Acute effects of theanine, caffeine and theanine-caffeine combination on attention

Nutr Neurosci. 2017 Jul;20(6):369-377. doi: 10.1080/1028415X.2016.1144845. Epub 2016 Feb 12.


Objective: l-theanine is a constituent of tea which is claimed to enhance cognitive functions. We aimed to determine whether theanine and theanine-caffeine combination have acute positive effects on cognitive and neurophysiological measures of attention, compared to caffeine (a positive control) and a placebo in healthy individuals.

Design: In a placebo-controlled, five-way crossover trial in 20 healthy male volunteers, we compared the effects of l-theanine (200 mg), caffeine (160 mg), their combination, black tea (one cup) and a placebo (distilled water) on cognitive (simple [SVRT] and recognition visual reaction time [RVRT]) and neurophysiological (event-related potentials [ERPs]) measures of attention. We also recorded visual (VEPs) and motor evoked potentials (MEPs) to examine any effects of treatments on peripheral visual and motor conduction, respectively.

Results: Mean RVRT was significantly improved by theanine (P = 0.019), caffeine (P = 0.043), and theanine-caffeine combination (P = 0.001), but not by tea (P = 0.429) or placebo (P = 0.822). VEP or MEP latencies or SVRT did not show significant inter-treatment differences. Theanine (P = 0.001) and caffeine (P = 0.001) elicited significantly larger mean peak-to-peak N2-P300 ERP amplitudes than the placebo, whereas theanine-caffeine combination elicited a significantly larger mean N2-P300 amplitude than placebo (P < 0.001), theanine (P = 0.029) or caffeine (P = 0.005). No significant theanine × caffeine interaction was observed for RVRT or N2-P300 amplitude.

Discussion: A dose of theanine equivalent of eight cups of back tea improves cognitive and neurophysiological measures of selective attention, to a degree that is comparable with that of caffeine. Theanine and caffeine seem to have additive effects on attention in high doses.

Keywords: Attention; Caffeine; Cognitive effects; Event-related potentials; P300; Reaction time; Tea; Theanine.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Attention*
  • Caffeine / administration & dosage*
  • Coffee
  • Cognition*
  • Cross-Over Studies
  • Dietary Supplements*
  • Evoked Potentials, Motor
  • Evoked Potentials, Visual
  • Glutamates / administration & dosage*
  • Humans
  • Male
  • Motor Activity
  • Nootropic Agents / administration & dosage*
  • Pattern Recognition, Visual
  • Performance-Enhancing Substances / administration & dosage*
  • Reaction Time
  • Sri Lanka
  • Students
  • Tea
  • Universities
  • Young Adult


  • Coffee
  • Glutamates
  • Nootropic Agents
  • Performance-Enhancing Substances
  • Tea
  • Caffeine
  • theanine