In a nutshell
- EFSA considers 150 µg of iodine a day adequate, 200 µg in pregnancy and breastfeeding.1
- Children of mothers who were iodine deficient in pregnancy more often had poorer verbal intelligence and reading scores.6
- Seaweed and seaweed supplements contain unpredictable amounts of iodine — often more than the upper level.4
1What it does and how much you need
Iodine is an essential part of the thyroid hormones, which control metabolism and the development of the brain and nerves. A long-term deficiency enlarges the thyroid (goitre); a deficiency is most serious in pregnancy and childhood.1
EFSA recommendation
150 µg
EFSA set the adequate intake of iodine at 150 µg a day for adults and 200 µg for pregnant and breastfeeding women. Over 90% of it is absorbed.1
Moderate evidence
23 countries
A standardised map from 23 European countries showed that iodine deficiency still exists in Europe: urinary iodine was low in 54% of studies in adults and in 64% of studies in pregnant women.3
2Where to find it
The iodine content of food and water varies a lot. Sea fish and seafood, eggs, milk and dairy products, and iodised salt provide the most.1
Weak evidence — analysis of 96 products
up to 62,400 µg
An analysis of 96 seaweed products on the Norwegian market: one portion of seaweed had 128 to 62,400 µg of iodine and seaweed supplements 5 to 5,600 µg per daily dose. For 54 products, one portion would exceed the upper level; label information was often missing or wrong.4
3Forms and the upper level
In the EU, supplements may contain iodine as sodium or potassium iodide or iodate.5 In food and water, iodine is mostly present as iodide.1
Upper level
600 µg
The upper level for adults is 600 µg of iodine a day, including in pregnancy and breastfeeding.2
4Pregnancy and vegans
Moderate evidence — a large observational study
1,040 women
In a follow-up of 1,040 pregnant women in Britain, children of women with iodine deficiency in the first trimester were more likely (by 58%) to score in the lowest quarter for verbal IQ and also for reading. The less iodine the mothers had, the worse the children’s results.6
Weak evidence — Cochrane
11 studies
A Cochrane review of iodine studies in pregnancy (over 2,700 women): there are too few data for clear conclusions on the benefits and harms of routine iodine supplementation.7
Moderate evidence — a review
127,094 people
A systematic review of studies with 127,094 adults: vegans have a higher risk of low intake and deficiency of iodine than people who also eat animal foods. But the differences between studies were huge — the highest intake of all was in one group of female vegans (1,448 µg a day).8
What to take from this
- Iodised salt, milk, eggs and sea fish give you iodine.1
- Pregnant or planning a pregnancy? Discuss iodine with a doctor — the baby’s brain development depends on it.1,6
- Vegan? Watch your iodine — iodised salt or a supplement after talking to a doctor can help.8
- Be careful with seaweed and seaweed supplements; they can contain extreme amounts of iodine.4
Sources
Written on , based on studies available at that date. Newer research may change the conclusions.
- EFSA NDA Panel (2014). Scientific Opinion on Dietary Reference Values for iodine. EFSA Journal 12:3660. doi.org/10.2903/j.efsa.2014.3660
- EFSA (2025). Overview on Tolerable Upper Intake Levels as derived by the Scientific Committee on Food (SCF) and the EFSA Panel on Nutrition (version 11). efsa.europa.eu
- Ittermann T. et al. (2020). Standardized map of iodine status in Europe. Thyroid 30:1346–1354. doi.org/10.1089/thy.2019.0353
- Aakre I. et al. (2021). Commercially available kelp and seaweed products — valuable iodine source or risk of excess intake? Food Nutr Res 65:7584. doi.org/10.29219/fnr.v65.7584
- Directive 2002/46/EC on food supplements, Annex II — forms of vitamins and minerals permitted in supplements (consolidated version 26 Nov 2025). eur-lex.europa.eu
- Bath S. C. et al. (2013). Effect of inadequate iodine status in UK pregnant women on cognitive outcomes in their children: results from the Avon Longitudinal Study of Parents and Children (ALSPAC). Lancet 382:331–337. doi.org/10.1016/S0140-6736(13)60436-5
- Harding K. B. et al. (2017). Iodine supplementation for women during the preconception, pregnancy and postpartum period. Cochrane Database Syst Rev CD011761. doi.org/10.1002/14651858.CD011761.pub2
- Eveleigh E. R. et al. (2020). Vegans, vegetarians, and omnivores: how does dietary choice influence iodine intake? A systematic review. Nutrients 12:1606. doi.org/10.3390/nu12061606
This is general information and does not replace a doctor. With thyroid disease, take iodine only after talking to a doctor.