The function of amino acids in bodybuilding supplements is to create and support muscle protein, restore energy to the body after a work-out, and banish fatigue, according to Bodybuilding.com. Amino acids also support an anabolic environment in the body, encourage motivation and endurance, metabolize fat, and allow the muscles to work optimally.
There are about 22 amino acids, states Bodybuilding.com. Most are made by the body, but others need to come from the diet. These are called essential amino acids.
Among the amino acids of use to bodybuilders are methionine, says Bodybuilding.com.This amino acid allows the body to metabolize fat more efficiently and improves digestion. It's also an antioxidant, and it protects cells from damage from free radical oxygen molecules. L-lysine helps prevent fatigue and helps the cells maintain its nitrogen balance. It also helps support lean body mass during fatigue and stress, produces useful hormones and enzymes, and helps heal damaged tissue.
Phenylalanine supports the nerves that permit the relaxation and contraction of muscles, according to Bodybuilding.com. It also enhances the bodybuilder's endurance. However, it is toxic in high doses and should be taken with care. Leucine is a BCAA, or branched chain amino acid. This amino acid regulates glucose levels and helps in the growth and repair of bodily tissues.