Category: Study Spotlight

Summary: Human clinical trials and reviews indicate that L-theanine may improve subjective sleep quality—primarily by reducing anxiety and promoting relaxation, rather than acting as a sedative. An effective oral dose supported by several studies and reviews is 200 mg taken before bed. Studies at 250–400 mg/day have also been explored in populations with comorbid anxiety, depressive disorders, or schizophrenia, with improvement in sleep quality consistently related to L-theanine’s anxiolytic effects. Details: Key Human Research (Relevant Dosages and Effects on Sleep): Systematic Review – Rao et al., JACN 2015 Design: Summary of multiple human studies (including actigraphy, sleep questionnaires, ANS monitoring). Dose: 200 mg L-theanine before bed. Population: Adults and children, some with sleep complaints. Effects: Improved sleep quality via reduction in anxiety (not direct sedation), better WASO scores, improved parasympathetic activity, and subjective sleep markers. Safety: No adverse events at 200 mg; NOAEL (no observed adverse effect level) above 2000 mg/kg in animal models. Open-Label Clinical Trial – Hidese et al., Acta Neuropsychiatrica 2017 Design: 8-week open-label supplementation. Dose: 250 mg/day. Population: 20 patients with major depressive disorder. Effects: Statistically significant improvements on the Pittsburgh Sleep Quality Index (PSQI), as well as anxiety and depression scores. Compliance/Limitations: Not placebo-controlled; findings need confirmation in RCTs. Randomized Controlled Trials/Neurocognitive Studies (Doses 200–400 mg): These studies typically used L-theanine for cognitive/attentional effects but also measured anxiety and sleep outcomes as secondary endpoints. Where reported, these doses were safe and associated with improved subjective sleep quality. Research Notes: Several animal studies support L-theanine’s sleep-improving effects especially by counteracting caffeine-induced sleep disruption. Main mechanism is anxiolysis (promotion of relaxation and decreased stress), which supports better sleep onset and maintenance without causing next-day drowsiness. Safety profile is robust; published adverse events at effective sleep-related doses (200–400 mg) are rare or absent. Compliance Note: US (FDA): “Supports relaxation” and “may help reduce occasional stress to support sleep quality” are generally acceptable structure/function claims, but “treats insomnia” or “induces sleep” is NOT compliant for supplements. EU (EFSA): No approved sleep claims specific for L-theanine; “relaxation” claims require documented human evidence and careful wording to avoid therapeutic claims. Key Doses Supported by Evidence (For Sleep): 200 mg L-theanine (most commonly studied, before bed) Up to 400 mg/day has been used in studies on populations with concurrent psychiatric symptoms No significant risk for adverse effects at these doses in clinical trials. Summary Table: Study Type Population Dose Effect on Sleep Notable Safety Issues Review (RCTs/Obs) Adults, Children 200 mg Improved quality (via relaxation/anxiolysis) None at studied dosage Clinical (Open-label) MDD patients 250 mg Improved PSQI scores None reported RCTs (Neurocogn.) Healthy adults 200–400 mg Less sleep disruption (secondary effect) None reported Bottom Line: Robust human data support 200 mg L-theanine (taken before bed) as a safe, effective dose for supporting better sleep quality through relaxation and anxiety reduction. Larger or longer-term studies may use up to 400 mg, but most marketing claims should emphasize “relaxation” and “sleep quality” rather than direct sleep induction, due to regulatory constraints. References (for citation): Rao TP et al., J Am Coll Nutr. 2015;34(5):436-447. doi:10.1080/07315724.2014.926153 Hidese S et al., Acta Neuropsychiatr. 2017;29(5):291-299. doi:10.1017/neu.2016.33 Let me know if you need sample compliant marketing language or additional regulatory details! Sources: L-theanine partially counteracts caffeine-induced sleep disturbances in rats. In Search of a Safe Natural Sleep Aid. Pharmacokinetics of L-theanine and the effect on amino acid composition in mice administered with L-theanine. Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study. +6 more Follow-Up Question(s): Certainly! Here are 3 insightful follow-up questions a reader might ask about using L-theanine for sleep: Are there any notable differences in the effectiveness or safety of L-theanine for sleep between younger adults, older adults, and children? How does L-theanine compare to other natural sleep-support ingredients—such as melatonin or valerian—in randomized clinical trials, both for effectiveness and for side effect profile? Can L-theanine be safely combined with other common sleep supplements or medications, and are there any contraindications or interactions to be aware of according to clinical research?