Dietary tryptophan-rich protein hydrolysate can acutely impact physiological and psychological measures of mood and stress in healthy adults

Figures & data

Table 1. Subject and dataset completion.

	Reference	0.5 g EPH	1 g EPH	Total
Screened subjects				53
Screening failure subjects				4
Withdrawn subjects				3
Randomised subjects	15 (100%)	16 (100%)	15 (100%)	46 (100%)
Drop-out subjects		1 (6.2%)		1 (2.2%)
Full analysis set	15 (100%)	15 (93.7%)	15 (100%)	45 (97.8%)

Full analysis set comprised randomized subjects who took the study product and for which data are available for at least one endpoint.

Table 2. Experimental procedure.

Timing (min)	Physiological measure	Assessment
PRE		Self-reports of mood states
PRE	HR, EDA	Rest
PRE		Blood sampling
T0		Product intake & liking rating
T5’		Rest and preparation
T40’		Practice session
T50’		Self-reports of mood states
T60’	HR, EDA	Rest
T65’	HR, EDA	Multi-task cognitive stressor
T95’		Blood sampling
T100’	HR, EDA, EEG	Attention & emotional reactivity tasks
T122’		Self-reports of mood states
T132’	HR, EDA	Rest

The timing is given relative to product intake with small variations to be considered due to the time taken to read the task instructions. PRE, baseline; HR, heart rate; EDA, electrodermal activity; EEG, electroencephalogram.

Table 3. Participant demographics and baseline blood measures.

Number of females	Reference	0.5 g EPH	1 g EPH
	8	6	10
BMI (kg/m^2)	21.73 (2.02)	22.30 (1.94)	22.32 (1.91)
Age (years)	33.33 (7.52)	32.47 (5.76)	34.07 (5.28)
TRP (umol / L)	58.91 (11.84)	56.63 (10.32)	59.73 (9.09)
TRP:LNAA ratio (%)	11.56 (2.02)	11.13 (2.04)	12.18 (1.99)
Cortisol (nmol / L)	287.52 (100.92)	264.11 (88.31)	255.72 (80.84)
Insulin (pmol / L)	87.81 (83.13)	77.11 (39.08)	82.03 (94.84)

Values in brackets are standard deviations of the mean. BMI, Body Mass Index; TRP, Tryptophan level in serum; TRP:LNAA Ratio, Level of tryptophan to other large neutral amino acids ratio in serum.

Figure 1. Effects of egg protein hydrolysate (EPH) dosing on serum levels of tryptophan (TRP, in μmol/L) and ratio of tryptophan to other large neutral amino acids (TRP:LNAA). The effect was calculated as a percentage change from baseline to 95 minutes post-product intervention. The letters ‘a’ and ‘b’ respectively represent the statistical differences between the 1 g EPH group and reference and, between the 1 g EPH and 0.5 g EPH groups (p < .05).

Table 4. Differences in blood biomarkers changes from baseline between groups.

Endpoint	0.5 g EPH vs Reference		1 g EPH vs Reference		1 g EPH vs 0.5 g EPH
	Effect size	p-value	Effect size	p-value	Effect size	p-value
TRP level	−0.09	.9739	8.22	.0033*	8.31	.0032
TRP:LNAA ratio	<−0.01	.7320	0.01	.0002*	0.02	.0001*
Cortisol level	−23.63	.4800	−33.36	.3200	−9.72	.7688
Insulin level	<0.01	.4672	<0.01	.2825	<0.01	.7519

*indicates significance. TRP level, Tryptophan level in serum (μmol/L); TRP:LNAA ratio, Level of tryptophan to other large neutral amino acids ratio in serum; Cortisol level, Cortisol level in the blood (nmol/L); Insulin level, Insulin level in the blood (nmol/L).

Table 5. Differences in product liking and post-stressor mood states between groups.

Endpoint	0.5 g EPH vs. Reference		1 g EPH vs. Reference		1 g EPH vs. 0.5 g EPH
	Effect size	p-value	Effect size	p-value	Effect size	p-value
Product liking	−10.53	0.1811	−18.25	0.0221	−7.71	0.4310
D-VAMS score	28.00	0.2848	−5.00	0.8519	−23.78	0.6784
STAI anxiety score	<0.01	0.5263	<0.01	0.6250	<0.01	0.7906
VAS stress score	−10.00	0.2115	−3.00	0.6624	3.00	0.6471

Product liking, Rated liking of product (mm); D-VAMS score, Pleasantness of mood score obtained with the Dynamic Visual Analog Mood Scale (mm); STAI anxiety score, Anxiety score obtained with the State Trait Anxiety Inventory; VAS stress score, Stress score obtained with the Visual Analog Scales (mm).

