A single large egg provides 12 percent of the daily requirement of protein for 70 calories. The 2010 Dietary Guidelines suggest Americans “eat a nutrient dense breakfast.” Evidence suggests that the high-quality protein in eggs provides steady and sustained energy because it does not cause a surge in blood sugar or insulin levels, which can lead to a rebound effect or energy “crash” as blood sugar levels drop. Recent research shows that eggs eaten at the start of the day help people feel more satisfied, allowing them to reduce their caloric intake for the rest of the day and prevent snacking between meals.
Eggs contain the highest quality protein and are often used as a standard to measure the quality of other protein sources. Eggs also have the highest biological value of any protein, meaning that the essential amino acids they provide are used very efficiently by the body. Eggs also contain varying amounts of vitamins A, D, E, K, B6, B12, folate, and a variety of minerals (particularly riboflavin, phosphorus, and iron). Because eggs are very easy to digest, they are frequently included in therapeutic diets.
The yolk makes up just over one third of an egg. It provides three-fourths of the calories, all of the fat-soluble vitamins (A, D, E, and K), and all of the choline, lutein, and zeaxanthin. The yolk also provides most of the phosphorus, iron, and folate and almost half of the protein and riboflavin. The white (albumen) provides more than half of the total protein and riboflavin. Choline, an essential nutrient, is shown to be important for proper brain development in the fetus and newborn and may play a role in memory function throughout life and into old age. Lutein and zeaxanthin may prevent macular degeneration, a leading cause of blindness in the elderly in the U.S.
Though these nutrients are present only in small amounts in eggs, research shows that they may be more bioavailable, or absorbed and utilized by the body, when obtained from egg yolk than from richer sources.
Learn more about the nutrition content of a large egg.