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Table 4 FAA in human milk (at 1 month of lactation), cow milk, and rat milk (Values are reported as means, standard deviation, minimum and maximum)

From: Use of UPLC-ESI-MS/MS to quantitate free amino acid concentrations in micro-samples of mammalian milk

Free amino acids μmol/L Human milk (n = 16) Rat milk (n = 8) Cow milk (n = 4)
Mean SD Min Max Mean SD Min Max Mean SD Min Max
Alanine 225.9 73.4 123.1 385.1 679.0 239.8 261.8 990.9 11.8 10.7 0.8 26.2
Arginine 19.5 12.4 1.5 42.8 53.8 34.0 14.1 119.1 10.7 4.9 3.8 15.4
Aspartic Acid 68.8 36.1 23.2 146.7 225.7 47.7 171.0 320.1 5.4 5.5 0.8 12.3
Citrulline 7.1 3.2 1.9 13.6 42.5 21.4 9.3 68.7 <LLOQ - - -
Cystine 21.0 8.7 11.2 43.0 33.1 21.3 4.2 64.2 <LLOQ - - -
Glx 1,860.7 586.2 926.0 3,040.4 413.5 102.2 212.4 528.0 136.2 64.5 58.9 216.5
Glycine 112.7 37.3 61.4 202.2 133.4 58.8 38.1 195.6 13.0 5.9 4.7 17.6
Histidine 31.4 14.3 12.4 67.5 39.6 19.6 10.8 69.3 2.6 1.6 0.5 4.4
Isoleucine 10.0 6.9 1.0 27.0 26.2 16.0 7.5 53.1 2.0 0.9 0.8 2.7
Leucine 30.0 12.3 12.7 60.6 59.8 33.1 18.9 114.8 2.3 1.3 0.8 3.8
Lysine 33.0 21.6 5.8 84.6 316.0 168.6 45.0 543.5 20.3 12.1 2.2 27.1
Methionine 6.9 5.4 0.8 18.1 81.4 25.0 42.5 118.4 <LLOQ - - -
Phenylalanine 12.9 4.5 5.8 19.8 39.8 20.5 13.5 71.6 <LLOQ - - -
Proline 40.4 15.8 17.6 82.5 424.4 108.5 221.7 588.7 12.8 1.3 10.9 13.9
Serine 97.6 28.8 55.4 143.6 204.2 67.5 73.9 291.1 3.2 2.0 0.8 5.4
Taurine 310.6 142.9 168.3 743.0 181.3 25.6 141.9 220.0 7.0 7.4 0.8 16.5
Threonine 81.5 27.7 45.4 132.0 309.3 122.4 99.3 528.4 3.5 2.0 0.8 5.7
Tryptophan 3.4 1.7 0.8 6.2 31.0 13.8 11.0 55.0 1.5 0.5 0.8 1.9
Tyrosine 15.6 11.0 0.8 35.3 67.4 32.8 21.4 119.8 <LLOQ - - -
Valine 51.5 17.4 27.1 93.6 98.8 45.6 37.6 166.5 4.7 3.1 0.8 7.8
Total (μM) 3,031.6 775.0 1,997.7 4,569.4 3,460.2 1,028.1 1,557.9 4,868.7 240.5 90.8 169.3 367.1
EAA (μM)b 274.6 94.2 177.0 524.0 1 055.6 464.8 300.2 1 826.0 49.0 25.3 11.7 65.1
EAA/Total (%) 9.1 2.2 6.3 12.8 29.2 5.8 19.3 37.5 21.2 13.1 6.5 38.0
NEAA (μM)b 2,757.0 715.8 1,767.2 4,192.2 2,404.6 585.7 1,257.6 3,042.7 191.5 82.1 105.0 302.0
NEAA/Total (%) 90.9 2.2 87.2 93.7 70.8 5.8 62.5 80.7 78.8 13.1 62.0 93.5
EAA/NEAA 0.10 0.03 0.07 0.15 0.42 0.11 0.24 0.60 0.30 0.23 0.07 0.61
Glx/Total (%) 60.6 5.5 46.4 69.3 12.2 1.5 10.2 13.9 55.6 15.4 34.8 71.8
SAA (μM)c 335.0 143.8 181.9 757.6 295.8 60.5 222.8 378.1 8.5 7.4 2.3 18.0
SAA/Total (%) 11.7 5.9 5.8 27.1 9.0 2.4 7.4 14.7 3.9 4.1 0.9 10.0
  1. aGlx: glutamine and glutamic acid.
  2. bEAA: Essential Amino Acids (Sum of His, Arg, Ile, Leu, Lys, Met, Phe, Thr, Trp, Val concentration), NEAA: Non-Essential Amino Acids (Sum of Ala, Asp, Asn, Glu, Gln, Cys-Cys, Pro, Gly, Ser, Tyr, Cit, Tau concentration) , these EAA were considered as essential for human.
  3. cSAA: Sulfur Amino Acids : taurine. cystine and methionin.