- 1 Composition of eggs
- 2 Nutritional properties of egg
- 3 The egg white is an excellent food but, what about the yolk?
- 4 What are the properties and benefits of the Egg Yolk?
- 5 Color of the Yolk
- 6 Nutritional value of the Egg Yolk
- 7 Protein content of the Egg Yolk
- 8 What are the vitamins and minerals from Egg Yolk?
- 9 Eggs, Essential for Athletes
- 10 Egg Proteins
- 11 Types of Egg
- 12 How to cook the egg?
- 13 Egg Protein Supplements
- 14 Best Recipes with Egg
- 15 Does egg increase the cholesterol?
- 16 How do you know if an egg is fresh?
- 17 How many eggs should I eat per week?
- 18 Absorption of raw egg proteins vs Absorption of cooked egg proteins
- 19 How is the egg protein absorbed?
- 20 The experts’ opinion about egg protein
- 21 Bibliography
Eggs are an excellent natural source of proteins. Moreover, egg proteins are perfect for all those people who follow a ovo-lacto or vegetarian diet because it allows them to get the animal proteins they need for their bodies to function efficiently.
That is why in this article we are going to develop this food and some of its aspects that have to be taken into account.
Composition of eggs
Eggs are a very healthy food, with a high protein content of a great biological value, something very important specially for those who practice sports. It is also low in calories and contains vitamins, specially from the B complex, vitamin B1, B3, B12, folic acid and biotin, which are closely related to the brain and energy function.
Eggs also contain some minerals that contribute to its antioxidant function such as selenium and zinc (which are key to maintain an adequate oxidative balance), phosphorus and iron.
Nutritional properties of egg
If we take an egg that weighs 60 grams as a reference, a 7.5 of them are proteins. Therefore, if we take an adult that weighs 75 kilograms, a single egg can provide 10% of his/her daily protein requirements.
On the other hand, it is important to point out that approximately a 60% of the proteins that are present in the whole egg are found in the white. On top of that, it also has an infinite number of excellent nutrients for our health. In this sense, it contains a lot of minerals such as calcium, iron, zinc, sodium and copper, as well as vitamin B12, niacin, folic acid, and riboflavin.
The problem lies in the way it is cooked since, quite frequently, we tend to fry it with plenty of oil.
The egg white is an excellent food but, what about the yolk?
The yolk itself has a greater nutritional value than the white. However, it also contains all the fats which, when metabolized, will become cholesterol in the body, although it is true that they are far less harmful than saturated fats.
On the other hand, we have also set out to debunk that phrase that you have probably heard some times and that says that eating raw egg is not healthy or that it is necessary to remove the yolk to make it safe.
The yolk of an egg makes up about a 34% of the liquid weight of the egg. It contains all the fat in the egg and slightly less than half the protein. The yolk of a large egg contains about 55 calories.
Aside from niacin and riboflavin, the yolk contains a higher amount of vitamins than the white, including vitamins B6 and B12, folic acid, pantothenic acid, and thiamine.
All vitamins A, D, E, and K from the egg are in the yolk.
Egg yolks are one of the few foods that naturally contain vitamin D. The yolk also contains more calcium, copper, iron, manganese, phosphorus, selenium, and zinc than the egg white.
What are the properties and benefits of the Egg Yolk?
When we speak of a healthy and balanced diet for our health, it is understood that it is a diet that includes all the foods (including eggs) that nature provides us in quantities and percentages that are adapted to each person, including macro and micro-nutrients: proteins, fats, carbohydrates, vitamins and minerals.
The egg can be part of a balanced diet due to its properties and benefits for our health. It is regarded as one of the most nutritionally dense foods.
This is a food that only contains 70 calories on average (like a fruit), although the egg white barely contains any fat and it is a little higher in protein than the yolk. Approximately, the total content of these is from 4 to 4.5g of fats per unit, of which 1.5g are saturated and the rest unsaturated (mainly monounsaturated fats, which are beneficial for the health of the organism).
The yolk is where the nutrients are stored: vitamins, minerals and other elements.
Color of the Yolk
The color of the yolk depends on the way the hen is fed. If a hen eats many pigments from yellow-orange plants called xanthophylls, they will be transferred to the egg yolk.
