Iodine
Also known as: Iodide, Potassium iodide, Iodised salt
Systematic reviews and controlled trials in populations with iodine deficiency show that oral iodine (including iodised oil or tablets) increases urinary iodine, reduces goitre prevalence and corrects biochemical markers of deficiency. Effects on child cognitive outcomes are mixed and trial quality is variable. In pregnancy, supplementation can prevent deficiency but in iodine-sufficient or mildly deficient populations higher-dose supplements (around ≥200 μg/day) have been associated with altered maternal thyroid function (increased risk of elevated TSH). Reported adverse effects in trials were generally uncommon and transient.
Last reviewed: 2026-10-14 · 5 indexed studies
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Overview
Iodine is an essential trace mineral required for thyroid hormone synthesis. Oral iodine supplementation is used to prevent iodine deficiency disorders, reduce goitre prevalence and meet increased needs in pregnancy and lactation.
Mechanism & Function
Mechanism of Action
Iodine is an essential substrate for thyroid hormone (T3/T4) synthesis; adequate iodine availability is necessary for normal production of thyroid hormones which regulate growth, neurodevelopment and metabolism. Supplementation restores iodine supply in deficiency, normalising thyroid hormone production and reducing TSH-driven thyroid enlargement (goitre).
Physiological Role
Precursor for thyroid hormones; supports fetal neurodevelopment via maternal thyroid hormone production; involved in metabolic rate regulation.
Primary Pathways
Performance / Health Relevance
In populations with insufficient iodine intake, correcting deficiency supports normal thyroid function and, during pregnancy, may help provide adequate maternal thyroid hormone for fetal development. Evidence does not consistently show cognitive or physical performance benefits beyond correction of deficiency.
Evidence Review
Practical Use & Dosage
- Minimum Effective Dose
- Varies by population; many trials used doses in the 100–200 μg/day range or iodised oil formulations.
- Optimal Range
- Not established from the provided abstracts; common trial doses include ~100–200 μg/day.
- Upper / Caution Level
- Not established in these abstracts. Observational data reported increased risk of elevated TSH with supplemental doses ≥200 μg/day in pregnancy in an iodine-sufficient/mildly deficient population.
- Timing
- Daily oral dosing; used during preconception, pregnancy and postpartum in trials/reviews.
- Best Format
- Tablets, drops, iodised oil (depending on setting); oral formulations used in trials.
- Bioavailability
- Iodide salts and iodised oil were used in trials; urinary iodine increases reliably after supplementation.
- Absorption Considerations
- Rapidly bioavailable as iodide; baseline iodine status influences biochemical and clinical responses.
Safety & Interactions
Side Effects
- •Transient minor adverse effects reported in a small percentage of children in trials
- •Possible perturbation of maternal thyroid function with higher supplemental doses in iodine-sufficient/mildly deficient populations
Contraindications
- None specified in these abstracts beyond population-specific caution (see whoShouldAvoid)
Drug Interactions
- •Not detailed in the provided abstracts
Who Should Avoid
- •Pregnant women in iodine-sufficient areas should use caution and follow local guidance due to possible thyroid function changes with supplemental doses ≥200 μg/day
Monitoring
In pregnancy or when supplementing in populations where iodine sufficiency is possible, monitoring maternal thyroid function (TSH, free T4) and assessing baseline iodine status is prudent.
Frequently Asked Questions
Auto-generated from indexed evidence — dosage, safety, interactions, and more.
When is Iodine typically used or indicated?
Iodine is most commonly used for: Prevention of iodine deficiency, Support for normal thyroid function, Pregnancy and lactation supplementation. Precursor for thyroid hormones; supports fetal neurodevelopment via maternal thyroid hormone production; involved in metabolic rate regulation.
How does Iodine work?
Iodine is an essential substrate for thyroid hormone (T3/T4) synthesis; adequate iodine availability is necessary for normal production of thyroid hormones which regulate growth, neurodevelopment and metabolism. Supplementation restores iodine supply in deficiency, normalising thyroid hormone production and reducing TSH-driven thyroid enlargement (goitre).
What is the recommended dose of Iodine?
The optimal range is Not established from the provided abstracts; common trial doses include ~100–200 μg/day.. with a minimum effective dose of Varies by population; many trials used doses in the 100–200 μg/day range or iodised oil formulations.. Best taken: Daily oral dosing; used during preconception, pregnancy and postpartum in trials/reviews.. Upper / caution level: Not established in these abstracts. Observational data reported increased risk of elevated TSH with supplemental doses ≥200 μg/day in pregnancy in an iodine-sufficient/mildly deficient population..
What are the side effects of Iodine?
Reported side effects include: Transient minor adverse effects reported in a small percentage of children in trials; and Possible perturbation of maternal thyroid function with higher supplemental doses in iodine-sufficient/mildly deficient populations. Monitoring: In pregnancy or when supplementing in populations where iodine sufficiency is possible, monitoring maternal thyroid function (TSH, free T4) and assessing baseline iodine status is prudent.
Does Iodine interact with medications?
Known or theoretical interactions: Not detailed in the provided abstracts. Always check with a clinician before combining with prescription medication.
Who should avoid Iodine?
Iodine is generally not recommended for: Pregnant women in iodine-sufficient areas should use caution and follow local guidance due to possible thyroid function changes with supplemental doses ≥200 μg/day; and None specified in these abstracts beyond population-specific caution (see whoShouldAvoid).
How strong is the evidence for Iodine?
Evidence level: Moderate (overall score 59/100), based on 5 indexed studies on SuppIndex.
Research & References (5)
Systematic review on evidence-based adolescent nutrition interventions.
Systematic review of adolescent and reproductive-age nutrition interventions including micronutrients, noting a paucity of trials specifically on iodine in adolescents.
WITHDRAWN: Iodine supplementation for preventing iodine deficiency disorders in children.
Cochrane review protocol/record on iodine supplementation for preventing iodine deficiency disorders in children (withdrawn record); identified multiple controlled trials in deficient areas with heterogeneous quality.
Iodine intake and maternal thyroid function during pregnancy.
Cross-sectional study of 1844 pregnant women in Spain assessing iodine intake and maternal thyroid function before 24 weeks' gestation.
Iodine supplementation for preventing iodine deficiency disorders in children.
Cochrane systematic review (search to Oct 2003) of iodine supplementation in children living in areas of iodine deficiency, including 26 prospective controlled trials.
Iodine supplementation for women during the preconception, pregnancy and postpartum period.
Cochrane review of iodine supplementation during preconception, pregnancy and postpartum including 11 trials (>2700 women) assessing benefits and harms.
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Research Overview
Moderate EvidenceCite this ingredient
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Stable URL
https://thesuppindex.com/ingredients/iodine
SuppIndex. (2026). Iodine: Evidence summary, dosage and clinical studies. Retrieved October 16, 2026, from https://thesuppindex.com/ingredients/iodine
Based on 5 indexed studies · Evidence level: Moderate.
Goal Ratings
Stack Compatibility
Often included in prenatal multivitamin/mineral formulations; interactions with other micronutrients not detailed in provided abstracts.