Engormix/Poultry Industry/Technical articles

Egg Nutritional Composition

Nutritional Importance of an Egg

Published on: 9/21/2011
Author/s : Mr. Zaib-ur-Rehman and Prof. Dr. Ahsan ul Haq (University of Agriculture Faisalabad, Pakistan)
To get balanced nutrition it is not necessary to eat expensive food. Apart from being inexpensive, egg is a wholesome food which contains balanced amount of essential nutrients like protein, vitamins and minerals. All these nutrients are in highly protected form. Nature has provide the protection to egg, from deterioration, by egg shell then by shell membranes and finally by the antibodies present in the egg.
Nutritional composition of an egg

Nutritional Importance of an Egg - Image 1

Chicken egg is one of the most common foods all over the world. Eggs have biological value of 93.79 % comparable values are 84.5 % for milk, 76 % for fish and 74.3 % for beef. Eggs really are the best protein that can be bought by spending money, and it has all those other valuable vitamins and minerals too.
Its major parts for human consumption are albumin and yolk.Albumen also known as egg white, Albumen accounts for most of an egg´s liquid weight, about 67%. Albumen comprises more than half the egg´s total protein, niacin, riboflavin, chlorine, magnesium, potassium, sodium and sulfur. The albumen encompasses four alternating layers of thick and thin consistencies. From the yolk to external, they are designated as the inner thick or chalaziferous white, the inner thin white, the outer thick white and the outer thin white. Egg white tends to thin out as an egg ages because its protein changes in character.
Yolk or yellow portion makes up about 33% of the liquid weight of the egg. It contains all of the fat in the egg and a little less than half of the protein. With the exception of riboflavin and niacin, the yolk contains a higher proportion of the egg´s vitamins than the white. All of the egg´s  vitamins A, D and E are in the yolk. Egg yolks are one of the few foods naturally containing vitamin D. The yolk also contains more phosphorus, manganese, iron, iodine, copper, and calcium than the white, and it contains all of the zinc. The yolk of a large egg contains about 59 calories. Yolk fatty acids have a central role in egg nutritional properties evaluation. The yolk weight of a typical chicken 60g egg is 20g, of which 50% is solid matter and 50% is water; it contains 6g of lipids and 3g of proteins. Egg lipid classes are: Triacylglycerol´s (65%), Phospholipids (28.3%), Free Cholesterol (5.2%), Cholesterol ester and free fatty acids (traces).
The term "cholesterol" refers to a group of chemicals containing both protein and fat components (lipoproteins) that are present in every living cell and perform following functions.
  •  Aids in hormone production.
  • Essential for brain and nerve development.
  • Starting material from which the liver produces bile acids, necessary for digestion of fats.
  • Key substances in the wall of every cell.
  • Precursor for production of steroid hormones by the adrenal glands and gonads.
They are an essential component of all cells in the body of chickens, humans and all animals.  They do not occur in plants. Cholesterol content of eggs became an important issue for consumers in the 1970´s and 1980´s when it was discovered that, among the human population, those with high cholesterol levels in their blood (usually referred to as "serum cholesterol") were at greater risk of heart attacks and/or atherosclerosis.  While this statistical connection is an important one in terms of human health, there have been decisive slipups in its explanation.  There is effectively no link between the cholesterol most people consume in their diets, and their serum cholesterol levels (Hu et al., 1999).
There are two types of cholesterol, Low density lipoproteins (LDL) and High density lipoproteins (HDL). Low density lipoproteins also called bad cholesterol carry most of the cholesterol in the blood. The cholesterol and fat from the LDLs are the chief source of dangerous build up and obstruction in the arteries. Thus, the more LDL cholesterol in the blood causes the greater chance of heart diseases. Nature has provided good cholesterol (HDL) in the egg yolk, it is in minute quantity but very effective. High density lipoproteins also named as good cholesterol, this cholesterol goes back to liver, which leads to its removal from the body so HDLs help to keep cholesterol from building up in the walls of arteries, if level of good cholesterol is low, risk of heart diseases is greater. Egg yolk consist of 68 percent LDL and 16 percent HDL.
There are many factors that influence serum cholesterol; these include exercise, smoking, inheritance, body weight, and more.  As far as diet is concerned, the most important factors are the consumption of saturated fats and trans-fats.  Saturated fats are found primarily in animal products: animal fat, milk fat and cheese.  The fat in egg yolks is about 2/3 unsaturated and 1/3 saturated.  Trans-fats are found in processed vegetable oils, frequently those used in preparation of fast foods.
