L-Theanine 200mg + Caffeine 100mg (Focus Capsules)
A 2:1 L-theanine to caffeine pairing, the ratio most used in cognition studies. Aims for alert focus with less of the jitter and crash of caffeine alone.
Resar evidence panel
0–100 · cited research only
Evidence Score
83
Strong
Safety Score
71
Good
Effectiveness Score
77
Strong
Research Confidence
77
Strong
Product Fit Score
76
Strong
Bottom line
Strong evidence (Strong) for cognitive enhancement — worth a closer look if this fits your goals.
Individual results vary. Summaries are educational — not medical advice.
Evidence Score
83
Strong
Price
$24.99
Resar may earn an affiliate commission on this purchase. Commissions never change scores — see our affiliate disclosure and conflicts policy. Scores reflect cited research, not medical advice.
Compare others in Cognitive EnhancementTop research
The strongest studies behind this product
Ranked by evidence hierarchy and how closely each study matches this product. Start with the strongest study, then read down. Every claim needs a trail.
The combined effects of L-theanine and caffeine on cognitive performance and mood
Randomized Controlled Trial · Nutritional Neuroscience · 2008 · n=27
What the research shows
Improved accuracy and attention on demanding cognitive tasks.
The effects of L-theanine, caffeine and their combination on cognition and mood
Randomized Controlled Trial · Biological Psychology · 2008 · n=48
Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial
Randomized Controlled Trial · Nutrients · 2019 · n=30
Scores reflect these cited studies, not medical advice. Expand the full evidence detail below for protocols, dose context, and reported side effects.
Claim ledger
Every claim, mapped to its source
Each product claim below is tied to a specific paper with study type, match strength, and limitations. Nothing here is medical advice — it is a research trail you can audit.
Claim match reflects how closely a specific paper supports this benefit — not AI confidence or medical certainty.
Full evidence detail
Study-by-study breakdown
Each paper below is ranked for this listing. Start with the highest match, then expand any study for a plain-language readout.
How to read this section
- Match % - how closely the study matches this product (not overall scientific quality).
- Evidence type - study design (RCT, review, etc.) and whether it is direct, category-level, or indirect.
- What it found - short summary and quoted extract from the paper metadata. Not medical advice.
In plain language
What the study reported
Verified extract — not AI generated
“Improved accuracy and attention on demanding cognitive tasks.”
Studies commonly used a 2:1 theanine:caffeine ratio.
No notable adverse effects at the doses tested.
Caveats
Small acute-dosing study; does not test long-term daily use.
Transparency
Score history
Human review is pending for this listing.
Reviews
Shopper feedback
4.5
average rating
2,043 Amazon reviews were available from the listing metadata.