. 2009 Feb 25;89(4):1068–1077. doi: 10.3945/ajcn.2008.27280

TABLE 6.

Effect of amino acid (AA) and glycomacropeptide (GMP) diets on fasting and postprandial (PP) concentrations of AAs in plasma¹

	AA diet			GMP diet			Response to diet fasting compared with PP
AA	PP²	Fasting²	P value³	PP²	Fasting²	P value¹	P value⁴
	μmol/L			μmol/L
Alanine	455 ± 52	356 ± 25	0.029	514 ± 45	401 ± 50	0.001	0.743
Arginine	62 ± 14	57 ± 5	0.694	47 ± 5	47 ± 6	0.845	0.551
Citrulline	37 ± 4	26 ± 5	0.138	23 ± 3	26 ± 4	0.084	0.063
Cystine	43 ± 1	43 ± 2	0.899	37 ± 2	41 ± 3	0.019	0.062
Glutamic acid	40 ± 8	50 ± 10	0.207	43 ± 10	49 ± 9	0.556	0.692
Glutamine	635 ± 29	628 ± 15	0.747	659 ± 33	623 ± 28	0.025	0.095
Glycine	415 ± 62	399 ± 55	0.473	346 ± 40	371 ± 47	0.099	0.112
Histidine	85 ± 9	78 ± 5	0.206	82 ± 6	75 ± 4	0.066	0.681
Isoleucine	57 ± 6	49 ± 4	0.352	119 ± 15	54 ± 5	0.015	0.004
Leucine	120 ± 20	96 ± 3	0.313	86 ± 11	83 ± 4	0.823	0.264
Lysine	210 ± 19	181 ± 9	0.062	191 ± 24	171 ± 16	0.138	0.311
Methionine	24 ± 2	24 ± 1	0.832	31 ± 4	25 ± 3	0.150	0.144
Ornithine	74 ± 7	60 ± 8	0.004	50 ± 4	62 ± 18	0.460	0.129
Phenylalanine	462 ± 100	508 ± 95	0.048	472 ± 106	483 ± 101	0.349	0.037
Proline	200 ± 15	144 ± 12	0.001	234 ± 37	160 ± 20	0.012	0.322
Serine	131 ± 21	122 ± 16	0.123	127 ± 14	120 ± 11	0.517	0.821
Taurine	73 ± 19	82 ± 18	0.154	73 ± 13	63 ± 11	0.145	0.027
Threonine	158 ± 22	135 ± 17	0.013	354 ± 44	265 ± 29	0.030	0.064
Tryptophan	48 ± 5	44 ± 3	0.269	34 ± 3	42 ± 2	0.048	0.006
Tyrosine	81 ± 8	38 ± 3	0.001	56 ± 10	29 ± 3	0.027	0.155
Valine	240 ± 9	194 ± 13	0.015	241 ± 21	187 ± 5	0.048	0.521
BCAA	417 ± 28	347 ± 14	0.084	445 ± 45	324 ± 8	0.048	0.062

Values are means ± SEMs; n = 6, except for cystine for which n = 5. BCAA, sum of leucine, isoleucine, and valine.

PP plasma concentrations of ornithine (P = 0.019) and tryptophan (P = 0.003) were significantly lower, but within the normal range, and isoleucine (P = 0.003) and threonine (P = 0.004) were significantly higher with ingestion of the GMP diet than with the AA diet and above the normal range. The only significant differences in fasting AA concentrations were a decrease in arginine (P = 0.008) and an increase in threonine (P = 0.001) with ingestion of the GMP diet compared with the AA diet.

There was a significant effect of time in the repeated-measures ANOVA. Statistical analysis by paired t test, pairing on subject, is from data collected on the last day of the AA diet (day 4) and the last day of the GMP diet (day 8).

⁴

The response to a diet is calculated first by finding the difference between fasting and PP AA concentrations for each subject on the AA diet and on the GMP diet and then by comparing the differences by paired t test, pairing on subject.