Key Takeaway
Four weeks of L-theanine (200mg/day) significantly reduced stress, anxiety, and depression scores while improving cognitive function in healthy adults
Summary
This well-designed RCT demonstrated that L-theanine supplementation provides meaningful benefits for stress-related symptoms and cognitive function in healthy adults over a 4-week period. The study provides strong evidence for L-theanine as a safe, well-tolerated nutraceutical for mental wellness.
Methods
- Design: Randomized, double-blind, placebo-controlled trial
- Participants: 30 healthy adults (ages 21-64)
- Intervention: 200mg L-theanine daily for 4 weeks vs placebo
- Measures: Depression, anxiety, sleep quality, cognitive function tests
- Assessments: Baseline, 2 weeks, and 4 weeks
Key Results
- Significant decreases in stress-related symptoms:
- Depression scores reduced
- Trait anxiety decreased
- Sleep quality improved
- Cognitive improvements:
- Verbal fluency increased
- Executive function enhanced
- L-theanine was safe and well-tolerated
- No significant adverse effects reported
- Compliance was excellent throughout the study
Figures
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Limitations
- Small sample size (n=30)
- Healthy population only - may not generalize to clinical anxiety
- 4-week duration - longer-term effects unknown
- Single dose level tested (200mg)
- Japanese population - cultural factors may influence stress responses