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An egg is really three separate foods, the
whole egg, the white, and the yolk, each with its own distinct
nutritional profile.
A whole egg is a high-fat,
high-cholesterol, high-quality protein food packaged in a high-calcium
shell that can be grounded and added to any recipe. The proteins in
eggs, with sufficient amounts of all the essential amino acids, are 99
percent digestible, the standard by which all other proteins are judged.
The egg white is a high-protein, low-fat
food with virtually no cholesterol. Its only important vitamin is
riboflavin (vitamin B2), a visible vitamin that gives egg white a
slightly greenish cast. Raw egg whites contain avidin, an antinutrient
that binds biotin a B complex vitamin formerly known as vitamin H, into
an insoluble compound. Cooking the egg inactivates avidin.
An egg yolk is a high-fat,
high-cholesterol, high-protein food, a good source of vitamin A derived
from carotenes eaten by the laying hen, plus vitamin D, B vitamins, and
heme iron, the form of iron most easily absorbed by your body.
One large egg has 5 g Eat (1.5 g saturated
fat), 212 mg cholesterol, 6 g protein, 950 IU vitamin A (19 percent of
the RDA for a man, 23.7 percent of the RDA for a woman), and 0.72 mg
iron (4.8 percent of the RDA for a woman of childbearing age).
One large egg white has 4 g protein, but
no Eat or cholesterol. One large egg yolk has 6 g fat (1.7 g saturated
fat), 272 mg cholesterol, 3 g protein, and 970 IU vitamin A (19.4
percent of the RDA for a man, 24 percent of the RDA for a woman).
The most nutritious way to server egg is
with extra whites and fewer yolks to lower the fat and cholesterol per
serving. Those on controlled-fat, low-cholesterol diet or low-protein
diet should exclude this food.
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