The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness

source extracted confidence: high 2026-04-09
#adolescent #adult #affect #attention #blood-pressure

The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness

Giesbrecht et al., 2010 | Nutr Neurosci | Rct

Citation

Giesbrecht T, Rycroft J A, ... De Bruin E A. The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness. Nutr Neurosci. 2010-Dec;13(6):283-90. doi:10.1179/147683010X12611460764840

Abstract

The non-proteinic amino acid L-theanine and caffeine, a methylxanthine derivative, are naturally occurring ingredients in tea. The present study investigated the effect of a combination of 97 mg L-theanine and 40 mg caffeine as compared to placebo treatment on cognitive performance, alertness, blood pressure, and heart rate in a sample of young adults (n = 44). Cognitive performance, self-reported mood, blood pressure, and heart rate were measured before L-theanine and caffeine administration (i.e. at baseline) and 20 min and 70 min thereafter. The combination of moderate levels of L-theanine and caffeine significantly improved accuracy during task switching and self-reported alertness (both P < 0.01) and reduced self-reported tiredness (P < 0.05). There were no significant effects on other cognitive tasks, such as visual search, choice reaction times, or mental rotation. The present results suggest that 97 mg of L-theanine in combination with 40 mg of caffeine helps to focus attention during a demanding cognitive task.

Key Findings

The present results suggest that 97 mg of L-theanine in combination with 40 mg of caffeine helps to focus attention during a demanding cognitive task.

Outcomes Measured

  • blood pressure

Population

Field Value
Population young adults
Sample Size 44
Age Range See abstract
Condition blood pressure

MeSH Terms

  • Adolescent
  • Adult
  • Affect
  • Attention
  • Blood Pressure
  • Caffeine
  • Cognition
  • Double-Blind Method
  • Fatigue
  • Female
  • Glutamates
  • Heart Rate
  • Humans
  • Male
  • Placebos
  • Reaction Time
  • Tea

Evidence Classification

  • Level: Rct
  • Publication Types: Journal Article, Randomized Controlled Trial, Research Support, Non-U.S. Gov't
  • Vertical: l-theanine-focus

Provenance

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