Eggs are the method of reproduction for many species. The best known are laid by female birds, but fish, reptiles, amphibians and even some mammals also have eggs. They have been consumed as food for a very long time, since the dawn of mankind. Not all eggs have the same structure. The ones of birds and reptiles are protected by a hard shell. Inside it there are thin membranes that separate the white part (albumen) and the yolk (vitellus). Chicken eggs are most commonly eaten, as well as the ones of ducks and quails. Fish roe and caviar are also very popular.
Even prehistoric humans relied on eggs as an important food source. They were initially gathered from the wild but birds were later domesticated and the supply of eggs became stable. It is very likely that chickens were initially domesticated for their eggs, earlier than 7500 BCE. Their ancestors were birds that inhabited the jungles of India and Southeast Asia. Domesticated birds reached Mesopotamia and Egypt around 1500 BCE. Ancient Greeks relied on quail eggs, until they imported chickens for the first time in the year 800 BCE.
A famous depiction of eggs can be found on an ancient Egyptian tomb from Thebes, dating from 1420 BCE. A scene in the tomb of Haremhab shows a man bringing eggs as offerings. The eggs are carried in bowls and are large in size, so they are probably ostrich or pelican eggs.
They were very popular in ancient Rome and often the first dish was prepared from eggs. The Romans also invented a series of methods to preserve them. They believed that evil spirits can hide in egg shells, so they were careful to always crush them in their plates. Eggs were considered a rich food source in the Middle Ages, so people weren't allowed to eat them during Lent. The word moyeu in medieval French (that meant center and designated the yolk) is the probable origin of the tem mayonnaise. Lemon curd was perhaps invented in France as well, since in the 17th century it was very common to prepare scrambled eggs with various acidic juices from fruits.
Egg processing started on an industrial scale in the 19th century, first with dried eggs and then with frozen ones. A drying process was used for the first time in 1878 by a company in St. Louis, Missouri. It transformed both the white part and the yolk into a dried brown powder. During the Second World War, the US Army used large amounts of dried eggs and also supplied them to other Allied armies.
Today, bird eggs remain very popular and are used in numerous recipes. They are a very common and versatile ingredient in the food industry as well.
Chicken eggs are by far the most common variety consumed by humans. Other types of eggs are also available in stores but are more expensive and tend to be considered a gourmet ingredient. Examples include duck, goose and quail eggs. Most of the world's production of eggs, 59 percent, comes from Asia. They are consumed in large amounts in all countries in the region, such as China or Thailand.
Ostrich eggs are the largest and are also edible but are more of a luxury food due to their high price. Gull eggs are consumed in Norway and other Scandinavian countries, as well as in England. Guinea fowl eggs are common during the spring in the markets of some African nations. The eggs of emus and pheasants are edible but very rarely available in stores. Only a few luxury food stores offer them, these eggs can also be acquired directly from farms. Some wild bird eggs are edible but collecting them at the right time is difficult. In most countries their collection is strictly controlled, it is only possible in certain conditions or even completely banned.
Eggs are well known for their high nutritional value. This is because of their composition, which includes many useful compounds. Since an egg must be able to create a small bird from a baby cell, it includes all of the required components.
The main nutrients supplied by a boiled egg are phosphorous, selenium and the vitamins A, B2, B5, folate and B12. It also provides lower amounts of calcium, zinc and the vitamins B6, D, E and K. In total, the white part of an egg provides 77 calories and supplies 6 grams of pure proteins and 5 grams of healthy fats. It is also extremely rich in the fatty acid omega-3, which is known for its health benefits.
However, eggs are rich in many others vitamins and minerals and provide an excellent mixture of compounds needed by our body. It is one of the best food choices, due to the low cost and powerful package of nutrients.
One of the most important health benefits of eggs is provided to the heart. Consuming eggs decreases the risk of heart diseases, boosts the cardiovascular function as a whole and allows it to work for a longer time.
Many people consider eggs to be unhealthy for people who suffer from heart conditions or diabetes. This widespread belief was investigated in a study that was completed in 2015. The study revealed that eggs consumption is actually beneficial, as long as the right type is chosen and they are eaten with moderation, even for people who suffer from these diseases.
The content of omega-3 fatty acids is considered to be one of the main reasons why eggs are healthy for the heart. The so-called free-range eggs are twice as rich in this compound than the normal ones. These eggs are produced by hens that are raised free, on a pasture. Compared with eggs from hens raised in cages, they are richer in healthy compounds and have lower amounts of the unhealthy ones. Fatty acids like omega-3 have the ability to reduce the level of cholesterol in the blood, as well as the amount of triglycerides.
The balance of triglycerides is very important for our health. While a high level is dangerous, a low amount is beneficial. If the level of triglycerides in the blood is low, the risk of heart diseases is reduced significantly.
A major benefit of consuming eggs is the balance of cholesterol in the blood. They can regulate the amount of cholesterol and keep inflammation in check, by maintaining the right ratio between LDL cholesterol (low-density lipoproteins) and HDL cholesterol (high-density lipoproteins). Potentially lethal coronary heart conditions can be prevented by lowering blood cholesterol.
Eggs are also rich in carotenoids, which provide many benefits. They improve eye health and boost visual accuracy. Lutein and zeaxanthin, two types of oxygenated carotenoids, are considered the most important for the eyes.
Around 600 different carotenoids exist but lutein and zeaxanthin are the only ones found inside our eyes. While they are also part of other body tissues, they have a much higher concentration in this area. These compounds are effective antioxidants and anti-inflammatories and provide protection to the eyes by filtering blue spectrums of light with high energy that can damage them.
The filtering process is a passive one and we are not aware of it. However, it is extremely important because filtering blue light prevents glaucoma, macular degeneration and many other common eye conditions. In order to have healthy eyes, include eggs and other food that provide these compounds in your daily diet.
Eggs are very rich in proteins and are a common ingredient in various protein-rich diets that are a must for body builders and athletes. In addition, eggs are an excellent choice for people who want to lose weight. This is mainly because of their high content of proteins, but there is another reason as well. While lutein is well-known for its benefits to eye health, scientists have recently discovered that it also improves the physical activity level, contributing to weight loss. Due to the high concentration of proteins, eggs provide a sensation of fullness and eliminate the need of small snacks between meals, which can ruin any weight-loss diet.
Choline is a compound required for a healthy liver, as well as the development of our brain. We can produce it inside our body in very low amounts and must get the rest from food. Eggs are some of the best natural sources for this rare and precious macronutrient.
The first sign of a diet poor in choline is a malfunctioning liver, since it needs this compound to operate properly. Fatty liver disease is especially linked with choline deficiency. Several studies have revealed that a low intake of choline can also directly cause some types of tumours.
The main role of lutein and zeaxanthin is to protect the eyes by filtering some types of dangerous light. However, they provide the same protection to the skin. UV radiation and other blue spectrum rays cause oxidative damage to the skin, which can be greatly reduced by these compounds found in eggs.
Skin cancer can be prevented by consuming eggs, since they provide the eight best nutrients that are able to prevent it. This is especially useful to people with sensitive skin, who have a much higher risk to develop skin cancer.