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Head-to-head evidence comparison — which supplement is right for you?
GABA vs L-Theanine: L-Theanine has the stronger overall evidence (6 vs 4/10); they're alternatives for reduce anxiety & stress — the best pick depends on your goals. Take the 60-second quiz for a pick tailored to your goals.
L-Theanine wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Too few graded studies
Top outcomes
Verdict
Too few graded studies
1 of 1 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.
250-300 mg (the one cited trial that states its dose used 300 mg a day). Label ranges go up to 750 mg, above that dose.
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
A systematic analysis of studies on how various herbal medicines act on GABA receptor subtypes in the context of sleep. It reviews mechanisms, not trials of GABA supplements.
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
80 children aged 5 to 16 with ADHD (38) or autism (42) took a probiotic (Lactiplantibacillus plantarum and Levilactobacillus brevis, strains linked to dopamine and GABA production) or placebo for 12 weeks. No GABA was given.
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=30
30 sedentary women with overweight or obesity doing physical exercise took GABA 200 mg or placebo once daily for 90 days.
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).
Single-dose trials of L-theanine alone. In a crossover trial of 27 young adults given 100, 200 and 400 mg (PMID 32777998), only 400 mg shortened the P3b attention signal, and no dose changed reaction time. In a crossover trial of 20 healthy men, 200 mg improved recognition reaction time (PMID 26869148). In a crossover trial, 250 mg alone raised headache ratings and lowered correct serial subtractions, and the benefits came with caffeine (PMID 18006208). Most cognitive gains in this literature are for L-theanine combined with caffeine, which this curve does not show. The 400 mg ceiling rests on an 8-week trial of 80 schizophrenia inpatients, where side effects at 400 mg a day matched placebo (PMID 37697164). No trial found a best dose.
AI-estimated from published studies. Interpret as directional guidance.
L-Theanine has a higher evidence score (6/10 vs 4/10) and wins in 2 of 3 categories.
For reduce anxiety & stress, L-Theanine has a higher relevance score (85 vs 75).
No documented interaction was found in the data searched. This does not establish that this exact combination is safe.
Ashwagandha, L-theanine, magnesium, saffron — what actually helps stress, and the safety caveats.
Melatonin, magnesium, glycine, L-theanine — tiered by evidence, plus a wind-down timeline.
The honest tier list — proven staples vs situational vs mostly marketing. The hub the other guides feed into.
Caffeine+L-theanine works; bacopa needs weeks; most "brain pills" are hype. The honest tier list.
The right pick depends on your goals. Answer a few quick questions for a personalised recommendation — or dig into the full evidence on each.