Egg white protein is often referred to as the perfect protein. This is due to its amino acid make-up and the body's ability to utilize it properly. Egg white protein is rich in the branched-chain amino acids (BCAAs), which include leucine, isoleucine, and valine. These are, as you know, critical aminos—particularly leucine, for driving muscle protein synthesis and therefore muscle growth. Research shows that egg white protein has similar effects on stimulating muscle protein synthesis as the milk proteins whey and casein, although it's not quite as effective as whey given whey's rapid digestion rate.
Egg white protein is also high in the amino acid arginine, which stimulates nitric oxide (NO) production in the body. NO dilates blood vessels, resulting in increased blood flow to muscles, which helps to deliver more oxygen, nutrients and anabolic hormones for better energy and a bigger pump during workouts and better muscle recovery and greater muscle growth after the workout. Arginine also works to boost growth hormone (GH) levels, which is critical during and after workouts.
Egg white protein is also rich in the amino acids alanine, glycine, serine, valine, and threonine. What's interesting about this is the fact that these five amino acids are the ones found in silk protein. And recent evidence suggests that silk protein may increase muscle strength, endurance, size and fat loss. This may be one reason why egg protein has always been very popular with bodybuilders.
Egg white contains as many as 40 different proteins. Of these, ovalbumin—a type of glycoprotein (protein that has carbohydrates attached to it)—composes the majority, making up about 55% of the protein in egg white. Ovotransferrin is an iron binding protein in egg white that provides antimicrobial properties and makes up over 10% of the protein content. Ovomucin is another type of glycoprotein that makes up less than 5% of egg white protein and provides the jellying property of egg white, as well as further antimicrobial properties.