Iodine For The Thyroid


Iodine is an element that’s required for the thyroid gland to produce thyroid hormones. Since the body does not produce iodine on its own, it needs to come from dietary sources—and striking the right balance is key. Inadequate levels or overconsumption of iodine can lead to or worsen thyroid disease, as well as cause other significant health concerns.

Thyroid function is crucial to the metabolism of almost all tissues and is critical for the development of the central nervous system in the fetus and children1). The effects of the thyroid come from two iodine containing-hormones, triiodothyronine (T3) and thyroxine (T4). Iodine (atomic number, 53; standard atomic mass, 126.9) is a rate-limiting element for the synthesis of thyroid hormones. At present, the only physiological role known for iodine in the human body is in the synthesis of thyroid hormones by the thyroid gland2).

The relationship between iodine deficiency and thyroid disease was known since early in the twentieth century. Iodine deficiency has been regarded as one of the most important preventable causes of brain damage worldwide3). In 2013, 30 countries remain iodine-deficient; 9 are moderately deficient, and 21 are mildly deficient by defined by median urinary iodine (UI) in school-aged children4). While the prevalence of severe iodine deficiency was reduced recently, the problems of iodine deficiency remerged in vulnerable populations, such as pregnant women and infants. Furthermore, some food or medications have very high iodine contents, which can result in thyroid dysfunction in some susceptible individuals.

The Republic of Korea (South Korea) is regarded as an iodine-sufficient area, while the Democratic People’s Republic of Korea (DPRK) is known to be an iodine-deficient area, although there has been no nation-wide evaluation of iodine levels.

This paper reviews the physiologic role of iodine, methods to assess iodine nutrition, clinical implications of iodine deficiency or excess, and iodine-related thyroid problems in the Korean Peninsula.

The Importance of Iodine

Iodine is considered an essential mineral for our bodies. It’s particularly important during pregnancy, and exposure in the womb may even help prevent certain health conditions later in life.

The following is a list of some of the most important uses and how they benefit the body.

1. Promoting thyroid health

Iodine plays a vital role in thyroid health. Your thyroid gland, which is located at the base of the front of your neck, helps regulate hormone production. These hormones control your metabolism, heart health, and more.

To make thyroid hormones, your thyroid takes up iodine in small amounts. Without iodine, thyroid hormone production can decrease. A “low” or underactive thyroid gland can lead to a condition called hypothyroidism.

Given the wide availability of iodine in western diets, thyroid health isn’t typically impacted by low iodine levels in the United States.

You can get enough iodine from your diet by eating dairy products, fortified foods, and salt water fish. Iodine is also available in plant foods that grow in naturally iodine-rich soil. You also can get the mineral by seasoning your food with iodized salt.

While iodine promotes overall thyroid health, too much iodine can have a negative effect on the thyroid gland. That’s why you shouldn’t take iodine supplements without your doctor’s recommendation.

2. Reducing risk for some goiters

A goiter is an enlarged thyroid gland. Your thyroid may become enlarged as a result from either hypothyroidism or hyperthyroidism. Hyperthyroidism is an overactive thyroid gland.

Non-cancerous thyroid nodules (cysts) can also cause thyroid gland enlargement.

Sometimes a goiter develops as a direct response to iodine deficiency. This is the most common cause of goiter worldwide, though it’s not as common a cause in the United States and other countries with access to iodine-rich foods.

Iodine-induced goiters may be reversed by adding iodine-rich foods or supplements in the diet.

3. Managing overactive thyroid gland

Your doctor may recommend a special type of iodine called radioactive iodine to treat an overactive thyroid gland. Also called radioiodine, this medication is taken by mouth. It’s used to destroy extra thyroid cells to help reduce excessive amounts of thyroid hormone.

The risk with radioactive iodine is that it can destroy too many thyroid cells. This can decrease the amount of hormone production, leading to hypothyroidism. For this reason, radioactive iodine is usually only recommended after anti-thyroid drugs have failed.

Radioactive iodine is not the same thing as iodine supplements. You should never take iodine supplements for hyperthyroidism.

4. Treating thyroid cancer

Radioiodine may also be a possible treatment option for thyroid cancer. It works in much the same way as hyperthyroid treatment.

When you take radioactive iodine orally, the medication destroys thyroid cells, including cancerous ones. It may be used as a treatment following thyroid surgery to make sure all cancerous cells have been removed from the body.

According to the American Cancer SocietyTrusted Source, radioactive iodine treatments significantly improve the chances of survival for people with thyroid cancer.

5. Neurodevelopment during pregnancy

You need more iodine in pregnancy. That’s because iodine intake during pregnancy is linked to brain development in fetuses. One reviewTrusted Source found that babies whose birth mothers had an iodine deficiency during pregnancy were more likely to grow up with lower IQ’s and other intellectual delays.

