Boiling eggs may seem simple, but it's actually quite a science. If done improperly, not only will the texture be poor, but the nutritional value of the egg will also be compromised.
Eggs are most susceptible to contamination by pathogenic bacteria like Salmonella. To ensure that all Salmonella is killed, many people simply toss eggs into the pot and boil them for a very long time, which is a very bad habit.
In fact, while prolonged high-temperature boiling can effectively sterilize the eggs, it creates another problem—increased nutrient loss and fat oxidation. Vitamin E, in particular, suffers significant loss; when eggs are boiled for too long, they become tough and difficult to swallow, and about 16% of the vitamin E is lost. Furthermore, the oxidation of fats and cholesterol produces substances that are harmful to health. The oxidized products of cholesterol, in particular, can damage the vascular endothelium.
Therefore, boiling eggs must be done just right. It's best to boil them so that they are soft, striking a balance between texture and nutrition. First, place the eggs in cold water, bring to a boil over high heat, then maintain the boil for another 3-5 minutes. Turn off the heat and let the eggs sit in the residual heat for a while, which usually takes about 8 minutes in total. Eggs cooked this way are the healthiest; the white is tender and the yolk is just set, making them fresh, tender, and easy to swallow.
It is best not to eat undercooked eggs. If the yolk is "runny," it indicates that sterilization is incomplete, increasing the risk of infection from pathogenic bacteria like Salmonella. By controlling the cooking time so that the yolk is fully set, you can avoid this problem.