Effect of L-theanine on selective attention in a traffic-related reaction task in sleep-deprived young adults: a double-blind placebo-controlled, crossover study.
- 2024-07-25
- Nutritional neuroscience 28(4)
- Umangi W Karunaratne
- Tharaka L Dassanayake
- PubMed: 39052627
- DOI: 10.1080/1028415x.2024.2383080
Study Design
- Type
- Randomized Controlled Trial (RCT)
- Population
- 24 healthy volunteers (age 20-25 years; 13 males) sleep-deprived overnight
- Methods
- Double-blind, placebo-controlled, counterbalanced, two-way crossover study; 200-mg dose of L-theanine vs placebo (150 ml of distilled water); computerised traffic-scene-based visual recognition reaction task
- Blinding
- Double-blind
- Duration
- one week apart (single dose, tested pre-dose and 45 min post-dose)
Background
L-theanine is a non-protein-forming amino acid found in tea. Limited evidence suggests that it improves selective attention. Sleep deprivation impairs attention and psychomotor reactions, affecting automobile driving. We aimed to determine whether L-theanine improves neurobehavioral measures of visual attention in acutely sleep-deprived healthy adults in a traffic-scene-based attention task.Methods
In a double-blind, placebo-controlled, counterbalanced, two-way crossover study, we compared the effects of a 200-mg dose of L-theanine with a placebo (150 ml of distilled water) on a computerised, traffic-scene-based visual recognition reaction task in 24 healthy volunteers (age 20-25 years; 13 males) sleep-deprived overnight. The participants made speeded button-presses to imminent accident scenes (i.e. hits), while ignoring safe scenes. They were tested pre-dose and 45 min post-dose, each treatment administered one week apart.Results
Hit rates were more than 90% in all sessions, and were similar in two treatments, pre- vs post-dose. L-theanine significantly reduced false alarms (i.e. responses to safe scenes) (p = 0.014) and increased A' (i.e. target-distractor discriminability) (p = 0.009), whereas placebo did not (p > 0.05). L-theanine reduced hit reaction time by 38.65 ms (p = 0.007), and placebo by 19.08 ms (p = 0.016), however reaction time changes from baseline were not significantly different between treatments (p > 0.05).Conclusions
L-theanine in high doses appears to improve selective visual attention by concurrently improving information processing speed and target-distractor discriminability in acutely sleep-deprived individuals. This is consistent with previous functional neuroimaging findings, where L-theanine suppressed distractor-processing and default-mode-network activity in visual selective attention tasks.Research Insights
Hit rates were more than 90% in all sessions, and were similar in two treatments, pre- vs post-dose.
- Effect
- Neutral
- Effect size
- Small
- Dose
- 200 mg
increased A' (i.e. target-distractor discriminability) (p = 0.009), whereas placebo did not (p > 0.05)
- Effect
- Beneficial
- Effect size
- Small
- Dose
- 200 mg
L-theanine significantly reduced false alarms (i.e. responses to safe scenes) (p = 0.014)
- Effect
- Beneficial
- Effect size
- Small
- Dose
- 200 mg
L-theanine reduced hit reaction time by 38.65 ms (p = 0.007), and placebo by 19.08 ms (p = 0.016), however reaction time changes from baseline were not significantly different between treatments (p > 0.05)
- Effect
- Neutral
- Effect size
- Small
- Dose
- 200 mg