Undercooked eggs pose significant risks. Raw eggs not only carry the risk of Salmonella contamination but also contain two harmful substances: antienzyme proteins and avidin. The former impairs protein digestion and absorption; the latter binds to biotin in food, leading to biotin deficiency in the human body and causing symptoms like mental fatigue and muscle soreness. Only when eggs are thoroughly cooked are these two substances destroyed.
Additionally, master these techniques to prevent nutrient loss: Ensure water fully submerges the eggs—otherwise, proteins in unsubmerged areas won't solidify properly, affecting digestion. Before boiling, soak eggs in cold water to reduce internal pressure. Use medium heat and bring cold water to a boil to prevent cracking and nutrient loss.
Boiling eggs may seem simple, yet mastering the timing is tricky. Undercooking leaves the yolk soft, while overcooking makes the egg tough and unpalatable. Dr. Chang Cuiqing from Peking University Third Hospital's Sports Medicine Institute explains that the optimal boiling time is actually easy to achieve: Start with cold water, bring to a boil, and count exactly 5 minutes. This method kills harmful pathogens while preserving nutrients most effectively.
Boiling eggs for over 10 minutes triggers chemical changes inside. Protein structures become denser, hindering contact with gastric digestive enzymes and making them harder to digest. Egg proteins contain significant methionine, which breaks down into sulfides during prolonged heating. These sulfides react with iron in the yolk to form iron sulfide—a compound poorly absorbed by the body, leading to substantial nutrient loss.