The Link Between Iodine Deficiency and Hypothyroidism

When you think about all the vitamins and nutrients you need to stay healthy, iodine may not be what first comes to mind. And most people easily have enough iodine in their diet, mainly from iodized salt and from the soil where our food is grown. But certain groups of people are at higher risk of iodine deficiency, and this can affect thyroid function. So let’s dive into how iodine supports the thyroid, who is at risk for iodine deficiency, and how to prevent iodine-related health problems. 

What is the link between iodine and thyroid function? 

Your thyroid gland needs iodine to function properly. The thyroid is a butterfly-shaped gland located in your neck. It is part of the body’s endocrine system, which is a set of organs that produce important hormones. 

The thyroid gland uses iodine to make hormones as well as regulate hormone release. The thyroid makes two hormones: T3 and T4. These hormones are essential to support growth, development, and metabolism. When the thyroid releases these hormones, they are distributed throughout the body where they affect many important systems. And when people have low levels of iodine, their body functions can be affected. This can lead to some health problems.

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What happens when you are iodine deficient?

Iodine deficiency affects your health by decreasing thyroid function. And decreased thyroid function leads to decreased thyroid hormone levels in the body. This is called hypothyroidism.

Hypothyroidism can lead to a lot of different symptoms. Some common ones include:

• Digestion problems

• Fatigue

• Dry skin or hair loss

• Weight gain

• Forgetfulness

Hypothyroidism can also cause the thyroid gland to grow bigger. When this happens, it looks like a large lump in your neck. This is called a goiter, and goiters can cause some bothersome symptoms on their own such as:

• A tight feeling in the throat 

• Coughing

• Difficulty breathing and swallowing 

Hypothyroidism can also be particularly problematic in infants and children. This is because the thyroid plays a key role in a child’s growth and development. Some health problems specific to children include:

• Delayed cognitive development

• Delayed physical development

• Infant mortality, in the most severe cases

Other health problems resulting from iodine deficiency may include heart problems, such as increased cholesterol levels, slowed heart rate, and hardening of the arteries. Hypothyroidism has also been associated with changes in liver function and can lead to an accumulation of fat in the liver known as non-alcoholic fatty liver disease. Chronic kidney disease can also occur as a result of low thyroid function.

Who is at risk of iodine deficiency?

While it’s very important for everyone to keep their iodine levels up, certain populations are at higher risk of being iodine deficient.

• Women who are pregnant or breastfeeding require higher levels of iodine than the general population. And severe iodine deficiency during pregnancy can cause a miscarriage or stillbirth.

• People who are vegan and vegetarian also tend to have lower dietary intake of iodine. This is because these diets exclude high-iodine foods like seafood and dairy. There are, however, plenty of other foods rich in iodine. More on this to come.

• People who live in mountain regions can also have lower levels of iodine in their diet. In these areas, there is not always enough iodine in the soil. So the crops that grow there absorb less iodine from the soil. 

• People that mainly use designer salts, such as Himalayan pink salt and other non-iodized salts, can have lower dietary intake of iodine. These salts have become increasingly popular. While Himalayan pink salt does contain some minerals, it has very little iodine. 

What are good sources of iodine in foods?

The daily recommended dietary intake of iodine is 150 µg/day for people 13 years and older. Pregnant women should consume 220 µg/day of iodine, and breastfeeding women should get 290 µg/day.

Even though experts provide these recommendations, figuring out your daily iodine intake is nearly impossible — and usually not necessary. But if you are at risk for iodine deficiency, it may help to know which foods tend to be iodine-rich.

The main source of iodine in the diet comes from table salt. You can check the label of your table salt to see if it has been “iodized.” This means that iodine was added during the manufacturing process.

In addition to iodized salt, other foods that contain high amounts of iodine include:

• Seaweed

• Whole-wheat and enriched white bread

• Cod

• Nonfat Greek yogurt

• Oysters

Many foods absorb a good amount of iodine from the soil when they are growing. The U.S. Department of Agriculture has also put together a detailed list of iodine-rich foods.

What should you do if you think you are iodine deficient?

Iodine deficiency is treatable. If you have noticed symptoms that may be due to hypothyroidism, or you are concerned about your risk of deficiency, talk to your healthcare provider. They can run some simple blood tests to analyze your thyroid function.

Treatment may include iodine supplements or finding ways to increase your levels through your diet. But make sure you talk to your provider before starting any treatment because iodine supplements can interact with some medications.

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Written by:

Loren DeVito, PhD

Loren DeVito, PhD, is a science journalist and neuroscientist who loves when these two sides come together to educate patients and consumers in an impactful way. She is a medical writer  with a decade of experience and has a freelance writing company, Sticky Ink, Inc.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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