Table of ContentsView AllTable of ContentsWhat Is Iodine?Health BenefitsSide EffectsIodine DeficiencyDosage and InteractionsSources
Table of ContentsView All
View All
Table of Contents
What Is Iodine?
Health Benefits
Side Effects
Iodine Deficiency
Dosage and Interactions
Sources
Your body can’t produce iodine independently. Instead, you must obtain it through your diet or as a supplement. Iodized salt is the primary source of this mineral in the United States.
In the United States, the Food and Drug Administration (FDA) does not regulate supplements the way it regulates prescription drugs. That means some supplement products may not contain what the label says. Whenchoosing a supplement, look for independently tested products and consult a healthcare provider, registered dietitian nutritionist (RD or RDN), or pharmacist.
1:31What is Iodine and How Does the Supplement Work?
1:31
What is Iodine and How Does the Supplement Work?
Iodine is an essential mineral found in foods, such as fish and dairy products. Most people get enough iodine from iodized salt.
What Are the Health Benefits of Iodine?
Fetal Development
About 50% more iodine isrequired during pregnancyto meet fetal developmental needs.
In a 2013 study published inLancet, researchers evaluated the effect of insufficient iodine in pregnancy on cognitive outcomes in children.Researchers measured urinary iodine concentration in 1,040 pregnant participants during the first trimester. Later, they also measured the children’s intelligence quotient (IQ) at age 8.
Compared to those with adequate iodine, those with mild-to-moderate iodine deficiency were more likely to have the lowest scores for verbal IQ, reading accuracy, and reading comprehension.
In addition, a 2019 study published inNutrientsevaluated educational outcomes in adolescents whose gestational parents had mild iodine deficiency in pregnancy.
First, researchers assessed the iodine concentration of 266 pregnant people attending antenatal clinics at the Royal Hobart Hospital in Australia from 1999 to 2000. Then, researchers compared their children’s standardized test scores in literacy and math when they were ages 8–9, 10–11, 12–13, and 14–15 years.
The study found that even mild iodine deficiency in pregnancy had long-term cognitive effects. For example, children whose parents had iodine deficiency during pregnancy had reduced scores in reading, spelling, and grammar, independent of other factors known to impact learning. These effects did not resolve with sufficient iodine intake during childhood.
Cognitive Function
In addition to iodine’s importance in pregnancy to support a child’s cognitive function, adequate iodine intake continues to be important throughout childhood and into adulthood.
Iodine deficiency can impair cognitive and motor development in children. In adults it can also lower IQ and affect productivity.
Fibrocystic Breasts
Fibrocystic breastsare a benign condition where breast tissue is lumpy. Since breast tissue has a high concentration of iodine, some research has evaluated whether the mineral could be helpful in treating fibrocystic breasts.
In a 2018 study published in theJournal of Women’s Health, researchers evaluated whether a nutritional supplement including iodine could decreasecyclical breast painand nodules.The randomized, multi-center, controlled, double-blind trial included 188 participants.
Researchers randomized participants to receive either a nutritional formula containing 1 gram (g)gamma-linolenic acid(GLA), 750 micrograms (mcg) iodine, and 70 mcgselenium, or aplacebodaily for threemenstrual cycles. While breast pain decreased in both groups, nodules decreased in the supplement group but not in the control group.
Infections
Iodine is in some topical antiseptic medications, or those applied to skin to help prevent or treat bacterial infections.Its antimicrobial properties may be helpful for minor cuts or scrapes.
Only use topical iodine under the guidance of a healthcare provider and follow the medication instructions carefully.
Thyroid Function and Goiter Risk
Small changes in iodine intake may help reset the thyroid system.However, you should see a healthcare provider to check and monitor thyroid hormone levels.
Thyroid cells need iodine to make thyroid hormone. If you don’t have enough iodine, it can lead thethyroid glandto grow too big, known as agoiter, or result inhypothyroidism(underactive thyroid).
