Iodine
Essential for thyroid hormone synthesis. Most people get enough from salt or seafood, but those who don't are genuinely deficient.
Adequate iodine prevents cretinism, goiter, and hypothyroidism — among the highest-impact public health interventions ever. Supplementing when not deficient provides no benefit; high-dose supplementation in already-replete people can trigger autoimmune thyroid disease (especially Hashimoto's flares).
Iodine is the structural atom in thyroid hormones (T3 has three iodines, T4 has four). Without it, the thyroid can't produce hormones, the body slows down, and a goiter develops. Mandatory salt iodisation eliminated severe deficiency across most of the developed world a century ago — but people on low-sodium diets, sea-salt-only diets, plant-based diets without seaweed, and pregnant women in particular can still fall short. Iodine has a narrow therapeutic window: too little causes hypothyroidism, too much can cause hyperthyroidism, autoimmune flares, or thyroid suppression.
- Form
- Potassium iodide (the standard, used in iodised salt and most supplements). Nascent iodine (atomic form, marketed as faster-absorbing — evidence for advantage is weak). Lugol's solution (iodine + potassium iodide combo, traditional clinical form). Kelp / seaweed is variable and can deliver erratic doses — fine as food, less so as a measured supplement.
- Dose
- 150 mcg/day RDA for adults. 220 mcg in pregnancy, 290 mcg in lactation. Multivitamins typically deliver 100–200 mcg. High-dose protocols (12–50 mg of Lugol's) are controversial — proceed only under supervision with thyroid monitoring.
- Timing
- AM with food. Anytime really.
- Schedule
- Daily.
- Side effects
- Acne (especially at higher doses). Metallic taste. Rarely: thyroid suppression or hyper-stimulation, acneiform rash, mucosal irritation.
- Interactions
- Lithium (additive thyroid suppression). Amiodarone (already iodine-rich). Anti-thyroid drugs (methimazole, PTU) — opposing actions. ACE inhibitors / potassium-sparing diuretics (if taking potassium iodide).
- Contraindications
- Autoimmune thyroid disease (Hashimoto's, Graves') — additional iodine can trigger flares. Always test thyroid antibodies (TPO, TgAb) before high-dose iodine. Active hyperthyroidism. Iodine-induced hyperthyroidism.
- Lab markers
- Urinary iodine (the standard population marker — preferably 24-hour collection). TSH, free T4, free T3 to assess thyroid function. TPO antibodies before high-dose iodine.
- Food sources
- Sea vegetables (kelp, nori, wakame, dulse — extremely high, almost too high). Seafood (cod, shrimp, tuna). Dairy (cows are supplemented or get iodine from feed). Eggs. Iodised salt — the simplest answer for most people. Note: sea salt is NOT a good iodine source unless specifically iodised.
Pairs with
Selenium (required for thyroid hormone conversion T4 → T3 and for protecting the thyroid from iodine-induced oxidative damage — these two should usually travel together). Zinc, iron, tyrosine (other thyroid cofactors).
within Minerals