The nutrients you'll gain from 1 cup of egg whites depends on how they're used. If you bake a cake, then each slice contains a fraction of the total nutrients. If you plan to make an omelet, however, it is possible to consume an entire cup of egg whites.
They're low enough in calories that you'll gain lots of protein without ruining your diet. Just be aware that one cup of egg whites is high in sodium.
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Egg White Calories and Protein
Egg whites contain about one-fourth of the whole egg's calories and a little more than half of its total protein. It takes seven to eight large eggs to produce 1 cup of egg whites, for a total of 126 egg white calories and 27 grams of protein, according to the USDA.
The protein in egg whites goes a long way toward the daily protein intake recommendations made by the National Academies of Sciences — 46 grams for women and 56 grams for men. All of the egg's fat is in the yolk, so the whites are fat free. You'll get a small amount of carbohydrates in the form of natural sugars.
Beware of High Sodium
Eggs naturally contain sodium, so when you use enough to fill one cup, the sodium accumulates to a significant amount. The University of Kentucky Cooperative Extension Service notes that two egg whites equal one whole egg, so 1 cup of whites makes the equivalent of a large, four-egg omelet.
If you ate the whole omelet, you would consume the entire 403 milligrams of sodium in 1 cup of egg whites. The American Heart Association recommends limiting your daily sodium intake to no more than 2,300 mg, or 1,500 mg if you have risk factors for heart disease.
Consider the Selenium
One cup of egg whites has 49 micrograms of selenium, which is 70 percent of the recommended daily value of 70 micrograms, according to the Linus Pauling Institute.
our body depends on selenium to produce an antioxidant called glutathione peroxidase, which works with vitamin E to protect cells from damage caused by free radicals.
You also need selenium to produce thyroid hormones that regulate metabolism and to keep your immune system working at optimal capacity.
Get Your B Vitamins
Vitamin B12 comes from animal products, including eggs. Egg whites do retain some of the whole egg's B12, with 1 cup of whites supplying 0.22 micrograms, or 4 percent of the daily value of 5 micrograms.
One cup of egg whites also provides 12 percent of the daily value of vitamin B5, or pantothenic acid, and 12 percent of the daily value for riboflavin, according to the National Academies of Sciences.
All of these B vitamins support your metabolism. Vitamins B12 and B5 also help produce healthy red blood cells, according to Harvard Health.
Read more: Can Eating Egg Whites Help You Lose Weight?
Understand the Downside
Eating egg whites has the benefit of eliminating all of the egg's fat and cholesterol, but you also lose several important nutrients found primarily in the yolk: iron, zinc and vitamin A, according to the USDA.
Egg whites provide barely a trace of iron and zinc. They don't contain any vitamin A, which means you will miss getting a significant amount of two antioxidants that help keep your eyes healthy, lutein and zeaxanthin.
- University of Kentucky: "Common Questions About Eggs"
- Linus Pauling Institute: "Selenium"
- Harvard Health Publications: "Listing of Vitamins"
- National Academies of Sciences: "Macronutrients"
- American Heart Association: "How Much Sodium Should I Eat per Day?"
- National Academies of Sciences: "Vitamins and Minerals"
- USDA FoodData Central: "Egg, White Only, Raw"
- USDA FoodData Central: "Egg, Yolk Only, Raw"