Iodine
Iodine is an essential trace mineral the thyroid needs to make its hormones. It comes mainly from seafood, dairy and iodized salt.
What it is studied for
The strongest rated effects first. Bars show the size of the effect, the letter grades the evidence, and each rating lists the studies behind it.
Why does the thyroid need iodine?
Iodine is needed to make thyroid hormones, which regulate metabolism and support growth and nervous-system development. Prolonged low intake can lead to an underactive or enlarged thyroid. 1
Key studies
The most recent publications linked to Iodine's ratings.
Why people take it
SuppCo community snapshot, 2026-09-28. Reasons for use are not evidence that it works.
Questions people ask
Does one urine sample diagnose iodine deficiency?
No. A spot sample is useful for population studies, not reliable individual diagnosis. 2
Did the German adult reference value change?
Yes. The 2025 reference value is 150 µg daily. 3
Is plant food a reliable iodine source?
Most plant foods grown in Germany contain little iodine because soils are iodine-poor. 4
Do the pregnancy trials prove supplements are useless?
No. They found better iodine status but no demonstrated improvement in the measured infant outcomes. Those are different questions. 5
Related nutrients
Potassium IodideSources
- Jod BfR
- Iodine: Health Professional Fact Sheet NIH Office of Dietary Supplements
