Amino AcidsL-Theanine

Theanine plus caffeine improves cognitive and mood outcomes in healthy participants

This meta-analysis of 15 RCTs found small-to-moderate benefits of theanine plus caffeine over placebo on cognition and mood outcomes, including choice reaction time (SMD -0.48 at 1 hour) and digit vigilance task accuracy (SMD 0.20 at 2 hours). Theanine alone also showed a small-to-moderate benefit on choice reaction time (SMD -0.35 at 1 hour). However, confidence intervals were wide, indicating uncertainty in effect magnitude.

Last updated: Aug 26, 2026•0 RCTs•1 Meta-analyses•📖 Read as article →

Evidence Score

Evidence Score49/100
Human RCT☆☆☆☆☆
Meta-analysis★★★☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. Effects of Tea (Camellia sinensis) or its Bioactive Compounds l-Theanine or l-Theanine plus Caffeine on Cognition, Sleep, and Mood in Healthy Participants: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

observational

Payne ER, Aceves-Martins M, Dubost J, Greyling A, de Roos B · Nutrition reviews (2025)

Participants: N/A
Duration: Not specified
Intervention: Theanine plus caffeine or theanine alone
Outcome: Cognition (choice reaction time, digit vigilance task accuracy, attention switching task accuracy) and mood
Effect Size: SMD -0.48 (95% CI -1.01 to 0.05) for choice reaction time at 1 hour (theanine plus caffeine vs placebo); SMD -0.35 (95% CI -0.61 to -0.10) for theanine alone vs placebo
Population: Healthy participants (from 50 RCTs, 15 included in meta-analysis)

Result:

PubMed: 40314930DOI: 10.1093/nutrit/nuaf054

Mechanism Graph

Theanine and caffeine modulate neurotransmitter systems
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Caffeine blocks adenosine receptors promoting alertness
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Theanine increases alpha brain waves and reduces stress
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Result: Improved cognitive performance and mood

Limitations

  • ⚠Confidence intervals were wide, highlighting uncertainty in direction and magnitude of effects
  • ⚠Only 15 of 50 included RCTs were eligible for meta-analysis, limiting generalizability

Frequently Asked Questions

Does theanine alone improve cognition?▼

Yes, theanine alone showed a small-to-moderate benefit on choice reaction time at 1 hour (SMD -0.35) compared to placebo.

What cognitive outcomes were improved by theanine plus caffeine?▼

Improvements were seen in choice reaction time, digit vigilance task accuracy, and attention switching task accuracy, particularly in the first two hours after intake.

Was the effect of theanine plus caffeine on mood significant?▼

There was a small-to-moderate difference favoring theanine plus caffeine on overall mood at 2 hours (SMD 0.26), but the confidence interval crossed zero, indicating uncertainty.

What population was studied in this meta-analysis?▼

The analysis included healthy participants from randomized controlled trials, though specific demographics (e.g., age, gender) were not detailed in the abstract.

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References

  1. 1.Payne ER, Aceves-Martins M, Dubost J, Greyling A, de Roos B. "Effects of Tea (Camellia sinensis) or its Bioactive Compounds l-Theanine or l-Theanine plus Caffeine on Cognition, Sleep, and Mood in Healthy Participants: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.." Nutrition reviews, 2025. PMID: 40314930 DOI: 10.1093/nutrit/nuaf054
Disclaimer: This content is for educational purposes only and is not medical advice. Evidence scores reflect the quality and quantity of available research, not clinical recommendations. Always consult a healthcare professional before starting any supplement or intervention.