| Effect | Increase |
| Values | BACS. Mean and SD. Category Fluency. Overall: Placebo: before 52.3 ± 9.80, after 54.7 ± 12.2. Theanine: before 50.3 ± 13.0, after 54.9 ± 10.4. Placebo: before 22.4 ± 4.48 after 23.3 ± 5.49. Theanine: before 21.9 ± 5.87, after 23.1 ± 5.30. Letter fluency: Placebo: before 29.9 ± 7.28, after 31.4 ± 9.68. Theanine: before 28.4 ± 8.43, after 31.7 ± 6.94. |
| Trial Design | Randomized trial |
| Trial Length | 2-4 Weeks |
| Number of Subjects | 30 |
| Sex | Both Genders |
| Age Range | 18-29, 30-44, 45-64, 65+ |
Each night of this 4-week (per treatment) randomized, controlled trial crossover, 30 healthy participants took 200 mg of l-theanine (suntheanine) or placebo before sleep.Funding issues for this study:
Anxiety, sleep quality, and depression were the primary outcomes, and there was a statistically significantly greater improvement for all compared with baseline, which became greater after 4 weeks compared with 2 weeks. There wasn't a statistically significantly greater improvement compared with placebo, though there was a greater improvement for all.
Measures of verbal fluency and executive function were improved more when taking theanine, whereas the trail-making test score improved more in the placebo group. However, these differences weren't statistically significant compared with each other, only when compared with baseline. Analyses stratified by the median split based on the mean pretreatment scores found that the lower half score on verbal fluency and letter fluency in the lower half was improved more when taking theanine.
"This study was supported by funding received from Taiyo Kagaku Co., Ltd., Mie, Japan. Yasukawa Z. and Ozeki M. are employees of Taiyo Kagaku Co., Ltd. which supplied the L-theanine and placebo tablets used in this trial."
