Eggs are commonly available highly nutritious food for all age groups. They are abundant sources of proteins, fats, vitamins, minerals, and bioactive compounds.
Eggs have white gel-like substance which is called egg white and a yellowish portion called egg yolk.
The egg white is composed mainly of water, fibrous structural proteins (ovomucins), glycoproteins (ovalbumin, protease inhibitors), antibacterial proteins (lysozyme), and peptides. Egg-white ovalbumin is an excellent source of amino-acids.
Egg white also contains antibacterial lysozyme which boost immunity against infections. The viscous nature of egg white is due to ovomucin proteins.
Chicken egg contains a large number of antioxidant compounds including vitamins, carotenoids, minerals, and trace elements along with egg-white proteins.
The egg yolk is a great source of vitamin A, D, E, K, B1, B2, B5, B6, B9, and B12. Egg yolk also contains iron and zinc in high amounts.
Egg is enriched with minerals such as phosphorus, calcium, potassium. It also contains moderate amounts of sodium. Trace elements including copper, iron, magnesium, manganese, selenium, and zinc also are included within eggs.
Eggs are lacking fibers and carbohydrate content also is low. Egg carbohydrates are distributed between egg yolk and egg white. Glucose is the main free sugar found in the egg.
Proteins in egg yolk include apolipoproteins, phosvitin, egg yolk globulin, and riboflavin binding protein. Proteins help bodybuilding and are used for the production of various hormones and enzymes in human body.
Egg proteins are distributed equally between egg white and egg yolk, while lipids, vitamins, and minerals are essentially concentrated in egg yolk.
The concentration of proteins is, on average, 12.5 g per 100 g of whole raw fresh egg.
Nutritional value of eggs
A medium-sized boiled egg (50 g) contains 78 kcal energy, 6.29 g protein, 0.56 g carbohydrate, and 5.3 g total fat, of which 1.6 g is saturated, 2.0 g is monounsaturated, 0.7g is polyunsaturated, and 186 mg is cholesterol.
Eggs are good sources of vitamins thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, vitamin A, vitamin E, vitamin D, and vitamin K. However, out of the group of all essential vitamins only vitamin C is lacking in eggs.
B group vitamins in eggs are important for proper functioning of heart and nervous system. They also take part as cofactors in various metabolic functions of the body as co factors.
Folates are very important for foetal development and maturation of nervous system in pregnant women.
Carotenoids in egg yolks essential for health of eyes. The two major carotenoids in eggs are carotene and xanthophylls (lutein, cryptoxanthin , and zeaxanthin) which are highly bioavailable in egg yolk. They help to improve vision and prevent macular degeneration and cataract. They have role in prevention of cancer and atheromatous clots in carotid artery.
Egg lipoproteins include LDL and HDL. About 98% of sterols in the egg yolk are cholesterol, and a small amount of phytosterols such as beta-sitosterol, methyl cholesterol, and sorbitol mycotoxins are also present in it [3].
Eggs also contain active lipid components, such as unsaturated fatty acids, phospholipids, choline, and carotenoids.
Phospholipids in eggs include phosphatidylcholine, phosphatidylethanolamine, lysophosphatidylcholine, sphingomyelin ,and some neutral lipids
Egg yolk is also a rich source of essential fatty acids such as linoleic acid.
Health benefits of eggs
consumption of eggs provide numerous health benefits.
• Rich in antioxidants
Egg proteins have been proved to possess antioxidants, such as phosvitin. Anti-oxidants help protect body from many chronic diseases ,particularly lifestyle diseases arising from free radical attack.
• Better brain health
B group vitamins and folate in eggs help brain and nervous system health.
• boosts heart health
Vitamins B and minerals potassium, magnesium and calcium in eggs play major roles in maintaining the health of heart.
• Improves bone health
Eggs are rich sources of vitamin D and minerals such as calcium, magnesium and phosphorus which are crucial for bone health.
• Helps brain development in foetus
Choline plays beneficial role in foetal and neonatal brain development, as deficient choline intake during pregnancy increases neural tube defects risk in infants.
•Improves vision
Carotenoids are highly bioavailable in egg yolk and reduce the risk of age-related macular degeneration and cataracts. It improves vision.
Facts about cholesterol raising potential of eggs &daily consumption
Eggs are considered as cholesterol rich food by many. But studies point out that although eggs consumption raises both serum LDL and HDL levels, the LDL/HDL ratio remains unchanged. Therefore, the adverse effect of LDL on heart and blood vessels might be reduced by the beneficial effect of HDL.
Amino acids such as glycine, glutamate, methionine, and cysteine in eggs play roles in regulating cholesterol metabolism. Egg yolk contains abundant unsaturated fatty acids which are good for heart health.
Therefore, currently it is presumed that the consumption of eggs does not enhance the risk of heart diseases in healthy people. However, it is recommended that people already having cardiovascular risks such as diabetes or hypertension have to be cautious about egg intake.
written by dr sanjana p
References
1. https://pubmed.ncbi.nlm.nih.gov/22953815/
2. Zhang T. Egg processing. Taipei, Taiwan: Huaxiangyuan Press; 1992. [Google Scholar]
3. Ma M. Processing science of egg and egg products. Beijing, China: China Agricultural Press; 2006. [Google Scholar]
4. https://pubmed.ncbi.nlm.nih.gov/15234930/
5. Journal of Nutrition. 2010;140(11):1970–1976. doi: 10.3945/jn.110.127647.