Eggs are an important source of protein, essential vitamins and minerals and can make a significant contribution to a healthy diet.
Nutritional requirements can vary considerably between men, women and children and can also vary in individuals from time to time.
To illustrate the contribution that eggs make to the diet and nutritional requirements, please refer to the table below.
The data on the nutritional content of a single egg is based on a medium egg and all percentage composition figures relate to the contents, excluding the shell.
|Nutritional analysis of egg without its shell||For a medium egg (Av 58g)|
|Constituent of Egg||Amount per egg||% of Reference Nutrient Intake (RNI)|
|For adult female 19-50 years||For adult male19-50 years|
|Inc saturated f.a.||g|
|MINERALS AND TRACE ELEMENTS|
1Assumes edible portion = 89%
*No RNI **Beyond age 65 years
Source: Royal Society of Chemistry/ MAFF 1991 The Composition of Foods (5th edition)
Energy value of eggs
A medium egg has an energy value of 76 kilocalories (318 kilojoules) and the consumption of one egg daily would contribute only around 3% of the average energy requirement of an adult man; 4% for an adult woman.
With their significant protein, vitamin and mineral content and relatively low saturated fat content, eggs are a valuable component in a healthy diet.
Protein in Eggs
Eggs are an excellent source of protein. Egg protein is of high biological value as it contains all the essential amino acids needed by the human body. Eggs therefore complement other food proteins of lower biological value by providing the amino acids that are in short supply in those foods. 12.5% of the weight of the egg is protein and it is found in both the yolk and the albumen. Although protein is more concentrated around the yolk, there is in fact more protein in the albumen.
On the evaluation scale most commonly used for assessing protein, egg is at the highest point, 100, and is used as the reference standard against which all other foods are assessed.
Vitamins in Eggs
Eggs contain most of the recognized vitamins with the exception of vitamin C. The egg is a good source of all the B vitamins, plus the fat-soluble vitamin A. It also provides useful amounts of vitamin D, as well as some vitamin E.
Minerals in Eggs
Eggs contain most of the minerals that the human body requires for health. In particular eggs are an excellent source of iodine, required to make the thyroid hormone, and phosphorus, required for bone health.
The egg provides significant amounts of zinc, important for wound healing, growth and fighting infection; selenium, an important antioxidant; and calcium, needed for bone and growth structure and nervous function.
Eggs also contain significant amounts of iron, the vital ingredient of red blood cells, but the availability of this iron to the body is uncertain.
Carbohydrate and dietary fibre in Eggs
Eggs contain only traces of carbohydrate and no dietary fibre.
Fat in Eggs
10.8% of the egg content is fat. The fat of an egg is found almost entirely in the yolk; there is less than 0.05% in the albumen.
Approximately 11% of an egg’s fatty acids are polyunsaturated, 44% monounsaturated and only 29% saturated.
Cholesterol in Eggs
Cholesterol and Lecithin are fat-like substances and are essential to the structure and function of all cells in the body. Cholesterol helps to maintain the flexibility and permeability of cell membranes and is also a raw material for the fatty lubricants that help to keep the skin supple. Cholesterol is essential for the production of sex hormones, cortisol, vitamin D and bile salts.
Lecithin is involved in general lipid transportation in the blood and in the metabolism of cholesterol.
The three tables below indicate the more recognised nutrients found in eggs and their benefits.
Fat Soluble Vitamins in Eggs
|Vitamin A||Essential for vision in dim light; necessary for maintenance of mucous membranes; skin and growth.||As retinol in milk, fortified margarine, butter, cheese, egg yolk, liver and fatty fish. As carotenes in milk, carrots, tomatoes, dark green vegetables.||Reduced night vision; loss of sight through gradual damage to the cornea. Lowered resistance to infection.||Vitamin A is stored in the liver and toxicity can occur.|
|Vitamin D||Promotes calcium and phosphate absorption from food and is thus essential for bones and teeth.||Sunshine, fortified margarine, oily fish, egg yolk, fortified breakfast cereals.||Failure of bones to grow and calcify leading to rickets in children and osteomalacia in adults.||Vitamin D can be toxic.|
|Vitamin E||Protects cell membranes from damage by oxidation.||Vegetable oils, nuts, vegetables and cereals.||Deficiency may occur in premature infants or due to malabsorption.||Not known.|
Water Soluble Vitamins
|Thiamin (B1)||Involved in the release of energy from carbohydrate. It is important for the brain and nerves, which use glucose for their energy needs.||Cereals, nuts and pulses are rich sources. Green vegetables, pork and fruits and fortified cereals contain thiamin.||Deficiency leads to beriberi. Alcoholics sometimes develop deficiency.||The body excretes excess thiamin.|
|Riboflavin (B2)||Involved in energy release, especially from fat and protein.||Rich sources are liver, milk, cheese, yoghurt, eggs, green vegetables and yeast extract, and fortified cereals.||Deficiency includes changes to the mucous membrane and skin around the mouth and nose.||The body excretes excess riboflavin. No known adverse effect.|
