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Head-to-head evidence comparison — which supplement is right for you?
L-Theanine wins 3 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Likely helps
5 of 5 studies with measurable effects showed benefit.
Top outcomes
Verdict
Likely helps
3 of 4 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (1)
Outcomes where both Alpha-GPC and L-Theanine have evidence — compare verdict strength side-by-side.
300-600mg daily
Morning for cognitive enhancement, 30-60 min before workout for performance
Alpha-GPC 50% powder or capsules
100-200mg
Morning with coffee for focus, Evening for relaxation, As needed for stress
Suntheanine® capsules or powder
1-2 hours
2-4 weeks
Acute
Same day
30-60 minutes
30-60 minutes
30-60 minutes
Varies
L-Alpha-Glycerylphosphorylcholine (L-α-GPC): A Comprehensive Review of Its Preparation Techniques and Versatile Biological Effects
Journal of food science (2025) · Systematic review
Due to its high choline content (41% by weight) and ability to cross the blood-brain barrier, GPC is considered one of the most utilized sources of choline.
Activity of Choline Alphoscerate on Adult-Onset Cognitive Dysfunctions: A Systematic Review and Meta-Analysis
Journal of Alzheimer's disease : JAD (2023) · Meta analysis · n=1326
We found significant effects of α-GPC in combination with donepezil on cognition [4 RCTs, mean difference (MD):1.72, 95% confidence interval (CI): 0.20 to 3.25], functional outcomes [3 RCTs, MD:0.79, 95% CI: 0.34 to 1.23], and behavioral outcomes [4 RCTs; MD: -7.61, 95% CI: -10.31 to -4.91].
Revisiting choline alphoscerate profile: a new, perspective, role in dementia?
The International journal of neuroscience (2013) · Systematic review
Choline alphoscerate (alpha-glyceryl-phosphorylcholine, alpha-GPC) is a semisynthetic derivative of phosphatidylcholine with central parasympathomimetic action.
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).
Based on RCTs showing cognitive improvements in healthy adults and dementia patients. Effect sizes were modest and some studies used combination therapy. Higher doses associated with increased headache risk.
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 3 of 3 categories.
Both Alpha-GPC and L-Theanine score equally (80) for sharpen focus.
No known interactions between Alpha-GPC and L-Theanine have been documented in our database. However, always consult a healthcare provider before combining supplements.