Supplement
L-Theanine
Calm focus in a capsule, best known next to caffeine.
L-theanine is an amino acid found in tea leaves. We grade L-Theanine B- on evidence and B for worth-it at about $10-15 per month.
Evidence
Worth it
Typical cost: $10-15/month
What it does
L-theanine is an amino acid found in tea leaves. It promotes alpha brain-wave activity associated with relaxed alertness, and it is most studied in combination with caffeine, where it smooths the stimulant edge.
What the research says
May promote relaxed alertness, especially with caffeine
Evidence: moderate. Several small RCTs show improved attention measures with the caffeine-theanine combo.
May support sleep quality as part of a stack
Evidence: emerging. Mostly studied within multi-ingredient sleep stacks, not alone.
DRAFT: consistent small-trial signal for calm focus; standalone sleep evidence is thinner.
What the experts say
Every position links to its source. We include skeptics alongside supporters.
Andrew Huberman
“Don't take theanine if you have overly intense dreams, sleep-walk, or have night terrors.”
Source, 2021 Includes 100-400mg theanine in his nightly sleep stack; cautions against it with vivid dreams, sleepwalking, or night terrors.
Daniel Amen
Source, 2023-01-25 Psychiatrist and brain-imaging specialist who lists theanine among the top supplements he recommends for patients experiencing tension or anxiety, alongside magnesium, ashwagandha, and GABA.
Is it worth it?
DRAFT: cheap with a real calm-focus signal.
Typical cost
$10-15/month
Common form, not a brand recommendation
Dosage contextemerging
100 to 400 mg, often taken with caffeine; the studied range.
Safety notes
Well tolerated in studies. Can cause vivid dreams in some people. Talk to your doctor if you take blood pressure medication. This page is information, not medical advice.
Longevity Lab Report
L-Theanine news, graded when it happens.
New studies, dose debates, and expert shifts on l-theanine, in one email a week. Free.
Changelog
Last updated 2026-10-15
- 2026-10-15|Batch 1 expansion entry, DRAFT. Grades provisional; expert positions unsourced unless noted.
- 2026-10-15|Goals/dosage added; prescription flag set where applicable.