SCIENCE ALERT: Theanine in cognitive function: a randomized placebo-controlled study (Journal of Medicinal Food)

Editor's Note

L-theanine is an amino acid found in green tea and also some fungal species that has been shown to affect brain functions by relieving stress disorders, improving mood, and maintaining normal sleep. Yet the precise cognitive functions for which theanine is effective are unclear. This double-blind, randomized, placebo-controlled study aimed to clarify which cognitive functions are positively affected by intake of l-theanine. The subjects were men and women aged 50–69 years that were certified as healthy by a physician based on hematological and biochemical blood test results, and also with self-assessed declined cognitive function. Cognitrax, a test to evaluate cognitive function which measures both reaction time and number of responses, was used to assess 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, increased the number of correct answers, and decreased the number of omission errors in working memory tasks. The authors of the study conclude that l-theanine may contribute to improving attention, thus enhancing working memory and executive functions.

April 2021

Journal of Medicinal Food

DOI: https://doi.org/10.1089/jmf.2020.4803

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

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.