Effects of acute essential amino acid intake on post-prandial raw bioimpedance and fluid shifts between healthy young and older adults: An exploratory pilot study

Unrein, Callie L.; Church, David D.; Ferrando, Arny A.; Wolfe, Robert R.; Hirsch, Katie R.

doi:10.2478/joeb-2025-0016

Figures & Tables

Experimental design. Timers indicate the start and stop of the study protocol. The bottle indicates when the EAA drink was consumed. The silhouettes refer to each MF-BIA measurement.

Bioelectrical impedance vector analysis between YA and OA. *Background watermark is not drawn to scale and provided solely for context.

Whole-body bioimpedance at 50 kHz between young adults (YA) and older adults (OA) across time. The EAA challenge was consumed at the 75th minute. *Significantly different from pre-EAA consumption timepoints (0, 30, 60, or 75 minutes; p<0.05).

Segmental resistance at 50 kHz between young adults (YA) and older adults (OA) across time. The EAA challenge was consumed at the 75th minute. *Significantly different from pre-EAA consumption timepoints (0, 30, 60, or 75 minutes; p<0.05).

Whole-Body fluid between young adults (YA) and older adults (OA). The EAA challenge was consumed at the 75th minute. *Significantly different from pre-EAA consumption timepoints (0, 30, 60, or 75 minutes; p<0.05).

Segmental intracellular water between young adults (YA) and older adults (OA). The EAA challenge was consumed at the 75th minute. *Significantly different from pre-EAA consumption timepoints (0, 30, 60, or 75 minutes; p<0.05).

Segmental bioimpedance results at 5, 50, and 250kHz for YA and OA_

Frequency	Segment	Bioimpedance	YA	OA	Interaction Effect (p-value)	Group Effect (p-value)	Time Effect (p-value)
5 kHz	Right Arm	Z (Ω)	400.34 ± 16.84	346.33 ± 14.24*	0.467	0.034	0.590
		R (Ω)	400.34 ± 16.84	346.33 ± 14.24*	0.467	0.034	0.590
		Xc (Ω)	15.46 ± 0.92	14.14 ± 0.78	0.423	0.299	0.161
		PhA (°)	2.22 ± 0.13	2.35 ± 0.11	0.466	0.460	0.055
	Left Arm	Z (Ω)	407.15 ± 15.65	339.93 ± 13.23*	0.503	0.008	<0.001
		R (Ω)	406.86 ± 15.64	339.66 ± 13.22*	0.504	0.008	<0.001
		Xc (Ω)	15.21 ± 0.97	13.42 ± 0.82	0.344	0.189	0.002
		PhA (°)	2.14 ± 0.14	2.27 ± 0.12	0.530	0.493	0.071
	Trunk	Z (Ω)	26.91 ± 0.88	24.18 ± 0.75*	0.841	0.040	0.004
		R (Ω)	26.86 ± 0.88	24.12 ± 0.75*	0.865	0.039	0.006
		Xc (Ω)	1.50 ± 0.22	1.52 ± 0.19	0.393	0.935	0.317
		PhA (°)	3.20 ± 0.50	3.62 ± 0.42	0.404	0.534	0.372
	Right Leg	Z (Ω)	312.38 ± 13.69	250.65 ± 11.57*	0.429	0.006	0.014
		R (Ω)	312.06 ± 13.68	250.46 ± 11.56*	0.429	0.006	0.014
		Xc (Ω)	14.05 ± 0.93	9.59 ± 0.78*	0.543	0.004	0.276
		PhA (°)	2.59 ± 0.14	2.17 ± 0.12*	0.692	0.049	0.544
	Left Leg	Z (Ω)	309.24 ± 13.55	254.73 ± 11.46*	0.220	0.012	0.004
		R (Ω)	308.93 ± 13.54	254.53 ± 11.45*	0.219	0.012	0.004
		Xc (Ω)	13.88 ± 0.90	9.91 ± 0.76*	0.647	0.077	0.011
		PhA (°)	2.58 ± 0.12	2.21 ± 0.10*	0.742	0.044	0.027

