Cooking eggs with some dietary fat can help your body absorb certain fat soluble nutrients, including carotenoids such as lutein and zeaxanthin. Eggs already contain fat in the yolk, which helps make these compounds highly bioavailable.
Butter can add additional dietary fat and vitamin A, which supports normal vision, skin, and immune function. However, butter itself is not necessary for absorbing these nutrients.
For a balanced meal, consider pairing eggs with vegetables and a moderate amount of dietary fat.