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Head-to-head evidence comparison — which supplement is right for you?
Alpha-GPC vs L-Theanine: L-Theanine has the stronger overall evidence (6 vs 7/10); they're alternatives for sharpen focus — 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
2 of 2 studies with measurable effects showed benefit.
Top outcomes
Verdict
Too few graded studies
1 of 1 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 (a typical label dose, not the dose used in the cited trial, which gave a single 1,000 mg intramuscular dose)
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) · 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
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) · 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).
Both points come from one placebo-controlled crossover trial of single doses in 20 resistance-trained men (PMID 39683633): Stroop scores improved more than placebo after 315 mg (d = 0.48) and 630 mg (d = 0.61), while the Flanker and N-Back tests did not change. Taken daily for 7 days, 250 and 500 mg did not change psychomotor vigilance in 48 young men (PMID 29042830). In older people with type 2 diabetes and mild cognitive decline, 1,200 mg a day raised MMSE against placebo at 12 months but not at 6 months (PMID 39703111). No trial compared chronic doses.
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 7/10) and wins in 2 of 3 categories.
For sharpen focus, L-Theanine has a higher relevance score (80 vs 40).
No documented interaction was found in the data searched. This does not establish that this exact combination is safe.
Caffeine+L-theanine works; bacopa needs weeks; most "brain pills" are hype. The honest tier list.
The honest tier list — proven staples vs situational vs mostly marketing. The hub the other guides feed into.
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 right pick depends on your goals. Answer a few quick questions for a personalised recommendation — or dig into the full evidence on each.