The yellow portion makes up about 33 percent of the liquid weight of the egg.
The egg yolk is rich in fat, that is about one third of the yolk is fat, especially of cholesterol and lecithin variety.
Egg yolk lecithin is a key source of compounds known as phospholipids, which are crucially important molecules with active roles in cell membranes particularly in the brain and nervous system.
The yolks of chicken eggs produced commercially contain large amounts of the carotenoid lutein and zeaxanthin (approx. 292 ug/yolk and 213 ug/yolk, respectively).
Several studies have linked lutein to a lower risk for eye, skin and other health disorders, probably though its antioxidant activity.
Lutein and zeaxanthin may protect the cardiovascular system and maintain normal cell differentiation in the tissues of the breasts, colon, and skin.
Some research into the health benefits of eggs suggest a link between eggs and a reduced risk of heart attack or stroke, primarily because the protein in egg yolk help prevent blood clots.
Egg yolk also is rich in vitamins, especially thiamin, riboflavin, vitamins A and D and their content in eggs upon the chicken’s diet. Egg yolk are one of the few foods naturally containing vitamin D.
The yolk’s content of phosphorus, manganese, iron, iodine, copper and calcium are higher than the whites and it contain all of the zinc.
Nutrient in egg yolk
