Iodine
Research reviewed: Up until 03/2026
Iodine (Iodide / Elemental Iodine) is a dietary supplement with 8 published peer-reviewed studies involving 4,120 participants, researched for Thyroid Function, Cognitive Development, Breast Health and 1 more areas.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Thyroid Function
StrongCognitive Development
ModerateBreast Health
ModerateAntioxidant & Immune Support
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Thyroid Function
To assess the effect of iodine supplementation on thyroid hormone levels and thyroid volume in mildly iodine-deficient adults.
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To assess the effect of iodine supplementation on thyroid hormone levels and thyroid volume in mildly iodine-deficient adults.
Dose
150 µg/day iodine
Participants
241 adults with mild iodine deficiency
Duration
24 weeks
Results
Iodine supplementation significantly increased urinary iodine, normalised TSH, and reduced thyroid volume compared to placebo. Free T4 increased modestly, indicating improved thyroid hormone production.
How They Measured It
Serum T3, T4, TSH; thyroid volume by ultrasound; urinary iodine
To quantify the effect of iodine supplementation on thyroid size in school-age children and adults.
Study Type
Meta-analysis
Purpose
To quantify the effect of iodine supplementation on thyroid size in school-age children and adults.
Dose
Various (iodised salt and supplements)
Participants
Pooled from multiple RCTs
Duration
12-24 months
Results
Iodine supplementation significantly reduced goitre prevalence and thyroid volume in iodine-deficient populations. The effect was consistent across different geographical regions.
How They Measured It
Thyroid volume by ultrasound across pooled RCTs
Cognitive Development
To evaluate iodine supplementation on cognitive function in mildly iodine-deficient school children.
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate iodine supplementation on cognitive function in mildly iodine-deficient school children.
Dose
400 µg/day iodine
Participants
310 school children aged 10-13 with mild iodine deficiency
Duration
28 weeks
Results
Iodine supplementation significantly improved perceptual reasoning and cognitive performance in mildly iodine-deficient children compared to placebo. Improvements were most marked in attention and information processing.
How They Measured It
Cognitive assessment battery: information processing, memory, attention
To summarise the evidence on iodine deficiency and cognitive impairment in children and pregnant women.
Study Type
Systematic review
Purpose
To summarise the evidence on iodine deficiency and cognitive impairment in children and pregnant women.
Dose
Various
Participants
Multiple study populations globally
Duration
Various
Results
Iodine deficiency is the leading preventable cause of cognitive impairment worldwide. Supplementation during pregnancy and early childhood protects against developmental delay and improves cognitive scores.
How They Measured It
Review of RCTs and cohort studies on iodine status and cognitive outcomes
Breast Health
To evaluate molecular iodine supplementation on fibrocystic breast disease symptoms.
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate molecular iodine supplementation on fibrocystic breast disease symptoms.
Dose
3-6 mg/day molecular iodine (I₂)
Participants
145 women with fibrocystic breast disease
Duration
6 months
Results
Molecular iodine significantly reduced breast pain and nodule size compared to placebo. Responder rates were significantly higher in the iodine group (72% vs 33%). No thyroid function changes were observed.
How They Measured It
Pain scores (VAS), breast nodule size by ultrasound, subjective assessment
Antioxidant & Immune Support
To examine the antioxidant and anti-inflammatory properties of iodine beyond thyroid function.
Study Type
Review
Purpose
To examine the antioxidant and anti-inflammatory properties of iodine beyond thyroid function.
Dose
N/A
Participants
N/A
Duration
N/A
Results
Iodine acts as an electron donor capable of quenching reactive oxygen species. Iodolipids formed from molecular iodine have demonstrated anti-inflammatory and antioxidant properties in mammalian tissues, particularly in breast and thyroid tissue.
How They Measured It
Review of mechanistic studies on iodine oxidative chemistry
To assess iodine supplementation on immune function markers in iodine-deficient subjects.
Study Type
Randomised, controlled trial
Purpose
To assess iodine supplementation on immune function markers in iodine-deficient subjects.
Dose
200 µg/day iodine
Participants
62 mildly iodine-deficient adults
Duration
12 weeks
Results
Iodine supplementation normalised thyroid-mediated immune regulation, improving lymphocyte proliferation responses and NK cell activity in previously deficient individuals.
How They Measured It
Lymphocyte proliferation assays, serum immunoglobulins, NK cell activity
To evaluate the antibacterial and antifungal properties of elemental iodine in wound models.
Study Type
Animal study
Purpose
To evaluate the antibacterial and antifungal properties of elemental iodine in wound models.
Dose
Topical iodine application
Participants
Rodent wound infection model
Duration
14 days
Results
Topical iodine effectively reduced bacterial load in infected wounds and accelerated healing compared to vehicle control. Broad-spectrum antimicrobial activity was confirmed against Gram-positive and Gram-negative bacteria.
How They Measured It
Bacterial colony counts, wound healing rate, histological scoring
Frequently Asked Questions
Common questions about Iodine research
There are currently 9 peer-reviewed studies on Iodine (Iodide / Elemental Iodine), involving 4,120 total participants. Research covers Thyroid function, Cognitive development, Breast health and 1 more areas. The overall evidence strength is rated as Very Strong.
The evidence is currently rated as "Very Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (7 human studies, 1 animal study), and reported outcomes.
Iodine has been researched for: Thyroid function, Cognitive development, Breast health, Antioxidant & immune support. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 7 out of 9 studies are human trials. The remaining 1 is an animal study. Human trials carry more weight in our evidence scoring system.
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