All animals have a natural level of serum cholesterol that is maintained by an internal homeostatic mechanism.  When more cholesterol is consumed in food, less is produced internally by body, and vice versa.  Within normal limits, this system naturally works well and maintains serum cholesterol at acceptable and non-dangerous levels. Studies of large groups of human subjects revealed that high serum cholesterol levels were often associated with increased risk of cardiovascular disease.  However, these data were unable to demonstrate the cause of the disparity in serum cholesterol levels.  In more recent studies, involving many thousands of subjects, the design allowed correction of data for such issues as age, heredity, and consumption of various foods. From these, we have been able to conclude that dietary cholesterol is not directly related to cardiovascular disease or heart attacks.
The commonly used drugs to lower blood pressure stop the production of the hormone angiotensin to narrowing the body´s blood vessels. The scientists identified several different peptides in boiled and fried eggs that act as potent Angiotensin Converting Enzyme (ACE) inhibitors. The scientists showed that enzymes in the stomach and small intestine produce these peptides from eggs. The protein produced by stomach enzymes after coming in contact with eggs acts in the same way as blood pressure lowering drugs. In conclusion eggs do not have any side effect on heart, blood pressure and serum cholesterol; and are safe in every aspect.
Egg benefits
  • Chicken eggs are abundant in antibodies such as IgY which can treat human rotavirus, Escherichia coli, streptococcus, pseudomonas, staphylococcus and salmonella infections.
  • The nutritionally balanced, high biological value of the egg is an excellent growth promoter in children. It is the best natural nutritional support for convalescents, especially those with tuberculosis or AIDS related infections. Lipoprotein and other high biological value proteins in the egg act as excellent growth promoters in children and animals.
  • Egg albumen can be used as an remedy in cases, where certain toxins and irritants may have been accidentally consumed. It protects the mucous membranes of the stomach and intestine, and prevents ulcer formation.
  • Studies carried out at Japan´s Kyoto University have revealed that egg contain the two substances-Lumiflavin and Lumichrome. These two substances, along with sulphoraphane, have the ability to restrict the multiplication of cancer-inducing viruses and also prevent the change of normal to cancerous cells. These compounds are also natural antioxidants.
  • The Gl-globulin lysozyme, the G2 and G3-globulins, ovomacroglobulin, antibody "IgY" as well as other natural antimicrobials and immunostimulants in the egg may prolong the lives of those with AIDS, not only due to their high nutritional value but also because of their antimicrobial properties.
  • Egg yolk and albumen chalaza are rich sources of "sialic acid," which has powerful antimicrobial, anti-inflammatory and antiviral properties, and hence is used in the cure of Helicobacter pylori and other microbial infections causing ulcers, colon cancer, gastritis and enteritis.
  • Lutein and zeaxanthin from eggs helps in maintaining the eye health and reducing the risks of age-related macular degeneration, a major cause of irreversible blindness.
  • Vitamin E, organic selenium and other antioxidants in functional eggs prevent oxidation, ageing, and formation of plaques in arteries.
  • The high-quality protein in eggs helps you to feel (prolong a feeling of fullness) full longer and stay energized, which contributes to maintaining a healthy weight.
  • A single egg contains 50 % of your daily required intake of Choline which is essential for normal functioning of all cells, including those involved with metabolism, brain and nerve function, memory, and the transportation of nutrients throughout the body. Choline also helps to prevent birth defects, as well as helps promote brain and memory development in infants.
  • Different vitamins and minerals play a very important role in the body which are as follows:
  1. Riboflavin: Helps to produce energy in all the cells of the body
  2. Pantothenic Acid: Helps to breakdown food and assists body cells in producing energy.
  3. Phosphorus: Essential for healthy bones, teeth and cell membranes. Phosphorus is also required for energy production in the body. It is also essential for  healthy bones, teeth and cell membranes. Phosphorus is also required for energy production in the body.
  4. Vitamin D: Works with calcium to strengthen bones and teeth.
  5. Calcium: Helps to build and maintain strong bones and teeth. This mineral also plays an important role in nerve function, muscle contraction and blood clotting.
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