Iodine Deficiency and Your Thyroid: What You Need to Know

An uncommon U.S. problem, but one that is seen in other parts of the world

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Your thyroid is an essential gland in your body, controlling metabolism and allowing other organs like your heart and brain to work properly.

One key mineral that your thyroid gland needs to function is iodine, which is used to produce the thyroid hormones, T3 (triiodothyronine and T4 (thyroxine).

Unfortunately, the body does not produce iodine on its own, so iodine needs to come from a water source and/or your diet.

In non-industrialized nations, getting enough iodine can be a problem. This can lead to iodine deficiency, and thus, thyroid disorders.

Consequences of Iodine Deficiency

Since iodine is needed to make thyroid hormone, as a person's iodine levels fall, hypothyroidism (an underactive thyroid gland) develops. In addition, iodine deficiency is linked to thyroid enlargement (called a goiter), which can lead to problems swallowing and breathing.

Children of mothers with iodine deficiency can suffer from stunted growth, severe and irreversible intellectual disabilities, and problems with movement, speech, and/or hearing. Even mothers with mild iodine deficiency (which is seen in the United States) can have children with low intelligence.

Iodine Recommended Intake

The Recommended Dietary Allowance (RDA) for iodine is 90 micrograms per day for children ages one to eight, 120 micrograms per day for children ages nine to thirteen years old, and 150 micrograms per day for adolescents and non-pregnant adults.

For pregnant women, 220 micrograms per day are recommended and 290 micrograms per day are recommended for women who are breastfeeding.

Due to the slightly higher required intake for pregnant and breastfeeding women, the American Thyroid Association recommends that pregnant and breastfeeding women take a prenatal vitamin that contains 150 micrograms of iodine per day.

Besides using iodized table salt, drinking water and eating foods that contain iodine (for example, saltwater fish, shellfish, dairy products, and some bread) can pretty much ensure that you are taking in a sufficient amount of iodine.

With that, it's important to mention that food labels in the United States do not list the amount of iodine, and about 50 percent of all multivitamins in the United States do not actually contain iodine.

Diagnosing Iodine Deficiency

You may wonder if you can test whether or not you have sufficient iodine levels. While it's true that iodine levels can be measured through a urine test (because iodine is released from the body through the urine), this is not traditionally done on individuals. This is because there is a day-to-day variation in iodine intake.

Rather, urine samples for iodine are really only done for research purposes. Studies reveal that in the United States, iodine levels are sufficient, although they did drop by about 50 percent between the 1970s and the early 1990s.

Levels have now stabilized and are still considered sufficient; although certain populations like pregnant women, lactating women, and women of childbearing years may be at risk for mild to moderate iodine deficiency—which is why taking a prenatal vitamin that contains 150 micrograms of iodine per day is important.

Unfortunately, in other parts of the world, iodine deficiency continues to remain a big problem.

Iodine Supplementation

While some alternative practitioners believe that thyroid patients should take iodine or an iodine-containing herb, like kelp or seaweed, that practice can be problematic. This is because many cases of autoimmune thyroid disease (which is by far the most common cause of thyroid conditions in the United States) are not due to iodine deficiency.

The likelihood that your thyroid problem is caused by iodine deficiency is a function of your geographic location, diet, and use of salt and iodized products, but the odds are, you are not iodine deficient.

If you decide on your own to try kelp, iodine, or one of the many thyroid-supporting supplements (almost all of them contain high amounts of iodine or kelp), it's important to be aware of the risks.

While the thyroid gland in people without thyroid disease can generally adapt well to various intakes of iodine (although chronic thyroid stimulation from mild to moderate iodine deficiency can lead to hyperthyroidism), too much iodine in people with thyroid problems tends to be more problematic. For instance, in people with Hashimoto's thyroiditis, taking too much iodide can trigger or worsen hypothyroidism.

A Word From Verywell

Apart from knowledge about iodine deficiency and its role in thyroid disease, a big take-home message here is that for women who are pregnant, lactating, or considering pregnancy, taking a prenatal vitamin with iodine (150 micrograms) is important.

It's also important and kind-hearted to think about iodine deficiency in non-industrialized nations, where it continues to remain a major health concern. 

Sources:

American Thyroid Association. Iodine Deficiency. 

Leung AM, Braverman LE, Pearce EN. History of U.S. Iodine Fortification and Supplementation. Nutrients. 2012 Nov;4(11):1740-46.

Pazirandeh S, Burns DL, Griffin IJ. (2017). Overview of dietary trace minerals. Seres D, ed. UpToDate. Waltham, MA: UpToDate Inc. 

Zimmerman MB, Boelaert K. Iodine deficiency and thyroid disorders. Lancet Diabetes Endocrinol. 2015 Apr;3(4):286-95.