Minerals
Iodine
Iodine is an essential trace mineral. Your body needs it to make thyroid hormones, which help regulate metabolism and support growth and development.
Iodine is a mineral needed in small amounts, so it is classified as a trace element. You must obtain it through your diet. Your thyroid gland uses iodine to make the hormones thyroxine (T4) and triiodothyronine (T3). Chemically, iodine is an element with the symbol I. Nutritional forms include iodide. Potassium iodide and sodium iodide are iodine-containing compounds used, for example, in supplements; they are not synonyms for the element itself.
Iodine is an essential trace mineral: your body needs only small amounts, but you must obtain them through your diet. Your thyroid gland uses iodine to make the hormones thyroxine (T4) and triiodothyronine (T3). These help regulate metabolism and support growth and development.
What iodine does in your body
Iodine contributes to the normal production of thyroid hormones and normal thyroid function. It also contributes to normal cognitive function, normal energy-yielding metabolism, normal functioning of the nervous system and the maintenance of normal skin. These claims are authorised under Regulation (EU) No 432/2012; they may only be used for foods that qualify as at least a source of iodine. This describes the importance of an adequate intake—not an extra benefit from taking more iodine. It does not establish that iodine supplements improve mental performance, speed up metabolism or help with weight loss. The skin claim does not cover hair or nails.
Which foods provide iodine?
Fish, seafood, dairy products and iodised salt are important sources of iodine. The amount you obtain depends on the particular food and how much you eat: these food groups do not have a uniform iodine content.
- When you use salt, iodised salt can contribute to iodine intake.
- Sea salt, Himalayan salt and other specialty salts are not necessarily iodised. Check the label.
- If you follow a vegan diet or eat little or no dairy, fish, seafood and eggs, your iodine intake may be insufficient. This does not prove deficiency. What matters is the iodine sources you actually use, such as iodised salt, fortified foods and any supplements.
Why more iodine is not better
How nutrition works
Statements & evidence
Iodine is an essential nutrient that you need to obtain through your diet. [4]
Your body cannot make iodine. An adequate intake is therefore part of a balanced diet.
EFSA sets an Adequate Intake for iodine of 150 µg per day for adults. [3]
This reference value covers your total intake from foods and any supplements. It is not a recommended supplement dose or an exact measurement of your individual requirement.
EFSA sets an Adequate Intake for iodine of 200 µg per day during both pregnancy and breastfeeding. [3]
This is higher than the reference value for other adults and concerns your total daily intake. It does not mean that you should take an additional 200 µg as a supplement.
Marine foods, dairy products and iodised salt are important dietary sources of iodine. [4][5]
How much iodine you obtain depends on the particular foods and how much you eat. These food groups do not have a uniform iodine content.
Sea salt, Himalayan salt and other specialty salts are not necessarily iodised. [5]
Check the label to see whether the salt is iodised. Its origin alone does not make it a reliable iodine source.
If you follow a vegan diet or eat little or no dairy, fish, seafood and eggs, your iodine intake may be insufficient. [5]
This is a risk factor, not proof of iodine deficiency. Your actual intake depends on the iodine sources you use, such as iodised salt, fortified foods and any supplements.
The European Scientific Committee on Food established a Tolerable Upper Intake Level for iodine of 600 µg per day for adults, including during pregnancy and breastfeeding. [6]
This value applies to habitual total intake from foods and supplements. It is an upper safety boundary, not a dietary target or a recommended supplement dose.
The iodine content of seaweed varies markedly, and some seaweed products can lead to iodine intakes above the Tolerable Upper Intake Level. [7]
EFSA identifies substantial differences between species and products. You should therefore not treat seaweed as a predictable iodine dose. Data gaps prevent a single assessment from being generalised to all seaweed products.
