Thyroid supplements: Which ones are safe?

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According to the British Thyroid Foundation, no specific dietary supplements can help treat thyroid disorders. The best way to promote thyroid health is to follow a balanced diet that includes the correct levels of necessary nutrients.

However, taking additional nutrients in supplement form may help promote thyroid health in some people who find it challenging to follow a balanced diet, including:

• those following a restrictive diet
• people who are pregnant or breastfeeding
• anyone with a thyroid condition
• people with other underlying health conditions

A person must contact their doctor before taking any nutritional supplements. A doctor can help identify the correct dosage and determine whether the supplements may affect thyroid blood test results.

Consuming high amounts of some nutrients can adversely affect thyroid health, cause side effects, or have general health risks.

Learn more about thyroid hormones and levels here.

The following nutrients can affect thyroid health in a variety of ways:

Iodine deficiency can cause thyroid disorders.

People with a healthy thyroid must have proper levels of iodine in their bodies. The recommended intake of iodine per day is relatively small, at 150 micrograms (mcg) for people over 19 years old. However, teens and people who are pregnant require a slightly higher dose at 220 mcg. And those who are breastfeeding need 290 mcg.

Taking too much iodine in the form of supplements can cause hypothyroidism, or an underactive thyroid, and hyperthyroidism, or an overactive thyroid.

In people with hypothyroidism and hyperthyroidism, taking iodine supplements can be unnecessary or potentially harmful.

Doctors typically prescribe medications containing hormones T3 and T4. The thyroid gland uses iodine to make these hormones.

However, some commercially available supplements contain a higher dosage of T3 and T4 than doctors prescribe. This can lead to iatrogenic thyrotoxicosis, which can be fatal.

Sources of iodine naturally available in food include:

• seaweed
• cod
• Greek yogurt
• eggs

Learn about signs of iodine deficiency here.

Kelp

A person should avoid supplements and natural boosters that contain kelp. It could have adverse effects on thyroid function.

People with thyroid disease may not derive any health benefits from consuming kelp.

The body requires selenium for antioxidant function and the metabolism of thyroid hormones. A deficiency of selenium can lead to thyroid dysfunction.

However, according to the National Institutes of Health (NIH), there is not enough evidence to suggest whether selenium supplements can lower a person’s risk of thyroid disorders.

Selenium supplements may be beneficial for people with Hashimoto’s disease.

However, high selenium intake in people without a deficiency may cause various conditions, such as hyperglycemia, atherosclerosis, or cancer.

Dietary sources of selenium include:

• seafood
• meat
• eggs
• dairy products
• bread
• cereals

Learn more about foods that contain antioxidants here.

The body requires zinc for thyroid function. Zinc plays a role in the synthesis and metabolism of thyroid hormones.

However, taking too much zinc for extended periods may cause digestive symptoms or lead to low copper levels or lowered immunity.

Good dietary sources of zinc include:

• oysters
• red meat
• poultry
• seafood, such as crab and lobsters
• fortified breakfast cereals

Learn the signs of zinc deficiency here.

Iron deficiency anemia may cause hypothyroidism.

However, taking too much iron can cause toxicity, decrease zinc absorption, and interact with medications.

For example, iron tablets and multivitamins that contain iron may affect the body’s ability to absorb thyroxine. Some people with hypothyroidism, goiter, or thyroid cancer may take thyroxine as a medication. Therefore, some doctors recommend waiting a couple of hours after taking thyroxine before taking an iron supplement.

A person can incorporate iron in their diet by consuming the following foods:

• lean meat
• seafood
• poultry
• fortified breakfast cereals
• white beans
• lentils
• spinach
• kidney beans
• peas

Learn more about iron-rich foods here.

Vitamin D is a common dietary supplement that helps the body regulate calcium and phosphate production.

Some studies have shown possible links between low vitamin D levels in thyroid cancer and autoimmune thyroid diseases, such as Hashimoto’s thyroiditis and Graves’ disease. However, these links are not definite, and researchers have called for more studies to confirm them.

