Eggs considered as mother nature’s original superfood are among the most complete and versatile foods on the planet. A protein powerhouse and loaded with 13 essential vitamins, 11 minerals, Omega-6 &omega-3 fatty acids and antioxidants, eggs have become an integral part of a healthy diet without a reason. The perfect balance and diversity in its nutrients along with high digestibility and an affordable price has put the egg in the spotlight as a basic food for humans.
Table 1: Nutritional composition* of hen eggs
An egg is formed of two main parts, the egg white (albumen) and the egg yolk.
Egg yolk Albumen
The egg white contains more than half the egg’s total protein, niacin, riboflavin, chlorine, selenium, magnesium, potassium, sodium, and sulphur and all the egg’s zinc.
The yolk contains all the fat in the egg and a little less than half of the protein. It also contains the fat-soluble vitamins A, D, and E. Egg yolks are one of the few foods naturally containing vitamin D. The yolk also provides riboflavin, pantothenic acid, vitamin B6, vitamin B12 and folic acid, and the minerals iron, calcium, copper, selenium, and phosphorus.
Trusted Source of Proteins: Eggs are a great protein source. According to the 2018 USDA National Nutrient Database, one large egg contains 6.3 g of protein distributed between the yolk and white portions (3.6 g in egg white and 2.7 g in egg yolk). It is well established that eggs are one of the best dietary sources of high-quality protein, with all of the essential amino acids, and are recognized for their high (93.7%) biological value (Kovas-Nolan J. et al., 2005). Based on the essential amino acids it provides, egg protein is second only to mother’s milk for human nutrition.
Protein quality is assessed by the protein digestibility-corrected amino acid score, or PDCAAS; the higher the value of the PDCAAS, the better the protein meets the requirements for all essential amino acids in regard to amounts provided and digestibility. For example, for children aged from 6 months to 5 years, the PDCAAS for eggs is 118%, compared to 92–94% for meat and fish, 90–93% for soy, and 35–57% for cereals including rice, wheat, and corn (Tome D., 2012).
Egg protein has been shown to stimulate new muscle growth and repair muscles, decrease malnutrition, increase satiety, and therefore contribute to weight loss(Vander Wal J.S. et al., 2008). It has other additional benefits including protection against infection (Li X. et al., 2016), decrease in blood pressure, as well as anti-cancer effects. Both the egg yolk and egg white contain different proteins. For example, in egg whites, ovotransferrin binds metal ions, ovomucin has antiviral properties, and lysozyme disrupts the cell walls of Gram-positive bacteria (Fernandez M.L., 2010). Egg yolk contains a protein called phosvitin(Yousr M., Howell N., 2015) which reduces inflammation and promotes gut health.It is worthy to mention, eggs have been reported to be the most digestible protein source by the World Health Organization, measured as 97%, compared to 95% for dairy and 94% for meat.
Table 2: Beneficial effects of egg protein
(Source: Puglisi MJ, Fernandez ML., 2022)
Low Carbs: Eggs in their most natural form, does not contain any fibers and have low-calorie (80 calories per egg) with very little carbohydrates (0.7%). According to the National Agricultural Library, a large egg has less than half a gram of carbohydrate and this makes eggs perfect for low-carb diet plans.
Essential fatty acids: These are essential nutrients and required through diet as the body cannot make them. The fatty acid composition of egg can change depending on the diet of laying hens. In general, eggs are rich in omega-3 and omega-6 fatty acids. Omega-3 fatty acids mainly in the form of ALA (Alpha-Linolenic Acid), EPA (Eicosapentaenoic Acid) & DHA (Docosahexaenoic Acid), are vital for early brain development and vision. Eggs from unsupplemented laying hens may contain 93 mg ALA and 173 mg total omega-3 fatty acid (ALA, EPA, and DHA)/50 g egg while adding 15% dietary flaxseed can increase ALA and total omega-3 fatty acid content to 358 mg and 468 mg/50 g egg, respectively (Jia et al., 2008; Samman et al., 2009). Altogether omega-3 fatty acids confer health benefits including reduction of blood pressure, blood triglycerides, inflammation, and the risks related to cardiovascular diseases. Along with omega-3 fatty acids, omega-6 fatty acids also play a crucial role in brain function, and normal growth and development. As a type of polyunsaturated fatty acid (PUFA), omega-6s help stimulate skin and hair growth, maintain bone health, regulate metabolism, and maintain the reproductive system.
