Apr 20, 2022

What are the nutritional values of an egg for health?

 In recent years, nutrition experts have been faced with a dilemma: to limit egg consumption, given its high cholesterol content, or to recommend it, given its high content of high-quality protein and several vitamins and minerals. Today, there are no longer any restrictions on egg consumption in healthy people. On the contrary, it is considered to be a health ally accessible to all and a must in the kitchen.


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Characteristics of the egg

  • Excellent source of protein;
  • Source of choline and carotenoids;
  • Source of cholesterol;
  • Rich in vitamins and minerals;
  • Good source of fat.


 Nutritional and caloric values of eggs

What is a 'portion' of an egg worth?

Volume/weight  2 eggs, medium size, 100 g 

Calories 140

Protein 12,7 g

Carbohydrates 0,27 g

Fat 9,83 g  100% of the fat is found in the yolk of the egg.

Dietary fibre  0,0 g

Focus on the micronutrients contained in eggs

Among the nutrients contained in eggs in good quantities, we can mention the following:


  • Selenium: eggs are an excellent source of selenium. This mineral works with one of the main antioxidant enzymes, preventing the formation of free radicals in the body. It also helps convert thyroid hormones into their active form;
  • Vitamin B2: Eggs are a good source of vitamin B2. This vitamin is also known as riboflavin. Like vitamin B1, riboflavin plays a role in the energy metabolism of all cells. In addition, it contributes to tissue growth and repair, hormone production and the formation of red blood cells. Most riboflavin is found in egg white;
  • Vitamin B12: Eggs are a good source of vitamin B12. This vitamin works together with folic acid (vitamin B9) to make red blood cells in the blood. It also helps to maintain nerve cells and bone tissue cells;
  • Phosphorus: eggs are a source of phosphorus. Phosphorus is the second most abundant mineral in the body after calcium. It plays an essential role in the formation and maintenance of healthy bones and teeth. It also participates in the growth and regeneration of tissues and helps to maintain a normal blood pH. Finally, phosphorus is one of the constituents of cell membranes;
  • Zinc: eggs are a source of zinc. Zinc is involved in immune reactions, the manufacture of genetic material, taste perception, wound healing and foetal development. Zinc also interacts with sex and thyroid hormones and is involved in the synthesis (manufacture), storage and release of insulin in the pancreas;
  • Pantothenic acid: Eggs are a source of pantothenic acid. Also known as vitamin B5, pantothenic acid is part of a key coenzyme that allows us to adequately use the energy in the food we eat. It is also involved in several steps in the synthesis (manufacture) of steroid hormones, neurotransmitters (messengers in nerve impulses) and haemoglobin;
  • Folate: Eggs are a source of folate. Folate (vitamin B9) is involved in the manufacture of all cells in the body, including red blood cells. This vitamin plays an essential role in the production of genetic material (DNA, RNA), in the functioning of the nervous system and the immune system, and in the healing of wounds and sores. As it is necessary for the production of new cells, adequate consumption is essential during periods of growth and for the development of the foetus;
  • Vitamin A: Eggs are a source of vitamin A. Vitamin A is one of the most versatile vitamins, playing a role in many functions of the body. Among other things, it promotes the growth of bones and teeth. It keeps the skin healthy and protects against infections. It also plays an antioxidant role and promotes good vision, especially in the dark. Most of the vitamin A is found in the egg yolk;
  • Vitamin D: Eggs are a source of vitamin D. Vitamin D interacts closely with bone and tooth health, making calcium and phosphorus available in the blood, among other things, for the growth of the bone structure. Vitamin D also plays a role in the maturation of cells, including those of the immune system. Most of the vitamin A is found in the egg yolk;
  • Vitamin E: Eggs are a source of vitamin E. A major antioxidant, vitamin E protects the membrane that surrounds the body's cells, particularly red and white blood cells (immune system cells).


 The benefits of eggs

Recent scientific evidence suggests that eggs are a food of choice and that eating one egg a day, even for people with high blood cholesterol, may be acceptable. Indeed, there is no substantial evidence to show a real association between dietary cholesterol intake and blood cholesterol levels. Eggs are nutritious, and versatile and offer excellent nutritional value at a low cost.

A perfect protein profile  

The eggs are made up of proteins of high biological value. Protein is primarily used to build, repair and maintain tissues such as skin, muscle and bone. They are also used to form digestive enzymes and hormones. The proteins contained in eggs are said to be complete because they contain all nine of the body's essential amino acids in optimal proportions.


