Iodine is an essential micronutrient that is critical to the health of the thyroid gland (1). It is present in many foods, in supplements, and added to some salts (2).
The thyroid uses iodine from our diet to create thyroid hormones, especially T4. The body’s tissues then convert that into the powerful metabolic hormone, T3 (3). Every cell in the body relies on thyroid hormone for regulation of their metabolism (4).
The thyroid is a butterfly-shaped gland located just below the center of the neck, responsible for hormone functioning and regulation (5). The thyroid gland is the body’s internal thermostat. It regulates body temperature by secreting hormones that control how quickly the body burns calories and uses energy for all body functions. It also secretes hormones that regulate breathing, heart rate, and digestion (6).
Iodine deficiency affects around 50 million people worldwide, although it is rare in the United States and Canada, where there is a greater abundance of iodine sources in the food supply (7).
Summary: While iodine deficiency is quite rare, iodine is an essential nutrient to support the function of the thyroid gland. The thyroid gland secretes hormones that help to regulate the body’s metabolism, temperature, breathing, heart rate and digestion.
Table of Contents
Symptoms of Iodine Deficiency
Do you think you are getting enough iodine in your daily diet? Find out more about the symptoms of iodine deficiency, causes, and the best foods to eat to boost your levels.
1. Swelling in the Neck (also called a Goiter)
A goiter is the most common symptom of a iodine deficiency (8). The thyroid gland requires an adequate amount of iodine to produce and convert thyroid hormones well. If you are low in iodine, you could experience swelling in the neck caused by the thyroid gland becoming enlarged, also called a goiter (9).
However, swelling in the neck can occur from many other potential factors (10). If you are experiencing swelling in the neck, consult with your doctor to discuss potential causes.
Summary: A swelling in the neck from an enlarged thyroid gland, also called a goiter, is the most common symptom of iodine deficiency. Consult with a health care provider if you experience swelling in your neck to determine the cause of this symptom.
2. Hair Loss
Hair loss is a potential sign of iodine deficiency because hair growth can only happen if the thyroid gland is producing thyroid hormones well (11).
The body uses iodine to stimulate hair follicles, creating hair growth. Because of this, some cases of iodine deficiency have reported hair loss (12). Although, many factors can contribute to hair loss and trouble with hair growth (13).
Summary: One potential symptom of iodine deficiency is hair loss, but hair loss may also be because of a variety of different factors. **
3. Skin Irritations and Dryness
Thyroid hormones help to keep your skin cells to reproduce. With low thyroid hormone levels, which can occur from iodine deficiency, dry skin and even skin irritations may develop (14).
In one study, up to three quarters of people with low thyroid levels experienced dry flaky skin (15). If your thyroid levels are low, your doctor may want to test for an iodine deficiency.
Summary: Dry, flaky skin is a potential symptom of hypothyroidism that can occur from an iodine deficiency.
4. Difficulty Concentrating or Poor Memory
Iodine insufficiency or deficiency may also cause cognitive issues, such as learning and memory difficulties (16).
Thyroid hormone is necessary for brain development and ensuring cognitive health (17). One study found that study participants with higher thyroid hormone levels performed better on learning and memory tests (18).
Without iodine in the diet to form thyroid hormone, low thyroid hormone levels can occur.
Summary: Iodine deficiency may lead to learning and memory difficulties because iodine and thyroid hormone are necessary for proper brain development.
5. Weight Gain
Faster weight gain is a common symptom of iodine deficiency because the thyroid gland regulates your metabolism (19).
Those who suffer from hypothyroidism are more likely to gain weight easily due to slower metabolism (20). When thyroid levels are low, fewer calories are burned at rest, leading to more calories being stored as fat (21).
Summary: Low iodine and low thyroid hormone levels can slow metabolism, leading to weight gain.
Digestion issues can occur from a variety of health consequences, but low iodine can be a culprit in it as well.
Low thyroid hormones can cause digestive distress as constipation (22).
Summary: Constipation can occur from low thyroid hormone levels. Hypothyroidism can occur from low iodine intakes.
7. Slower Heart Rate
Iodine is necessary for the production of thyroid hormone, which affects heart rate (23).
The thyroid hormones do not only regulate metabolism in the form of metabolism; they are also responsible for regulating heart rate. Hypothyroidism can cause lower heart rate (24).
Summary: Slower heart rate can be the result of low thyroid hormone levels from iodine deficiency.
Groups at Risk of Iodine Deficiency
Iodine deficiency is rare in the United States and Canada, where sources of iodine are common (25). Iodine is added to some table salts, and they are naturally present in many foods, including marine foods and those that are grown in soils that are rich in iodine (26), (27).
Groups who are at risk of iodine deficiency include those who have higher iodine needs or who do not have many sources of iodine-rich foods in their diet, including (28), (29):
- Pregnant women
- Those living in regions with iodine deficient soils
- People who do not use iodized salt
Not sure how much iodine you are getting? Ask your doctor to test your levels to make sure your thyroid functioning is not coming from a deficiency.
Summary: Iodine deficiency is uncommon, but groups who are at higher risk include those who have higher iodine needs, including pregnant women, and those who do not get a lot of iodine-rich foods in their diet.
Foods that Contain Iodine
Many foods are high in iodine, with an emphasis on sea and marine foods. Seaweed provides the most iodine out of all the foods listed (30). Check out the list below to see where you can start adding more foods with iodine to your diet today.
- Seaweed (kelp, sea vegetables, fortified seasonings)
- Fish (cod, shrimp, tuna, sardines)
- Dairy products
- Iodized table salt
- Lima beans
Not all table salts contain iodine. Many speciality salts do not contain iodine, including sea salt, himalyan salt, kosher salt, and fleur de sel (30). Check the label of your salt to see if it indicates that it is “iodized” and contains iodine.
Fruits and vegetables will also contain some iodine, depending on the iodine content of the soil where these foods are grown (30).
Is there somewhere you can start adding more iodine to your diet? If you are eating these foods regularly, and you still have symptoms of iodine deficiency, reach out to your doctor or healthcare professional.
Summary: Many foods naturally contain iodine, including seaweed and seafoods. Other foods that contain iodine include dairy products, eggs, and meat. Fruits and vegetables grown in iodine rich soils contain iodine, and some table salts also have iodine added.
Iodine deficiency is rare in countries with iodine rich soil, iodized salt, and lots of fresh seafood available. If you are eating a healthy balanced diet full of iodine-rich foods like eggs, meat, fish, nuts, and more, you are likely getting enough iodine.
With a healthy diet, full of the foods listed above, you should be able to get adequate levels of this micronutrient in your diet. Consult with your health care provider if you are experiencing any of the symptoms above to determine if low iodine levels are a concern.
Summary: Iodine deficiency can affect the thyroid gland and the production of thyroid hormones, which have many affects on the body. Those at risk of deficiency are those who have higher iodine needs or not many iodine food sources in their diet. Consult with your doctor if you are experiencing any of the symptoms of hypothyroidism to evaluate the cause.