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Head-to-head evidence comparison — which supplement is right for you?
L-Theanine wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Mostly mechanism / observational
2 of 2 studies with measurable effects showed benefit.
Top outcomes
Verdict
Likely helps
3 of 4 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (2)
Outcomes where both GABA and L-Theanine have evidence — compare verdict strength side-by-side.
250-750mg
30-60 minutes before desired effect, Before bed for sleep, Before stressful events for anxiety
Capsules or powder
100-200mg
Morning with coffee for focus, Evening for relaxation, As needed for stress
Suntheanine® capsules or powder
30-60 minutes
30-60 minutes
30-60 minutes
30-60 minutes
30-60 minutes
30-60 minutes
Varies
Herbal Remedies and Their Possible Effect on the GABAergic System and Sleep
Nutrients (2021) · Systematic review
Gamma-aminobutyric acid (GABA) is an inhibitory neurotransmitter that plays a major role in controlling different vigilance states.
Effect of Probiotics on the Symptomatology of Autism Spectrum Disorder and/or Attention Deficit/Hyperactivity Disorder in Children and Adolescents: Pilot Study
Research on child and adolescent psychopathology (2025) · Rct · n=80
A better comfort score (quality of life) was shown in children with ASD (probiotic: p = 0.010, Cohen's d = 0.722; placebo: p = 0.099, Cohen's d = 0.456).
GABA Supplementation, Increased Heart-Rate Variability, Emotional Response, Sleep Efficiency and Reduced Depression in Sedentary Overweight Women Undergoing Physical Exercise: Placebo-Controlled, Randomized Clinical Trial
Journal of dietary supplements (2024) · Rct · n=90
Moreover, an improved emotional response was observed, characterized by diminished negative affect.
The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis
Sleep medicine reviews (2025) · Meta analysis · n=897
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.
Efficiency of Different Supplements in Alleviating Symptoms of ADHD with or Without the Use of Stimulants: A Systematic Review
Nutrients (2025) · Systematic review
The evidence revealed the potential use of supplements as complementary ADHD treatments under clinical guidance.
Analysis of the Effects of Known Sleep-Support Supplements in Relation to Life Habits, Sleep Conditions, and Sleep Problems
Nutrients (2023) · Rct · n=160
All the tested supplements were found to ameliorate sleep problems significantly (Analysis 1).
Limited direct GABA supplementation studies. Most evidence comes from GABA receptor agonist research showing somnolence as primary effect (RR 4.56). Effectiveness estimates are conservative given sparse direct supplementation data and questionable oral bioavailability of GABA across blood-brain barrier.
Meta-analysis (n=897) and multiple RCTs support sleep benefits. Studies often used L-theanine in combination with other compounds, limiting pure L-theanine effect attribution. Effects include reduced sleep onset latency and improved subjective sleep quality.
AI-estimated from published studies. Interpret as directional guidance.
L-Theanine has a higher evidence score (9/10 vs 8.5/10) and wins in 2 of 3 categories.
For reduce anxiety & stress, L-Theanine has a higher relevance score (85 vs 75).
No known interactions between GABA and L-Theanine have been documented in our database. However, always consult a healthcare provider before combining supplements.