Egg yolks deliver great nutrition with only 55 calories. The yolk is the primary source of some nutrients found in a whole egg. It has all of the vitamins A, D, E and K, and most of the egg's folate, calcium and phosphorus. On the downside, the yolk also contains all of the fat.
Protein
Just one large yolk provides 2.7 g of complete protein, according to the USDA Nutrient Database. Based on the Institute of Medicine's recommended dietary allowance of 56 g/day for men, and 46 g/day for women, the yolk delivers 5 to 6 percent of the daily value of protein.
Vitamins
You'll get 245 IU of vitamin A, which represents about 9 percent of the daily value, from just one egg yolk. Vitamin A is an antioxidant that's essential for vision and keeps your skin healthy. Your body can't absorb calcium unless it also has vitamin D. Eating an egg yolk provides 37 IU, or 6 percent of this important vitamin. You'll also get 0.4 mg of the antioxidant vitamin E and a small amount of vitamin K. Egg yolks contain all of the B vitamins, but they're an especially good source of folate and vitamin B-12. You'll get 25 micrograms, or 6 percent, of folate and 0.3 micrograms, or 12 percent, of B-12. Both vitamins lower your chance of heart disease by reducing homocysteine levels in the blood.
Minerals
Egg yolks contain all of the essential minerals, including calcium, potassium and 3 to 6 percent of the daily value of iron. They provide 66 mg, or 9 percent of the daily intake for phosphorus, which is needed for building bones and teeth. They're a great source of the trace mineral selenium, which is an antioxidant needed by many enzymes. One egg yolk has 9.5 micrograms, or 17 percent of the daily value, of selenium.
Fats
The bad news is that egg yolks have 184 mg of cholesterol. The good news is that they also contain heart-healthy omega-3 and omega-6 fatty acids. They have 39 mg of omega-3 and 693 mg of omega-6. The recommended adequate intake for omega-3 is 1.6 g/day for men and 1.1 g/day for women, according to the Linus Pauling Institute. Men should have 17 g/day, while women should have 12 g/day of omega-6.
Choline
Choline is an essential nutrient that forms the structure of cell membranes. It is also needed for the synthesis of the neurotransmitter acetylcholine and is required for fats to be absorbed and transported through the blood. Egg yolks provide 116 mg of choline, which is 21 to 27 percent of the recommended daily intake.
Carotenoids
Yolks provide 186 micrograms of lutein and zeaxanthin. These carotenoids protect the retina from damage by absorbing blue light. They may slow the development of age-related macular degeneration and cataracts.
References
- USDA Nutrient Database Search; Egg Yolk; NDB No. 01125
- Institute of Medicine: Dietary Reference Intakes
- Linus Pauling Institute; Essential Fatty Acids; Victoria Drake, Ph.D.; April 2009
- Linus Pauling Institute; Choline; Victoria Drake, Ph.D.; Jan. 2008
- Linus Pauling Institute; Carotenoids; Victoria Drake, Ph.D.; June 2009
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