Skip to main content
Evidence-Based Supplement Research
Evidence-Based Supplement Research
Pillser
Search
Sign UpLog In

The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis.

  • 2025-06
  • Sleep medicine reviews 81
    • Amanda Bulman
    • Nathan M D'Cunha
    • Wolfgang Marx
    • Murray Turner
    • Andrew McKune
    • Nenad Naumovski

Study Design

Type
Meta-Analysis
Sample size
n = 897
Population
humans of all ages and health status
Methods
Systematic review and meta-analysis of randomised controlled trials; literature searches in five electronic databases and one register from inception until September 2024
This systematic review ansd meta-analysis aimed to evaluate the effects of L-theanine, a non-proteinogenic amino acid found in tea, on sleep outcomes. Literature searches were conducted in five electronic databases (APA PsycINFO, CINAHL, Medline, Scopus, Web of Science), and one register (Cochrane Central Register of Controlled Trials) from inception until September 2024. Randomised controlled trials investigating the effects of L-theanine supplementation on sleep quality in humans of all ages and health status were included. Nineteen articles (N = 897 participants) were selected and 18 included in the meta-analysis. L-theanine was shown to significantly improve subjective sleep onset latency (SMD = 0.15, 95 % CI [0.01, 0.29], p = 0.04; n = 10 studies), subjective daytime dysfunction (SMD = 0.33, 95 % CI [0.16, 0.49], p < 0.001; n = 9 studies), and overall subjective sleep quality score (SMD = 0.43, 95 % CI [0.04, 0.83], p = 0.03; n = 12 studies). The findings indicate the potential use of L-theanine in the management of sleep disturbances; however, the lack of studies on "pure" L-theanine warrants further investigation. Future studies are needed to determine the adequate dose and duration of L-theanine supplementation for improving and maintaining sleep quality in healthy and clinical populations.

Research Insights

  • L-Theanine→Improved Daytime Dysfunction

    subjective daytime dysfunction (SMD = 0.33, 95 % CI [0.16, 0.49], p < 0.001; n = 9 studies)

    Effect
    Beneficial
    Effect size
    Moderate
  • L-Theanine→Improved Sleep Onset Latency

    L-theanine was shown to significantly improve subjective sleep onset latency (SMD = 0.15, 95 % CI [0.01, 0.29], p = 0.04; n = 10 studies)

    Effect
    Beneficial
    Effect size
    Small
  • L-Theanine→Improved Sleep Quality

    overall subjective sleep quality score (SMD = 0.43, 95 % CI [0.04, 0.83], p = 0.03; n = 12 studies)

    Effect
    Beneficial
    Effect size
    Moderate
Back to top