The recommended daily intakeTrusted Source of iodine during pregnancy is 220 mcg. By comparison, the recommended amount in non-pregnant adults is 150 mcg a day.

If you’re pregnant, ask your doctor about iodine supplementation, especially if your prenatal vitamin doesn’t have iodine (many do not). Iodine supplements may also be necessary if you’re deficient in the mineral.

You’ll also need to continue monitoring your iodine intake if you’re breastfeeding. The recommended daily amount of iodine while nursing is 290 mcg. That’s because the iodine you take up from diet and supplementation is transferred via breast milk to your nursing infant. This is a crucial brain developmental period, so infants need 110 mcg per day until they’ve reached 6 months of ageTrusted Source.

6. Improving cognitive function

The same neurological benefits of iodine during pregnancy may extend to healthy brain function during childhood. This also includes a reduced riskTrusted Source of intellectual disability.

It is likely your child gets all the iodine they need through their diet, but if you have any questions about their iodine intake, talk to their pediatrician.

7. Improving birth weight

As with brain development, iodine during pregnancy is associated with a healthy birth weight. One studyTrusted Source of pregnant women with goiters found that 400 mg of iodine taken daily for six to eight weeks was helpful in correcting goiters related to iodine deficiency. In turn, there was an overall improvement in birth weight in newborns.

While iodine intake can impact a baby’s birth weight and overall development, it’s important to note that the above study focused on women in developing areas who were already deficient in iron.

Unless your doctor has determined you are iodine deficient, taking supplements aren’t likely to impact your baby’s weight at birth. In fact, taking iodine unnecessarily can cause health issues.

8. May help treat fibrocystic breast disease

It’s possible that iodine supplements or medications can help treat fibrocystic breast disease. This non-cancerous condition is most common in women of reproductive age, and it can cause painful breast lumps.

Although there is some promise that iodine might help with fibrocystic breast cysts, you shouldn’t attempt self-treatment. Only take iodine for this condition if your doctor specifically recommends it. Otherwise, you could be at risk of side effects from iodine toxicity.

9. Disinfecting water

Iodine is just one method of water disinfection. This may be especially helpful if you don’t have access to potable water due to traveling or effects from a natural disaster.

Two percent liquid iodine tincture may be added to water in five-drop increments per one quart of clear water. If the water is cloudy, add ten drops per quart.

Iodine tablets may also be used, but the instructions can vary by manufacturer.

Despite the role iodine can play in disinfecting drinking water, there’s also some concerns that it can increase total iodine intake in humans and lead to adverse health effects. Total iodine intake shouldn’t exceed 2 mg per dayTrusted Source.

10. Protection from nuclear fallout

In the case of nuclear emergencies, the Centers for Disease Control and Prevention recommends the use of potassium iodide (KI) to protect the thyroid gland from radiation injuries. These are available in tablet and liquid formulas.

While not completely foolproof, the sooner KI is taken, the better the thyroid is thought to be protected in the event of this kind of emergency.

There are serious risks associated with KI, including gastrointestinal upset, inflammation, and allergic reaction. You’re also at increased risk for thyroid disease. Your risk for complications is higher if you already have thyroid disease.

iodine for the thyroid11. Treating infections

Iodine can be used topically in a liquid form to help treat and prevent infections. It works by killing bacteria in and around mild cuts and scrapes.

Topical iodine should not be used on newborn babies. It should also not be used for deep cuts, animal bites, or burns.

Follow directions on the packaging for dosage information, and do not use for more than 10 days unless directed by your doctor.

This can occur for a number of reasons, including taking in too little or too much iodine.

How Much Iodine You Need

According to the Food and Nutrition Board of the National Academies (formerly the National Academy of Science), the recommended dietary allowance (RDA) for iodine in the United States ranges anywhere from 90 mcg per day for toddlers to 150 mcg for teens and adults.3

Considering that one cup of plain low-fat yogurt contains about 75 mcg, 3 ounces of fish sticks contain about 54 mcg, a cup of cooked pasta contains about 27 mcg, and a quarter teaspoon of iodized salt contains about 71 mcg, that’s generally an easy amount for most people to consume.

Pregnant and Breastfeeding Women

The American Thyroid Association recommends that all pregnant and breastfeeding women in the United States and Canada take a prenatal vitamin containing 150 mcg of iodine a day as part of an overall recommended intake of 220 mcg/day and 290 mg/day, respectively. Excess iodine, however, can be particularly dangerous in these women.4

Iodine Sources

Most Americans have no trouble meeting the recommended intake of iodine because of the iodization of salt in the United States and incorporation of iodine-rich foods such as the following:5

  • Cod (3 ounces): 99 mcg
  • Plain low-fat yogurt (1 cup): 75 mcg
  • Reduced fat milk (1 cup): 56 mcg
  • White enriched bread (2 slices): 45 mcg
  • Shrimp (3 ounces): 35 mcg
  • Enriched macaroni (1 cup): 27 mcg
  • Egg (1 large): 24 mcg
  • Canned tuna in oil (3 ounces): 17 mcg
  • Dried prunes (5 prunes): 13 mcg
  • Cheddar cheese (1 ounce): 12 mcg
  • Raisin bran cereal, (1 cup): 11 mcg
  • Apple juice (1 cup): 7 mcg
  • Frozen green peas (1/2 cup): 3 mcg
  • Banana (1 medium): 3 mcg
ways to hit your daily iodine
Illustration by Cindy Chung, Verywell

Supplements (e.g. potassium iodide, sodium iodide, kelp) and iodine-containing herbs, such as bladderwrack, are other sources that can be considered.

