Iodine
Iodine is a trace element essential for thyroid hormone synthesis, which regulates metabolism, growth, and neurodevelopment. Iodine deficiency remains the leading preventable cause of intellectual disability worldwide, and supplementation is critical in deficient populations, particularly pregnant women and those on plant-based diets.
Quick Verdict
Essential if deficient — particularly critical for pregnant women and those on plant-based diets who avoid iodized salt and dairy.
If you consume iodized salt and dairy regularly, you likely get enough. If you are vegan, avoid iodized salt, or are pregnant, supplementation is strongly recommended. Do not mega-dose — excess iodine can harm the thyroid just as deficiency can.
At a Glance
Dose
150mcg/day for adults
When to Take
Any time of day, with food
Best Form
Potassium iodide
Evidence
83% avg
What It Is
Iodine is a mineral found primarily in seafood, dairy, iodized salt, and seaweed. The thyroid gland concentrates iodine to produce thyroxine (T4) and triiodothyronine (T3), hormones that regulate metabolic rate, growth, and brain development. While iodized salt programs have largely eliminated severe deficiency in developed nations, mild-to-moderate deficiency persists in many populations, especially those avoiding dairy, seafood, and iodized salt.
How It Works
The thyroid gland actively transports iodide from the bloodstream via the sodium-iodide symporter (NIS). Within thyroid follicular cells, iodide is oxidized by thyroid peroxidase and incorporated into thyroglobulin to form T3 and T4. These hormones regulate basal metabolic rate, protein synthesis, and are critical for fetal and infant brain development. Insufficient iodine leads to compensatory thyroid enlargement (goiter), hypothyroidism, and in severe cases during pregnancy, irreversible cognitive impairment (cretinism) in offspring.
Evidence by Goal
cognitive development
Strong evidence that adequate iodine during pregnancy and early childhood is essential for normal cognitive development. Deficiency is the world's leading preventable cause of intellectual impairment.
thyroid function
Iodine is a direct substrate for thyroid hormone synthesis. Supplementation in deficient individuals restores normal thyroid function and prevents goiter.
Dosage & Usage
Standard Dose
150mcg/day for adults
Loading Protocol
250mcg/day during pregnancy and lactation
Timing
Any time of day, with food
Best Form
Potassium iodide (most common), kelp-derived iodine (variable content)
📅 What to Expect
Week 1-4
Iodine incorporated into thyroid. Thyroid hormone synthesis normalizing.
Week 4-8
If deficient: TSH decreasing, T3/T4 normalizing. Energy may improve.
Month 2-3
Thyroid function fully normalized if iodine was the limiting factor.
Ongoing (pregnancy)
Critical throughout pregnancy for fetal brain development. Do not exceed 1100mcg/day.
🎯 How to Know It's Working
Thyroid function normalizes if deficient
Energy and metabolism improve
Less brain fog
If not working: If no improvement after 4 weeks, get thyroid panel checked. Excess iodine can worsen thyroid conditions — don't over-supplement.
🏷️ Buying Guide
✓ Look For
- • Potassium iodide or kelp-derived
- • 150mcg per serving (RDA)
- • Third-party tested for heavy metals
✗ Avoid
- • Mega-doses above 1100mcg (thyroid disruption)
- • Kelp supplements with variable iodine content
🥗 Get It From Food
🛡️ Safety Profile
Common Side Effects
- • metallic taste
- • GI upset at high doses
⚠️ Contraindications
- 🚫 Graves' disease
- 🚫 autonomous thyroid nodules
- 🚫 dermatitis herpetiformis
💊 Drug Interactions
- • lithium (additive hypothyroid effect)
- • anti-thyroid drugs (amiodarone, methimazole)
🔴 Serious Risks
- • thyroid dysfunction (both hypo- and hyperthyroidism) with excess intake
- • iodine-induced thyrotoxicosis in those with autonomous thyroid nodules
Long-Term Safety
Safe at recommended doses (150-250mcg/day). Chronic excess above 1100mcg/day (adult UL) can cause thyroid dysfunction. Populations previously iodine-deficient may be more susceptible to excess.
👥 Who Benefits Most
Best For
- ✓ pregnant and lactating women
- ✓ vegans and vegetarians (limited dietary sources)
- ✓ those avoiding iodized salt and dairy
- ✓ children in iodine-deficient regions
Less Effective For
- — those consuming adequate iodized salt and dairy
- — individuals with Hashimoto's thyroiditis (excess may worsen)
📚 Key Research
3 peer-reviewed studies supporting this supplement's effects.
Iodine deficiency
Zimmermann MB, Jooste PL, Pandav CS · Endocrine Reviews (2009)
Comprehensive review establishing iodine deficiency as the most common cause of preventable brain damage and intellectual disability worldwide.
Mild iodine deficiency during pregnancy is associated with reduced educational outcomes in offspring: a systematic review
Hynes KL, Otahal P, Hay I, Burgess JR · Nutrients (2013)
Systematic review found that even mild iodine deficiency during pregnancy is associated with measurable cognitive deficits in children.
Effect of inadequate iodine status in UK pregnant women on cognitive outcomes in their children
Bath SC, Steer CD, Golding J, et al. · The Lancet (2013)
UK cohort study showing maternal iodine deficiency during pregnancy was associated with lower IQ and reading scores in children at ages 8-9.
💰 Cost & Forms
Estimated Monthly Cost
$4-10
🔗 Related Evidence Reviews
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