Approximate dose-response bands. Individual response varies — these are starting points, not prescriptions.
Well below target. Risk of deficiency symptoms tied to thyroid hormones.
Below the recommended daily target. Long-term adequacy not assured.
Daily target met. Standard nutritional support for thyroid hormones.
Common for specific health goals. Check the evidence for your situation before sustaining this level.
Approaching the tolerable upper limit. Monitor and consider clinical guidance.
Above the tolerable upper limit. Risk of adverse effects — back off or consult a clinician.
You're at 0% of your iodine target. The biggest single-serving sources to top it off:
Trace mineral required for thyroid hormone synthesis (T3, T4) and only thyroid hormone synthesis. Universal salt iodisation programs have eliminated cretinism and goitre across most of the world, but deficiency remains a public health issue and excess from kelp supplements can trigger thyroid dysfunction.
Iodide is actively transported into the thyroid follicular cell via the Na/I symporter (NIS), oxidised by thyroid peroxidase, and incorporated into tyrosine residues on thyroglobulin to form MIT and DIT. Coupling produces T4 and T3, stored in colloid, and released into circulation under TSH stimulation. Severe iodine deficiency in pregnancy causes irreversible neurological damage in offspring.
Mild-to-moderate deficiency affects ~2 billion people globally despite iodisation programs. Pregnant women in regions without iodised salt or seafood are highest risk.
Excess can trigger hypothyroidism (Wolff-Chaikoff effect) or hyperthyroidism (Jod-Basedow), particularly in adults with subclinical thyroid nodules. Kelp supplements are the typical culprit — content varies 100× batch-to-batch.
Potassium iodide (from a multivitamin or prenatal at 150 mcg) is reliable. Kelp-based supplements vary 100× in iodine content batch-to-batch and can deliver doses far above the UL. Pregnant and breastfeeding women should specifically check that their prenatal contains iodine — many do not.
Iodide is ~95% absorbed. Iodine bound to algae (kelp) or amino acids requires more digestion but is also well-absorbed. The thyroid concentrates iodide ~30–40× plasma levels via the Na/I symporter.
Adequacy throughout life supports normal metabolic rate, cognition, and fertility. Pregnancy iodine deficiency has the largest population-level legacy effect — IQ reductions persist for the child's lifetime. Excess from kelp / unregulated supplements is the modern over-correction.
Thyroid hormone (T3/T4) synthesis.
The mechanisms and systems this nutrient feeds. Click any to drill into what runs on it.
★ = load-bearing / primary cofactor. Track these in My Journey.
Whole foods that contribute meaningfully (≥10% DV per 100 g serving). Click any food to see its full nutrient profile and what else it brings to the table.
See all foods high in Iodine, ranked →