Background: Tryptophan is the precursor to the mood regulating neurotransmitter serotonin. Its brain bioavailability from food can be dependent on the dietary source. Egg protein hydrolysate (EPH), a dietary supplement rich in tryptophan, has previously shown to acutely impact cognition, mood and stress benefits at 2 g dose. No data exist on the acute effects of lower doses in a food matrix.
Methods: This exploratory study tested the acute effects of low-doses EPH (0.5, 1 g) in a food matrix on cognition, mood and stress. The study employed a double-blinded randomized controlled parallel design in 45 participants with three arms. The effects of the interventions were measured after a multi-task cognitive stressor on blood biomarkers, self-reported mood states, performances of attention, autonomic parameters and, emotional reactivity responses from electroencephalographic recording.
Results: As compared to the reference, the 1 g EPH dose increased tryptophan bioavailability from baseline, and, both doses improved heart rate variability parameters related to parasympathetic activation while showing differences in the late neural response to negative versus neutral emotions. Post-hoc analyses indicated a gender difference in the baseline tryptophan bioavailability and further examination suggested the change in mood rating depends on the interaction between gender and change from baseline of tryptophan bioavailability.
Conclusions: Overall, this study suggests that low levels of tryptophan rich EPH in a food matrix positively impact mood or stress in acute settings and adds to the body of evidence linking tryptophan and dietary sources thereof with these benefits. Confirmatory randomized controlled trials are needed to confirm these findings.Trial registration number: CER-VD N°2019-00218.
Keywords: Tryptophan; cognition; event-related potential; heart-rate-variables; mood; nutrition; serotonin; stress.