovascular disease risk in the general population.<ref>{{cite journal |vauthors=Mah E, Chen CO, Liska DJ |title=The effect of egg consumption on cardiometabolic health outcomes: an umbrella review |journal=Public Health Nutr |volume=23 |issue=5 |pages=935–955 |date=October 2019 |pmid=31599222 |doi=10.1017/S1368980019002441 |pmc=10200385 |s2cid=204029375}}</ref> Another umbrella review found no association between egg consumption and cardiovascular disorders.<ref>{{cite journal |vauthors=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 |display-authors=etal |title=Egg consumption and human health: an umbrella review of observational studies. |journal=International Journal of Food Sciences and Nutrition |date=2020 |volume=71 |issue=3 |pages=325–331 |pmid=31379223 |doi=10.1080/09637486.2019.1648388 |s2cid=199437922 |url=https://figshare.com/articles/journal_contribution/9250040 |access-date=15 July 2022 |archive-date=24 September 2022 |archive-url=https://web.archive.org/web/20220924220536/https://figshare.com/articles/journal_contribution/Egg_consumption_and_human_health_an_umbrella_review_of_observational_studies/9250040 |url-status=live}}</ref>

A 2013 meta-analysis found no association between egg consumption and heart disease or stroke.<ref>{{cite journal |last1=Rong |first1=Ying |last2=Chen |first2=Li |last3=Tingting |first3=Zhu |last4=Yadong |first4=Song |last5=Yu |first5=Miao |last6=Shan |first6=Zhilei |last7=Sands |first7=Amanda |last8=Hu |first8=Frank B |last9=Liu |first9=Liegang |display-authors=3 |year=2013 |title=Egg consumption and risk of coronary heart disease and stroke: dose-response meta-analysis of prospective cohort studies |journal=British Medical Journal |volume=346 |article-number=e8539 |doi=10.1136/bmj.e8539 |pmc=3538567 |pmid=23295181}}</ref><ref>{{cite web |title=No link between eggs and heart disease or stroke, says BMJ meta-analysis |date=25 January 2013 |url=http://www.foodnavigator.com/Science-Nutrition/No-link-between-eggs-and-heart-disease-or-stroke-says-BMJ-meta-analysis |access-date=22 January 2018 |archive-date=19 February 2013 |archive-url=https://web.archive.org/web/20130219063451/http://www.foodnavigator.com/Science-Nutrition/No-link-between-eggs-and-heart-disease-or-stroke-says-BMJ-meta-analysis |url-status=live}}</ref> 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.<ref name="Shin2013" /> Another 2013 meta-analysis found that eating four eggs per week increased the risk of cardiovascular disease by six percent.<ref name="ReferenceA" />

Eggs are one of the largest sources of [[phosphatidylcholine]] ([[lecithin]]) in the human diet.<ref>{{cite web |last=Patterson |first=Kristine |title=USDA Database for the Choline Content of Common Foods |url=https://www.ars.usda.gov/ARSUserFiles/80400525/Data/Choline/Choln02.pdf |access-date=25 April 2013 |publisher=U.S. Department of Agriculture |archive-date=19 October 2013 |archive-url=https://web.archive.org/web/20131019164652/http://www.ars.usda.gov/SP2UserFiles/Place/12354500/Data/Choline/Choln02.pdf |url-status=live}}</ref> A study published in the scientific journal, ''[[Nature (journal)|Nature]]'', showed that dietary phosphatidylcholine is digested by bacteria in the gut and eventually converted into the compound [[Trimethylamine N-oxide|TMAO]], a compound linked with increased heart disease.<ref>{{cite journal |last=Wang |first=Zeneng |date=7 April 2011 |title=Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease |journal=Nature |volume=472 |issue=7341 |pages=57–65 |bibcode=2011Natur.472...57W |doi=10.1038/nature09922 |pmc=3086762 |pmid=21475195}}</ref><ref>{{cite journal |last=Willyard |first=Cassandra |date=30 January 2013 |title=Pathology: At the heart of the problem |journal=Nature |volume=493 |issue=7434 |pages=S10–S11 |bibcode=2013Natur.493S..10W |doi=10.1038/493s10a |pmid=23364764 |doi-access=free |s2cid=4355857}}</ref> 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.<ref>{{cite journal |last1=Jinzhu Jia |last2=Pan Dou |last3=Meng Gao |last4=Xuejun Kong |last5=Changwei Li |last6=Zhonghua Liu |last7=Tao Huang |display-authors=3 |date=September 2019 |title=Assessment of Causal Direction Between Gut Microbiota–Dependent Metabolites and Cardiometabolic Health: A Bidirectional Mendelian Randomization Analysis |url=https://diabetes.diabetesjournals.org/content/68/9/1747 |journal=[[Diabetes (journal)|Diabetes]] |volume=68 |issue=9 |pages=1747–1755 |doi=10.2337/db19-0153 |pmid=31167879 |access-date=15 June 2021 |doi-access=free |archive-date=20 March 2021 |archive-url=https://web.archive.org/web/20210320222409/https://diabetes.diabetesjournals.org/content/68/9/1747 |url-status=live|url-access=subscription }}</ref>

