Eggs

Energy value of eggs

A medium egg has an energy value of 78 kilo calories (324 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

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

Eggs contain most of the recognised 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

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 fiber

Eggs contain only traces of carbohydrate and no dietary fiber.

Fat

11.2% 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 17% of an egg’s fatty acids are polyunsaturated, 44% monounsaturated and only 32% saturated.

Cholesterol

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.

Harvard Health has an article on the nutrition of eggs and heart disease. You can read it here.

I know some people believe that the little white stuff inside of an egg is sperm, but it's not. I used to believe that also and used to take out the white part with a fork before cooking the egg. It is called chalazae. It keeps the yolk from sloshing around inside the egg. Normally there are two chalazae, which connect the yolk to either end of the egg and keep it suspended in the middle. They're found in all types of eggs. Sometimes you only see one or none because they stick to the egg shell rather than the yolk. The chalaza are made of semisolid albumen, basically the same stuff that egg white is made of.