1 They may help your eye health.
Egg yolks contain the phytochemical lutein, which is also what gives the yolk that gorgeous yellow hue.
Lutein has been linked with eye health. Specifically, lutein has been connected to preventing macular degeneration—the cause of vision loss, which may occur as you age.

2 They give you muscle-building protein.
The yolk contains almost half the protein in the entire egg.
Generally speaking, a whole egg is rich with nearly 13% protein. If you're eating one extra-large egg that consists of 7 grams of protein, 3 of those grams would belong to the egg yolk.
Protein helps with a variety of functions, including building muscles, so don't toss those golden yolks.

3 They may help heart health.
The yolk also provides omega-3 fats, which have been shown to help promote heart health and reduce the risk of dying from heart disease.
Certain omega-3 fats have also been linked to potentially killing cancer cells and may help with arthritis.

4 They may help bone health.
The egg yolk is one of the only food sources of vitamin D. Vitamin D helps calcium get absorbed—and both help keep your bones healthy.
It's important for both children and adults to get enough of this nutrient to prevent the risk of bone diseases. This includes rickets in children and osteoporosis in adults.