An egg contains calories equivalent to half an apple or half a cup of milk, but it also has the body's daily requirements of 8% phosphorus, 4% zinc, 4% iron, 12.6% protein, 6% vitamin D, 3% vitamin E, 6% vitamin A, 2% vitamin B, 5% vitamin B2, 4% vitamin B6. These nutrients are essential to the human body, they play a vital role in the body. Essential, they play an extremely important role, such as repairing body tissues, forming new tissues, consuming energy and participating in complex metabolic processes.