Iron vs Melatonin for cognition: which has better evidence?
Melatonin has the stronger evidence for cognition (Iron Grade C vs Melatonin Grade B). For cognition, Melatonin has the stronger evidence grade.
Platform evidence comparison
These existing platform assessments are separate from the source-reported findings below. They do not represent a direct trial comparing these treatments.
| Iron | Melatonin | |
|---|---|---|
| Grade | grade C | grade B |
| Certainty | low | moderate |
| Effect | improves attention/cognition when iron deficiency is present; no benefit if replete | Meta-analysis of RCTs in older adults with cognitive impairment: melatonin produced a modest improvement in cognition (MMSE +1.8 points) and total sleep time (+12.4 minutes), with a small reduction in neuropsychiatric symptoms. The authors conclude effects approach — but fall short of — definitive clinical efficacy, with substantial heterogeneity between trials. |
| Studied dose | 18–65 mg/day | varies; taken at bedtime |
| Population | iron-deficient adults | older adults with cognitive impairment |
| Safety | 0 modeled interaction(s) | 1 modeled interaction(s) |
Grade C / low: hints of benefit in small trials; a well-run RCT could easily push this to B or to null.
Direct comparison evidence
There are no direct RCTs in our corpus comparing Iron and Melatonin head-to-head for cognition. What we present above is an indirect comparison: each side's own trials, contrasted. This is standard practice for supplement comparisons — dose, population, and outcome-instrument differences between the two evidence bases add uncertainty on top of each side's own grade.
Can you take both?
No modeled interaction between Iron and Melatonin in our corpus. Absence of a recorded interaction is not proof of additive benefit — combined-effect trials are usually absent for supplement pairs, so treat "stack" claims skeptically.
Decision guidance
- If certainty matters most — choose whichever side carries the higher certainty rating at a similar grade.
- If you're on medications — check each side's interaction pages before deciding; safety differences dominate small evidence-grade gaps.
- If your population is under-studied — the smaller-effect side with better population evidence often wins over the higher-grade side studied in a different demographic.
- If cost matters — form and dose page differences (Iron vs Melatonin) can invert the practical winner.
Grade history
No grade changes yet. Initial grade assigned; re-reviewed on every 6 months (Grade C+) — next review by . Methodology v1.
Re-review cadence: every 6 months (Grade C+) · next scheduled by · methodology v1.
Frequently asked
Which has stronger evidence: Iron or Melatonin for cognition?
Iron carries Grade C at low certainty; Melatonin carries Grade B at moderate. The stronger evidence points to Melatonin, subject to the caveat that direct head-to-head trials are usually absent for supplement pairings.
Can I take Iron and Melatonin together?
No modeled interaction between Iron and Melatonin; combining is not documented to be problematic, but combined-effect trials are also absent, so treat additive benefit claims skeptically.
Have Iron and Melatonin been compared head-to-head?
Direct RCTs comparing the two for cognition are uncommon. This page contrasts each side's own trial evidence — that is an indirect comparison, which introduces confounds from population and dose differences. See the direct-comparison block above.
What decides between Iron and Melatonin for me?
Read the decision guidance below — the split usually comes down to population fit, interaction risk with your other medications, and how much certainty you want behind the recommendation.
Related
Cite this page
Citation is encouraged. The proposed reuse license is CC-BY-4.0; status: pending-governance-ratification.
Plain-text citation
Substrate. Iron vs Melatonin for cognition. https://evidencebased.info/compare/iron-vs-melatonin-for-cognition. Updated 2026-07-14.
BibTeX
@misc{substrate_elatoninforcognition,
author = {Substrate editorial},
title = {Iron vs Melatonin for cognition},
year = {2026},
url = {https://evidencebased.info/compare/iron-vs-melatonin-for-cognition},
note = {evidencebased.info}
}