From five tibetan rite book
The proper use of eggs was another interesting and useful thing that I learned during my stay in the monastery. The Lamas would not eat whole eggs unless they had been performing hard manual labor. Then they might eat one whole medium boiled egg. But they would frequently eat raw egg yolks, discarding the whites. At first it seemed to me a waste of perfectly good food to throw the whites to the chickens. But then I learned that the egg whites are utilized only by the muscles and should not be eaten unless the muscles are exercised." I had always known that egg yolks are nutritious, but I learned of their value only after talking with another Westerner at the monastery, a man who had a background in biochemistry. He told me that common hen eggs contain fully half of the elements required by the brain, nerves and organs of the body. It is true that these elements are needed only in small quantities, but they must be included in the diet if you are to be exceptionally healthy and robust, both mentally and physically.