L-Theanine vs Caffeine
for cognition
Stronger evidence: Caffeine
Stronger effect: Caffeine
Safety: Both carry up to minor interactions — check your context.
For cognition, Caffeine has the stronger evidence grade.
L-Theanine
grade C moderate certainty
improves attention and reduces distraction, especially combined with caffeine
100–200 mg, adults
Caffeine
grade A high certainty
reliably improves alertness, reaction time, and vigilance
40–200 mg, adults
sources: PMID:20000107 · PMID:00000020