Iodine
The thyroid mineral. Iodine is incorporated into every molecule of thyroid hormone. Without it, metabolism grinds to a halt. Deficiency remains common even in developed countries.
🦋 Iodine in Thyroid Hormones
T4 (Thyroxine)
Contains 4 iodine atoms. The storage/transport form. Relatively inactive. Must be converted to T3 by selenium-dependent deiodinase enzymes.
T3 (Triiodothyronine)
Contains 3 iodine atoms. The active form. Binds to receptors in nearly every cell to regulate metabolism, energy, and gene expression.
The thyroid gland concentrates iodine to ~30x plasma levels to make these hormones.
⚠️ Halogen Displacement
Other halogens compete with iodine for uptake. Modern environments are high in iodine-blockers:
Bromine
Bread (bromated flour), flame retardants, pesticides, pools/hot tubs
Fluorine
Water fluoridation, toothpaste, some medications
Chlorine
Tap water, pools, cleaning products
These halogens can occupy iodine receptors and block thyroid hormone production even when dietary iodine seems adequate.
🔻 Iodine Deficiency
Iodine deficiency causes hypothyroidism and is the #1 preventable cause of intellectual disability worldwide:
Goiter
Thyroid enlargement as it works harder
Hypothyroidism
Fatigue, weight gain, cold intolerance
Cognitive Issues
Brain fog, memory problems
Pregnancy
Miscarriage, developmental delays, cretinism
Fibrocystic Breasts
Breast tissue also concentrates iodine
Dry Skin/Hair
Secondary to hypothyroidism
🌊 Food Sources
Best Sources
- • Seaweed (kelp, nori, wakame)
- • Cod and other fish
- • Shrimp and shellfish
- • Dairy products (variable)
- • Eggs
Other Sources
- • Iodized salt (76mcg/1/4 tsp)
- • Lima beans
- • Prunes
- • Cranberries
- • Strawberries (small amounts)
Note: Seaweed iodine content varies dramatically (kelp can have 2000+ mcg per gram). Start low.
💊 Supplementation Considerations
Start Low, Go Slow
Sudden high iodine in deficient people can trigger thyroiditis or hyperthyroidism. Start with 150-300mcg and increase gradually.
Support Nutrients
Selenium (for T4→T3 conversion), iron (for TPO), vitamin A, and zinc should be adequate before increasing iodine significantly.
Hashimoto's Caution
High-dose iodine may worsen autoimmune thyroiditis in some people. Work with a practitioner if you have Hashimoto's.
Forms
Potassium iodide, Lugol's solution, nascent iodine, kelp supplements. Some protocols use both iodine and iodide (Lugol's).
🧪 Testing Iodine Status
Urinary Iodine
24-hour collection or spot urine. Most accurate for population studies. Optimal: 100-200 mcg/L.
Iodine Loading Test
Take 50mg iodine, measure 24h urine. Less than 90% excreted suggests deficiency/saturation.
Metabolic Connections
Thyroid
Iodine is the core component of thyroid hormones T4 and T3
Selenium
Required for converting T4 to active T3
Iron
Thyroid peroxidase needs iron to incorporate iodine
Zinc
Supports thyroid hormone receptor function
Vitamin A
Required for thyroid hormone synthesis
Bromine
Competes with iodine for uptake (halogen displacement)