|Vitamin B6 (Pyridoxine)||Involved in the metabolism of protein.||Found in a variety of foods: beef, fish and poultry are rich sources.||Deficiency may occur as a complication of disease and drug effects.||High intakes (from vitamin pills) may be harmful.|
|B12||Is necessary for the proper formation of blood cells and nerve fibres.||Rich sources are offal and meat. Eggs and milk also contain B12. Almost no plant foods contain B12. Fortified breakfast cereals are a useful source.||Deficiency leads to pernicious anaemia.||No toxic effects known.|
|Folate||Involved in the formation of blood cells.Reduces the risk of Neural tube defects in babies.||Liver, orange juice, dark green vegetables are rich sources. Nuts, wholemeal bread, and fortified breakfast cereals are sources.||Deficiency leads to megaloblastic anaemia.||No toxic effects known.|
Minerals in Eggs
|Calcium||Calcium is the main constituent of hydroxyapatite, the principal mineral in bones and teeth. An adequate calcium intake is vital to health, particularly in times of growth, e.g. childhood, adolescence, pregnancy, and also during lactation.||In milk and dairy products calcium is readily available, but it is usually less available from plant foods. Calcium is sometimes bound by phytates (found in wholegrain cereals and pulses) and oxalates (found in spinach and rhubarb) in foods, which make i||Deficiency of calcium in bones can result from an inadequate supply of vitamin D, which is essential for its absorption. This condition is known as rickets in children and osteomalacia in adults.||No known toxic effects.|
|Phosphorus||80% of the phosphorus in the body is present as calcium salts in the skeleton.||Phosphorus is present in all plant and animal cells.||Affects calcium balance.|
|Iron||Iron is required for the formation of haemoglobin in red blood cells, which transport oxygen around the body.||Iron is found in plant and animal sources. Bread and many breakfast cereals are fortified with iron in the UK.||A lack of iron leads to lower iron stores in the body and eventually to iron deficiency anaemia.||No known toxic effects.|
|Iodine||Iodine is used to make thyroid hormones, which control many metabolic activities.||Seafood, salt and bread, dairy products and eggs.||Lethargy and swelling of the thyroid gland in the neck to form a goitre. Nowadays this is rare in the UK. Infants born of severely iodine deficient mothers may be mentally retarded (cretinism).||No known toxic effects.|
|Selenium||As an antioxidant it protects cell membranes against oxidation.||Cereals, meat, fish, offal, cheese and eggs.||Keshan disease (type of heart disease).||Excess selenium is toxic.|
|Zinc||Essential for growth, and sexual maturation. Involved in enzyme activity and taste perception.||Milk, cheese, meat, eggs and fish, wholegrain cereals and pulses.||Dietary deficiency is rare; may cause delayed puberty and retarded growth.||Interferes with copper metabolism.|
1. Suzen M. Moeller, Paul F. Jacques, Jeffrey B. Blumberg, The Potential of Dietary Xanthophylls in Cataract and Age-Related Macular Degeneration, Journal of the American College of Nutrition, 19, 522S, 2000
2. Steven H.Zeisel, Choline: Needed for Normal Development of Memory, Journal of the American College of Nutrition, 19, 528S, 2000
The body requires different amounts of each vitamin and mineral because each of them has a different function. People have different requirements according to their age, sex, level of activity and state of health.
The UK Department of Health has drawn up Dietary Reference Values (DRVs) for all nutrients for all different groups of healthy people in the UK1. The Reference Nutrient Intake (RNI) level meets the needs of practically all of the population.
The tables below indicate the RNI values for the vitamins and minerals found in eggs and also what percentage of each vitamin and mineral is found in a medium sized egg (average weight 58g, assumes edible portion 89%).
|% in an egg||Vitamin D|
|% in an egg||Thiamin mg/d||% in an egg||Niacin mg/d||% in an egg||Riboflavin mg/d||% in an egg||Vitamin B6|
|% in an egg||Vitamin B12|
|% in an egg||Folate mg/d||% in an egg|
*No increment **After age 65 the RNI is 10 m g/d for men and women ***For last trimester only
1 Department of Health – 1991
|Age||Calcium mg/d||% in an egg||Phosphorus mg/d||% in an egg||Potassium mg/d||% in an egg||Magnesium mg/d||% in an egg||Zinc mg/d||% in an egg||Iron mg/d||% in an egg|
* No increment
|Age||Copper mg/d||% in an egg||Iodine mg/d||% in an egg||Selenium mg/d||% in an egg|
* No increment
We have rapidly moved from a paradigm where we only had to assure that food was safe to eat to one where we need to demonstrate and communicate clearly that food is not only safe but has beneficial effects.
The body requires different amounts of each vitamin and mineral because each has a different function. People have different requirements according to their age, sex, level of activity and state of health.
There is however, increasing evidence that other nutrients that have been found in eggs, the carotenoids, lutein and zeaxanthin might be involved in the prevention of cataracts and age-related macular degeneration (AMD), a major cause of blindness in elderly people.
Eggs are also rich in choline, an essential component of all cells. Recent research suggests that choline may have a role in normal development of memory.
There you have it! The scientific proof that eggs are a nutritional power house that you should be eating more of. Don’t forget to share.
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