Hens fed with yellow corn purée or alfalfa flour lay eggs with medium yellow yolks, while those that eat wheat or barley produce a lighter color.
A “colorless” diet, such as white corn flour, results in almost colorless yolks. Natural yellow-orange substances, such as calendula petals, can be added to light-colored foods to improve the color of the yolk. Artificial additives are forbidden.
Nutritional value of the Egg Yolk
The approximate weight of a large egg yolk is about 17g, so the nutritional value of a yolk would be:
|of which saturated||1.6g|
|of which monounsaturated||1.9g|
|of which polyunsaturated||0.72g|
Protein content of the Egg Yolk
A proper supply of protein in the diet should include all the essential amino acids that your body needs on a daily basis because it does not synthesize them. The egg has all of them: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
These amino acids are present in a pattern that closely matches the pattern that the human body needs, so the egg is often the standard by which other protein foods are measured.
What are the vitamins and minerals from Egg Yolk?
Although this food has traditionally been moved away from balanced diets due to its association with an increase in cholesterol, its nutritional properties have a lot of benefits for the body, as long as we control its consumption.
The egg yolk is a powerful source of vitamins and minerals for our health:
- Vitamin A, which is closely related the functioning of the sight and the immune system
- Vitamin E, which has an antioxidant effect on the body
- Vitamin D, a protective shield of the immune system
- Vitamin H or Biotin, which contributes to a healthy growth of the skin and hair
- Folic acid, a key element for growth, as well as before and during pregnancy
- Vitamin B12, a source of energy for the body and the nervous system
- Vitamin B6, the most important coenzyme in the metabolism of amino acids
- Vitamin B2, which supports the transformation of proteins and fats, as well as being involved in the formation of red blood cells and antibodies
- Vitamin B1, which helps to produce energy, strengthens the heart and encourages muscle growth
Egg yolks are one of the few foods that naturally contain vitamin D. The yolk also has an excellent source of phosphorus, potassium and magnesium.
- It has other substances called Choline and Inositol (the white has only traces), which are involved in the development of the memory during the embryonic stage. In addition, eggs are one of the most important foods for the functioning of all cells.
- They also contain two important antioxidants: lutein and zeaxanthin, which support eye health by preventing macular degeneration and the risk of suffering from cataracts, enhancing the effect of vitamin A.
Eggs, Essential for Athletes
Eggs are a source of nutrients for athletes.
I don’t think that there are many other foods that gather such a variety of nutrients, apart from a proper supply of proteins. There are many athletes who are somewhat reluctant to consume egg yolk due to its supply of saturated fat. But the truth is that if you are a person with a high wear, I cannot think of another way to contribute to improve the diet of athletes both calorically and nutritionally. Sometimes, the advice on the consumption of “good fats” such as polyunsaturated fats does not take into account the balance between omega 3 and omega 6, which is a very important factor in avoiding certain disorders.
Saturated fats fulfil important hormonal functions, let’s not forget that this type of fat and cholesterol are two conditioning factors for the synthesis and production of testosterone.
Each egg has several types of protein:
Ovotransferrin is a type of protein known as metalloprotein which binds to iron, providing antimicrobial properties and making up more than a 10% of the protein content. Like serum transferrin, ovotransferrin is also similar to the lactoferrin in milk in terms of structure and function.
Ovomucin, another type of glycoprotein, which makes up less than a 5% of egg white protein, is responsible for providing the gelatinous texture.
|Egg Size||Amount of Proteins|
|Egg Size S (less than 40g)||4.9g|
|Egg Size M (between 40-50g)||5.5g|
|Egg Size L (between 50-65g)||6.5g|
|Egg Size XL (between 70g)||7g|
|Egg Size Jumbo (more than 70g)||8.5g|
Egg size and protein content (approximate value)
How to cook the egg?
Although the fried egg is one of the most common ways to cook it, mainly because it is much more appetizing and tasty, it is not healthiest because frying it adds fats that the egg has already.
One way to cook it that is healthier and easier to digest than the first choice is to make a omelette or scrambled eggs. The dish still feels tasty but needs less oil and therefore, less fat.
