L-theanine sleep review reports possible benefits, with key details missing
Trials reported benefits on several sleep measures, but the abstract provides no effect sizes or study-by-study results to show how consistent or substantial those benefits were.
Based on the published abstract. The full paper may contain additional methods, results and limitations.
The 30-second takeaway
This review identified sleep-related benefits in trials of L-theanine taken as a standalone supplement. However, the abstract does not quantify the improvements or show which trials supported each outcome. It cannot establish a preferred dose, demonstrate effectiveness for clinical insomnia, or support a broad safety conclusion without more detailed results.
The abstract lacks trial durations, comparator details, effect estimates, and adverse-event results. It includes uncontrolled studies alongside randomized trials and calls for better research using objective sleep measurements, including in people with clinical insomnia.
What sleep outcomes were reported
Reported benefits involved falling asleep, maintaining sleep, sleep efficiency, satisfaction with sleep, and feeling refreshed or recovered on waking. Both objective measurements and participant reports appeared among the outcomes, but the abstract does not separate their results.
What the review cannot settle
Some included studies lacked a control group, while others were randomized trials. Without separate results, it is unclear how much the conclusions depend on each design or whether benefits were consistent across participants and sleep measures.
The original publication
Examining the effect of L-theanine on sleep: a systematic review of dietary supplementation trials.
Cotter J, Caddick CE, Harper JL et al.
Nutr Neurosci · 2026
- PubMed ID
- 41176609
- Record checked
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