Focus
Attention rides on arousal chemistry: adenosine pressure dragging alertness down, catecholamines pushing it up, and the narrow band between alert and jittery where good work happens. Most focus supplements move one of those dials — caffeine blocks adenosine, and theanine adds a calm-alert signature measurable on EEG.
The ceiling is lower than the marketing implies. The firmest evidence is for caffeine, and for the caffeine–theanine pairing improving attention accuracy beyond either alone. Creatine and rhodiola show narrower, situational signals — sleep loss, exam stress. Sleep itself remains the active ingredient no capsule replaces; the list below is graded accordingly.
Ranked by evidence
- Caffeine 50–200 mg as needed; pairing with l-theanine smooths the edge
- L-theanine 100–200 mg with caffeine for attention work; fine alone for calm alertness
- Creatine monohydrate 3–5 g daily; cognitive support shows mainly under sleep loss or low dietary creatine
- Rhodiola rosea 200–400 mg in the morning during demanding stretches; not an everyday stimulant
Grades are per goal–ingredient pairing, hand-assigned from the evidence records linked on each monograph. Ingredients without a link have a monograph on the way.
What does not work (yet)
- L-theanine alone for demanding attention work. The attention-task data are for the caffeine pairing. Alone, theanine supports calm alertness — a different job.
- Escalating caffeine past your usual intake. Habitual high intake blunts the effect and disturbs sleep. Dose discipline outperforms escalation.
The list above is the general case. Your medications, current stack, budget, and other goals change it — sometimes a lot.