Eggs contain certain amounts of constituent nutrients, which remain virtually the same regardless of how you cook them. Whether boiled, poached or scrambled without added ingredients, eggs have essentially the same nutritional value. Keep in mind, however, that adding ingredients to eggs during preparation or frying them in fat affects the nutrient profile of the final dish.
Proteins and Fats
Eggs contain high concentrations of protein and fats along with a small amount of carbohydrates. A raw or cooked large egg contains approximately 6.3 g of protein. Roughly 60 percent of the protein in an egg is contained in the white. This contrasts with the fat content, 90 percent of which is located in the egg yolk. A large egg contains approximately 5 g of fat, including approximately 1.6 g of saturated fat and 210 mg of cholesterol. The amount of saturated fat and cholesterol in eggs may raise an eyebrow, especially if you have heart disease or risk factors for the condition, such as high blood pressure, type 2 diabetes or abnormal blood fat levels. If this is a concern, try substituting egg whites for whole eggs and cook them without added fat. Depending on your blood fat levels, you may want to eat a whole egg occasionally to obtain the nutrients concentrated in the yolk.
Vitamins and Minerals
Regardless of how you cook them, eggs provide you with a diverse array of vitamins and minerals. Most of the vitamins and minerals in eggs are concentrated in the yolk, including vitamins A, D, E, B-6 and B-12, folate, thiamin, calcium, iron, zinc and selenium. Egg whites contain the majority of the potassium and magnesium in eggs. Phosphorus is found in high concentrations in both the white and yolk of an egg.
Cooking and Egg Protein
Cooking eggs changes the structure of their constituent proteins. Proteins in raw eggs are tightly packed together and held in place by weak chemical bonds. When you heat egg proteins during cooking, some of these bonds break and the proteins strands begin to separate from one another. This makes the egg proteins more easily digestible and absorbable. Although the protein content is the same in raw and cooked eggs, your body is better able to utilize the protein from a cooked egg compared to a raw egg. In addition to providing a nutritional advantage, cooking eggs is important for safety reasons. Eggs that appear normal may carry bacteria that can cause food poisoning; cooking destroys these bacteria. To reduce your risk of egg-borne food poisoning, always cook eggs thoroughly before eating them.
The nutritional value eggs cooked without added fat and other ingredients is much different from that of many popular egg dishes. For example, two large, soft-boiled eggs contain approximately 155 calories, 12.5 g of protein and 10.6 g of total fat. Frying these eggs in a tablespoon of butter adds approximately 100 calories and 11.5 g of fat. A slice of cheese quiche — one-eighth of a 9-inch pie — contains nearly 570 calories, 16.7 g of protein and an astonishing 44 g of fat. Although your cooking method does not significantly affect the nutritional content of eggs per se, what you mix with them during preparation most certainly can.