Effect of tryptophan-rich egg protein hydrolysate on brain tryptophan availability, stress and performance

Background & aims: Reduced brain serotonin function is involved in stress-related disturbances and may particularly occur under chronic stress. Although serotonin production directly depends on the availability of its plasma dietary amino acid precursor tryptophan (TRP), previously described effects of tryptophan-rich food sources on stress-related behavior are rather modest. Recently, an egg protein hydrolysate (EPH) was developed that showed a much greater effect on brain TRP availability than pure TRP and other TRP-food sources and therefore may be more effective for performance under stress. The aim of the present study was to investigate the effects of EPH compared to placebo protein on plasma amino acids, stress coping and performance in subjects with high and low chronic stress vulnerabilities. Methods: In a placebo-controlled, double-blind, crossover study, 17 participants with high and 18 participants with low chronic stress vulnerabilities were monitored for mood and performance under acute stress exposure either following intake of EPH or placebo. Results: EPH significantly increased plasma TRP availability for uptake into the brain, decreased depressive mood in all subjects and improved perceptual-motor and vigilance performance only in low chronic stress-vulnerable subjects. Conclusions: The acute use of a TRP-rich egg protein hydrolysate (EPH) is an adequate method to increase plasma TRP for uptake into the brain and may be beneficial for perceptual-motor and vigilance performance in healthy volunteers. (C) 2010 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.