Iodine and Thyroid
Trace Element for Hormone Production
Iodine is a trace mineral that plays a vital role in hormone production—particularly in the thyroid gland. Though needed only in tiny amounts, iodine is essential for synthesizing the two main thyroid hormones: thyroxine (T4) and triiodothyronine (T3). Without adequate iodine, the thyroid cannot produce enough hormones, leading to symptoms of hypothyroidism, the development of goiter, or, in severe cases, growth and developmental delays in children.
Thyroid hormones influence nearly every system in the body, regulating metabolism, energy levels, mood, skin and hair health, body temperature, and even fertility. When iodine is deficient, the thyroid gland struggles to function properly.
How Iodine Supports the Thyroid
The thyroid absorbs iodine from the bloodstream and uses it to manufacture T4 and T3.
When iodine is lacking, the brain sends out signals trying to "push" the thyroid into working harder. Over time, this overstimulation can cause the thyroid to enlarge, forming a goiter—a classic sign of iodine deficiency.
Who’s at Risk of Iodine Deficiency?
While iodized salt has greatly reduced iodine deficiency in many countries, certain individuals remain at higher risk. Vegetarians and vegans may be at risk due to limited seafood consumption, one of the richest natural iodine sources.
Other risk factors include excessive intake of goitrogens—naturally occurring compounds in raw cruciferous vegetables such as broccoli, kale, and cabbage—which can interfere with iodine uptake. Gut health also matters: conditions like small intestinal bacterial overgrowth (SIBO) or malabsorption syndromes can hinder iodine absorption. Exposure to competing halogens like fluoride, chlorine, and bromide—commonly found in water and some medications—may also reduce iodine’s availability to the thyroid.
Pregnant and breastfeeding women have higher iodine needs and must be particularly careful to ensure adequate intake, as both the mother and developing baby depend on sufficient thyroid hormone for healthy development.
Should You Supplement with Iodine?
In certain cases, iodine supplementation may be beneficial—particularly for individuals with confirmed deficiency, thyroid nodules, or goiter, and for women who are trying to conceive or are already pregnant. However, iodine should never be supplemented casually.
Too much iodine can be just as problematic as too little. In people with autoimmune thyroid conditions like Hashimoto’s thyroiditis or Graves’ disease, high doses of iodine may actually worsen inflammation or trigger flare-ups. For this reason, it is crucial to test the level and to start with low doses, assess thyroid antibody status and monitor thyroid function regularly.
Therapeutic iodine dosing—sometimes used in functional or integrative medicine approaches—may involve short-term, higher doses, but should only be done under medical supervision and in combination with selenium to protect the thyroid from oxidative stress.
Food Sources of Iodine
Because the body cannot produce iodine on its own, it must be obtained from food or supplements. Sea vegetables are by far the most concentrated natural sources—kelp, wakame, dulse, and nori offer significant amounts of iodine, though kelp is so potent that overconsumption can pose a risk. Iodized salt remains a reliable and inexpensive source; just a quarter teaspoon provides about 75 micrograms.
Seafood such as cod, shrimp, and sardines offer additional iodine, along with beneficial nutrients like selenium and omega-3 fats. Eggs, dairy products, and even certain fruits like cranberries and strawberries contribute small but meaningful amounts. Some plant-based milks are fortified with iodine—check labels to confirm.
Balancing Iodine for Optimal Thyroid Health
For most adults, the recommended daily iodine intake is 150 micrograms. This increases to 220–250 micrograms for pregnant women and up to 290 micrograms for those who are breastfeeding. While it’s possible to meet these needs through a whole-food diet, individuals with increased demands or restricted diets may benefit from supplementation, provided it’s done thoughtfully and with clinical oversight.
In autoimmune thyroid disease, even small changes in iodine intake can have outsized effects. Co-supplementing with selenium—typically 100 to 200 micrograms per day—can help buffer iodine’s impact and reduce thyroid antibody levels.
Iodine is one of the smallest but most powerful nutrients when it comes to hormone health. Its role in thyroid hormone production makes it indispensable for metabolism, fertility, brain development, and overall vitality. But like all things hormonal, balance is key. Both iodine deficiency and excess can cause serious thyroid dysfunction.
If you suspect you’re deficient, or are navigating a thyroid condition, speak with a knowledgeable healthcare provider before starting supplementation. With targeted support and the right nutritional foundation, you can help your thyroid—and your entire endocrine system—function at its best.
