PrometheusGeneral

L-Theanine and Caffeine

Each entry’s own grades, side by side. A grade says how strong the evidence is for one outcome — it does not rank one entry over the other.

Compound or practice

L-Theanine

The calm in green tea — pairs with caffeine to keep the focus and drop the jitter.

Grade B3 graded outcomesrevised Jul 10, 2026

A structured monograph in Prometheus's bundled library. Its grades are the monograph's own reading of the evidence, not a peer-reviewed review.

Compound or practice

Caffeine

The most-used and best-evidenced cognitive and physical stimulant on earth — precise dosing and a hard afternoon cutoff are the whole skill.

Grade A4 graded outcomesrevised Jul 10, 2026

A structured monograph in Prometheus's bundled library. Its grades are the monograph's own reading of the evidence, not a peer-reviewed review.

Swap the two

Graded in both

Outcomes are matched by name. Two entries can describe the same outcome in different words, so one listed further down may still be graded in the other.

No outcome has the same name in both entries. They may still overlap under different wording — read the two lists below.

Graded only in L-Theanine

  • Attention (with caffeine) Moderate effectEvidence grade B
  • Acute stress / anxiety Small effectEvidence grade B
  • Sleep quality Small effectEvidence grade C

Graded only in Caffeine

  • Alertness / reaction time Moderate effectEvidence grade A
  • Endurance performance Moderate effectEvidence grade A
  • Strength / power Small effectEvidence grade B
  • Sleep (afternoon dosing) Moderate effectEvidence grade A

What each entry says about the other

  • L-Theanine’s entry · Works together: The A-grade nootropic pairing.
  • L-Theanine’s entry · Goes with: The A-grade nootropic pairing.
  • Caffeine’s entry · Works together: The A-grade pairing — focus without the jitter.
  • Caffeine’s entry · Goes with: The A-grade pairing — focus without the jitter.

Both columns are read from the entries as they stand in this library. A comparison is not advice to take either one, and it is no substitute for a clinician who knows the person.