L-Theanine
Found in green tea. Produces a calm kind of alert rather than drowsiness.
L-theanine is an amino acid naturally found in tea leaves that promotes alpha-wave brain activity associated with relaxed, focused attention, without the sedation of a typical calming supplement. It is commonly paired with caffeine, since it appears to soften the jittery edge of caffeine while the alertness benefit is largely retained, which is why the two often appear together in tea itself and in nootropic blends. Suntheanine, a patented branded form, and generic L-theanine perform comparably, both backed by strong human evidence for this specific calm-focus effect.
Reference values
Daily reference values from official nutrition authorities. These are population reference figures, not personal recommendations.
| RDA | Upper limit | Source |
|---|---|---|
| 200 mg | 1200 mg | UK |
Forms and bioavailability
Not all forms are absorbed equally. The form on your supplement label affects how much your body can actually use.
| Form | Absorption | With food | Timing | Evidence |
|---|---|---|---|---|
| L-theanine | Typical | Either | Either | Strong |
| Suntheanine | Typical | Either | Either | Strong |
How it pairs with other supplements
Works well with
L-theanine modulates alpha waves while 5-HTP supports serotonin; complementary relaxation pathways.
Stack Almanac tracks your L-theanine intake alongside any caffeine you log, so the pairing that's doing the work is visible rather than hidden inside a blend.
Track your L-Theanine in Stack Almanac
Last reviewed: 2026-07-08. Reference values are adult-general RDAs from UK. Individual needs may vary. This page is for informational purposes only and is not a substitute for professional medical advice.