Boiled eggs are another very healthy way to add this food to our diet and to make a delicious Post-workout salad, for example.
Egg Protein Supplements
Taking egg protein supplements is a way to increase the daily protein supply and, above all, contribute to completing the necessary amount of protein. A highly recommended option is to use egg protein powder to blend it with other types, like whey, so that we will obtain a sequential release protein, because in terms of absorption, the egg protein would be “average”, while whey would be the fastest fraction found in milk.
Egg white powder is a very interesting resource, particularly if we buy liquid egg whites and we see that we do not have enough time to eat them and they expire.
Best Recipes with Egg
Eggs play an important role in the kitchen, since they are one of the ingredients that can be found in any home. Including a good protein supply in our diet has never been easier.
Some of the best recipes are:
It consists on cooking the eggs once they have been beaten. This recipe provides a much better nutritional supply than those sugary flakes which tend to be sold by a happy animal…
Scrambled eggs for breakfast is one of the best ways of starting the day off
One of my favorite breakfasts without getting rid of the yolks. Most people tend to make pancakes by separating the yolks and keeping the egg whites. In this sense, the white only provides protein, while the content in micronutrients, as well as a good part of proteins along with the fats will remain in the trash… Eggs have many possibilities when it comes to making pancakes: we can use oat or rice flour, gluten-free recipes, sweet potato, carrot, add fresh cheese, vegetables, protein powder or whey…
Boiled Eggs and Avocado Salad
It’s one of my favorite combinations, since I eat salads almost daily, specially during the summer. Avocado has an excellent nutritional value, and even though it is catalogued as a very caloric fruit, it has other properties for our health.
Salad made with Boiled Eggs, Avocado and Tomato on Spinach leaves
Spanish (with or without onion) or French Omelette is a very easy meal to cook that will fit in any type of weight control diet at any time of the day. My favorite one is stuffed with avocado and natural tomato…
Does egg increase the cholesterol?
Regarding the relationship between egg and cholesterol, which is one of the most popular myths surrounding this food, the point of view has changed. This is due to the fact that it has been proven that the relationship between saturated and unsaturated fats is the main factor that increases the levels the cholesterol, instead of the intake of cholesterol, as it was previously thought.
That is why those who tend to produce an excess of cholesterol should change their lifestyle, do more exercise, eat less fat and more fruit, fewer sugars, not smoke, and drink moderately.
Not eating egg is NOT the solution!
How do you know if an egg is fresh?
To know if an egg is fresh without breaking it, we only have to put it inside a glass of water and see:
- If the egg sinks quickly and stays at the bottom: The egg is fresh.
- If the egg sinks more or less quickly and stays at the bottom: This means that the egg is good, but not as fresh.
- If the egg sinks little by little and remains standing (at the bottom): It means that the egg is about to become bad although it may still be edible.
- If the egg neither sinks nor goes to the bottom: It means that the egg is bad. There are other sources that claim that it is still edible, so it is up to you to decide.
- If the egg floats: It means it is bad. When organic matter rots it creates gases, which is the reason why the egg floats in the water.
How many eggs should I eat per week?
In general, there is not a limit for the amount of eggs you can consume each week.
You can eat 1, 2, 3, half a dozen or up to 12 a week, which has been proven by Dr. Nick Fuller from the Boden Institute for Obesity, Nutrition, Exercise and Eating Disorders at the University of Sydney. In his clinical trial, he revealed that eating up to 12 eggs a week does not increase the risk of heart problems in those who suffer type 2 diabetes, for example.
Dr Fuller stated that “although eggs themselves are high in cholesterol and people with type 2 diabetes tend to have higher levels of low-density lipoprotein (LDL) or “bad cholesterol”, this study supports existing research that shows how eating eggs has a minimal effect on the blood cholesterol levels in people who consume eggs”.
However, some people may be forced to reduce or limit their consumption under a doctor’s prescription.
This is why the consumption of eggs should not be avoided without a reasonable cause, since it would entail a great loss of nutrients.
Absorption of raw egg proteins vs Absorption of cooked egg proteins
It is crucial to understand that raw egg white is cannot be digested by our body at all, in fact, it is not advisable to eat it this way specially for its taste, because it will not be very pleasant in this way and it can also be harmful for health if they are not cooked, since they can be infected with salmonella.
