Essential Amino Acid (EAA)

    Written by:
    Kamal Patel
    Last Updated: April 13, 2026

    Proteins are composed of amino acids, some of which the body can synthesize and others it cannot. The 9 amino acids that are needed but cannot be synthesized and thus need to be ingested are called essential amino acids (EAAs). A protein is said to be complete when it has enough of each EAA.

    Summary

    Proteins are composed of amino acids, some of which the body can synthesize and others it cannot. The 9 amino acids that are needed but cannot be synthesized and thus need to be ingested are called essential amino acids (EAAs). Among those, branched-chain amino acids (BCAAs) are crucial for muscles,[1] and leucine is especially anabolic.

    Amino acids: requirements of adults and contents of proteins

    Essential Amino Acid (EAA)mg/kg/dayCompleteMilkPeaRiceSoyWhey
    Leucine (BCCA)
    39
    59
    97
    97
    88
    80
    116
    Isoleucine (BCCA)
    20
    30
    50
    54
    40
    43
    59
    Valine (BCCA)
    26
    39
    58
    81
    55
    44
    58
    Cystine
    4
    6
    9
    14
    17
    12
    20
    Histidine
    10
    15
    30
    17
    24
    26
    21
    Lysine
    30
    45
    80
    83
    33
    60
    102
    Methionine
    10
    16
    27
    5
    29
    10
    23
    Methionine + cysteine
    15
    22
    30
    8
    39
    14
    36
    Phenylalanine + tyrosine
    25
    30
    99
    94
    111
    90
    66
    Threonine
    15
    23
    47
    43
    38
    37
    76
    Tryptophan
    4
    6
    13
    11
    14
    13
    20

    mg/kg/day = daily requirement in milligrams (of a given amino acid) per kilogram (of body weight) per day | Complete/Milk/Pea/Rice/Soy/Whey = milligrams of amino acid per gram of complete/milk/pea/rice/soy/whey protein (mg/g)
    References: World Health Organization. Protein and Amino Acid Requirements in Human Nutrition, page 245, table 49. 2007.[2] Kalman. Foods. 2014.[3] Gorissen et al. Amino Acids. 2018.[4] USDA Food Composition Databases (accessed: 2018 Sep)

    A protein is called complete when, proportionally to its overall amino-acid content, it has enough of each EAA. The main advantage of animal proteins is that most are complete.