Anti-stress Effect of Green Tea with Lowered Caffeine on Humans: A Pilot Study

Abstract

Theanine, an amino acid in tea, has significant anti-stress effects on animals and humans. However, the effect of theanine was blocked by caffeine and gallate-type catechins, which are the main components in tea. We examined the anti-stress effect of green tea with lowered caffeine, low-caffeine green tea, on humans. The study design was a single-blind group comparison and participants (n=20) were randomly assigned to low-caffeine or placebo tea groups. These teas (≥500 mL/d), which were eluted with room temperature water, were taken from 1 week prior to pharmacy practice and continued for 10 d in the practice period. The participants ingested theanine (ca. 15 mg/d) in low-caffeine green tea. To assess the anxiety of participants, the state-trait anxiety inventory test was used before pharmacy practice. The subjective stress of students was significantly lower in the low-caffeine-group than in the placebo-group during pharmacy practice. The level of salivary α-amylase activity, a stress marker, increased significantly after daily pharmacy practice in the placebo-group but not in the low-caffeine-group. These results suggested that the ingestion of low-caffeine green tea suppressed the excessive stress response of students. This study was registered at the University Hospital Medical Information Network (ID No. UMIN14942).

Psychotropic effects of L-theanine and its clinical properties: From the management of anxiety and stress to a potential use in schizophrenia

“…Overall, several studies have shown that the administration of L-theanine improved anxiety and stress outcomes, alongside improvements in other manifestations such as depression and psychopathological symptoms ( Table 1). An overall improvement in anxiety symptoms was often accompanied by improvements in biomarkers, including salivary α-amylase, cortisol, chromogranin A and immunoglobulin A [27][28][29][30]. White and colleagues, employing the technique of magnetoencephalography, found that posterior resting alpha activity was significantly higher in the high trait anxiety group receiving L-theanine as compared to the matched placebo group [29].…”

Stress-Reducing Function of Matcha Green Tea in Animal Experiments and Clinical Trials

“…To enhance the stress-reducing effect of green tea, low-caffeine green tea with reduced caffeine content can be prepared from tea leaves by irrigating them with hot water at 95 °C for three minutes. Published data showed that a significant stress-reducing effect of low-caffeine green tea was observed in participants in their 20 s, 40 s–50 s, and 80 s–90 s relative to barley tea or standard green tea [ 18 , 19 , 20 ].…”

Reduced Stress and Improved Sleep Quality Caused by Green Tea Are Associated with a Reduced Caffeine Content

“…Since green tea is generally eluted with hot water, the eluate is rich in EGCG and caffeine. However, the solubility of EGCG and caffeine is low in room temperature water (EGCG is <5 mg/mL and caffeine is 22 mg/mL) [ 12 ]. On the other hand, the solubility of theanine is high (370 mg/mL), even at room temperature.…”

“…Therefore, in this experiment, we examined the anti-stress effect of SGT and LCGT that had been eluted with room temperature water. Indeed, the ingestion of LCGT that was steeped in room temperature water significantly suppressed the stress response in mice and in young individuals [ 11 , 12 ].…”