50 kHz	Right Arm	Z (Ω)	358.42 ± 15.56	311.51 ± 13.15*	0.494	0.044	0.676
		R (Ω)	357.00 ± 15.54	310.50 ± 13.13*	0.494	0.045	0.678
		Xc (Ω)	31.81 ± 1.21	25.08 ± 1.02*	0.467	0.022	0.444
		PhA (°)	5.10 ± 0.14	4.63 ± 0.12*	0.433	0.027	0.340
	Left Arm	Z (Ω)	366.47 ± 14.60	307.67 ± 12.34*	0.605	0.012	<0.001
		R (Ω)	365.13 ± 14.59	306.73 ± 12.33*	0.608	0.012	<0.001
		Xc (Ω)	31.31 ± 1.26	23.91 ± 1.06*	0.411	0.001	<0.001
		PhA (°)	4.91 ± 0.18	4.48 ± 0.15*	0.634	0.099	0.171
	Trunk	Z (Ω)	23.55 ± 0.83	21.59 ± 0.70	0.909	0.103	0.055
		R (Ω)	23.36 ± 0.83	21.47 ± 0.71	0.917	0.115	0.066
		Xc (Ω)	2.99 ± 0.15	2.21 ± 0.13*	0.509	0.003	0.002
		PhA (°)	7.31 ± 0.39	5.90 ± 0.33*	0.457	0.021	0.048
	Right Leg	Z (Ω)	276.37 ± 12.17	227.48 ± 10.29*	0.330	0.012	0.006
		R (Ω)	274.85 ± 12.14	226.73 ± 10.26*	0.328	0.013	0.006
		Xc (Ω)	28.50 ± 1.82	18.38 ± 1.54*	0.521	0.002	0.018
		PhA (°)	5.96 ± 0.35	4.61 ± 0.29*	0.451	0.014	0.050
	Left Leg	Z (Ω)	273.45 ± 11.72	231.10 ± 9.91*	0.145	0.020	0.004
		R (Ω)	271.95 ± 11.66	230.35 ± 9.85*	0.143	0.021	0.004
		Xc (Ω)	28.39 ± 1.85	18.45 ± 1.56*	0.485	0.002	0.004
		PhA (°)	5.97 ± 0.30	4.55 ± 0.26*	0.588	0.005	0.018

250 kHz	Right Arm	Z (Ω)	323.72 ± 14.28	284.75 ± 12.07	0.468	0.064	0.670
		R (Ω)	322.73 ± 14.25	284.05 ± 12.04	0.470	0.065	0.676
		Xc (Ω)	25.37 ± 1.03	19.90 ± 0.87*	0.314	0.002	0.087
		PhA (°)	4.50 ± 0.10	4.02 ± 0.08*	0.387	0.004	0.048
	Left Arm	Z (Ω)	331.89 ± 13.56	281.75 ± 11.46*	0.624	0.018	<0.001
		R (Ω)	330.87 ± 13.54	281.07 ± 11.44*	0.625	0.018	<0.001
		Xc (Ω)	25.96 ± 1.03	19.55 ± 0.87*	0.611	0.001	0.001
		PhA (°)	4.61 ± 0.16	3.95 ± 0.14*	0.696	0.010	0.013
	Trunk	Z (Ω)	20.15 ± 0.81	19.10 ± 0.69	0.917	0.345	0.154
		R (Ω)	19.90 ± 0.82	18.82 ± 0.70	0.913	0.339	0.156
		Xc (Ω)	3.10 ± 0.24	3.18 ± 0.20	0.334	0.794	0.490
		PhA (°)	8.85 ± 0.82	9.70 ± 0.69	0.297	0.442	0.618
	Right Leg	Z (Ω)	247.83 ± 11.12	209.96 ± 9.40*	0.295	0.026	0.006
		R (Ω)	246.88 ± 11.09	209.47 ± 9.37*	0.294	0.028	0.006
		Xc (Ω)	21.46 ± 1.27	14.17 ± 1.08*	0.523	0.001	0.009
		PhA (°)	2.73 ± 0.27	4.14 ± 0.23*	0.784	0.002	0.066
	Left Leg	Z (Ω)	245.23 ± 10.44	213.34 ± 8.82*	0.136	0.042	0.003
		R (Ω)	244.27 ± 10.38	212.88 ± 8.77*	0.136	0.043	0.004
		Xc (Ω)	21.60 ± 1.40	13.97 ± 1.18*	0.595	0.002	0.001
		PhA (°)	5.04 ± 0.21	3.72 ± 0.18*	0.802	0.001	0.027