===Other===

Egg consumption does not increase [[hypertension]] risk.<ref>{{cite journal |vauthors=Zhang Y, Zhang DZ |title=Red meat, poultry, and egg consumption with the risk of hypertension: a meta-analysis of prospective cohort studies |journal=Journal of Human Hypertension |date=2018 |url=https://www.nature.com/articles/s41371-018-0068-8 |volume=32 |issue=7 |pages=507–517 |doi=10.1038/s41371-018-0068-8 |pmid=29725070 |s2cid=19187913 |access-date=4 January 2022 |archive-date=4 January 2022 |archive-url=https://web.archive.org/web/20220104123950/https://www.nature.com/articles/s41371-018-0068-8 |url-status=live|url-access=subscription }}</ref><ref>{{cite journal |vauthors=Kolahdouz-Mohammadi R, Malekahmadi M, Clayton ZS, Sadat SZ, Pahlavani N, Sikaroudi MK, Soltani S |title=Effect of Egg Consumption on Blood Pressure: a Systematic Review and Meta-analysis of Randomized Clinical Trials |journal=Current Hypertension Reports |date=2020 |volume=22 |issue=3 |article-number=24 |pmid=32114646 |doi=10.1007/s11906-020-1029-5 |pmc=7189334}}</ref> A 2016 meta-analysis found that consumption of up to one egg a day may contribute to a decreased risk of total [[stroke]].<ref>{{cite journal |vauthors=Alexander DD, Miller PE, Vargas AJ, Weed DL, Cohen SS |title=Meta-analysis of Egg Consumption and Risk of Coronary Heart Disease and Stroke |journal=Journal of the American College of Nutrition |date=2016 |volume=35 |issue=8 |pages=704–716 |pmid=27710205 |doi=10.1080/07315724.2016.1152928 |s2cid=37407829}}</ref> Two recent meta-analyses found no association between egg intake and risk of stroke.<ref>{{cite journal |vauthors=Bechthold A, Boeing H, Schwedhelm C, Hoffmann G, Knüppel S, Iqbal K, De Henauw S, Michels N, Devleesschauwer B, Schlesinger S, Schwingshackl L |display-authors=3 |title=Food groups and risk of coronary heart disease, stroke and heart failure: A systematic review and dose-response meta-analysis of prospective studies |journal=Critical Reviews in Food Science and Nutrition |date=2019 |url=https://www.tandfonline.com/doi/full/10.1080/10408398.2017.1392288 |volume=59 |issue=7 |pages=1071–1090 |pmid=29039970 |doi=10.1080/10408398.2017.1392288 |hdl=1854/LU-8542107 |s2cid=38637145 |hdl-access=free |access-date=11 September 2021 |archive-date=11 September 2021 |archive-url=https://web.archive.org/web/20210911203419/https://www.tandfonline.com/doi/full/10.1080/10408398.2017.1392288 |url-status=live}}</ref><ref>{{cite journal |vauthors=Godos J, Micek A, Brzostek T, Toledo E, Iacoviello L, Astrup A, Franco OH, Galvano F, Martinez-Gonzalez MA, Grosso G |title=Egg consumption and cardiovascular risk: a dose–response meta-analysis of prospective cohort studies |journal=European Journal of Nutrition |date=2021 |volume=60 |issue=4 |pages=1833–1862 |pmid=32865658 |doi=10.1007/s00394-020-02345-7 |issn=1436-6207 |pmc=8137614}}</ref>

