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Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study
Double-blind RCT in Japanese adults aged 50–69 (MMSE-J ≥24) found acute l-theanine improved attention task reaction time and aspects of working memory versus placebo, with sponsor-provided test foods and independent CRO conduct.
Design
Double-blind RCT; Cognitrax battery; assessments baseline, after single dose, and after 12 weeks; population 50–69 y with MMSE-J ≥24.
Cognitive endpoints (abstract)
- Single dose: faster reaction time on Stroop part 1 attention task
- Working memory: more correct answers and fewer omission errors on 4-part CPT part 4
- Authors conclude l-theanine may support attention / executive aspects of cognition in this sample
Evidence hygiene
Industry-sponsored test foods (Ito En) and contracted CRO operations—treat as hypothesis-building for cognition, not a blanket sleep claim (sleep keywords appear in background, primary endpoints here are cognitive).
Publication
Baba Y, Inagaki S, Nakamura S, et al. J Med Food. 2021 Apr;24(4):333-341. PMID 33751906; UMIN000033812.
Outcomes
- Single l-theanine dose shortened reaction time on Stroop attention task Part 1 vs placebo (middle-aged/older Japanese adults).
- Single dose increased correct answers and decreased omission errors on 4-part CPT Part 4 (working memory); MMSE-J ≥24; industry-sponsored test article—see trial tables for effect magnitudes.