Iodine Deficiency

Since iodine is needed to make thyroid hormone, diminished levels can lead to hypothyroidism (low thyroid function). Iodine deficiency is also linked to the development of goiter (thyroid enlargement).

The impact of too little iodine reaches further. Children born to mothers with severe iodine deficiency can suffer from stunted growth, severe and irreversible intellectual disabilities, and problems with movement, speech, and hearing.

Even mild iodine deficiency during pregnancy can lead to subtle intellectual deficits, although many children improve with iodine supplementation. Mild iodine deficiency can also cause miscarriage.

Fibrocystic breast disease, a benign condition characterized by lumpy, painful breasts mostly in women of reproductive age, is also associated with iodine deficiency.

Risk Factors

The World Health Organization (WHO) estimates that two billion people, including 285 million school children, are iodine deficient. Among them, iodine deficiency disorders (IDD) affect some 740 million.6

In the United States, however, the risk of iodine deficiency is relatively low; incidence of IDD has dropped significantly since the iodization of salt first began in the 1920s. To further stem the risks of thyroid disease worldwide, the American Thyroid Association (ATA) called for the universal iodization of salt in 2017.7 That said, there are certain risk factors for iodine deficiency that everyone should be aware of no matter where they live:

  • Pregnancy
  • A low- or no-salt diet
  • An iodine-poor diet high in goitrogenic foods such as soy, cassava, and cruciferous vegetables (e.g. cabbage, broccoli, and cauliflower), which may significantly impact your body’s ability to utilize any iodine it does get

Preventive Supplementation When You Have Thyroid Disease

Some healthcare providers are almost knee-jerk in their insistence that anyone with a thyroid problem requires iodine supplementation; alternative healthcare providers may recommend iodine-containing herbs, like kelp or seaweed.

This can be particularly risky, in part because iodine supplements can interact with several types of drugs, including anti-thyroid drugs used to treat hyperthyroidism.5 Taking high doses of iodine with anti-thyroid medications can have an additive effect and could cause hypothyroidism.

If iodine deficiency isn’t the cause of hypothyroidism, then iodine supplements won’t be helpful.

You’ll want to be very careful about upping your iodine intake unless you and your healthcare provider have some very strong evidence that you’re deficient. This is especially true if you’re pregnant or planning to become pregnant.

Excess Iodine

Given the strong link between iodine and thyroid health, it’s reassuring to learn that iodine deficiency is rare in the United States and other developed countries where iodized salt is used. Indeed, as an International Journal of Molecular Sciences study reported in 2014, iodine excess is currently a more frequent occurrence in these places. This, though, is not without concern.8

For some people with abnormal thyroid glands, excessive iodine can trigger or worsen hypothyroidism. While initially, you may have more energy, high doses can cause an “iodine crash” that leaves you feeling exhausted and achy within a few days.

That’s because high iodine intake can initiate and exacerbate infiltration of the thyroid by lymphocytes, the white blood cells that accumulate due to chronic injury or irritation.

In addition, large amounts of iodine block the thyroid’s ability to make thyroid hormones. A 2014 study in the journal Endocrinology and Metabolism found that more-than-adequate or excessive iodine levels are unsafe and may lead to hypothyroidism and autoimmune thyroiditis (Hashimoto’s thyroiditis, chronic lymphocytic thyroiditis), especially for people with recurring thyroid disease.9

Women who take too much supplemental iodine during pregnancy may give birth to babies with congenital hypothyroidism, a thyroid deficiency that, if left untreated, can lead to mental, growth, and heart problems, according to a 2012 study published in The Journal of Pediatrics.10

While iodine poisoning is rare, the overconsumption of iodine can be just as problematic as consuming too little.

Are You Getting Enough or Too Much?

While iodine can be detected in urine, relying on such a test is not helpful, since 90 percent of the iodine you ingest is quickly expelled. Rather, healthcare providers use thyroid tests to determine if your iodine intake is concerning or not.

In addition, iodine deficiency is typically suspected based on the development of goiter, hypothyroidism, or congenital hypothyroidism (low thyroid function at birth).11

Be sure that any adjustments you make to your iodine intake, whether you have a circumstance that seems to call for them or not, are cleared by your healthcare provider first.

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