In fact, the protein quality of eggs is such that they are used as a reference food for assessing the quality of other food proteins. It should be noted that amino acids are said to be essential when the body cannot produce them. They must therefore come from the diet. Almost 60% of the egg's protein is found in the white, while the remaining 30% is in the yolk.

Carotenoid content

The egg yolk contains two powerful antioxidants from the carotenoid family: lutein and zeaxanthin. These two compounds give the egg yolk its colour. Carotenoids, which are related to vitamin A, are antioxidants known to help prevent age-related diseases such as cataracts, macular degeneration, cardiovascular disease and certain cancers.

These antioxidants neutralise or reduce free radicals in the body and thus limit cell damage. Observational studies indicate that consumption of lutein-rich foods, such as eggs, may help prevent age-related macular degeneration, a leading cause of blindness in people aged 65 and over, and reduce the risk of cataracts. The possible role of carotenoids in the prevention of cardiovascular disease (CVD) would be to decrease the oxidation of LDL-cholesterol ("bad cholesterol") and to reduce the formation of plaque in the artery walls.

Finally, carotenoids could reduce the risk of certain cancers by protecting against the development of tumours. Data from a prospective study, the Nurses' Health Study, involving 83,234 nurses showed that the higher the intake of lutein and zeaxanthin, the lower the risk of breast cancer in perimenopausal women.

Source of choline

Eggs are an excellent source of choline, a compound that plays an important role in the development and function of the brain, primarily the memory centre. Choline is mainly found in the yolk of the egg. The need for choline is important during embryonic development, as during pregnancy and lactation, low intakes of choline can have long-term effects on the development of the child's brain. An animal study showed that choline supplementation during embryonic development of rats or immediately after birth improved cognitive function and thus attention and memory.

Furthermore, in a study of pregnant women with low folic acid intakes, the authors reported that mothers with the lowest choline intakes were four times more likely to deliver a child with a neural tube defect than those with the highest intakes, irrespective of folic acid intake.

Eggs and cholesterol: what should we think?

Since it is now known that high blood cholesterol levels are associated with an increased incidence of cardiovascular disease (CVD), most nutritional recommendations for the treatment of CVD are to reduce the intake of cholesterol-rich foods and thus limit egg yolks to two or three per week.

However, these recommendations have been questioned as many studies show a weak relationship between dietary cholesterol and the incidence of cardiovascular disease. It appears that the consumption of as much as one egg per day has no significant impact on cardiovascular risk. A prospective study of 117,000 healthy men and women showed no significant association between egg consumption and cardiovascular disease. According to this study, the risk was no higher in those who consumed less than one egg per week than in those who consumed more than one egg per day.

Other studies, including a recent one, have shown that foods high in cholesterol but low in saturated fat, such as egg yolks have minor effects on blood cholesterol levels. Several studies indicate that blood lipid control is best achieved by reducing the intake of trans and saturated fats, rather than eliminating dietary cholesterol. In fact, the American Heart Association (AHA) states that consumption of one egg yolk per day may be acceptable, even for hypercholesterolemic individuals, if consumption of other cholesterol-rich foods, such as cheeses, cream, butter and red meats, is limited.

A word from the nutritionist

If you have trouble digesting cooked eggs, the cause may lie in the fat you use to cook them, not in the egg itself. For information, one portion of the egg is 2 units or about 125g with the shell.


 How to choose eggs?

Eggs have been consumed by humans since prehistoric times. Today, most people eat chicken eggs, but this has not always been the case. In fact, cane and goose eggs have long been an integral part of the diet, although they are less widely consumed today. An egg weighs on average 60g with its shell and 55g without.

Identity card of the egg 

  • Origin: Europe and Asia ;
  • Season: available all year round;
  • Colour: white to beige;
  • Taste: pronounced.

Brown or white?

There is no difference in nutritional value or taste between white and brown-shelled eggs. The colour of the shell depends on the breed of the hen. However, brown-shelled eggs would have a thicker shell and a darker yolk.

Omega-3 eggs

Omega-3 eggs are identical to conventional eggs in terms of total fat and cholesterol content. Only the omega-3 polyunsaturated fatty acid content of one differs from the other. Omega-3-enriched eggs are produced by adding flaxseed to the hen's feed. Flaxseed is rich in alpha-linolenic acid (ALA), a type of omega-3 fatty acid. 