Segmental fluid between YA and OA_

Fluid	Segment	YA	OA	Interaction Effect (p-value)	Group Effect (p-value)	Time Effect (p-value)
TBW (L)	Right arm	1.98±0.19	2.18±0.16	0.632	0.453	0.837
	Left arm	1.95 ± 0.19	2.20 ± 0.16	0.606	0.327	0.003
	Trunk	16.92 ± 1.18	18.11 ± 1.00	0.700	0.460	0.092
	Right leg	5.59 ± 0.42	6.17 ± 0.30	0.708	0.311	0.052
	Left leg	5.58 ± 0.39	6.11 ± 0.31	0.346	0.323	0.017
ICW (L)	Right arm	1.24 ± 0.09	1.35 ± 0.10	0.655	0.499	0.830
	Left arm	1.22 ± 0.11	1.36 ± 0.10	0.629	0.369	0.003
	Trunk	10.55 ± 0.72	11.00 ± 0.60	0.651	0.647	0.204
	Right leg	3.48 ± 0.23	3.60 ± 0.25	0.639	0.639	0.045
	Left leg	3.47 ± 0.23	3.51 ± 0.24	0.143	0.540	0.020
ECW (L)	Right arm	0.74 ± 0.07	0.83 ± 0.06	0.562	0.386	0.811
	Left arm	0.73 ± 0.07	0.84 ± 0.07	0.586	0.268	0.004
	Trunk	6.37 ± 0.46	7.11 ± 0.35	0.851	0.249	0.023
	Right leg	2.10 ± 0.12	2.44 ± 0.10	0.801	0.142	0.084
	Left leg	2.11 ± 0.12	2.43 ± 0.11	0.440	0.148	0.039
ECW/ICW	Right arm	0.60 ± 0.06	0.62 ± 0.05*	0.722	0.002	0.475
	Left arm	0.60 ± 0.04	0.62 ± 0.00*	0.791	0.003	0.488
	Trunk	0.60 ± 0.06	0.65 ± 0.07*	0.923	0.002	0.130
	Right leg	0.60 ± 0.06	0.66 ± 0.06*	0.709	0.003	0.141
	Left leg	0.61 ± 0.06	0.66 ± 0.06*	0.714	0.004	0.102

Female-Only Demographics

	YA	OA
Age (yrs)	28.5 ± 1.9	73.8 ± 2.1*
Height (cm)	163.3 ± 4.5	163.0 ± 1.8
Weight (kg)	76.8 ± 26.8	75.6 ± 8.8
BMI (kg/m²)	28.7 ± 9.2	28.5 ± 3.7
SMM (kg)	24.9 ± 3.4	24.5 ± 0.80
%BF	37.1 ± 16.7	39.7 ± 6.1

Female-Only Fluid Between YA and OA

Fluid	YA	OA	Interaction (p-value)	Group (p-value)	Time (p-value)	Group Partial eta	Time Partial eta
TBW	33.09 ± 1.43	33.37 ± 1.43	0.739	0.894	0.157	0.003	0.246
ICW	20.59 ± 0.90	20.29 ± 0.90	0.723	0.823	0.322	0.823	0.172
ECW	12.50 ± 0.55	13.08 ± 0.55	0.750	0.489	0.026	0.083	0.372
ECW/ICW	0.607 ± 0.01	0.645 ± 0.01*	0.589	0.044	0.025	0.518	0.362

