Eggs and Nutrition - 10 interesting facts about eggs!

Eggs are the house of the embryo in almost all animals except mammals. Therefore, they are rich in nutrients, stored to supply the embryo until it grows into a living being. Other than this high nutritional value, eggs are a delicacy in most cultures in the world. This article points out ten interesting facts about eggs in relation to its composition and its nutritional value.

Since eggs are formed to contain the embryo, protect it and allow it to mature by supplying nutrients; they are rich in most of the nutrients. Here the egg white is for protection of embryo against microbial factors and egg yolk is working as food reserve for the young chick.

About 12% of a hen’s egg is shell, 58% egg white and 30%yolk. Average egg weighing about 60g provides 7g of protein, 6g fat, 30mg calcium, 1.5mg iron, 250mg cholesterol. The energy content of average sized egg is 335kJ (80kcal)

The egg white contains 36% water, 13% of protein 0.25% fat and mineral salts. Hence, egg white is a source rich in protein and low inc cholesterol.

The yolk contains 51% water 16.6% protein 31.7% fat, minerals 1% and vitamin A, D, thiamin and riboflavin. Egg yolk is rich in cholesterol (about 250mg per egg). So it is recommended to take 2 to 3 eggs per week only.

The egg white proteins differ markedly from the proteins of egg yolk in biological functions and structure. Egg white is almost pure solution of protein, almost all the proteins being active as enzymes, inhibitors and antibodies. It has the ability to form stable foams. Egg white proteins are easily denatured, and the foaming capacity is impaired as a result of heating, freezing and dehydration. Avidin an egg white protein prevents absorption of the vitamin Biotin. But avidin is inactivated by heat.

Egg yolk is rich in lysine and leucine, they are compounds of major egg protein lipovitellin. The egg yolk is used extensively as an emulsifier in mayonnaise, cake butter and confectionary.

A darker yolk does not mean a higher concentration of vitamin A or carotene as its color is mainly due to xanthophyll  pigments which is yellow color. The nutritional value of an egg does ot increase with the colour of the yolk.

Whole egg proteins are very well balanced with essential amino acids and particularly rich in arginine and the sulphur containing amino acids.

Eggs are a good source of calcium. Each egg supplies 30mg of calcium.

Although egg yolk is rich in iron, it is a poor source of iron as in egg yolk proteins bind with iron forming an insoluble chelate preventing iron getting absorbed. Absorption of iron in nutritional supplements is also reduced with eggs. Ascorbic acid (vitamin C), sugar, amino acids and dicarboxylic acids form soluble chelates with Fe³⁺ and prevent its precipitation. Hence the iron absorption from egg yolk is increased if it can be combined with any of the above.