Goiter is often the first sign of iodine deficiency. This enlargement happens because the thyroid grows to try to absorb as much iodine as possible.
If iodine deficiency becomes severe, it can cause hypothyroidism (underactive thyroid) because the thyroid has too little iodine to make thyroid hormone.However, excess iodine is also associated with the development of hypothyroidism.
Thyroid Cancer
In addition to cancer treatments, iodine may also help prevent thyroid cancer after nuclear emergencies. Nuclear accidents can release radioactive iodine into the environment, increasing the risk of thyroid cancer in those exposed. Thus, some research has evaluated whether iodine supplementation could reduce cancer risk in high-risk populations following some historic nuclear disasters.
That study found that where potassium iodide was widely used, thyroid cancer rates did not increase substantially in the following years. On the other hand, in Belarus and Ukraine, where people did not use iodine supplements, thyroid cancer increased significantly among children and adolescents.
The FDA recommends potassium iodide as a thyroid blocking agent in nuclear emergencies.
Side Effects of Iodine
Your healthcare provider may recommend you take iodine during pregnancy or for deficiency. However, consuming a supplement like iodine may have potential side effects. These may be common or severe.
In general, moderate iodine consumption from iodized salt or the food in your diet shouldn’t cause problems. That is because the body eliminates extra iodine through the urine.
Allergies and sensitivities to iodine have been reported. However, more recent research suggests thatiodine allergiesmay actually be due to another substance and not iodine. Usually, this occurs with exposure to iodine contrast material for medical testing, not from iodine supplements.
For example, a 2021 review in theAmerican Journal of Health-System Pharmacylooked at common misperceptions of iodine allergy.Researchers found that among 81 articles, iodine was not seen as the allergen responsible for allergic reactions to iodinated contrast media, amiodarone (a drug that regulates heart rate),povidone-iodine(antiseptic skin disinfectant used before surgery), and other iodine-containing compounds.
Mild allergic reactions to iodine contrast materials include:
Although rare, allergic reactions can also be severe.Anaphylaxisis a life-threatening emergency that can occur without warning due to exposure to an allergen. Symptoms include:
If you experience any of the above symptoms, it is critical to seek emergency medical care immediately.
Betadine vs. Iodine: What’s the Difference?
If your iodine intake falls below 10–20 mcg/day, you may become deficient.Iodine deficiencyleads to problems with thyroid hormone production, which can result in thyroid disease.
In addition, iodine deficiency can lead to cognitive disabilities in children whose gestational parent did not have adequate intake during pregnancy.
Since the introduction of iodized salt, iodine deficiency has been rare in the U.S. However, some groups are at increased risk for a deficiency, including:
A goiter is often the first sign of iodine deficiency. It is sometimes visible or palpable through the neck.
Goiter symptoms include:
In addition, if you have iodine deficiency, you may develop hypothyroidism.Hypothyroidismcan cause a variety of symptoms, including:
Children with hypothyroidism may experience the same effects as adults along withadditional symptomsincluding slow physical growth, mood problems, trouble concentrating, and learning difficulties.
Newborn screening tests can detect iodine deficiency in infants. Deficiency may cause babies to developcongenital hypothyroidism. Symptoms may include trouble eating, excessive sleepiness, or constipation. Sometimes, it may not cause any symptoms at all.
Iodine supplements may interact with some medications, including:
If you take any medications, talk to a healthcare provider or pharmacist about the safety of any supplements you consider taking.
Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.
Since your body produces thyroid hormones on an ongoing basis, all children and adults need to consume iodine regularly. In addition, pregnant people need higher amounts to support the developing fetus.
The United States Institute of Medicine recommends the amount of iodine a person should ingest daily.
During pregnancy the recommended intake of iodine is 220 mcg per day. When breastfeeding, it’s 290 mcg per day.
