TABLE 2.

Mean term and preterm human milk amino acid and derivative concentrations measured over the first month of lactation by ¹H NMR spectroscopy¹

		Day 0–5		Day 14		Day 28
Amino acids and derivatives and infant maturity at birth	P2	Concentration, mmol/L	Biological CV, %	Concentration, mmol/L	Biological CV, %	Concentration, mmol/L	Biological CV, %
2-Aminobutyrate
T	<0.0001	0.005 ± 0.004	84	0.009 ± 0.005	62	0.011 ± 0.005	47
PT	0.22	0.005 ± 0.004	80	0.007 ± 0.004	55	0.008 ± 0.004	53
2-Hydroxybutyrate
T	0.14	0.006 ± 0.003	45	0.004 ± 0.001	33	0.004 ± 0.001	35
PT	0.88	0.006 ± 0.004	57	0.007 ± 0.004*	54	0.006 ± 0.002	34
Acetylcarnitine
T	<0.0001	0.033 ± 0.010	30	0.022 ± 0.009	40	0.015 ± 0.005	32
PT	0.37	0.041 ± 0.017	41	0.024 ± 0.010	41	0.035 ± 0.022	62
Alanine
T	0.01	0.135 ± 0.056	41	0.171 ± 0.081	47	0.213 ± 0.074	35
PT	0.02	0.137 ± 0.123	90	0.206 ± 0.092	45	0.271 ± 0.109	40
Asparagine
T	0.42	0.012 ± 0.007	54	0.012 ± 0.007	59	0.014 ± 0.007	49
PT	0.92	0.017 ± 0.015	85	0.011 ± 0.005	48	0.016 ± 0.008	48
Aspartate
T	0.10	0.049 ± 0.014	27	0.032 ± 0.016	51	0.040 ± 0.028	71
PT	0.10	0.044 ± 0.026	57	0.049 ± 0.018*	37	0.078 ± 0.038	49
Betaine
T	<0.0001	0.051 ± 0.011	22	0.030 ± 0.006	21	0.031 ± 0.006	18
PT	0.27	0.050 ± 0.024	47	0.037 ± 0.010	28	0.033 ± 0.005	15
Carnitine
T	<0.001	0.011 ± 0.006	54	0.016 ± 0.010	61	0.022 ± 0.009	43
PT	0.85	0.017 ± 0.012	68	0.019 ± 0.011	60	0.017 ± 0.009	50
Glutamate
T	<0.001	0.747 ± 0.288	39	0.929 ± 0.346	37	1.30 ± 0.421	32
PT	0.22	0.878 ± 0.674	77	1.16 ± 0.364	31	1.34 ± 0.345	26
Glutamine
T	<0.0001	0.042 ± 0.095	224	0.168 ± 0.186	111	0.385 ± 0.279	72
PT	0.27	0.061 ± 0.083	134	0.131 ± 0.121	92	0.160 ± 0.133*	83
Histidine
T	0.03	0.018 ± 0.006	33	0.021 ± 0.008	40	0.025 ± 0.008	33
PT	0.16	0.020 ± 0.013	67	0.021 ± 0.008	36	0.028 ± 0.005	19
Isoleucine
T	0.03	0.012 ± 0.012	104	0.008 ± 0.005	65	0.006 ± 0.004	61
PT	0.72	0.020 ± 0.019	96	0.011 ± 0.005	48	0.016 ± 0.010	59
Leucine
T	0.56	0.031 ± 0.041	131	0.020 ± 0.011	53	0.021 ± 0.009	42
PT	0.93	0.052 ± 0.060	115	0.023 ± 0.009	38	0.035 ± 0.016	45
Lysine
T	<0.001	0.033 ± 0.028	87	0.011 ± 0.005	48	0.009 ± 0.002	25
PT	0.30	0.066 ± 0.049	74	0.030 ± 0.026*	85	0.040 ± 0.045	114
Methionine
T	0.12	0.009 ± 0.006	66	0.007 ± 0.003	40	0.006 ± 0.002	29
PT	0.76	0.014 ± 0.011	81	0.007 ± 0.004	52	0.010 ± 0.005	44
Phenylalanine
T	0.29	0.010 ± 0.005	49	0.010 ± 0.004	37	0.012 ± 0.005	42
PT	0.23	0.013 ± 0.010	75	0.011 ± 0.003	27	0.017 ± 0.005	32
Proline
T	0.24	0.062 ± 0.078	125	0.026 ± 0.016	62	0.025 ± 0.009	35
PT	0.45	0.069 ± 0.073	106	0.026 ± 0.011	41	0.035 ± 0.025	73
Taurine
T	<0.001	0.348 ± 0.155	45	0.259 ± 0.064	25	0.188 ± 0.062	33
PT	0.42	0.323 ± 0.103	32	0.286 ± 0.073	25	0.261 ± 0.109	42
Threonine
T	0.27	0.065 ± 0.024	37	0.065 ± 0.036	55	0.083 ± 0.042	51
PT	0.61	0.081 ± 0.050	61	0.083 ± 0.039	47	0.093 ± 0.036	39
Tryptophan
T	0.88	0.003 ± 0.006	168	0.002 ± 0.002	86	0.003 ± 0.002	67
PT	0.27	0.010 ± 0.014	132	0.002 ± 0.002	100	0.003 ± 0.004	127
Tyrosine
T	0.34	0.016 ± 0.012	78	0.012 ± 0.006	48	0.012 ± 0.005	38
PT	0.98	0.029 ± 0.022	75	0.019 ± 0.011	56	0.028 ± 0.018	63
Urea
T	0.02	2.73 ± 0.965	35	3.46 ± 0.987	29	3.61 ± 0.912	25
PT	0.37	2.90 ± 0.838	29	3.56 ± 1.33	37	3.72 ± 1.25	34
Valine
T	0.01	0.032 ± 0.022	67	0.032 ± 0.010	31	0.043 ± 0.013	31
PT	0.85	0.062 ± 0.048	77	0.043 ± 0.018	41	0.060 ± 0.024	40

¹Values are means ± SDs unless otherwise indicated; day 0–5, n = 15 term and n = 10 preterm; day 14, n = 14 term and n = 10 preterm; and day 28, n = 15 term and n = 6 preterm. Mean concentrations include both secretors and nonsecretors. *Significant difference between mean concentrations of term and preterm milk as determined by two-tailed t test, P < 0.05. The biological percentage CV (%CV) was calculated as SD/mean × 100. PT, preterm; T, term.

²P values are based on linear mixed-effects or linear models, which tested whether term or preterm milk metabolite concentrations significantly changed over the first month of lactation.