A 2019 meta-analysis revealed that egg consumption has no significant effect on serum biomarkers of [[inflammation]].<ref>{{cite journal |vauthors=Sajadi Hezaveh Z, Sikaroudi MK, Vafa M, Clayton ZS, Soltani S |title=Effect of egg consumption on inflammatory markers: a systematic review and meta-analysis of randomized controlled clinical trials |journal=Journal of the Science of Food and Agriculture |date=2019 |volume=99 |issue=15 |pages=6663–6670 |doi=10.1002/jsfa.9903 |pmid=31259415 |pmc=7189602 |bibcode=2019JSFA...99.6663S}}</ref> A 2021 review of clinical trials found that egg consumption has beneficial effects on macular pigment optical density and serum lutein.<ref>{{cite journal |vauthors=Khalighi Sikaroudi M, Saraf-Bank S, Clayton ZS, Soltani S |title=A positive effect of egg consumption on macular pigment and healthy vision: a systematic review and meta-analysis of clinical trials |journal=J Sci Food Agric |date=2021 |volume=101 |issue=10 |pages=4003–4009 |pmid=33491232 |doi=10.1002/jsfa.11109 |bibcode=2021JSFA..101.4003K |s2cid=231700748}}</ref>

=== Contamination ===
[[File:EggCleaningKaffiholen.jpg|thumb|Egg cleaning on a farm in Norway]]
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.<ref name="cspinet">"[http://www.cspinet.org/nah/eggs-ja.htm Eggs – No Yolking Matter] {{Webarchive |url=https://web.archive.org/web/20080509043408/http://www.cspinet.org/nah/eggs-ja.htm |date=9 May 2008 }}." ''Nutrition Action Health Letter,'' July/August 1997.</ref> As with [[meat]], containers and surfaces that have been used to process raw eggs should not come in contact with ready-to-eat food.

A study by the U.S. Department of Agriculture in 2002 (Risk Analysis April 2002 22(2):203-18) suggests the problem is not so prevalent in the U.S. as once thought. It showed 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.<ref name=ccni>{{cite journal |last1=Kimura |first1=Akiko C. |display-authors=3 |title=Chicken Consumption Is a Newly Identified Risk Factor for Sporadic Salmonella enterica Serotype Enteritidis Infections in the United States: A Case-Control Study in FoodNet Sites |journal=Clinical Infectious Diseases |volume=38 |pages=S244–S252 |year=2004 |doi=10.1086/381576 |pmid=15095196 |last2=Reddy |first2=V |last3=Marcus |first3=R |last4=Cieslak |first4=PR |last5=Mohle-Boetani |first5=JC |last6=Kassenborg |first6=HD |last7=Segler |first7=SD |last8=Hardnett |first8=FP |last9=Barrett |first9=T |doi-access=free}}</ref><ref name=phis>{{cite journal |last1=Little |first1=C.L |display-authors=3 |title=Public health investigations of Salmonella Enteritidis in catering raw shell eggs, 2002–2004 |journal=Letters in Applied Microbiology |volume=44 |issue=6 |pages=595–601 |year=2007 |doi=10.1111/j.1472-765X.2007.02131.x |pmid=17576219 |last2=Surman-Lee |first2=S |last3=Greenwood |first3=M |last4=Bolton |first4=FJ |last5=Elson |first5=R |last6=Mitchell |first6=RT |last7=Nichols |first7=GN |last8=Sagoo |first8=SK |last9=Threlfall |first9=EJ |s2cid=19995946 |doi-access=free}}</ref><ref name=lost>{{cite journal |last1=Stephens |first1=N. |title=Large outbreaks of Salmonella Typhimurium phage type 135 infections associated with the consumption of products containing raw egg in Tasmania |journal=Communicable Diseases Intelligence |volume=31 |issue=1 |pages=118–24 |year=2007 |pmid=17503652 |last2=Sault |first2=C |last3=Firestone |first3=SM |last4=Lightfoot |first4=D |last5=Bell |first5=C |display-authors=3 |doi=10.33321/cdi.2007.31.8 |doi-access=free }}</ref>
Egg shells act as [[hermetic seal]]s 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]]''.<ref>[http://egginfo.co.uk/page/ukeggs Knowledge Guide] {{webarchive |url=https://web.archive.org/web/20100206125826/http://www.egginfo.co.uk/page/ukeggs |date=6 February 2010 }}, British Egg Information Service. Retrieved 26 February 2010.</ref><ref>[https://web.archive.org/web/20110203140150/http://www.lioneggs.co.uk/files/lioneggs.co.uk/pdfs/LionCodeSummary.pdf Lion Code of Practice]. Retrieved 26 February 2010.</ref><ref>[http://www.farminguk.com/news/Irish-salmonella-outbreak-traced-to-rare-strain_17812.html Farming UK news article] {{Webarchive |url=https://web.archive.org/web/20120310062846/http://www.farminguk.com/news/Irish-salmonella-outbreak-traced-to-rare-strain_17812.html |date=10 March 2012 }}. Retrieved 26 February 2010.</ref>

