Table 4.
Percentage of free amino acids relative to total amino acids in human milk in months 1–6 of lactation.
| FAA/TAA Ratio (%) | Month 1 (n = 22) |
Month 2 (n = 25) |
Month 3 (n = 24) |
Month 4 (n = 18) |
Month 5 (n = 23) |
Month 6 (n = 22) |
Statistical Analysis of the Changes |
|---|---|---|---|---|---|---|---|
| EAA | |||||||
| Histidine | 1.26 ± 0.083 | 1.45 ± 0.093 | 1.47 ± 0.095 | 1.41 ± 0.074 | 1.39 ± 0.058 | 1.50 ± 0.10 | c * |
| Isoleucine | 0.24 ± 0.040 | 0.30 ± 0.038 | 0.25 ± 0.022 | 0.33 ± 0.021 | 0.30 ± 0.025 | 0.36 ± 0.039 | a o |
| Leucine | 0.36 ± 0.047 | 0.46 ± 0.048 | 0.42 ± 0.031 | 0.58 ± 0.10 | 0.47 ± 0.037 | 0.60 ± 0.10 | a * |
| Lysine | 0.50 ± 0.067 | 0.57 ± 0.10 | 0.45 ± 0.041 | 0.63 ± 0.16 | 0.58 ± 0.052 | 0.64 ± 0.082 | a o |
| Methionine | 0.17 ± 0.038 | 0.28 ± 0.041 | 0.26 ± 0.026 | 0.44 ± 0.10 | 0.39 ± 0.038 | 0.40 ± 0.044 | a ** |
| Phenylalanine | 0.61 ± 0.074 | 0.80 ± 0.071 | 0.74 ± 0.050 | 0.87 ± 0.084 | 0.76 ± 0.044 | 0.85 ± 0.066 | a o |
| Threonine | 1.41 ± 0.11 | 2.09 ± 0.17 | 2.13 ± 0.16 | 2.38 ± 0.17 | 2.58 ± 0.16 | 2.50 ± 0.20 | a **, c ** |
| Valine | 0.95 ± 0.076 | 1.27 ± 0.092 | 1.19 ± 0.075 | 1.35 ± 0.11 | 1.12 ± 0.057 | 1.20 ± 0.080 | c * |
| NEAA | |||||||
| Alanine | 4.54 ± 0.41 | 5.28 ± 0.31 | 5.84 ± 0.35 | 6.39 ± 0.32 | 6.35 ± 0.037 | 5.81 ± 0.39 | a *, c ** |
| Arginine | 0.60 ± 0.054 | 0.75 ± 0.12 | 0.68 ± 0.060 | 1.11 ± 0.31 | 0.86 ± 0.12 | 0.84 ± 0.072 | a * |
| Asx | 0.55 ± 0.064 | 0.84 ± 0.079 | 1.14 ± 0.17 | 1.21 ± 0.14 | 1.49 ± 0.17 | 1.33 ± 0.18 | a **, c ** |
| Glx | 9.12 ± 0.77 | 13.81 ± 0.66 | 15.69 ± 0.76 | 17.50 ± 0.3 | 17.97 ± 0.69 | 18.33 ± 0.90 | a **, c ** |
| Glycine | 2.04 ± 0.19 | 2.86 ± 0.18 | 3.37 ± 0.20 | 3.63 ± 0.16 | 3.77 ± 0.20 | 3.88 ± 0.27 | a **, c ** |
| Serine | 1.39 ± 0.14 | 2.08 ± 0.15 | 2.50 ± 0.21 | 2.60 ± 0.12 | 2.59 ± 0.17 | 2.57 ± 0.21 | a **, c ** |
| Tyrosine | 0.59 ± 0.064 | 0.71 ± 0.076 | 0.64 ± 0.047 | 0.72 ± 0.076 | 0.70 ± 0.059 | 0.85 ± 0.070 | a * |
| Total | |||||||
| FAA to TAA | 2.56 ± 0.20 | 3.81 ± 0.19 | 4.36 ± 0.23 | 4.91 ± 0.26 | 4.97 ± 0.20 | 5.04 ± 0.29 | a **, c ** |
FAA: free amino acid; TAA: total amino acid; EAA: essential amino acid; NEAA: non-essential amino acid; Asx: aspartate + asparagine; Glx: glutamate + glutamine. Values are given as mean ± SEM. Significant changes (o p < 0.10, * p < 0.05, ** p < 0.01) of the percentage of FAA to TAA in time as follows: a: Significant increase from months 1–6 of lactation; b: Significant decrease from months 1–6 of lactation; c: Significant increase from months 1–3 of lactation; d: Significant decrease from months 1–3 of lactation; e: Significant increase from months 4–6 of lactation; f: Significant decrease from months 4–6 of lactation.