Iodine may not be the first nutrient that comes to mind when thinking about a balanced diet, but it has an essential role in thyroid hormone production. Iodine deficiency remains a concern in some populations, even as iodized salt programs have improved iodine nutrition worldwide. In the United States and Canada, deficiency is uncommon, according to the NIH Office of Dietary Supplements. The goal is to get an appropriate amount of iodine, not simply as much as possible.
Why Do People Need Iodine?
The thyroid gland needs iodine to make thyroid hormones, which help regulate metabolism and many other processes. These hormones also play an important role in normal brain and bone development during pregnancy and infancy. For more background, read why your body needs iodine.
Warning Signs of an Iodine Deficiency
Consistently inadequate iodine intake can impair thyroid hormone production and, in some cases, contribute to an enlarged thyroid gland (goiter) or hypothyroidism. Possible symptoms of low thyroid hormone levels include:
- Unusual fatigue
- Feeling cold more often than usual
- Dry skin
- Unexplained weight changes
- Swelling in the neck
These symptoms have many possible causes and do not establish that someone has an iodine deficiency. Thyroid problems can also occur when iodine intake is adequate. A healthcare professional can evaluate persistent symptoms and determine whether testing or treatment is needed.
How to Get More Iodine
Choose iodine-containing foods: Fish and shellfish, milk, yogurt, cheese and eggs can contribute iodine to the diet. Iodized table salt is another source; many specialty salts and salts used in processed foods are not iodized. If you use salt, choosing an iodized variety can help without adding extra sodium. Seaweed contains iodine, but the amount varies greatly by type and serving.
Consider supplements when appropriate: Some multivitamins already contain iodine. If your diet provides too little, a supplement may help fill a gap, but it is important to check the amount on the Supplement Facts label and account for all dietary sources. Supplementation is not automatically necessary or suitable for everyone.
Pregnancy, Breastfeeding and Thyroid Conditions
Iodine needs increase during pregnancy and breastfeeding. U.S. recommended dietary allowances are 150 mcg per day for most adults, 220 mcg during pregnancy and 290 mcg while breastfeeding. People who are pregnant, breastfeeding or planning a pregnancy should discuss iodine intake and their prenatal supplement with their healthcare professional.
Iodine supplements are not a substitute for prescribed thyroid medication. People being treated for a thyroid condition should not stop, replace or adjust their medication without advice from the clinician managing their care. The American Thyroid Association also cautions that excess iodine can be harmful to the thyroid.
Can You Get Too Much Iodine?
Yes. Excessive iodine can cause thyroid problems, including in people who may be especially sensitive to iodine. The NIH lists an upper intake level of 1,100 mcg per day for adults from food, beverages and supplements combined, with lower limits for children. This is a safety limit, not a goal for daily intake. For detailed food sources, recommended amounts and safety information, consult the NIH iodine fact sheet and the WHO overview of iodine status.