Iodine
A trace mineral essential for thyroid hormone production.
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What it is
Iodine is required to make thyroid hormones, which regulate metabolism. Iodized salt and seafood are primary sources; deficiency was largely solved by salt iodization but can recur with certain diets.
How it works
Iodine is a required building block of thyroid hormones, which regulate metabolism, growth, and development. Both too little and too much can disrupt thyroid function.
What it's been studied for
Used to support thyroid function and to prevent deficiency, notably in pregnancy.
What the evidence shows
Iodine is essential and deficiency impairs thyroid function and fetal development. In populations using iodized salt, most people get enough, and both too little and too much can disrupt the thyroid.
Who should consider it
In regions using iodized salt, most people get enough. It matters most in pregnancy (for fetal brain development) and for people who avoid iodized salt, dairy, and seafood. Kelp products can deliver excessive amounts.
Amounts commonly studied
Needs are small (around 150 mcg daily; more in pregnancy). High-dose kelp or iodine products can far exceed safe limits.
How to take it
Needs are small (about 150 mcg daily; more in pregnancy). Prenatal vitamins often include it. Avoid high-dose iodine or large amounts of kelp without guidance, especially with a thyroid condition.
Forms & absorption
Potassium iodide or kelp-based. Prenatal vitamins often include it.
Food sources
Iodized salt, seafood and seaweed, dairy, and eggs.
Safety & interactions
Both deficiency and excess harm the thyroid — avoid high-dose iodine or large amounts of kelp without guidance, especially with existing thyroid conditions.
Myths & what it won't do
Myth: more iodine means a healthier thyroid. Reality: excess iodine can trigger or worsen thyroid problems just as deficiency can. Myth: everyone needs an iodine supplement. Reality: iodized salt and a normal diet cover most people.
Common questions
- Do I need extra iodine?
- Most people using iodized salt don't. Pregnancy and diets low in salt, dairy, and seafood are the main situations to consider it — ideally via a prenatal.
- Is kelp a good source?
- Kelp can provide iodine but often in highly variable, excessive amounts, which can disrupt the thyroid. Use caution.
- Can too much harm the thyroid?
- Yes — both deficiency and excess can cause thyroid dysfunction, so moderation matters.
The amounts listed here are what published research has used — not a prescription or a recommended dose for you. Confirm anything you plan to take with your own healthcare provider, especially if you take medications, are pregnant or nursing, or have a health condition.
Related goals
Research on Iodine
Recommendations on this page are informed by published research. This is educational information, not medical advice.
- Zimmermann MB, Boelaert K. Iodine deficiency and thyroid disorders. Lancet Diabetes Endocrinol. 2015;3(4):286-295. View study →Note: Covers how both too little and too much iodine can disrupt thyroid function.