In 2017, authorities blocked millions of eggs from sale in the Netherlands, Belgium, and Germany because of contamination with the [[insecticide]] [[2017 Fipronil egg scandal|fipronil]].<ref name=guardian>{{cite news |url=https://www.theguardian.com/world/2017/aug/03/eggs-removed-from-european-shelves-over-toxicity-fears-fipronil |author=Daniel Boffey |title=Millions of eggs removed from European shelves over toxicity fears |work=The Guardian |location=London |date=3 August 2017 |access-date=3 August 2017 |archive-date=7 August 2017 |archive-url=https://web.archive.org/web/20170807205801/https://www.theguardian.com/world/2017/aug/03/eggs-removed-from-european-shelves-over-toxicity-fears-fipronil |url-status=live}}</ref>

=== Food allergy ===
{{Main|Egg allergy}}

One of the most common [[food allergy|food allergies]] in infants is eggs.<ref name="food_allergy">[http://www.sswahs.nsw.gov.au/rpa/allergy/resources/allergy/eggallergy.pdf Egg Allergy Brochure] {{Webarchive |url=https://web.archive.org/web/20111125112704/http://www.sswahs.nsw.gov.au/rpa/allergy/resources/allergy/eggallergy.pdf |date=25 November 2011 }}, distributed by [[Royal Prince Alfred Hospital]]</ref> Infants usually have the opportunity to grow out of this allergy during childhood, if exposure is minimized.<ref>[http://www.aafa.org/display.cfm?id=9&sub=20&cont=523 "Egg Allergy Facts"] {{Webarchive |url=https://web.archive.org/web/20130112200539/http://www.aafa.org/display.cfm?id=9&sub=20&cont=523 |date=12 January 2013 }} Asthma and Allergy Foundation of America</ref> [[Allergy|Allergic reaction]]s against egg white are more common than reactions against egg yolks.<ref name="isbn3-540-20768-6">{{cite book |author=Arnaldo Cantani |title=Pediatric Allergy, Asthma and Immunology |url=https://archive.org/details/fundamentalspowd00pech_440 |url-access=limited |publisher=Springer |location=Berlin |year=2008 |pages=[https://archive.org/details/fundamentalspowd00pech_440/page/n728 710]–713 |isbn=978-3-540-20768-9}}</ref> In addition to true allergic reactions, some people experience a [[food intolerance]] to egg whites.<ref name="isbn3-540-20768-6" /> 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.<ref>[https://www.food.gov.uk/sites/default/files/food-allergen-labelling-technical-guidance.pdf "Food allergen labelling and information requirements under the EU Food Information for Consumers Regulation No. 1169/2011: Technical Guidance"] {{Webarchive |url=https://web.archive.org/web/20170707062644/https://www.food.gov.uk/sites/default/files/food-allergen-labelling-technical-guidance.pdf |date=7 July 2017 }} (April 2015).</ref>

== Farming ==
{{See also|Poultry farming}}
[[File:GroceryStoreEggs.JPG|thumb|Eggs for sale at a grocery store]]
[[File:6-Pack-Chicken-Eggs.jpg|thumb|White and brown eggs in an egg crate]]

Most commercially farmed chicken eggs intended for human consumption are unfertilized, since the laying hens are kept without [[rooster]]s. Fertile eggs may be eaten, with little nutritional difference when compared to the unfertilized. Fertile eggs will not contain a developed [[embryo]], as refrigeration temperatures inhibit cellular growth for an extended period of time. Sometimes an embryo is allowed to develop, but eaten before hatching as with [[balut (egg)|balut]].

=== Grading by quality and size ===
{{See also|Food grading|Chicken egg sizes}}
[[File:Egg scale.jpg|thumb|A scale for grading eggs]]
The U.S. Department of Agriculture grades eggs by the interior quality of the egg (see [[Haugh unit]]) and the appearance and condition of the egg shell. Eggs of any quality grade may differ in weight (size). Grade AA and Grade A eggs are best for frying and poaching, where appearance is important.
* U.S. Grade AA
** Eggs have whites that are thick and firm; have yolks that are high, round, and practically free from defects; and have clean, unbroken shells.
* U.S. Grade A
** Eggs have characteristics of Grade AA eggs except the whites are "reasonably" firm.
** This is the quality most often sold in stores.
* U.S. Grade B
** Eggs have whites that may be thinner and yolks that may be wider and flatter than eggs of higher grades. The shells must be unbroken, but may show slight stains.
** This quality is seldom found in retail stores because usually they are used to make liquid, frozen, and dried egg products, as well as other egg-containing products.