Rich in Minerals: Eggs are rich in phosphorus, calcium, potassium, and contains moderate amounts of sodium (142 mg per 100 g of whole egg). Eggs also contain all essential trace elements including copper, iron, magnesium, manganese, selenium, and zinc (Table 1), with egg yolk being the major contributor to iron and zinc supply.Iron is essential for red blood cell formation & therefore carrying oxygen to the cells. It helps prevent anaemia, development of connective tissue and providing energy. Phosphorus is an element in all body cells, mostly known as part of the bone ant teeth matrix. It also contributes to the energy metabolism and muscle growth. Iodine is required to make thyroid hormones; important for healthy growth and metabolic regulation. Iodine is also very important in brain development during pregnancy and early years. Zinc is crucial for healthy growth and development, especially during periods of rapid growth, such as infancy and during pregnancy. Selenium works with vitamin E to act as an antioxidant to help prevent the breakdown of body tissues due to free radicals.
Extra Vitamins: Eggs are a rich source of various vitamins. Vitamin A in eggs contributes to growth, reproduction, skin health, and eye tissue and helps strengthen immune system. Vitamin D plays a fundamental role in maintaining calcium and phosphorus balance within the body, influencing intestinal absorption, bone health, kidney function, immune system modulation, and muscular cell growth and may help protect against certain cancers and auto-immune diseases. Vitamin E is an antioxidant that plays a role in maintaining good health and preventing disease. Vitamin K3 serves as a pivotal coenzyme for blood clotting, coagulation and bone mineralization. All of the B vitamins are cofactors that work with a cognate enzyme, or chemical precursors of a cofactor. Vitamin B2 or Riboflavin is involved in many vital metabolic processes in the body and is necessary for normal cell function, growth and energy production. Vitamin B12 helps maintain the health of your blood cells, nervous system, DNA, and brain and reduces tiredness and fatigue. Folate helps produce and maintain new cells; helps prevent a type of anemia, helps protect against serious birth defects if taken prior to pregnancy and during the first 3 months of pregnancy.
Vital Choline: Choline is an incredibly important nutrient for our body. Choline is a water-soluble essential nutrient, that the body requires for neurotransmitter synthesis (acetylcholine), cell-membrane signalling (phospholipids), lipid transport (lipoproteins), and methyl-group metabolism (Penry J, Manore M., 2008).A single egg has about 100 milligrams of this nutrient and therefore is one of the best sources of it. Choline plays important roles in brain and memory development in the foetus and appears to decrease the risk of the development of neural tube defects (Rees W. et al., 2006).
Abundance of Antioxidants: Eating eggs, especially the yolk part offers an abundance of Lutein and Zeaxanthin- two newly-recognized nutrients, that has put the egg in the “functional food” category. A functional food is one that provides health benefits beyond its basic nutrient content.
These nutrients are known to slow down the degenerative process of eyesight and lower the risk of age-related macular degeneration (AMD), a leading cause of blindness in old people. These nutrients accumulate in the retina of your eyes and prevent them from aging effects. The nutrients are best known to work against cataracts and macular degeneration.
Cholesterol Myth: Unfortunately, there is a lot of confusion around cholesterol and eggs. one large egg contains about 200 mg cholesterol. Various research reported that dietary cholesterol (including cholesterol in eggs) has very limited impact on the blood cholesterol level. Only 15% of circulating cholesterol in the blood comes from what we eat. The other 85% comes from the liver.
Again, there are two different types of cholesterol: low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDL can build up in our blood vessels and is therefore called the “bad cholesterol”. While the most relevant function of HDL is to promote the efflux of excess cholesterol from peripheral tissues to the liver for excretion; a pathway known as reverse cholesterol transport (Khera AV et al., 2011) and therefore HDL is called as the “good cholesterol”. The efflux of cholesterol is important for maintaining cellular cholesterol homeostasis (Duong M et al., 2006). Egg yolk contains high amount of HDL. Egg yolk HDL can be used to treat cardiovascular diseases (Eftekhar S et al., 2015), stroke and other health issues.
The Bottom Line:
Overall, eggs are a highly nutritious food that can play an important role in a healthy diet and may be a particularly valuable inclusion in the diet of vulnerable groups. Eggs are one of our best tools to ensure food security, human nutrition, and overall well-being. While potential malnutrition is increasing in many countries, it may be an“egg-cellent” choice to place more significance on the egg, which has been found to be a rich source of many essential nutrients.