High-dose L-theanine-caffeine combination improves selective attention in acutely sleep-deprived young adults
A double-blind, placebo-controlled crossover trial found that a combination of 200 mg L-theanine and 160 mg caffeine significantly improved hit rate (P=0.02) and target-distractor discriminability (P=0.047) in a visual selective attention task compared to placebo. The combination also produced a significantly greater pre-post-dose reaction time improvement (38.1 ms, P=0.003) and enhanced P3b ERP amplitudes with reduced latencies.
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High-dose L-theanine-caffeine combination improves selective attention in acutely sleep-deprived young adults The current body of evidence comprises 1 study, including 1 randomized controlled trial. EvidenceHub rates the overall confidence at 42/100 (low).
The Claim
High-dose L-theanine-caffeine combination improves selective attention in acutely sleep-deprived young adults
This conclusion is most relevant to: 37 overnight sleep-deprived healthy adults aged 22-30 years (21 men).
What the Research Shows
The conclusion draws on 1 linked study. Highlights from the cited literature:
- ▸High-dose L-theanine-caffeine combination improves neurobehavioural and neurophysiological measures of selective attention in acutely sleep-deprived young adults: a double-blind, placebo-controlled crossover study. (The British journal of nutrition, 2025) —
How It Works
The proposed biological pathway:
- ▸Ingestion of L-theanine-caffeine combination
- ▸Increased neural resource allocation in attentional networks
- ▸Greater and faster P3b ERP component (increased amplitude, reduced latency)
- ▸Improved accuracy and speed of selective attention to traffic scenarios
Who Might Benefit
Evidence fit by population:
- ▸37 overnight sleep-deprived healthy adults aged 22-30 years (21 men)
Recommended Dose
200 mg L-theanine + 160 mg caffeine
Limitations & Caveats
Important context when interpreting this evidence:
- ▸Acute sleep deprivation model may not generalize to chronic sleep loss or non-sleep-deprived populations
- ▸Single dose design; long-term effects and optimal dosing regimen unknown
Frequently Asked Questions
What is the recommended dose of L-theanine and caffeine for attention improvement?▼
This study used a single dose of 200 mg L-theanine combined with 160 mg caffeine, but optimal dosing may vary by individual and context.
How long does it take for the L-theanine-caffeine combination to affect attention?▼
In this study, effects were measured 50 minutes after ingestion.
Is this combination effective for non-sleep-deprived individuals?▼
This study only tested acutely sleep-deprived young adults; effects in well-rested individuals were not assessed.
What are the potential side effects of this combination?▼
The abstract does not report side effects; caffeine can cause jitteriness or insomnia in sensitive individuals.
References
- 1.Nawarathna GS, Ariyasinghe DI, Dassanayake TL. “High-dose L-theanine-caffeine combination improves neurobehavioural and neurophysiological measures of selective attention in acutely sleep-deprived young adults: a double-blind, placebo-controlled crossover study..” The British journal of nutrition, 2025. PMID: 40789769 DOI: 10.1017/S0007114525104169