L-theanine improves neurophysiological measures of attention in a dose-dependent manner: a double-blind, placebo-controlled, crossover study.
- 2020-08-11
- Nutritional neuroscience 25(4)
- Tharaka L Dassanayake
- Chanaka N Kahathuduwa
- Vajira S Weerasinghe
- PubMed: 32777998
- DOI: 10.1080/1028415x.2020.1804098
Study Design
- Type
- Randomized Controlled Trial (RCT)
- Population
- 27 healthy young adults
- Methods
- double-blind, placebo-controlled, counterbalanced, 4-way crossover study comparing 3 doses of L-theanine (100, 200 and 400 mg) with a placebo (distilled water) on latencies of amplitudes of attentive and pre-attentive cognitive event-related potentials (ERPs) recorded in an auditory stimulus discrimination task, before and 50 min after dosing
- Blinding
- Double-blind
- Duration
- 50 min after dosing
Objective: L-theanine, a non-proteinic amino acid found in tea, is known to enhance attention particularly in high doses, with no reported adverse effects. We aimed to determine whether oral administration of L-theanine acutely enhances neurophysiological measures of selective attention in a dose-dependent manner.Methods: In a double-blind, placebo-controlled, counterbalanced, 4-way crossover study in a group of 27 healthy young adults, we compared the effects of 3 doses of L-theanine (100, 200 and 400 mg) with a placebo (distilled water) on latencies of amplitudes of attentive and pre-attentive cognitive event-related potentials (ERPs) recorded in an auditory stimulus discrimination task, before and 50 min after dosing.Results: Compared to the placebo, 400 mg of theanine showed a significant reduction in the latency of the parietal P3b ERP component (p < 0.05), whereas no significant changes were observed with lower doses. A subsequent exploratory regression showed that each 100-mg increase in dose reduces the P3b latency by 4 ms (p < 0.05). No dose-response effect was observed in P3b amplitude, pre-attentive ERP components or reaction time.Discussion: The findings indicate L-theanine can increase attentional processing of auditory information in a dose-dependent manner. The linear dose-response attentional effects we observed warrant further studies with higher doses of L-theanine.
Research Insights
No dose-response effect was observed in P3b amplitude, pre-attentive ERP components or reaction time.
- Effect
- Neutral
- Effect size
- Small
- Dose
- 100, 200 and 400 mg
No dose-response effect was observed in P3b amplitude, pre-attentive ERP components or reaction time.
- Effect
- Neutral
- Effect size
- Small
- Dose
- 100, 200 and 400 mg
No dose-response effect was observed in P3b amplitude, pre-attentive ERP components or reaction time.
- Effect
- Neutral
- Effect size
- Small
- Dose
- 100, 200 and 400 mg
400 mg of theanine showed a significant reduction in the latency of the parietal P3b ERP component (p < 0.05), whereas no significant changes were observed with lower doses. A subsequent exploratory regression showed that each 100-mg increase in dose reduces the P3b latency by 4 ms (p < 0.05).
- Effect
- Beneficial
- Effect size
- Small
- Dose
- 100, 200 and 400 mg
Adverse Events Reported
L-theanine, a non-proteinic amino acid found in tea, is known to enhance attention particularly in high doses, with no reported adverse effects.
- Finding
- Reported