An omega-3 egg covers 25% to 30% of our ALA requirements, which can provide a complimentary intake of these fatty acids. It is interesting to note that some liquid egg products have been enriched with omega-3 from marine sources. Unlike ALA, these marine fats do not require longer chain processing before being used for certain functions in the body. However, it is important to mention that eggs from flaxseed-fed hens also contain long-chain omega-3s, as the hen metabolises some of the ALA into EPA and DHA (two omega-3s found in abundance in oily fish).

Recognising a fresh egg  

If you are not sure whether an egg is fresh, you can immerse it in a bowl of water. Since the air pocket in a fresh egg is not very large, it sinks to the bottom and lies on its side. Since the air pocket is larger, the older the egg floats with the large end facing up.

Tips to avoid food poisoning

Keep eggs refrigerated at all times. In total, they should not be kept out of the refrigerator for more than two hours (including cooking and serving time). If eggs need to be at room temperature for a recipe, take them out half an hour beforehand or warm them up in warm water a few minutes before using.

To avoid the risk of cross-contamination, wash your hands and kitchen utensils after handling meat and fish and before handling eggs (and vice versa). Do not use broken or cracked eggs, which may be contaminated. The occasional blood spot in an egg is not dangerous. It can be removed with the tip of a knife if desired.

For optimal storage

  • In the refrigerator: whole eggs in their shells can be kept for five weeks from the date of packaging (about 3 weeks after purchase) without any significant loss of quality. After this time, the flesh may dry out. Once the shell has been removed, the whites and yolks can be kept for two days. Hard-boiled eggs can be kept for an average of one week;
  • In the freezer: the whites can be frozen separately for later use. Put them in the ice cube tray, freeze and transfer them to a freezer bag. Thaw in the refrigerator, not at room temperature. To freeze the whole egg, mix the white and yolk thoroughly before placing them in an airtight container in the freezer. Do not freeze the whole egg as the shell will burst in the cold.
  • To freeze the yolks, it is recommended that you add the equivalent of 1 1/2 teaspoons of sugar or corn syrup (for 4 eggs) if you plan to use them in a sweetened preparation, or 1/8 teaspoon of salt for other types of preparations. This treatment will prevent them from becoming lumpy in the freezer.

Organic eggs?

Organic eggs are now available on the market. These eggs are laid by free-range hens in open-air coops with nests and perches. The hens are fed an organic diet prepared to strict specifications. Organic egg producers are certified by an official body, which guarantees the consumer that these products meet organic farming standards.

 How to prepare eggs?

In the kitchen, eggs are an essential ingredient that can be used in a wide range of everyday recipes. It is used for baking as well as for basic and express recipes. Thanks to its excellent protein content and low cost, it is the ideal ingredient for simple, tasty and nutritious cooking.

Cooking eggs

Since it is not advisable to eat eggs raw (even for classic preparations such as mayonnaises, soufflés and mousses), here is how to prepare them:

  • Cooking the yolks normally used raw in cooking: cook over low heat in a heavy-bottomed saucepan, adding about 2 tablespoons of water or other liquid per yolk. Stir continuously and cook until the mixture forms a thin film on a metal spoon, or until the internal temperature reaches 71ºC (160ºF). Place the pan in ice water until the mixture cools and use immediately;
  • Cooking the whites normally used raw in cooking: Cook them over low heat in a double boiler with 2 tablespoons sugar, 1 tablespoon water and 1/8 teaspoon cream of tartar per white, stirring continuously at low speed with a hand mixer until they reach an internal temperature of 71ºC (160ºF). Pour into a large bowl and beat on high speed until the mixture forms fluffy peaks. Then follow the recipe as usual.

Eggs, an essential ingredient in French cuisine

If eggs are the basis of soufflés, flans, quiches or crêpes, here are some other suggestions:

  • In a salad. Serve soft-boiled eggs on a salad of fine greens. Soft-boiled eggs can be added to a vegetable salad of your choice, or in the Niçoise salad, with cubed potatoes, tomatoes, snow peas, tuna, olives and baby greens. Drizzle with a Dijon mustard vinaigrette. Or make a sandwich filling with parsley and chives or other herbs;
  • Deviled eggs. Cook the eggs and cut them in half lengthwise. Remove the yolk and mash it with mustard, mayonnaise, sour cream or yoghurt, lemon juice, capers, salt and pepper and fill the whites with this mixture. Refrigerate before serving. You can vary by replacing the capers with sliced olives and adding hot pepper or Tabasco sauce;
  • Omelettes. Chives, watercress, parsley, tarragon and lemon balm go very well with eggs;
  • Pickled hard-boiled eggs. Put hard-boiled eggs in a jar. Heat vinegar and concentrated orange juice, a cinnamon stick and cloves in a saucepan for a few minutes. Pour over the eggs, close the jar and allow to cool to room temperature, then place in the refrigerator. Wait at least a week, and up to three or four weeks, before eating;
  • Soft-boiled egg, soft-boiled egg, hard-boiled egg. What is the difference? In fact, only the cooking time varies. A soft-boiled egg is an egg whose white is starting to coagulate and whose yolk is still liquid. A soft-boiled egg is an egg where the white is solid, but the yolk is still runny. Finally, the hard-boiled egg is an egg with a firm white and yolk;
  • The single egg can also be poached, scrambled, fried, fried or spun;
  • Scrambled eggs. The egg can also be poached, scrambled, fried or spun; Scrambled eggs. Various ingredients are added to the eggs: grated cheese, diced tomatoes seasoned with basil, sour cream flavoured with chives, pieces of canned sardines or anchovies, curried crabmeat, capers, pieces of bacon or sausage, mushrooms, finely chopped vegetables, etc. ;
  • Huevos rancheros. Prepare a salsa that is more or less spicy according to taste, pour it into an oven dish and hollow out "nests" in which to place raw eggs. Garnish with strips of pimiento (pepper) and sprinkle with grated cheese. Bake until eggs are firm in a 215ºC (420ºF) oven;
  • Florentine Soup. Heat finely chopped spinach in chicken or vegetable stock with nutmeg for a few minutes. Add beaten eggs to the soup, stirring well. Remove from heat immediately. Serve in bowls with grated Parmesan cheese, if desired;
  • Provençal omelette. First cook five slobbery omelettes, the first with green onions, the second with spinach or another green leafy plant, the third with garlic, the fourth with tomato and the fifth with herbs. Stack them in order in a buttered or oiled round pan. Put the mould in the oven for about twenty minutes in a container half-filled with water. Serve hot or cold, slicing to show the different colours;
  • French toast. Dip slices of bread in eggs beaten with milk, fry in a pan and serve with maple syrup or brown sugar;
  • Frittata or 'western omelette'. Almost every country has a version of this dish, which consists of sautéed vegetables (potatoes, tomatoes, courgette, broccoli, spinach, depending on the season), mushrooms, diced ham or sausage, and other foods of choice until they are cooked, and then pour beaten eggs flavoured with herbs and grated cheese on top. You can vary this by adding pasta or oriental noodles, shrimp or smoked salmon, and sun-dried tomatoes;
  • Egg in the hole. Remove some of the crumbs from a slice of bread. Brown the slice in a frying pan and crack an egg through the opening. Cook until the white is firm and serve. The same can be done with partially hollowed-out potato slices, which are baked for about 15 minutes.

Discover the hundred-year-old egg

A true classic of Chinese cuisine, the hundred-year-old egg is actually preserved for only a few months in a mixture of saltpetre, tea leaves, clay and other materials that turn the shell black and give the flesh a greenish colour and hard-boiled egg texture. They are usually thinly sliced and served as an appetizer with other fine foods.

 Contraindications and allergies to eggs

Eggs are among the foods that cause allergic reactions of varying degrees of severity in some sensitive individuals. Although egg allergy often diminishes with age, this is not always the case, so great care should be taken. Moreover, eggs are a very fragile food, so it is advisable to cook them carefully to avoid food poisoning, the consequences of which can be very serious.
Egg allergy
Eggs, along with milk, peanuts and shellfish, are one of the main causes of food allergies. Egg allergy is usually caused by the immune system's reaction to one of the protein fractions in the egg white. However, in some people, it is the proteins in the yolk that cause the allergy. As it is not possible to separate the yolk and the egg white, 100%, the only way to avoid an allergic reaction is to exclude foods or products containing eggs or egg derivatives and foods that may have been in contact with eggs.

People allergic to raw eggs cannot usually eat cooked eggs. Although cooking alters the protein in a raw egg, it is not enough to prevent an allergic reaction. Fortunately, egg allergy disappears in most children after the age of five. However, when the allergy is severe, it can last a lifetime. As a preventive measure, egg white should not be introduced into a child's diet before the age of one.
The most common symptoms of egg allergy are gastrointestinal (vomiting, diarrhoea), and respiratory (asthma, bronchitis) and are also often related to skin problems (eczema).


