Unno Keiko, Yamada Hiroshi, Iguchi Kazuaki, Ishida Hitoshi, Iwao Yasunori, Morita Akio, Nakamura Yoriyuki
Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka.
Tea Science Center, Graduate Division of Nutritional and Environmental Sciences, University of Shizuoka.
Biol Pharm Bull. 2017;40(6):902-909. doi: 10.1248/bpb.b17-00141.
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).
茶氨酸是茶叶中的一种氨基酸，对动物和人类具有显著的抗应激作用。然而，茶氨酸的这种作用会被咖啡因和没食子酸型儿茶素（茶叶中的主要成分）所阻断。我们研究了低咖啡因绿茶（即降低了咖啡因含量的绿茶）对人类的抗应激作用。研究设计为单盲组比较，参与者（n = 20）被随机分配到低咖啡因茶组或安慰剂茶组。这些茶（≥500 mL/天）用室温的水冲泡，从药学实习前1周开始饮用，并在实习期间持续饮用10天。参与者通过饮用低咖啡因绿茶摄入茶氨酸（约15 mg/天）。为了评估参与者的焦虑程度，在药学实习前使用了状态-特质焦虑量表测试。在药学实习期间，低咖啡因组学生的主观压力显著低于安慰剂组。唾液α-淀粉酶活性（一种应激标志物）水平在安慰剂组学生每日药学实习后显著升高，而在低咖啡因组则没有升高。这些结果表明，饮用低咖啡因绿茶可抑制学生过度的应激反应。本研究已在大学医院医学信息网络注册（注册号：UMIN14942）。
