A triple blind, randomized study investigating the stress reducing effects of L-theanine following caffeine intake

BackgroundCaffeine is the most widely consumed nootropic worldwide and is frequently used to temporarily enhance cognitive performance. However, caffeine-induced effects on physiological arousal are also associated with side effects, which can exacerbate psychological stress symptoms in social performance situations. The amino acid L-theanine has shown potential to modulate these adverse effects of caffeine by reducing caffeine-augmented stress responses without impairing its desired cognitive effects. The aim of this study was to investigate the spontaneous modulatory effects of L-theanine on caffeine-enhanced stress in acute social stress situations.MethodA total of 46 healthy participants (83% female, aged 18–30 years) were examined for differences in stress reactivity during a standardized psychological stress test (Trier Social Stress Test for Groups, TSST-G). The study compared the effects of a single dose of caffeine alone versus a combination of caffeine and L-theanine. Specific stress constituents including subjective stress, anxiety, physical discomfort, desire to leave the situation, tension, and perceived control were assessed. Furthermore, group effects, trait anxiety, caffeine consumption, and temporal changes in reported stress were analyzed using repeated measures ANOVA with covariates.ResultsThe combination of caffeine and L-theanine resulted in a spontaneous attenuation of tension in social stress situations compared to caffeine alone. ConclusionsResults suggest that L-theanine attenuates certain stress effects of caffeine in acute social stress situations. This highlights the potential of the L-theanine and caffeine combination as a dual nootropic agent, offering both stress-reducing effects and the practicality of a substance suitable for cognitive performance enhancement. Future research should further investigate the mechanisms underlying these effects by incorporating physiological markers such as cortisol and cognitive performance tests.