In [[Australia]]<ref>{{cite web |title=Requirements for the Egg Industry in the 2001 Welfare Code |url=http://www.poultryhub.org/egg-industry/requirements-for-the-egg-industry-in-the-2001-welfare-code/#Free_range_systems_.28non_cage_systems.29 |access-date=23 January 2011 |archive-url=https://web.archive.org/web/20110330102743/http://www.poultryhub.org/egg-industry/requirements-for-the-egg-industry-in-the-2001-welfare-code/ |archive-date=30 March 2011 }}</ref> and the [[European Union]], eggs are graded by the hen raising method, [[free range]], [[battery cage]]d, etc.

Chicken eggs [[Chicken egg sizes|are graded by size]] for the purpose of sales. Some maxi eggs may have double-yolks and some farms separate out double-yolk eggs for special sale.<ref>{{cite news |last1=Merwin |first1=Hugh |title=Noticed November 25, 2014 10:00 a.m. You Can Now Buy Double-Yolk Eggs by the Dozen |url=http://www.grubstreet.com/2014/11/sauders-double-yolkers-eggs.html |access-date=26 November 2014 |work=Grub Street |date=25 November 2014 |archive-date=4 December 2014 |archive-url=https://web.archive.org/web/20141204190816/http://www.grubstreet.com/2014/11/sauders-double-yolkers-eggs.html |url-status=live}}</ref>

<gallery>
File:Egg and maxi egg 1.jpg|{{center|Comparison of an egg and a maxi egg with a double-yolk - closed (1/2)}}
File:Egg and maxi egg 2.jpg|{{center|Comparison of an egg and a maxi egg with a double-yolk - opened (2/2)}}
File:Egg with two yellows.jpg|{{center|Double-yolk egg - opened}}
</gallery>

=== Color of eggshell ===
[[File:Egg colours.jpg|thumb|left|White, speckled (red), and brown chicken eggs]]
Although eggshell color is a largely cosmetic issue, with no effect on egg quality or taste, it is a major issue in production due to regional and national preferences for specific colors, and the results of such preferences on demand. For example, in most regions of the [[United States]], chicken eggs generally are white. However, 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!".<ref>{{Cite web |last=Willard |first=L. F. |date=1 August 2022 |title=Are Brown Eggs the Only Local Eggs? |url=https://newengland.com/food/brown-eggs-vs-white-eggs/ |access-date=25 November 2023 |website=New England |language=en}}</ref> 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 (red), green, and blue (as laid by certain breeds, including araucanas,<ref>Blue eggs, sometimes thought a joke, are a reality, as reported here [https://web.archive.org/web/20111103173514/http://www.costacalidachronicle.com/articles/food-and-drink/blue-hen-eggs.html], for example.</ref> heritage skyline, and cream leg bar) 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.

[[File:7oeufs.JPG|thumb|upright|Very dark brown eggs of [[Marans]], a [[France|French]] breed of [[chicken]]]]
These cultural trends have been observed for many years. ''The New York Times'' reported during the Second World War that housewives in Boston preferred brown eggs and those in New York preferred white eggs.<ref>See ''New York Times'' [https://timesmachine.nytimes.com/timesmachine/1919/12/21/98584419.pdf historical archive] {{Webarchive |url=https://web.archive.org/web/20210225035025/https://timesmachine.nytimes.com/timesmachine/1919/12/21/98584419.pdf |date=25 February 2021 }} for details – link opens on correct page.</ref> In February 1976, the ''[[New Scientist]]'' magazine, in discussing issues of chicken egg color, stated "Housewives are particularly fussy about the colour of their eggs, preferring even to pay more for brown eggs although white eggs are just as good".<ref name=newscientist>{{cite magazine |url=https://books.google.com/books?id=AhC9t3Q3YMcC&q=housewife+prefers+brown+egg&pg=PA449 |title=A Blue Story |magazine=[[New Scientist]] |date=26 February 1976 |volume=69 |issue=989 |access-date=6 April 2011 |archive-date=5 April 2023 |archive-url=https://web.archive.org/web/20230405030009/https://books.google.com/books?id=AhC9t3Q3YMcC&q=housewife+prefers+brown+egg&pg=PA449 |url-status=live}}</ref> 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.<ref>Evidence cited here [https://web.archive.org/web/20121105203443/http://www.highbeam.com/doc/1G1-16609821.html].</ref> 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.<ref>El-banna company website, product information, available here [http://www.elbannapoultry.com/products.htm] {{Webarchive|url=https://web.archive.org/web/20130617074420/http://www.elbannapoultry.com/products.htm|date=17 June 2013}}.</ref>

