Caffeine
settled caffeine — well-studied; evidence and use are aligned
⚠ Safety in context
- minorwith L-Theanine: Commonly paired; L-theanine is said to smooth caffeine’s jitter. Low-stakes.
Evidence by outcome
cognitiongrade Ahigh certainty— reliably improves alertness, reaction time, and vigilance
energy / fatiguegrade Bmoderate certainty— reduces perceived fatigue; tolerance develops with regular use
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sources: PMID:00000020 · PMID:00000021