title: Acute effects of theanine, caffeine and theanine-caffeine combination on attention.
abstract: 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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors: a Department of Physiology, Faculty of Medicine , University of Peradeniya , Sri Lanka.|b Department of Nutritional Sciences , Texas Tech University , Lubbock , USA.
authors: Chanaka N
authors: CN
authors: Kahathuduwa
authors: a Department of Physiology, Faculty of Medicine , University of Peradeniya , Sri Lanka.
authors: Tharaka L
authors: http://orcid.org/0000-0002-7963-9012
authors: TL
authors: Dassanayake
authors: c Department of Chemistry, Faculty of Science , University of Kelaniya , Sri Lanka.
authors: A M Tissa
authors: AMT
authors: Amarakoon
authors: a Department of Physiology, Faculty of Medicine , University of Peradeniya , Sri Lanka.
authors: Vajira S
authors: VS
authors: Weerasinghe
mesh_terms: D000328:Adult; D001288:Attention; D002110:Caffeine / Q000008:administration & dosage*; D003069:Coffee; D003071:Cognition; D018592:Cross-Over Studies; D019587:Dietary Supplements; D019054:Evoked Potentials, Motor; D005074:Evoked Potentials, Visual; D005971:Glutamates / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D009043:Motor Activity; D018697:Nootropic Agents / Q000008:administration & dosage*; D010364:Pattern Recognition, Visual; D058573:Performance-Enhancing Substances / Q000008:administration & dosage*; D011930:Reaction Time; D013188:Sri Lanka; D013334:Students; D013662:Tea; D014495:Universities; D055815:Young Adult
chemical_list: D003069:Coffee; D005971:Glutamates; D018697:Nootropic Agents; D058573:Performance-Enhancing Substances; D013662:Tea; D002110:Caffeine; C026166:theanine
keywords: Attention; Caffeine; Cognitive effects; Event-related potentials; P300; Reaction time; Tea; Theanine