Do essential amino acid (EAA) supplements help build muscle better than dietary protein or protein supplements?

Answer:

No. Although essential amino acids (EAAs) are the building blocks of protein, there is no evidence that consuming free EAAs helps build muscle better in healthy individual than consuming "complete" or "high-quality" protein, that is, protein that contains all essential amino acids.

Many studies show that eating high-quality protein can increase muscle mass and strength when combined with resistance exercise; however, consuming EAAs alone (in free form rather than combined as protein) might not be as beneficial as protein. For example, a study among elderly adults involved in resistance training who supplemented with protein (in the form of a whey protein isolate) or free form EAAs showed that slightly more amino acids obtained from the protein were incorporated into muscle protein compared to EAAs from the free-form supplement (Kerksick, J Int Soc Sports Nutr 2018).

It should be noted that there is some evidence that EAAs may be somewhat more effective than protein at improving muscle strength in older adults with acute or chronic conditions not involved in exercise, such as those in nursing homes and hospitals (Cheng, Br J Nutr 2018).

Interestingly, while the ability of EAAs to promote protein synthesis has been largely attributed to three specific EAAs called branched chain amino acids (BCAAs), which consist of leucine, isoleucine, and valine, a study showed that taking free-form BCAAs was slightly less effectively than taking free-form EAAs (which included BCAAs along with other EAAs) in promoting protein synthesis (Moberg, Am J Physiol Cell Physiol 2016). Furthermore, although BCAAs may help reduce loss of muscle during long periods of muscle disuse in some settings, the evidence is mixed as to whether BCAAs boost muscle strength.

Information about the pros and cons of different types of protein found in supplements — including whey, casein, soy, and rice and their various marketed forms (such as concentrates, isolates, hydrolysates, and ion-exchange purified products) — is found in the ConsumerTips section of our Protein Powders, Shakes, and Drinks Review. The Review includes our tests and comparison of popular protein powders and our Top Picks among them. Also see our Protein Bars Review.