The main proteins found in egg whites are Ovoalbumin and Ovotransferrin and their structures are long chains of amino acids which have a sturdy or elongated form when they are raw. This means that it is impossible for our digestive system to break them down and absorb their amino acids.
But also, the raw egg whites contain Ovomucoids and Ovoinhibitors that block the enzymes that are in charge of digesting the proteins that we consume in our body (enzymes that are involved in the digestion of proteins by breaking the peptide links that keep the long amino acid chains bound together).
Solution: denature the protein
The protein from egg whites has to be denatured before being absorbed by our organism, that is, the process through which their structure changes but their amino acid composition is not affected. This means that a denatured protein does not lose its properties when it is consumed, the only thing that changes is the fact that it is partially digested because some of its links have been destroyed to facilitate its absorption. This process does not damage the protein, rather, it helps the body with the absorption.
Denatured proteins are hydrolyzates which have broken peptide links, so that the amino acids are much easier to absorb
How is the egg protein absorbed?
If we want to absorb a 100% of the amino acids from egg protein, we have mainly two choices:
Mechanical or physical action
When we whisk the egg white until it becomes stiff we change the structure of the egg protein so that it can be easier to digest by the organism. However, whisking is not enough to avoid salmonella or the effect of the ovomucoids and ovoinhibitors.
Don’t forget that even though the protein is denatured through a physical action, the bacteria that are present in raw egg are still there, so the best choice would be to use pasteurized egg whites
Without any doubt, the best way to denature egg protein is through heat. The kinetic energy caused by an increase in temperature will enhance the vibration of the molecules that make up the protein, breaking the links and leaving the amino acids intact.
If the egg protein is heated at 56ºC, the non-absorbable proteins from the egg whites are denatured. However, they must be cooked at 80ºC if we want to absorb them completely (a 94%).
Denaturing the protein from egg white like ovalbumin, ovotransferrin, ovoglobulins, etc, is just a process that consists on transforming long amino acid chains that are found raw in some kind of bubbles or protein globules so that they can be absorbed.
The experts’ opinion about egg protein
1. Egg protein favors the immune system
Several research lines carried on the field of orthomolecular medicine have proven that the content of sulfur amino acids from egg protein, like methionine and cysteine, plays an important role in the functioning of the immune system.
2. Egg protein favors the formation and growth of the muscles
A Canadian study has proven that 20 grams of egg protein encourage the optimal growth of the muscle after training. At the same time, the loss of muscle mass is reduced and the regeneration is shortened.
3. Egg protein does not have side effects nor interactions with medicines
Taking egg protein in the indicated dose is completely safe and it does not have side effects nor contraindications. However, you should consult your doctor before taking egg protein if you have suffered renal or liver damage, or if you are pregnant or lactating.
- Chang C., Lahti T., Tanaka T., Nickerson MT. (2018). Egg proteins: fractionation, bioactive peptides and allergenicity
- Kritchevsky SB.(2004). A review of scientific research and recommendations regarding eggs
- Qureshi AI., Suri FK., Ahmed S., Nasar A., Divani AA., Kirmani JF. (2007). Regular egg consumption does not increase the risk of stroke and cardiovascular diseases
- Scrafford CG., Tran NL., Barraj LM., Mink PJ. (2011). Egg consumption and CHD and stroke mortality: a prospective study of US adults
- North Caroline Egg Association. Yolks VS Whites
- Van Vliet S., Shy EL., Abou Sawan S., Beals JW., West DW., Skinner SK., Ulanov AV., Li Z., Paluska SA., Parsons CM., Moore DR., Burd NA.(2017). Consumption of whole eggs promotes greater stimulation of postexercise muscle protein synthesis than consumption of isonitrogenous amounts of egg whites in young men
- Kritchevsky SB., Kritchevsky D. (2000). Egg consumption and coronary heart disease: an epidemiologic overview
- Larsson SC., Åkesson A., Wolk A. (2015). Egg consumption and risk of heart failure, myocardial infarction, and stroke: results from 2 prospective cohorts
- The great myths of nutrition