Eggs are a nutritious source of protein, but they do contain cholesterol and saturated fat. Dieters who consume only egg whites to keep calories under control miss out on a number essential nutrients found only in the yolk. Understanding what nutrients are found in the yolk and the white can help you best incorporate each into your diet.
Calories and Macronutrients
A large egg yolk contains 54 calories, while an egg white contains just 16. Almost all of the 5 g of fat in a large egg is contained in the yolk, with just trace amounts of fat found in the white. An egg yolk contains all 2 g of an egg's saturated fat and all 210 mg of cholesterol. Eggs contain only a trace amount of carbohydrate but are a source of protein. One egg white contains almost 4 g of protein, while an egg yolk contains approximately 3 g.
Vitamins
Egg yolks contain most of the vitamins present in an egg. One large egg yolk provides 5 percent of the recommended dietary allowance for vitamin A, vitamin D, riboflavin and pantothenic acid, based on a 2,000-calorie diet. It also provides 6 percent for folate and vitamin B12. A large egg yolk provides 3 percent of the RDA for vitamin B6 and 2 percent for vitamin E and thiamin. Egg whites offer more riboflavin than yolks, with 9 percent of the RDA, but only 1 percent of pantothenic acid and no other notable vitamins.
Minerals
One egg white provides very few minerals, especially when compared to egg yolks. One large egg white provides 1 percent of the RDA for magnesium, 2 percent for potassium and 9 percent for selenium. A large egg yolk, however, provides 2 percent of the RDA for calcium, 3 percent for iron, 7 percent for phosphorus, 3 percent for zinc, 14 percent for selenium and 1 percent for copper and potassium.
Additional Nutrients
Egg yolks are a source of lutein, an antioxidant important to vision health. One large egg yolk provides .2 mg of the USDA recommended 4 to 8 mg you need daily. Egg whites contain none of this antioxidant. One large egg yolk also provides 116 mg of choline, a nutrient grouped with the B vitamins. Choline supports cell structure and communication, nerve function and fat metabolism. The USDA recommends most adults consume between 400 and 550 mg of choline daily. Egg whites contain only trace amounts of this essential nutrient.
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