Safety information
Side effect
Excess iodine can disturb thyroid function
Excess iodine can cause an underactive or overactive thyroid; thyroid inflammation has also been reported. People with existing thyroid disease are particularly susceptible. These are not expected effects of an intake that meets nutritional needs. [5]
Upper level · Adults
European upper intake level: 600 µg daily
The European tolerable upper intake level for healthy adults is 600 µg iodine a day, including pregnancy and breastfeeding. It applies to habitual total intake from foods and supplements, not to a recommended supplement dose. It does not guarantee safety for people with thyroid disease. [9][5]
Upper level · Children and adolescents (1–17 years)
Children have lower upper intake levels
European upper levels for habitual total intake are: ages 1–3, 200 µg/day; 4–6, 250 µg/day; 7–10, 300 µg/day; 11–14, 450 µg/day; and 15–17, 500 µg/day. These are not intake targets or recommended supplement doses. [9]
Caution
Check supplements if you have thyroid disease
If you have Hashimoto's thyroiditis, Graves' disease or autonomous thyroid nodules, seek medical advice before using iodine supplements or iodine-rich seaweed products. Older people with a history of prolonged iodine deficiency may also be more susceptible. This is not a blanket reason to avoid normal iodine-containing foods. [5][10]
Caution
Seaweed is not a reliably dosed iodine source
The iodine content of seaweed and kelp products varies widely and can be very high. Do not use them on your own to correct a suspected iodine deficiency. Also check whether several supplements are contributing iodine at the same time. [11]
Caution
Avoid iodine excess during pregnancy and breastfeeding
During pregnancy and breastfeeding, adequate iodine intake matters, but excess can also affect your baby's thyroid. Seek professional advice on appropriate supplementation and avoid seaweed supplements as an uncontrolled iodine source. [11]
Interaction
Interaction with antithyroid medicines
If you take an antithyroid medicine such as methimazole, use high-dose iodine only under medical direction. The combination can further suppress thyroid function and contribute to hypothyroidism. Do not change prescribed treatment yourself. [5]
Interaction
Avoid seaweed products with lithium or amiodarone
ANSES advises against seaweed products if you take lithium or iodine-containing medicines such as amiodarone. Have additional iodine supplements reviewed by your doctor or pharmacist. Do not stop prescribed medicines yourself. [11]
Interaction
Potassium iodide interactions depend on the preparation
NIH ODS lists a risk of raised blood potassium when potassium iodide is combined with ACE inhibitors or potassium-sparing diuretics. This warning concerns the potassium-containing preparation; it does not establish a common risk from ordinary microgram-dose iodine supplements. Have the specific product checked. [5]
Interaction
Iodine can interfere with radioiodine treatment
If radioiodine treatment is planned, tell your treatment team about iodine supplements, multivitamins, iodine-containing medicines and recent contrast agents. These can affect radioiodine uptake. Your team should determine any withdrawal periods or temporary low-iodine diet. [12]
Caution
Seaweed products with kidney failure or heart disease
ANSES advises people with kidney failure or heart disease against seaweed-containing foods and supplements. This is a targeted caution about seaweed products with high or variable iodine exposure, not a blanket restriction on all iodine-containing foods. [11][13]
Frequently asked questions
What does your body need iodine for?
Your body needs iodine to make thyroid hormones. These help regulate metabolism and support growth and development.
How much iodine do you need each day?
EFSA sets an Adequate Intake of 150 µg of iodine per day for adults and 200 µg during pregnancy and breastfeeding. These values cover total intake from foods and any supplements, not an additional supplement dose.
Which foods provide iodine?
Fish, seafood, dairy products and iodised salt are important sources of iodine. Sea salt and Himalayan salt are not necessarily iodised, so check the label. Getting iodine is not a reason to eat more salt.
Do you need to pay attention to iodine on a vegan diet?
Yes, a vegan diet can leave your iodine intake insufficient, but this does not automatically mean you have a deficiency. Your intake depends on the sources you use, such as iodised salt, fortified foods and any supplements.
Can too much iodine be harmful?
Yes, excess iodine can cause an underactive or overactive thyroid, especially in people with existing thyroid disease. The European upper intake level for healthy adults is 600 µg per day from all sources; it is not a target and does not guarantee safety for people with thyroid disease. Seaweed and kelp products can provide highly variable, very large amounts of iodine.
More entries
Calcium
Calcium is an essential mineral. It provides structure to bones and teeth and contributes to normal muscle function, nerve transmission and blood clotting.
