Iodine: Why this tiny mineral matters for your thyroid, brain, and energy

Iodine is a trace mineral that runs the thyroid engine. Too little and your thyroid slows, causing fatigue, weight gain, and goiter. Too much can also cause thyroid trouble. That makes the right balance important — especially if you're pregnant, breastfeeding, or have a known thyroid condition.

How much iodine do you need?

Most adults need about 150 micrograms (mcg) per day. Pregnant women should aim for roughly 220–250 mcg daily because the fetus needs iodine for brain development. Breastfeeding raises the need too, around 250–290 mcg. The tolerable upper limit for adults is 1,100 mcg/day; regularly going above that can trigger hyper- or hypothyroidism in some people.

If you already have autoimmune thyroid disease (like Hashimoto’s or Graves’), talk with your clinician before starting supplements. Iodine can change antibody activity and shift thyroid function unexpectedly.

Food sources, supplements and safety

Iodized table salt is the simplest way to cover basic needs — one teaspoon provides plenty for most people. Natural sources include sea fish (cod, tuna), shrimp, dairy, eggs, and seaweed. Note: seaweed like kelp or kombu can contain hugely variable iodine amounts — one kelp tablet might be safe or wildly excessive.

If you choose a supplement, a standard multivitamin typically gives 150 mcg, which is enough for most adults. If a provider prescribes higher doses for deficiency, they’ll monitor your thyroid. Avoid high-dose kelp supplements unless guided by a clinician, and be cautious about supplements if you take amiodarone, lithium, or are due to have iodinated contrast scans.

Testing for iodine status isn’t routine. A spot urinary iodine test can show recent intake but varies day to day. More useful are thyroid blood tests (TSH, free T4, sometimes antibodies) if you have symptoms. For pregnant women, clinicians may screen more carefully because the stakes for fetal brain development are higher.

Watch for deficiency signs: an enlarged neck (goiter), feeling cold, slow heartbeat, fatigue, dry skin, and unexplained weight gain. In children, even mild deficiency can affect learning and attention. On the flip side, sudden high iodine intake can cause palpitations, sweating, or temporary thyroid overactivity.

Practical tips: if you use iodized salt, eat a balanced mix of fish, dairy, or eggs weekly. If you’re vegan or avoid dairy and live inland without iodized salt, consider a low-dose supplement. Pregnant and breastfeeding people should choose a prenatal that lists 150–250 mcg iodine. Always tell your doctor about supplements so they can check thyroid tests if needed.

Iodine is small but powerful. A little planning — food choices, sensible use of iodized salt, and talking with your clinician when needed — keeps your thyroid running smoothly and protects brain development in pregnancy and early life.