Whole-body bioimpedance results at 5, 50, and 250 kHz for YA and OA_

	Bioimpedance	YA	OA	Interaction Effect (p-value)	Group Effect (p-value)	Time Effect (p-value)
5 kHz	Z (Ω)	741.46 ± 26.14	620.0 ± 22.09*	0.238	0.005	<0.001
	R (Ω)	740.82 ± 26.12	619.49 ± 22.08*	0.237	0.005	<0.001
	Xc (Ω)	30.8 ± 1.54	25.05 ± 1.31*	0.751	0.018	0.001
	PhA (º)	2.39 ± 0.11	2.31 ± 0.09	0.884	0.597	0.005
50 kHz	Z (Ω)	660.9 ± 23.73	560.47 ± 20.06*	0.241	0.009	<0.001
	R (Ω)	657.82 ± 23.65	558.62 ± 19.99*	0.241	0.009	<0.001
	Xc (Ω)	62.99 ± 2.73	45.12 ± 2.31*	0.350	0.001	<0.001
	PhA (º)	5.53 ± 0.18	4.67 ± 0.16*	0.296	0.005	0.017
250 kHz	Z (Ω)	594.48 ± 21.57	514.0 ± 18.23*	0.238	0.017	<0.001
	R (Ω)	704.1 ± 38.3	510.82 ± 32.37*	0.193	0.003	0.001
	Xc (Ω)	50.29 ± 2.19	36.97 ± 1.85*	0.281	0.001	<0.001
	PhA (º)	4.11 ± 0.1	4.15 ± 0.08	0.663	0.757	0.680

Participant demographics

	YA	OA
12 (4M/8F)	5 (1M/4F)	7 (3M/4F)
Age (yrs)	27.4 ± 1.3	75.1 ± 0.9*
Height (cm)	165.2 ± 2.6	168.4 ± 2.7
Weight (kg)	75.4 ± 10.5	79.6 ± 3.3
BMI (kg/m²)	27.6 ± 3.7	28.1 ± 1.0
SMM (kg)	26.2 ± 1.8	27.5 ± 1.5
%BF	33.8 ± 7.5	36.5 ± 2.3
SMM of Right Leg	7.2 ± 1.1	7.9 ± 1.1*
FM of Right Leg	3.9 ± 2.5	4.0 ± 0.7

Whole-body fluid between YA and OA_

Fluid	YA	OA	Interaction Effect (p-value)	Group Effect (p-value)	Time Effect (p-value)
TBW (L)	34.81 ± 2.36	37.40 ± 2.00	0.873	0.421	0.018
ICW (L)	21.71 ± 1.45	22.71 ± 1.23	0.843	0.608	0.059
ECW (L)	13.10 ± 0.92	14.69 ± 0.78	0.882	0.217	0.002
ECW/ICW	0.60 ± 0.01	0.65 ± 0.01*	0.699	0.002	0.025

Female-Only Whole-Body Bioimpedance Between YA and OA at 50kHz

Bioimpedance	YA Mean ± SD	OA Mean ± SD	Interaction (p-value)	Group (p-value)	Time (p-value)	Group Partial eta	Time Partial eta
R	681.52 ± 20.04	580.85 ± 20.04*	0.256	0.012	<0.001	0.678	0.646
Xc	64.27 ± 3.53	46.62 ± 3.53*	0.334	0.012	<0.001	0.676	0.598
PhA	5.39 ± 0.22	4.63 ± 0.22	0.127	0.048	0.031	0.505	0.351

Effects of acute essential amino acid intake on post-prandial raw bioimpedance and fluid shifts between healthy young and older adults: An exploratory pilot study

Figures & Tables

Fig.1:

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Fig.6:

Segmental bioimpedance results at 5, 50, and 250kHz for YA and OA_

Segmental fluid between YA and OA_

Female-Only Demographics

Female-Only Fluid Between YA and OA

Whole-body bioimpedance results at 5, 50, and 250 kHz for YA and OA_

Participant demographics

Whole-body fluid between YA and OA_

Female-Only Whole-Body Bioimpedance Between YA and OA at 50kHz

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