Research conducted by a French institute in the 1970s demonstrated blue chicken eggs from the Chilean [[araucana]] fowl may be stronger and more resilient to breakage.<ref name=newscientist/>

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.<ref>Results of the study are [http://agris.fao.org/agris-search/search/display.do?f=1993/JP/JP93003.xml;JP9301809 published here] {{Webarchive |url=https://web.archive.org/web/20110811060849/http://agris.fao.org/agris-search/search/display.do?f=1993%2FJP%2FJP93003.xml%3BJP9301809 |date=11 August 2011 }}.</ref>

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.<ref>Virtually any on-line chicken supply company will state the egg color of each breed supplied. [http://www.freewebs.com/happy_hens/meetourlayinghens.htm This] {{Webarchive |url=https://web.archive.org/web/20111128071253/http://www.freewebs.com/happy_hens/meetourlayinghens.htm |date=28 November 2011 }} is one example.</ref> 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.<ref>{{cite web |title=Eggs and Egg Colour Chart |url=http://www.themaransclub.co.uk/eggs-and-egg-colour-chart/4541995077 |website=The Marans Club |access-date=30 October 2017 |archive-date=29 October 2017 |archive-url=https://web.archive.org/web/20171029183726/http://www.themaransclub.co.uk/eggs-and-egg-colour-chart/4541995077 |url-status=live}}</ref>

=== Living conditions of birds ===
<!-- ATTENTION! Please discuss any potentially controversial changes to this section on the talk page before making them here. Thank you.-->
{{Further|Battery cage|Yarding}}
[[File:Battery hens -Bastos, Sao Paulo, Brazil-31March2007.jpg|thumb|upright|Laying hens in battery cages]]
Commercial [[Intensive animal farming|factory farming]] operations often involve raising the hens in small, crowded cages, preventing the chickens from engaging in natural behaviors, such as wing-flapping, dust-bathing, scratching, pecking, perching, and nest-building. Such restrictions may lead to pacing and [[escape response|escape behavior]].<ref>{{cite web |url=http://www.hsus.org/farm/resources/research/welfare/scientists_and_experts_on_battery_cages.html |archive-url=https://web.archive.org/web/20080501091340/http://www.hsus.org/farm/resources/research/welfare/scientists_and_experts_on_battery_cages.html |archive-date=1 May 2008 |title=Scientists and Experts on Battery Cages and Laying Hen Welfare |publisher=Hsus.org |access-date=10 January 2010}}</ref>

Many hens confined to battery cages, and some raised in cage-free conditions, are [[debeaking|debeaked]] to prevent them from harming each other and engaging in [[cannibalism]]. According to critics of the practice, this can cause hens severe pain to the point where some may refuse to eat and starve to death. Some hens may be [[forced molting|forced to molt]] to increase egg quality and production level after the [[molting]].<ref>{{cite web |url=http://ianrpubs.unl.edu/poultry/mp70/mp70-15.htm |title=Eggs and force-moulting |publisher=Ianrpubs.unl.edu |access-date=10 January 2010 |archive-url=https://web.archive.org/web/20081019165352/http://ianrpubs.unl.edu/poultry/mp70/mp70-15.htm |archive-date=19 October 2008}}</ref> Molting can be induced by extended food withdrawal, water withdrawal, or controlled lighting programs.

Laying hens often are euthanized when reaching 100 to 130 weeks of age, when their egg productivity starts to decline.<ref>{{cite web |url=http://ag.ansc.purdue.edu/poultry/publication/commegg/ |title=Commercial Egg Production and Processing |publisher=Ag.ansc.purdue.edu |access-date=10 January 2010 |archive-url=https://web.archive.org/web/20091012015330/http://ag.ansc.purdue.edu/poultry/publication/commegg/ |archive-date=12 October 2009}}</ref> Due to modern [[selective breeding]], laying hen [[strain (biology)|strain]]s differ from meat production strains. As male birds of the laying strain do not lay eggs and are not suitable for meat production, they generally are killed soon after they hatch.<ref>{{cite web |title=Why Go Vegan |url=https://www.vegansociety.com/go-vegan/why-go-vegan/animals |website=[[The Vegan Society]] |access-date=2025-02-18}}</ref>

