AStrong evidence, for the people named belowMineral
The short answer
Narrow safe range. Worth attention on a plant-based diet or in pregnancy, and worth avoiding casually.
Who this is actually for
People who avoid dairy and fish, those on plant-based diets, and anyone pregnant or breastfeeding, when dietary intake is low.
What it is legally allowed to claim
Quoted from the EU register of authorised health claims, Regulation (EU) 432/2012. A product may only make these claims if it supplies enough of the nutrient to qualify.
- Iodine contributes to the normal production of thyroid hormones and normal thyroid function
How much is too much
EFSA tolerable upper intake level 600 micrograms per day for adults.
Cautions and interactions
Too much iodine causes thyroid dysfunction just as too little does. If you have any thyroid condition or take levothyroxine, do not start iodine without asking. Kelp supplements vary wildly in dose and are a common cause of overdose.
Ask a pharmacist before you start anything. Interactions with prescribed medicines are the most common way supplements cause harm, and they are easy to check. Bring the actual packet, or a photo of the ingredients panel, because doses and forms vary enormously between products. Nothing here is a substitute for advice about your own situation.