Table 6. Post-stressor differences in attention performances between groups.

Endpoint	0.5 g EPH vs. Reference		1 g EPH vs. Reference		1 g EPH vs. 0.5 g EPH
	Effect size	p-value	Effect size	p-value	Effect size	p-value
RVIP HIT	2.08	0.7397	−4.17	0.7087	−4.17	0.6034
RVIP FA	−0.18	0.0713§	<0.01	0.6589	0.18	0.2485
RVIP RT	9.60	0.4067	0.99	0.9010	−8.71	0.3615
1-back HIT	−3.33	0.3104	−10.00	0.0044*	−6.67	0.0698§
1-back FA	<0.01	0.6042	<0.01	0.5776	<0.01	0.8921
1-back RT	3.78	0.2385	3.37	0.2905	−0.45	0.9055

§ indicates trend-level significance and * indicates significance. EPH, Egg protein hydrolysate; RVIP HIT, Hit rate in Rapid Visual Information Processing task; RVIP FA, False alarm rate in Rapid Visual Information Processing task; RVIP RT, Reaction time in Rapid Visual Information Processing task (ms); 1-back Hit, Hit rate in 1-back face task; 1-back FA: False alarm rate in 1-back face task; 1-back RT: Reaction time in 1-back face task (ms).

Figure 2. Effects of egg protein hydrolysate (EPH) dosing on low frequency peak (Hz), high frequency peak (Hz) and, the ratio of low frequency to high frequency peaks of the heart rate variability spectrum. The letters ‘a’ and ‘b’ respectively represent the statistical differences between the 1 g EPH group and reference and, between the 0.5 g EPH group and reference (p < .05).

Table 7. Overall differences in autonomic parameters between groups.

Endpoint	0.5 g EPH vs. Reference		1 g EPH vs. Reference		1 g EPH vs. 0.5 g EPH
	Effect size	p-value	Effect size	p-value	Effect size	p-value
HR	0.39	0.6897	0.62	0.5234	0.22	0.8324
RMSSD	0.99	0.9679	1.10	0.6792	1.11	0.6550
LF	−0.01	0.0644§	−0.01	0.0015*	−0.01	0.1533
HF	0.04	0.0032*	0.05	0.0019*	<0.01	0.8891
LF: HF	−1.11	0.0003*	−0.14	<.0001*	−0.03	0.3576
SCL	0.74	0.2012	0.94	0.8051	1.28	0.3074

§indicates trend-level significance and * indicates significance. EPH, Egg protein hydrolysate; HR, Heart rate (BPM); RMSSD, Root mean square successive difference (ms); LF, Low frequency peak of the heart rate variability spectrum (Hz); HF, High frequency peak of the heart rate variability spectrum (Hz); LF:HF, Ratio of low frequency to high frequency peaks of the heart rate variability spectrum; SCL, Skin Conductance Level (μS).

Figure 3. Microstate segmentations, calculated from global field powers (GFPs, in microvolt), of event-related potentials (ERPs) to angry, happy, and neutral face stimuli for the reference, 0.5 g EPH and 1 g EPH groups, using the algorithm for hierarchical clustering. Each color in the graph represents a stable microstate associated with a scalp topographic pattern and an ERP peak (P1, N170, P2 or LPP). Time is given relative to stimulus onset.

Figure 4. Global field powers (GFPs, in microvolt) of event-related potentials to angry, happy, and neutral face stimuli for the reference, 0.5 g EPH and 1 g EPH groups. Time is given relative to stimulus onset. Statistical differences between GFPs to angry and neutral face stimuli (p < .1) are highlighted in blue.

Figure 5. Differential effect of the ratio of tryptophan to other large neutral amino acids (TRP:LNAA) change on Dynamic Visual Analogue Mood Scale (D-VAMS, in mm) score change by gender. Changes are calculated from baseline to 95 minutes post-product intervention.