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

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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

Nawarathna et al., 2025 | Br J Nutr | Rct

Citation

Nawarathna Gayani S, Ariyasinghe Dewasmika I, Dassanayake Tharaka L. 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. Br J Nutr. 2025-Aug-14;134(3):195-204. doi:10.1017/S0007114525104169

Abstract

L-theanine, an amino acid found in tea, and caffeine, found in tea and coffee, are claimed to enhance attention. We conducted a double-blind, placebo-controlled, counterbalanced, two-way crossover trial to determine the acute effects of a high-dose L-theanine-caffeine combination on neurobehavioural (reaction time) and neurophysiological (P3b cognitive event-related potential (ERP)) measures of selective attention in acutely sleep-deprived healthy adults. Thirty-seven overnight sleep-deprived healthy adults (aged 22-30 years, twenty-one men) completed a computerised traffic-scene-related visual stimulus discrimination task before and 50 min after ingesting 200 mg L-theanine-160 mg caffeine combination or a placebo. The task involved selectively responding to imminent accident scenes (20 % probability) while ignoring randomly intermixed, more frequent safe scenes (80 % probability). A 32-channel electroencephalogram was recorded concurrently to derive ERP. The L-theanine-caffeine combination significantly improved the hit rate (P = 0·02) and target-distractor discriminability (P = 0·047), compared with the placebo. Although both L-theanine-caffeine combination (△ = 52·08 ms, P < 0·0001) and placebo (△ = 13·97 ms, P = 0·024) improved reaction time to accident scenes, the pre-post-dose reaction time improvement of the L-theanine-caffeine combination was significantly greater than that of placebo (△ = 38·1 ms, P = 0·003). Compared with the placebo, the L-theanine-caffeine combination significantly increased the amplitudes and reduced the latencies of P3b ERP component. Our findings suggest that L-theanine-caffeine combination improves the accuracy and speed of deploying selective attention to traffic scenarios in sleep-deprived individuals. This improvement is brought about by greater and faster neural resource allocation in the attentional networks of the brain.

Key Findings

This improvement is brought about by greater and faster neural resource allocation in the attentional networks of the brain.

Outcomes Measured

  • Requires manual extraction

Population

Field Value
Population See abstract
Sample Size See abstract
Age Range aged 22-30
Condition sleep

MeSH Terms

  • Humans
  • Glutamates
  • Male
  • Double-Blind Method
  • Caffeine
  • Cross-Over Studies
  • Adult
  • Young Adult
  • Attention
  • Female
  • Sleep Deprivation
  • Electroencephalography
  • Reaction Time
  • Evoked Potentials

Evidence Classification

  • Level: Rct
  • Publication Types: Journal Article, Randomized Controlled Trial
  • Vertical: l-theanine-sleep

Provenance

Source extracted via PubMed E-utilities API on 2026-04-09