Iron
Iron is an essential trace element and a component of haemoglobin, which transports oxygen in the blood.
Selenium
Selenium is an essential trace element. Your body needs small amounts to make selenium-containing proteins involved in thyroid hormone metabolism and protection against oxidative damage.
Zinc
Zinc is an essential trace element that you obtain through your diet. It has important roles in enzymes and other proteins.
Magnesium
Magnesium is an essential mineral. Your body needs it for energy metabolism, normal muscle and nerve function, and bone structure, among other roles.
Potassium
Potassium is an essential mineral and electrolyte. It supports normal nerve and muscle function and helps regulate the distribution of fluid in the body.
Sources
- 01European Commission · 2012Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods, other than those referring to the reduction of disease risk and to children's development and healthOpen source
- 02EFSA Journal · 2009Scientific Opinion on the substantiation of health claims related to iodine and thyroid function and production of thyroid hormones (ID 274), energy-yielding metabolism (ID 274), maintenance of vision (ID 356), maintenance of hair (ID 370), maintenance of nails (ID 370), and maintenance of skin (ID 370) pursuant to Article 13(1) of Regulation (EC) No 1924/2006EFSA Panel on Dietetic Products, Nutrition and AllergiesDOI 10.2903/j.efsa.2009.1214
- 03EFSA Journal · 2014Scientific Opinion on Dietary Reference Values for iodineEFSA Panel on Dietetic Products, Nutrition and AllergiesDOI 10.2903/j.efsa.2014.3660
- 04European Food Safety Authority · 2014Dietary reference values: EFSA proposes adequate intakes of iodineOpen source
- 05National Institutes of Health, Office of Dietary SupplementsIodine — Health Professional Fact SheetOpen source
- 06Scientific Committee on Food; EFSA Scientific Panel on Dietetic Products, Nutrition and Allergies · 2006Tolerable Upper Intake Levels for Vitamins and MineralsOpen source
- 07EFSA Journal · 2023Dietary exposure to heavy metals and iodine intake via consumption of seaweeds and halophytes in the European populationDOI 10.2903/j.efsa.2023.7798
- 08European Parliament and Council of the European Union · 2011Regulation (EU) No 1169/2011 on the provision of food information to consumersOpen source
- 09European Food Safety AuthoritySummary tables of tolerable upper intake levels for vitamins and minerals, version 8Open source
- 10German Federal Institute for Risk AssessmentIodine intake in Germany on the decline again — tips for a good iodine intakeOpen source
- 11French Agency for Food, Environmental and Occupational Health & SafetyANSES Opinion — iodine exposure from seaweed consumption, reference 2017-SA-0086Open source
- 12European Medicines AgencyGuideline on core SmPC and Package Leaflet for sodium iodide (131I) for therapeutic useOpen source
- 13ANSES; hosted by the European Food Safety Authority · 2018Information on ANSES recent opinions and newsOpen source
- 14European Food Safety Authority · 2017Dietary Reference Values for nutrients: Summary reportOpen source
- 152017Effect of excess iodine intake on thyroid diseases in different populations: A systematic review and meta-analyses including observational studiesPubMed 28282437Open source
- 16European Journal of Endocrinology · 2014Impact of iodine supplementation in mild-to-moderate iodine deficiency: systematic review and meta-analysisTaylor et al.DOI 10.1530/eje-13-0651PubMed 24088547
- 17Royal Society of ChemistryIodine - Element information, properties and uses | Periodic TableOpen source
- 18National Institutes of Health, Office of Dietary SupplementsIodine — Fact Sheet for ConsumersOpen source
- 19CochraneIodine supplementation for women before, during or after pregnancyOpen source
- 20European Food Safety Authority · 2024Summary report on tolerable upper intake levels for vitamins and mineralsOpen source
- 21The American Journal of Clinical Nutrition · 2020Systematic review and meta-analysis of the effects of iodine supplementation on thyroid function and child neurodevelopment in mildly-to-moderately iodine-deficient pregnant womenDineva et al.DOI 10.1093/ajcn/nqaa071PubMed 32320029