Supplement evidence

006 / 575Mineral

Iodine

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The short answer

Preventing iodine deficiency; requirements increase during pregnancy and lactation.

Evidence and scope: Established for an indicated use
This status does not grade the ingredient for every goal, outcome, or person.
Important limitation: Extra iodine does not enhance thyroid function when intake is adequate.
Before deciding: Both deficiency and excess can disrupt thyroid function; seaweed intake already supplies large amounts in Japan.

01 / PRACTICAL GUIDE

Dose, absorption, and combinations

These are indication-specific reference or studied ranges—not a personalized prescription. Start with the objective, then check the form, label, medicines, and health conditions.

Reference range by objective

Meeting usual needs150 mcg/day for most adults

Reference or studied range—not a personalized prescription. The product label or a clinician may specify a different dose.

Dose source ↗

Pregnancy-related need220 mcg/day pregnancy; 290 mcg/day lactation from all sources

Reference or studied range—not a personalized prescription. The product label or a clinician may specify a different dose.

Dose source ↗

More is not automatically better. A clinician or product label may specify a different amount.

Absorption / solubilityWater-soluble

Water-soluble or readily water-dispersible. This does not mean excess is always harmless.

How it is commonly taken

Take consistently; account for seaweed and iodized salt.

Do not combine casually

Avoid stacking iodine with kelp in thyroid disease unless supervised.

Dose and use source ↗

Dose and use links lead to primary or official source material. Search links are discovery tools, not proof that every returned paper applies.

02 / EVIDENCE

What the research says

We keep supportive, mixed, negative, safety, and contextual findings together. The headline never replaces the underlying papers.

5research papers in this ledger

13unique primary studies represented

3,753unique participants represented

These are audited counts for this JIVANA collection, not search-result totals. Participants are counted once when multiple papers use the same cohort; review papers are not added again to participant totals.

Open the research timelineResearch timeline

Entries are ordered by publication year. A study period appears only when the source reports it.

2021

Mixed or qualifiedPMID 33112293

Effects of iodine supplementation during pregnancy on women and their offspring

Supplementation improved iodine-status markers but did not improve pooled birth size or early neurodevelopment. This review overlaps the pregnancy trials above and is displayed without adding to aggregate totals.

Published: 202114 primary studies represented

Study design and methods

Design: Systematic review of 14 trials with five trials pooled for infant outcomes
Population: Pregnant women and their infants across differing iodine-status settings
Intervention: Iodine supplementation during pregnancy versus control
Outcome: Maternal iodine and thyroid markers, birth size, and infant cognitive, language, and motor development

Open research record ↗

2017

Mixed or qualifiedPMID 28260263

Iodine supplementation for women during preconception, pregnancy and postpartum

Evidence was low or very low certainty and insufficient for firm conclusions about routine supplementation. Postpartum hyperthyroidism decreased in three small trials, while digestive intolerance increased in one trial; dose and deficiency setting varied greatly.

Published: 2017n=2,737 participants11 primary studies represented

Study design and methods

Design: Cochrane systematic review of 11 contributing randomized or quasi-randomized trials
Population: 2,737 women before, during, or after pregnancy across iodine-deficient settings
Intervention: Oral or injected iodine at widely varying doses versus no iodine
Outcome: Maternal thyroid outcomes, pregnancy outcomes, adverse effects, and infant outcomes

Open research record ↗

2017

Does not support the tested claimPMID 29030199 · NCT00791466

Effect of iodine supplementation in pregnant women on child neurodevelopment

Supplementation did not improve IQ or executive function at age 5–6. Attrition was substantial, and the result applies to mild deficiency—not severe deficiency, where correcting iodine status remains essential.

Published: 2017Duration: Supplementation to delivery; child follow-up to age 5–6 yearsn=832 participants

Study design and methods

Design: Randomized, double-blind, placebo-controlled trial in India and Thailand
Population: 832 mildly iodine-deficient pregnant women; about 315 children completed neurodevelopment testing
Intervention: Iodine 200 µg/day from early pregnancy until delivery or placebo
Outcome: Child verbal and performance IQ and executive function

Funding or conflict note: Funded by public and academic sources plus the Nestlé Foundation; the trial reported no neurodevelopment benefit.

Open research record ↗

2009

Supports a specific usePMID 19726593 · ACTRN12608000222347

Iodine supplementation improves cognition in mildly iodine-deficient children

Iodine status improved and the overall cognitive score was 0.19 SD higher, driven by two reasoning subtests; two other subtests did not improve. This supports correcting documented deficiency, not supplementing iodine-replete children.

Published: 2009Duration: 28 weeksn=184 participants

Study design and methods

Design: Randomized, double-blind, placebo-controlled trial
Population: 184 New Zealand children aged 10–13 with mild iodine deficiency
Intervention: Iodine 150 µg/day or placebo
Outcome: Iodine status and four cognitive subtests

Open research record ↗

2006

Safety signalPMID 16807415

Effect of iodine intake on thyroid diseases in China

More-than-adequate and excessive intake were associated with more subclinical hypothyroidism and autoimmune thyroiditis. Regional exposure and observational design prevent a precise supplement dose-effect estimate, but support avoiding indiscriminate high-dose iodine.

Published: 2006Duration: 5 yearsn=3,761 participants

Study design and methods

Design: Prospective regional cohort comparing different population iodine exposures
Population: 3,761 unselected adults at baseline; 3,018 completed follow-up
Intervention: Regional exposure ranging from mildly deficient to more-than-adequate and excessive iodine intake
Outcome: Overt and subclinical hypothyroidism and autoimmune thyroiditis

Open research record ↗

Unscreened discovery appendix—not evidence175 candidate publicationsSearch run: Aug 21, 2026

Complete for the displayed PubMed query at the search timestamp—not for all databases or every possible synonym. Candidates can be irrelevant, duplicate the same study, or report negative findings. They are never summed as evidence or participants until screened.

03 / SOURCES

Start with the source material

Official evidence overviewNIH Office of Dietary Supplements Live PubMed discovery searchNational Library of Medicine

The live search is for discovery only. Search-result counts change and are not included in the audited totals above.

Recent PubMed discovery recordsDirect links to the first 12 records returned by the reproducible search. These are discovery candidates—not reviewed summaries or a count of supportive findings.

04 / EXPERT CONTEXT

Expert context—not evidence

Expert positions are dated context—not scientific evidence. They never raise the evidence status or become consensus by repetition.

No direct, source-verified endorsement is currently recorded. Research authorship or discussion alone is not treated as endorsement.