[[Free-range eggs]] are considered by some advocates to be an acceptable substitute to factory-farmed eggs. [[Free-range]] laying hens are given outdoor access instead of being contained in crowded cages. Questions regarding the living conditions of free-range hens have been raised in the United States of America, as there is no legal definition or regulations for eggs labeled as free-range in that country.<ref>{{cite web |url=http://www.cok.net/lit/freerange.php |title=Free-range eggs |publisher=Cok.net |access-date=10 January 2010 |archive-url=https://web.archive.org/web/20100124174339/http://www.cok.net/lit/freerange.php |archive-date=24 January 2010 }}</ref>

In the United States, increased public concern for [[animal welfare]] has pushed various egg producers to promote eggs under a variety of standards. The most widespread standard in use is determined by [[United Egg Producers]] through their voluntary program of certification.<ref>{{cite web |url=http://www.uepcertified.com/abouttheprogram.html |archive-url=https://web.archive.org/web/20080108231358/http://www.uepcertified.com/abouttheprogram.html |archive-date=8 January 2008 |title=United Egg Producers Certified |date=8 January 2008 |access-date=22 January 2018}}</ref> The United Egg Producers program includes guidelines regarding housing, food, water, air, living space, beak trimming, molting, handling, and transportation, however, opponents such as [[The Humane Society]] have alleged UEP certification is misleading and allows a significant amount of unchecked animal cruelty.<ref>{{cite web |url=http://www.hsus.org/farm/resources/pubs/uep_certified_logo.html |archive-url=https://web.archive.org/web/20080518094024/http://www.hsus.org/farm/resources/pubs/uep_certified_logo.html |archive-date=18 May 2008 |title=Wondering What The "UEP Certified" Logo Means? |publisher=Hsus.org |access-date=10 January 2010}}</ref> Other standards include "Cage Free", "Natural", "Certified Humane", and "[[Certified Organic]]". Of these standards, "Certified Humane", which carries requirements for stocking density and cage-free keeping and so on, and "Certified Organic", which requires hens to have outdoor access and to be fed only organic vegetarian feed and so on, are the most stringent.<ref>{{cite web |url=http://www.eggindustry.com/cfi/faq/ |title=Egg Labels |publisher=EggIndustry.com |access-date=10 January 2010 |archive-date=4 September 2009 |archive-url=https://web.archive.org/web/20090904164954/http://www.eggindustry.com/cfi/faq/}}</ref><ref>{{cite web |author=The Humane Society of the United States |url=http://www.hsus.org/farm/resources/pubs/animal_welfare_claims_on_egg_cartons.html |archive-url=https://web.archive.org/web/20080518094024/http://www.hsus.org/farm/resources/pubs/uep_certified_logo.html |archive-date=18 May 2008 |title=A Brief Guide to Egg Carton Labels and Their Relevance to Animal Welfare |publisher=Hsus.org |access-date=10 January 2010}}</ref>

Effective 1 January 2012, the [[European Union]] banned conventional battery cages for egg-laying hens, as outlined in EU Directive 1999/74/EC.<ref>{{cite web |url=http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31999L0074:EN:HTML |title=EUR-Lex – 31999L0074 – EN |publisher=Eur-lex.europa.eu |access-date=10 January 2010 |archive-date=16 June 2011 |archive-url=https://web.archive.org/web/20110616082508/http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31999L0074:EN:HTML |url-status=live}}</ref> The EU permits the use of "enriched" [[furnished cages]] that must meet certain space and amenity requirements. Egg producers in many member states have objected to the new quality standards while in some countries, even furnished cages and family cages are subject to be banned as well. 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.

