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Head-to-head evidence comparison — which supplement is right for you?
L-Theanine vs Thiamine: Thiamine has the stronger overall evidence (7.5 vs 6/10); 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.
Thiamine wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Too few graded studies
1 of 1 studies with measurable effects showed benefit.
Top outcomes
Verdict
Too few graded studies
2 of 2 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (1)
Outcomes where both L-Theanine and Thiamine have evidence — compare verdict strength side-by-side.
100-200mg
Morning with coffee for focus, Evening for relaxation, As needed for stress
Suntheanine® capsules or powder
50-100mg daily; 150-600mg benfotiamine for neuropathy
With food, Morning with other B vitamins
Benfotiamine (fat-soluble, higher bioavailability)
30-60 minutes
30-60 minutes
30-60 minutes
Varies
2-4 weeks
4-8 weeks
4-12 weeks
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).
Dietary supplements for dysmenorrhoea
The Cochrane database of systematic reviews (2016) · Meta analysis · n=3101
Supplements versus other supplementsThere was no evidence of a difference in effectiveness between ginger and zinc sulphate (MD 0.02 points, 95% CI -0.58 to 0.62; one RCT, 101 women).
Evaluation of the Efficacy of the Addition of a Combination of Pyrimidine Nucleotides and Vitamin B1 and B12 to Standard Treatment in the Management of Painful Radiculopathy and in the Quality of Life of Patients
Nutrients (2024) · Rct · n=122
Both groups showed pain improvement, but the VAS reduction (control: 24.58 vs. experimental: 31.35) was not statistically significant.
Efficacy of B-vitamins and vitamin D therapy in improving depressive and anxiety disorders: a systematic review of randomized controlled trials
Nutritional neuroscience (2023) · Systematic review · n=2256
We identified 20 RCTs that matched all eligibility criteria, totaling 2,256 subjects, diagnosed with MDD, GAD, and depressive or anxiety symptoms.
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.
Both points come from one phase III trial of benfotiamine, a fat-soluble thiamine derivative, in 165 patients with diabetic polyneuropathy (BENDIP, PMID 18473286): 300 mg or 600 mg a day or placebo for 6 weeks. The Neuropathy Symptom Score differed between groups in the per-protocol analysis (p = 0.033) and narrowly missed significance in the intention-to-treat analysis (p = 0.055), and the Total Symptom Score did not differ. Improvement was more pronounced at 600 mg, and both doses were well tolerated, so 600 mg, the highest dose tested, is the ceiling. Thiamine hydrochloride doses were not tested and cannot be read off this axis, and one 6-week trial cannot establish a minimum or optimal dose.
AI-estimated from published studies. Interpret as directional guidance.
Thiamine has a higher evidence score (7.5/10 vs 6/10) and wins in 2 of 3 categories.
For sharpen focus, L-Theanine has a higher relevance score (80 vs 20).
No documented interaction was found in the data searched. This does not establish that this exact combination is safe.
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.
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.