What is Iodine?
An essential trace mineral critical for thyroid hormone production.
Iodine is required for thyroid hormones T3 and T4. Deficiency causes goiter and hypothyroidism. However, excess iodine can also cause thyroid dysfunction. Iodized salt has reduced deficiency in many countries. Those avoiding salt or eating non-iodized salt may be at risk.
What the evidence says
The overall evidence grade for Iodine is A (strong — consistent, high-quality human evidence (systematic reviews, well-powered RCTs)). Essential for thyroid function. Both deficiency and excess problematic.
Specific findings with supporting evidence:
- Essential for thyroid hormone production. Evidence grade A.
- Excess can harm thyroid. Evidence grade A.
Best-supported outcomes:
- Thyroid function support.
Where marketing outpaces evidence:
- Marketing often overstates: More iodine boosts metabolism.
Dose and timing
The typical effective dose for Iodine is 150–290 mcg. Upper limit 1100mcg; excess is problematic.
Take it in the morning. Part of multivitamin or standalone.
Who it's for, and who should skip it
Most relevant for:
- Those avoiding iodized salt.
- People on restricted diets.
- Pregnant women (higher needs).
Not appropriate for:
- Those with autoimmune thyroid conditions.
- People with existing thyroid nodules.
Safety and cautions
Caution: Thyroid conditions. Excess iodine can worsen autoimmune thyroid disease. Caution: Kelp caution. Kelp supplements can contain highly variable iodine amounts.
Common mistakes
- Taking kelp without knowing iodine content.
- Supplementing with thyroid conditions.
- Assuming more helps metabolism.
Myths vs reality
A common misconception: Iodine boosts metabolism. In reality, only if deficient. Excess harms the thyroid.
How it interacts with other compounds
- Iodine works well alongside selenium — both essential for thyroid function.
Questions people ask
Should I supplement iodine? Most get enough from iodized salt. Supplement only if avoiding salt or confirmed deficient.
Editorial note
This guide summarizes the published evidence on Iodine. It is educational content, not medical advice. Confirm with your clinician if you take prescription medications or manage a chronic condition.