Healthy Eating

During the kids' lunch today I was standing by the door, beginning to peel the shell off a hard boiled egg that I had brought for a snack today. One of the girls seated nearby calls from her seat "Miss Conner, what are you doing?". I tell her that I am eating the hardboiled egg, but since I do not like the yellow part, I am throwing that away and just eating the white outside. Another girl turns around, and in a very repremanding way, says "but Miss Conner, the yellow part is such an excellent source of protien!".
Not only was I baffled that a 4-year-old understands protien, eggs, and health, but then I felt like I had to explain myself, that I usually eat the yellow parts when my eggs are scrambled, just not when they are not hard boiled.