L-Theanine vs Iron

for cognition

Stronger evidence: tie

Stronger effect: L-Theanine

Safety: L-Theanine carries a minor interaction; Iron has none recorded.

For cognition, the two are evidence-matched; the difference is in effect and safety.

grade C moderate certainty

improves attention and reduces distraction, especially combined with caffeine

100–200 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:20000107 · PMID:20000115