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Randomized Controlled Trial
. 2021 Apr;24(4):333-341.
doi: 10.1089/jmf.2020.4803. Epub 2021 Mar 22.

Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study

Yoshitake Baba  1 , Shun Inagaki  1 , Sae Nakagawa  1 , Toshiyuki Kaneko  2 , Makoto Kobayashi  1 , Takanobu Takihara  1
Affiliations
Randomized Controlled Trial

Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study

Yoshitake Baba et al. J Med Food. 2021 Apr.

Abstract

l-theanine (γ-glutamylethylamide), an amino acid in green tea, has been shown to affect brain functions by relieving stress disorders, improving mood, and maintaining normal sleep. However, the cognitive functions for which theanine is effective are unclear. This study aimed to clarify which cognitive functions are positively affected by intake of l-theanine. A double-blind, randomized, placebo-controlled study was conducted. The subjects were Japanese men and women aged 50-69 years. Mini Mental State Examination-Japanese version score was 24 or higher. Cognitrax was used as a test battery for cognitive function. Evaluations were performed before the intervention, after a single dose of l-theanine, and after 12 weeks of regular intake. The single dose of l-theanine reduced the reaction time to attention tasks (Stroop test, Part 1), and it increased the number of correct answers and decreased the number of omission errors in working memory tasks (4-Part continuous performance test, Part 4). In conclusion, our study indicated that l-theanine may contribute to improving attention, thus enhancing working memory and executive functions. Clinical Trial No.: UMIN000033812.

Keywords: Cognitrax; attention; brain function; executive function; green tea amino acid; working memory.

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Conflict of interest statement

ITO EN, Ltd. covered the testing costs and provided the test food as the study sponsor. Huma R&D Corp., Contract Research Organization, conducted subject recruitment, selection, allocation, observation, and data collection. Kureha Special Laboratory Co., Ltd. conducted statistical analysis. T.K. was the principal investigator for this study and was contracted by Huma R&D to conduct the study. The study was performed by a third party. The remaining authors report that no competing financial interests exist.

Figures

FIG. 1.
FIG. 1.
Study flow diagram.
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