Iodine is an essential mineral your body needs to make thyroid hormones. These hormones help regulate metabolism and support normal growth and development. Because the body cannot make iodine, it must come from food or, when appropriate, dietary supplements. Iodine deficiency remains a public-health concern in some populations, although it is uncommon in the United States and Canada, according to the NIH Office of Dietary Supplements.
What Is Iodine?
So, what is iodine exactly? It is a trace mineral found naturally in certain foods and added to some types of salt. The thyroid gland uses iodine to make the hormones thyroxine (T4) and triiodothyronine (T3). These hormones are involved in metabolism and are especially important for normal brain and bone development during pregnancy and infancy.
How Can I Get Enough Iodine?
Many people can meet their iodine needs through a varied diet. Common dietary sources include:
- Fish and other seafood, such as cod, tuna and shrimp
- Milk, yogurt and cheese
- Eggs
- Iodized table salt
- Seaweed, although its iodine content can vary substantially
Not all salt contains iodine. Specialty salts, including many sea salts, are usually not iodized, and commercially processed foods often are not made with iodized salt. Checking food labels can help you identify iodized salt without increasing your overall salt intake.
How Much Iodine Do You Need?
In the United States, the recommended dietary allowance is 150 micrograms (mcg) per day for most adults, 220 mcg during pregnancy and 290 mcg while breastfeeding. Requirements differ for children and other age groups. Adequate iodine is particularly important during pregnancy and breastfeeding because thyroid hormones are needed for fetal and infant development. The NIH iodine fact sheet provides recommendations by life stage.
What About Iodine Supplements?
If food alone does not provide enough iodine, a supplement may be useful in some circumstances. However, taking an iodine supplement does not automatically ensure the right intake for every person. Consider iodine from food, iodized salt, multivitamins and any other supplements together. People who are pregnant or breastfeeding, have a thyroid condition, or take thyroid medication should discuss their iodine needs with a qualified healthcare professional.
More is not always better: excessive iodine intake can also disrupt thyroid function. The NIH lists an upper intake level of 1,100 mcg per day for adults from food and supplements combined, with lower limits for children; this limit is not a recommended target.
For more practical information, see our article on preventing iodine deficiency. For global public-health context, see the World Health Organization's guidance on salt iodization.