Just like branched-chain amino acids, essential amino acids muscle be obtained through the diet. Essential amino acids can be thought of as the building blocks of protein that support our muscle and connective tissues in the body. The nine essential amino acids (which include the branched-chains leucine, isoleucine, and valine) are histidine, lysine, tryptophan, phenylalanine, threonine, and methionine. The best sources of essential amino acids include animal proteins like eggs, chicken, and steak.
Since the explosion of the rodent research circa 2006 which had everyone grasping for their nearest tub of branched-chain amino acids at the local supplement store, more recent research actually suggests that consuming the full complement of the nine essential amino acids is more beneficial for supporting muscle protein synthesis as opposed to consuming the three branched-chains in isolation. Thinking intuitively this makes a lot of sense, as to achieve the outcome of building a new muscle protein it seems likely that all amino acids would need to be present, not just a select few acting independently (remember a new muscle protein needs to contain all the essential amino acids).
Essential amino acids have also been shown in the research to reduce muscle wastage/loss, enhance muscle growth and support metabolic rate. Studies also suggest that consuming essential amino acids close to your workout can expedite the muscle recovery process.