When you have a thyroid condition, you will no doubt be told to take iodine supplements. You may hear this advice from your holistic practitioner, your nutritionist, and even the clerk at your vitamin store. Are they right? Do thyroid patients need iodine? Let’s explore the answer to this controversial question.
Iodine and your thyroid
Iodine is an essential element found in food, iodized salt, and supplements. It is the primary ingredient your thyroid gland needs to make thyroid hormones. The iodine you ingest from food, iodized salt, and supplements is used by your thyroid to make the key thyroid hormones: thyroxine (known as T4 for its four molecules of iodine) and triiodothyronine (known as T3 for its three molecules of iodine).
Your relationship with iodine is like Goldilocks and the three bears: You need your level to be “just right,” because too little or too much can both cause problems:
- Moderate iodine deficiency is associated with an increased risk of both hypothyroidism and hyperthyroidism, as well as goiter (an enlarged thyroid). A severe deficiency of iodine can lead to iodine deficiency disorder (IDD), which is considered the leading preventable cause of mental retardation worldwide. IDD is rare in developed countries, but common in parts of Asia and Africa. When a pregnant woman has a severe iodine deficiency, her baby can be born with a disabling, life-long health condition known as cretinism. Children born with cretinism can have significant mental retardation and severely impaired growth.
- At the other end of the spectrum, excessive iodine intake — both severe and moderate — is associated with an increased risk of developing Hashimoto’s thyroiditis, hypothyroidism, and goiter.
How common is iodine deficiency?
Some important statistics:
- The World Health Organization (WHO) estimates that 2 billion people worldwide — more than 10 percent of them children of school age — are deficient in iodine. Even mild iodine deficiency in children can stunt growth, lower IQ or cause mental retardation, and lead to developmental disabilities.
- The WHO estimates that 740 million people experience more severe iodine deficiency disorders.
- The WHO estimates that 50 million people have brain damage or mental retardation as a result of iodine deficiency.
According to the Iodine Global Network, iodine deficiency and more severe iodine deficiency disorders are more common in:
- Areas that are not near the ocean. Sea water contains iodine, and the iodine is introduced into food grown near ocean coasts via rain.
- Inland and mountainous areas that were never covered by the ocean.
- Areas subject to heavy snow, rainfall, and flooding, all which leach iodine out of the soil.
- Countries and regions that have not instituted an iodized salt program.
The highest rates of iodine deficiency and IDD are found in areas of Africa and Asia, mountainous regions such as the Alps and the Andes, and some other “hotspots” in Europe, Australia, and other parts of the world.
In past decades, the United States and a number of other nations adopted programs to iodize salt, which significantly reduced iodine deficiency rates. More recently, however, as the public cut back on iodized salt intake and iodine-fortified processed foods for health reasons, we are seeing a slow and steady increase in rates of iodine deficiency in developed countries. According to WHO, only 66 percent of households worldwide have access to iodized salt. In 2017, the American Thyroid Association (ATA) joined with WHO, UNICEF, and a number of other health advocacy groups in issuing a call for universal salt iodization globally.
Of particular concern is an increase in the rate of pregnant women with iodine deficiency, including in the United States. The 2003–2004 National Health and Nutrition Examination Surveys found that among American women of childbearing age, more than 37 percent have a mild iodine deficiency. The rate is increasing steadily.
Do you need supplemental iodine?
According to WHO and the United States Institute of Medicine, the recommended daily allowance (RDA) of daily iodine intake is as follows:
- Infants and children up to age 6: 90 mcg/day.
- Children age 6 to 12: 120 mcg/day.
- Adolescents over the age of 12 and adults: 150 mcg/day.
- Preconception and pregnancy: 220-250 mcg/day.
- Lactating women: 290 mcg/day.
Do you need more iodine than the RDA? The best way to find out if you are iodine deficient is to have your levels tested. Three key tests:
- The Urinary Iodine Loading/Clearance, sometimes called the Urinary Excretion Test. Doctors administer a loading dose of iodine and then evaluate iodine levels in your urine over a specified period of time, usually 24 hours.
- A regular urinary iodine, which does not include a loading dose of iodine. This test can identify iodine deficiency, but the results are considered less precise.
- A blood test for iodine levels. Again, this test result is considered less precise.
A warning: You may see the “iodine patch test” recommended on the Internet. The idea is that you paint some iodine on your arm, and watch how quickly it disappears as a way to gauge your iodine status. It if disappears quickly, then you are supposedly iodine deficient and need to take iodine. The truth? Reputable researchers have found that there is no evidence that the rate that liquid iodine evaporates off your arm has any connection to whether you are iodine deficient. Stick with the proven urine or blood tests for iodine.
Getting supplemental iodine
If you are iodine deficient, your doctor may suggest an iodine supplement. Experts recommend an iodide form, which is better absorbed. Lugols’ solution (a liquid) and Iodoral (a pill) are frequently recommended formulations. Avoid kelp or bladderwrack supplements, which don’t provide a consistent dosage.
Some practitioners routinely recommend very high doses of iodine, with levels of 10 mg or more per day. A warning: Research shows that excessive intake of iodine can worsen hypothyroidism or lead to enlargement of your thyroid (goiter) or onset or worsening of Hashimoto’s thyroiditis.
If you can’t tolerate iodine as a supplement form, you’re not alone. Some patients report fatigue, worsening hypothyroidism symptoms, and tenderness and inflammation in the thyroid gland after starting supplementation. You may find that you feel better eating more iodine-rich foods, including:
- Sea vegetables, including dried seaweed and seaweed salads made from kelp, arame, kombu, wakame, and hiziki
- Milk, yogurt, cheese, and dairy products
- Navy beans
- Seafood, including codfish, shrimp, and tuna
- Himalayan salt, Celtic sea salt
A special note for expectant mothers
If you are planning to get pregnant or are currently pregnant or breastfeeding, experts recommend that whether or not you have iodine testing that shows a deficiency, your doctor will most likely recommend that you supplement with iodine. Iodine is especially important before and during pregnancy because your baby is unable to manufacture its own thyroid hormone — necessary for proper brain and physical development — during the first trimester. A pregnant woman needs extra iodine so she can manufacture enough thyroid hormone for both herself and her baby.
A note of caution: Don’t assume that your prenatal vitamin contains iodine. According to the New England Journal of Medicine, 72 percent of prescription prenatal vitamins do not include iodine, and 32 percent of over-the-counter prenatal vitamins do not contain iodine. Check labels carefully, and choose a prenatal vitamin that includes the recommended amount of iodine, or add an iodine supplement before and during pregnancy, and while breastfeeding.
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Mary Shomon is a thyroid disease, hormonal and autoimmune health writer, and patient advocate. For two decades, Mary has been a leading force advocating for more effective, patient-centered thyroid and hormonal health care. Mary is the New York Times bestselling author of “The Thyroid Diet Revolution,” “Your Healthy Pregnancy with Thyroid Disease,” “Living Well With Hypothyroidism,” and 10 other books on thyroid disease and integrative health. She co-stars in two PBS health specials, “Healthy Hormones,” and “Vibrant for Life.” Follow her on Twitter at @thyroidmary or at her Facebook communities: ThyroidSupport and ThyroidDiet.