Haskell Crystal F, Kennedy David O, Milne Anthea L, Wesnes Keith A, Scholey Andrew B
Human Cognitive Neuroscience Unit, Division of Psychology, Northumbria University, Newcastle upon Tyne NE1 8ST, UK.
Biol Psychol. 2008 Feb;77(2):113-22. doi: 10.1016/j.biopsycho.2007.09.008. Epub 2007 Sep 26.
L-Theanine is an amino acid found naturally in tea. Despite the common consumption of L-theanine, predominantly in combination with caffeine in the form of tea, only one study to date has examined the cognitive effects of this substance alone, and none have examined its effects when combined with caffeine. The present randomised, placebo-controlled, double-blind, balanced crossover study investigated the acute cognitive and mood effects of L-theanine (250 mg), and caffeine (150 mg), in isolation and in combination. Salivary caffeine levels were co-monitored. L-Theanine increased 'headache' ratings and decreased correct serial seven subtractions. Caffeine led to faster digit vigilance reaction time, improved Rapid Visual Information Processing (RVIP) accuracy and attenuated increases in self-reported 'mental fatigue'. In addition to improving RVIP accuracy and 'mental fatigue' ratings, the combination also led to faster simple reaction time, faster numeric working memory reaction time and improved sentence verification accuracy. 'Headache' and 'tired' ratings were reduced and 'alert' ratings increased. There was also a significant positive caffeine x L-theanine interaction on delayed word recognition reaction time. These results suggest that beverages containing L-theanine and caffeine may have a different pharmacological profile to those containing caffeine alone.
L-茶氨酸是一种天然存在于茶叶中的氨基酸。尽管人们普遍摄入L-茶氨酸，主要是以茶的形式与咖啡因一起摄入，但迄今为止只有一项研究单独考察了这种物质的认知效应，且没有研究考察过其与咖啡因联合使用时的效果。本随机、安慰剂对照、双盲、平衡交叉研究考察了L-茶氨酸（250毫克）和咖啡因（150毫克）单独及联合使用时的急性认知和情绪效应。同时对唾液中的咖啡因水平进行了监测。L-茶氨酸增加了“头痛”评分，并减少了正确的连续七减法测试成绩。咖啡因使数字警觉反应时间加快，提高了快速视觉信息处理（RVIP）的准确性，并减轻了自我报告的“精神疲劳”的增加。除了提高RVIP准确性和“精神疲劳”评分外，联合使用还使简单反应时间加快、数字工作记忆反应时间加快，并提高了句子验证准确性。“头痛”和“疲劳”评分降低，“警觉”评分增加。在延迟单词识别反应时间上，咖啡因与L-茶氨酸之间也存在显著的正向交互作用。这些结果表明，含有L-茶氨酸和咖啡因的饮料可能具有与仅含咖啡因的饮料不同的药理特性。