===Killing of male chicks===
{{main|Chick culling}}
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.<ref name=egg>{{cite web |title=Egg Production & Welfare |author=Vegetarian Society |url=http://www.vegsoc.org/page.aspx?pid=587# |access-date=22 October 2012 |archive-url=https://web.archive.org/web/20180316205339/https://www.vegsoc.org/page.aspx?pid=587 |archive-date=16 March 2018}}</ref> As of June 2023, this practice has been banned in Germany, France, Luxembourg, and Italy.<ref>{{Cite web |last=Torrella |first=Kenny |date=1 May 2023 |title=Save the male chicks |url=https://www.vox.com/future-perfect/2023/5/1/23700952/egg-industry-male-chick-culling-animal-welfare |access-date=29 June 2023 |website=Vox |language=en}}</ref><ref>{{Cite web |date=2024-09-17 |title=Animal protection in Luxembourg |url=http://gouvernement.lu/en/dossiers/2018/tierschutz.html |access-date=2025-08-25 |website=gouvernement.lu |language=en}}</ref> 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.<ref>{{Cite news |last=Blond |first=Josie Le |date=22 December 2018 |title=World's first no-kill eggs go on sale in Berlin |language=en-GB |work=The Guardian |url=https://www.theguardian.com/environment/2018/dec/22/worlds-first-no-kill-eggs-go-on-sale-in-berlin |access-date=29 June 2023 |issn=0261-3077}}</ref> As of April 2025, five companies offer commercially available in-ovo sexing technology, which is used for 28 percent of the European layer population.<ref>{{Cite web |title=In-Ovo Sexing Overview |url=https://www.innovateanimalag.org/egg-sexing |access-date=25 August 2025 |website=Innovate Animal Ag |language=en-US}}</ref>

== Cultural significance ==
{{Further|Egg decorating|Easter egg}}
[[File:Easter eggs - straw decoration.jpg|thumb|''Hanácké kraslice'', Easter eggs from the [[Haná]] region, the [[Czech Republic]]]]
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 decorating|egg painting]] exists in areas of the world influenced by the culture of [[Persian empire|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.<ref>{{Cite web |last=Hall |first=Stephanie |date=6 April 2017 |title=The Ancient Art of Decorating Eggs {{!}} Folklife Today |url=https://blogs.loc.gov/folklife/2017/04/decorating-eggs/ |access-date=25 November 2023 |website=The Library of Congress}}</ref> In Northern Europe and North America, Easter eggs may be hidden by adults for children to find in an [[Egg hunt|Easter egg hunt]]. They may be [[egg rolling|rolled]] in some traditions.<ref>{{Cite web |title=History of the Hunt: How an Easter Tradition Was Hatched |url=https://www.english-heritage.org.uk/visit/inspire-me/blog/articles/the-history-of-the-egg-hunt/ |access-date=25 November 2023 |website=English Heritage}}</ref> In Eastern and Central Europe, and parts of England, easter eggs may be [[egg tapping|tapped against each other]] to see whose egg breaks first.<ref>{{Cite web |last=Bociąga |first=Przemysław |date=7 April 2023 |title=A Worldwide Easter Tradition With Central European Roots |url=https://3seaseurope.com/egg-tapping-may-have-spread-from-central-europe/ |access-date=25 November 2023 |website=3 Seas Europe |language=en-US}}</ref>

Since the sixteenth century, the tradition of a [[dancing egg]] is held during the feast of [[Corpus Christi (feast)|Corpus Christi]] in Barcelona and other [[Catalonia|Catalan]] cities. It consists of a hollow eggshell, positioned over the water jet from a fountain, which causes the eggshell to revolve without falling.<ref>{{Cite web |title=Dancing eggs for Corpus Christi {{!}} Barcelona Cultura |url=https://www.barcelona.cat/barcelonacultura/en/recomanem/corpus-christi-dancing-eggs-open-days |access-date=25 November 2023 |website=www.barcelona.cat}}</ref>

== See also ==
{{Portal|Food}}
* [[Egg substitutes]] 
* [[Lists of foods]]
* [[List of egg dishes]]
* [[Roe|Fish eggs]]
* [[Yolkless egg]]
* [[Ham and eggs]]

== References ==

{{Reflist}}

== External links ==
{{Sister project links|Egg}}
* [https://web.archive.org/web/20080617163340/http://www.cfsan.fda.gov/~dms/fs-eggs6.html Fact Sheet on FDA's Proposed Regulation: Prevention of Salmonella Enteritidis in Shell Eggs During Production] (archived 17 June 2008)
* [https://web.archive.org/web/20130616195011/http://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/Eggs/default.htm Egg Information] U.S. Food and Drug Administration (2011)
* [http://anrcatalog.ucdavis.edu/Details.aspx?itemNo=8154 Egg Basics for the Consumer: Packaging, Storage, and Nutritional Information] {{Webarchive |url=https://web.archive.org/web/20140525200738/http://anrcatalog.ucdavis.edu/Details.aspx?itemNo=8154 |date=25 May 2014 }}. (2007) University of California Agriculture and Natural Resources. Retrieved 23 May 2014.

{{Eggs}}

{{Authority control}}

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[[Category:Eggs as food| ]]
[[Category:Types of food]]
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