L-Theanine

Consistent small-trial evidence for calm focus, especially synergistic with caffeine. One of the best-tolerated amino acid supplements.

A rough internal score reflecting quantity, quality, and consistency of human evidence. Not a clinical recommendation.

Multiple randomized trials show improvements in subjective calm, attention, and reaction time, particularly when combined with caffeine. EEG studies confirm increased alpha-wave activity within 30–60 minutes of dosing. Effect sizes are moderate.

• Promotes calm focus without drowsiness
• Synergistic with caffeine for attention and alertness
• May modestly improve sleep quality

100–200 mg, often combined with 50–100 mg caffeine. Can also be taken alone before bed for relaxation.

• Rare headache at high doses

Very low risk at normal intakes. Theoretical interaction with blood-pressure medications due to mild hypotensive effect.

Most studies are short-duration, small-sample. The caffeine combination is better studied than theanine alone.

• Focus78
• Anxiety72
• Sleep60
• Stress55