Taking too much vitamin D can be dangerous. This almost always happens due to taking supplements and can lead to kidney failure.

A person can incorporate more vitamin D into their diet by consuming the following foods:

• fatty fish
• fish liver oils
• fortified foods, such as:
  • milk
  • orange juice
  • cereals

Learn more about vitamin D-rich foods here.

Vitamin A regulates thyroid hormone metabolism and inhibits thyroid-stimulating hormone (TSH).

Researchers in a 2017 review highlight the critical role vitamin A plays in thyroid function. For example, deficiency in vitamin A can worsen thyroid disorders that have happened due to iodine deficiency. Retinoids, a type of vitamin A, can adversely affect iodine metabolism.

However, they went on to say that more research is necessary to confirm any benefits of treating thyroid disorders with vitamin A.

Dietary sources of vitamin A include:

• beef liver
• salmon
• green leafy vegetables
• dairy products

Learn more about foods that are high in vitamin A here.

Hashimoto’s disease is an autoimmune disorder that is the most common cause of hypothyroidism in the United States. In this disease, antibodies attack the thyroid gland, which leads to it being unable to produce enough thyroid hormones.

The following supplements may promote healthy thyroid function in a person with Hashimoto’s disease:

• Selenium: A 2018 study found that giving 200 mcg of selenium supplements per day could decrease thyroid antibodies in people with Hashimoto’s. Side effects were also minimal.
• Myo-Inositol: This sugar aids thyroid function. A 2017 study found that giving people with Hashimoto’s 600 milligrams (mg) of Myo-Inositol and 83 mcg of selenium could promote thyroid health.
• Iron: People with Hashimoto’s disease are more likely to have iron deficiency, especially menstruating females.

Learn about the best diet for Hashimoto’s here.

Graves’ disease is an autoimmune disorder that causes hyperthyroidism. If a doctor does not treat Graves’ disease, it can cause serious health problems with the heart, muscles, and bones and affect a fetus during pregnancy.

• Selenium: Selenium supplementation may improve the function of some thyroid medication and promote thyroid health in people with Graves’ disease. A person could speak with their doctor about starting a 6-month trial period of selenium.
• Vitamin D: People with Graves’ disease may be more likely to be vitamin D deficient, so supplementation or eating vitamin D-rich foods could help counter this. More research could help confirm other benefits of vitamin D in Graves’ disease.
• Vitamin B12: People with Graves’ disease may have a higher risk of becoming vitamin B12 deficient. It may be more difficult to notice symptoms of vitamin B12 deficiency that thyroid dysfunction symptoms could cover. A person should discuss vitamin B12 supplements or dietary intake with their doctor.

Learn more about vitamin B12 food sources here.

Thyroid cancer is the fifth most common cancer in women in the U.S. However, the impact of nutrition and supplements on the disease is still unclear.

A 2020 review looked at the relationship between thyroid cancer, nutritional factors, and dietary habits.

The authors concluded that correcting iodine deficiency can make thyroid cancer subtypes less aggressive without affecting the overall risk for cancer.

Furthermore, they noted that the clinical usefulness of selenium and vitamin D supplementation is still uncertain.

Learn more about thyroid cancer here.

People with a thyroid disorder must speak to a healthcare professional to check that supplements are safe for them to take. Some supplements can interact with a person’s existing medication or be unsafe to take before surgery or chemotherapy.

The Food and Drug Administration (FDA) does not regulate dietary supplements for safety or effectiveness, but they have established good manufacturing practices for supplement companies. Additionally, people can look out for quality assurance seals from independent organizations.

Learn more about how supplements and drugs can interact here.

Thyroid disorders are complex health issues that require treatment from qualified health professionals. Taking supplements may benefit some people in some circumstances but may also cause symptoms to worsen or lead to other health risks.

Some supplements, such as vitamin D and selenium, may be beneficial for thyroid disorders, but currently, the research is inconclusive.

A person who wishes to take supplements to boost thyroid health must first contact their doctor to see if it is suitable.