You can not measure iodine levels in the blood, but you can measure it in the urine. Normal urinary iodine concentrations range between 100 and 200 micrograms per liter. Values lower than 20 micrograms per liter suggest inadequate iodine intake.
Iodine Sources
Iodine is found in food sources and is also available as a supplement. Most people can meet their iodine needs through food sources.
Food
The most common source of iodine is iodized salt, which contains 76 mcg (51% of the daily recommended intake for adults) in 1/4 teaspoon. However, this concentration may differ depending on the manufacturer. For precise amounts, check the label’s nutritional information.
In addition, plenty of foods contain iodine. Fish andseaweedare the foods richest in iodine. For example, one 3-ounce serving of cod contains about 158 mcg of iodine, and one serving of seaweed contains about 116 mcg of iodine. Other iodine-rich foods include:
Supplements
Vitamins and supplements vary in their iodine content. You can find the specific amount of iodine on the label. Talk with your healthcare provider before taking a supplement.
Iodine supplements most often come as potassium iodide or sodium iodide. Some iodine supplements are also sourced from kelp (seaweed).They are available in drops, capsules, and tablets. If you are vegan or havefood allergies, read labels carefully to ensure there are no animal products or allergens.
Iodine is quickly absorbed in the stomach andsmall intestine. Next, it travels through the bloodstream. From there, iodine receptors located in the thyroid bind to it and take it in.
Summary
Iodine is a mineral your body needs for producing thyroid hormones. These hormones have essential roles in regulating body weight and maintaining energy.
Iodine deficiency can result in an enlarged thyroid, called a goiter. It can also lead to hypothyroidism, where the thyroid doesn’t produce enough hormones.
Common sources of iodine include salt, supplements, and foods like vegetables and seafood. Consult a healthcare provider before taking any supplements.
How Herbs Can Affect Thyroid Disease
20 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Hynes KL, Otahal P, Burgess JR, Oddy WH, Hay I.Reduced educational outcomes persist into adolescence following mild iodine deficiency in utero, despite adequacy in childhood: 15-year follow-up of the gestational iodine cohort investigating auditory processing speed and working memory [published correction appears in Nutrients. 2019 Jun 05;11(6):].Nutrients. 2017;9(12):1354. Published 2017 Dec 13. doi:10.3390/nu9121354
World Health Organization.Nutrition: effects of iodine deficiency.
Mansel RE, Das T, Baggs GE, et al.A randomized controlled multicenter trial of an investigational liquid nutritional formula in women with cyclic breast pain associated with fibrocystic breast changes.J Womens Health (Larchmt). 2018;27(3):333-340. doi:10.1089/jwh.2017.6406
UpToDate.Iodine content in some iodine-containing medications and radiographic contrast agents.
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American Cancer Society.Radioactive iodine (radioiodine) therapy for thyroid cancer.
U.S. Food and Drug Administration.Potassium iodide as a thyroid blocking agent in radiation emergencies.
Wulf NR, Schmitz J, Choi A, Kapusnik-Uner J.Iodine allergy: Common misperceptions.Am J Health Syst Pharm. 2021;78(9):781-793. doi:10.1093/ajhp/zxab033
Bottinor W, Polkampally P, Jovin I.Adverse reactions to iodinated contrast media.Int J Angiol. 2013;22(3):149-154. doi:10.1055/s-0033-1348885
American Academy of Allergy, Asthma & Immunology.Anaphylaxis.
Merck Manual Consumer Version.Iodine deficiency.
Endocrine Society.Goiter.
American Thyroid Association.Hypothyroidism (underactive).
American Thyroid Association.Hypothyroidism in children and adolescents.
U.S. National Library of Medicine.Congenital hypothyroidism.
Kalra S, Unnikrishnan AG, Sahay R.The hypoglycemic side of hypothyroidism.Indian J Endocrinol Metab. 2014;18(1):1-3.doi:+10.4103/2230-8210.126517
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