The green tea amino acid, L-theanine (L-THE) is associated with several health benefits, including improvements in mood, cognition and a reduction of stress and anxiety-like symptoms. This systematic review evaluated the effect of pure L-THE intake, in the form of orally administered nutritional supplements, on stress responses and anxiety levels in human randomised controlled trials. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist, 9 peer-reviewed journal articles were identified where L-THE as a supplement was compared to a control. Our findings suggest that supplementation of 200–400 mg/day of L-THE may assist in the reduction of stress and anxiety in people exposed to stressful conditions. Despite this finding, longer-term and larger cohort clinical studies, including those where L-THE is incorporated into the diet regularly, are needed to clinically justify the use of L-THE as a therapeutic agent to reduce stress and anxiety in people exposed to stressful conditions.

中文翻译：

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绿茶氨基酸 L-茶氨酸消耗对压力和焦虑水平管理能力的影响：系统评价

绿茶氨基酸 L-茶氨酸 (L-THE) 与多种健康益处有关，包括改善情绪、认知以及减轻压力和焦虑样症状。该系统评价评估了纯 L-THE 摄入（以口服营养补充剂的形式）对人体随机对照试验中的压力反应和焦虑水平的影响。在系统评价和元分析 (PRISMA) 清单的首选报告项目之后，确定了 9 篇同行评议的期刊文章，其中 L-THE 作为补充与对照进行了比较。我们的研究结果表明，每天补充 200-400 毫克的 L-THE 可能有助于减轻暴露于压力条件下的人的压力和焦虑。尽管有这一发现，长期和更大的队列临床研究，