Caffeine vs Iron

for cognition

Stronger evidence: Caffeine

Stronger effect: Caffeine

Safety: Caffeine carries a minor interaction; Iron has none recorded.

For cognition, Caffeine has the stronger evidence grade.

grade A high certainty

reliably improves alertness, reaction time, and vigilance

40–200 mg, adults

grade C low certainty

improves attention/cognition when iron deficiency is present; no benefit if replete

18–65 mg/day, iron-deficient adults

sources: PMID:00000020 · PMID:20000115