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Hands holding essential amino acid capsules and protein powder


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). Also, one small study suggested that EAAs may have greater benefit than whey protein at improving walking distance in low physical functioning older adults with mild heart failure, although the study lacked a placebo control (Azhar, Mol Nutr Food Res 2024; Azhar, J Gerontol A Biol Sci Med Sci 2021).

Interestingly, while the ability of EAAs to promote protein synthesis has been largely attributed to three specific EAAs called branched chain amino acids (BCAAs) (see our BCAAs Review), 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.

If you are trying to build muscle and burn fat, it is sometimes recommended to exercise while in a fasted state (i.e., not having eaten since the prior evening). However, having some protein or EAAs within an hour after exercising generally seems to helps boost the production of new muscle – although there is some mixed evidence regarding optimal timing (Fujita, J Appl Physiol 2009; Dreyer, Am J Physiol Endocrinol Metab 2008; Tipton, Am J Physiol Endocrinol Metabl 2007; Tipton, Am J Physiol Endocrinol Metab 2001). There does not appear to be any conclusive evidence about which type of supplement — protein or essential amino acid — is better for boosting muscle protein synthesis after fasted exercise.

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.

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