Risk of food-borne diseases

The safety of eggs is of primary importance, given the risk of contamination by bacteria or viruses (e.g. Salmonella and H5N1). The Canadian Egg Marketing Agency has been working to improve the natural defences of the egg (hard shell, two membranes and antimicrobial properties in the albumen), through the Clean First - Clean Always? The program is based on a hazard management approach. In Canada, in 2003 and 2004, the compliance rate of inspected egg products was 97% (3% of eggs were non-compliant or unsafe).

Although the risk of Salmonella infection is minimal, to eliminate this risk, Health Canada recommends that consumers, especially pregnant women, the elderly, very young children and people with weakened immune systems due to illness, cook eggs until the white and yolk have a solid consistency. There are pasteurised liquid egg preparations on the market that can be used instead of raw eggs, since pasteurisation has destroyed any bacteria, including salmonella, that may be contained in the egg.

 History and anecdotes

A little history

The eggs of various bird species have undoubtedly been eaten since ancient times. The Phoenicians feasted on ostrich eggs, while in ancient times the Romans ate blue peacock eggs and Chinese pigeon eggs. In fact, the eggs of any egg-laying species, including turtles and alligators, can be used as food.
However, over the course of evolution, the hen's egg has gradually taken precedence over all others, but this has happened rather recently. Although Apicius, the famous ancient Roman gastronome, gave various recipes for custards and omelettes in his culinary work, the egg remained a marginal food for a long time, partly because of religious prohibitions and superstitious beliefs, and partly for economic reasons: in fact, the general public considered it much more profitable to wait for the egg to turn into a hen or a rooster. The exception to this rule was the Chinese, who considered it an excellent source of nutrition and spread its use throughout East Asia.
There is no mention of eggs in the few writings on the Middle Ages in Europe, perhaps because, like meat, they were forbidden by the Catholic Church to be eaten on lean days, i.e. For more than 160 days a year. However, chickens, which did not follow the liturgical calendar, but the calendar of the seasons and their biological cycle, laid abundantly during Lent, when daylight was again abundant. To avoid losing this precious resource, they were preserved in liquid fat or wax until Easter, the day of celebration par excellence.

To improve their appearance after their prolonged stay in the vault, they were decorated in various ways. This is how the tradition of Easter eggs originated. By the middle of the 17th century, at least 60 recipes were known for the preparation of this increasingly popular menu item.


Improving productivity

In the 18th century, the discovery by the French of an artificial brooding technique practised by the Egyptians using low-temperature ovens aroused great interest among breeders, who multiplied crossbreeding. In the 19th century, much more productive breeds of hens, selected by the Chinese, appeared in the West, creating a real stir among breeders who all wanted to own some of these "new" birds, which were very different from the known Mediterranean and European breeds. During this century, a hundred other breeds were created, some of which were bred only for meat, others for eggs, and others for both purposes.
This was a good period for the egg, which was considered a perfect food until the 1980s. However, its popularity waned when it was discovered that its yolk was particularly high in cholesterol, which was blamed for causing cardiovascular disease. In that decade alone, sales of fresh eggs fell by 25%. The increasing number of salmonella outbreaks during the same period and until recently will add to this fate. It is therefore not advisable to eat the raw egg that used to be used in many dishes, including mayonnaise. In recent years, the egg has regained some of its lost popularity, after various clinical studies have shown that for the majority of the population it is excellent food.
In addition to fresh eggs, dehydrated, liquid and frozen egg preparations (albumen only, yolk only, whole egg, albumen and yolk mixed in various proportions) are now available on the market.
Ecology and environment
Until the Second World War, eggs were mainly produced on small family farms, with an average of only 400 laying hens. Various innovations, notably in veterinary medicine and in the formulation of enriched feeds, as well as the creation of complex mechanical equipment, will lead to battery farming as we know it today, with hundreds of thousands or even millions of hens per production unit. For example, in the United States, one of the world's largest poultry-producing countries, 95% of production is carried out by 260 farms, of which 65 have more than one million hens and 9 have more than five million. The smallest farms in the USA have a minimum of 30,000 hens.
On these farms, the hens are, in most cases, confined to narrow cages in which they can barely move. They have no access to outside air or daylight, their production cycle being entirely controlled by artificial lighting. The conditions in which they live, especially the high number of individuals in a given space, create a permanent state of stress that weakens their immune system, necessitating the administration of antibiotics. In addition, the manure produced by the hens on these farms is a major source of pollution of surface and groundwater, particularly in terms of phosphorus.
In Europe, for humanitarian and public health reasons, the trend toward battery farming seems to be reversing. In several countries on this continent, cage farming is banned. In Germany, it goes even further, as it is now forbidden by law to keep more than 6,000 hens in a single hen house.

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