A person’s diet can have an effect on the symptoms of hyperthyroidism. Some foods can improve the condition, while others can make symptoms worse or interfere with medications.

Hyperthyroidism, a type of thyrotoxicosis, is a condition in which the thyroid gland produces too much thyroid hormone. Some people refer to this condition as an overactive thyroid. The most common cause of hyperthyroidism is an autoimmune condition called Graves’ disease.

The symptoms of an overactive thyroid include unintentional weight loss, anxiety, sweating, frequent bowel movements, difficulty sleeping, and muscle weakness. Hyperthyroidism is much more common in women than in men.

In this article, we discuss how diet affects hyperthyroidism and provide lists of foods to eat and avoid.

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Eating certain foods will not cure hyperthyroidism, but some nutrients and minerals play a role in managing the underlying condition. Diet can affect both the production of thyroid hormones and how the thyroid functions.

The following nutrients and chemicals are among those that can affect hyperthyroidism:

  • Iodine, which the thyroid gland uses to produce thyroid hormone. Too much iodine in the diet can increase the production of thyroid hormone.
  • Calcium and vitamin D are vital because hyperthyroidism can cause problems with bone mineral density.
  • Foods and drinks containing caffeine can worsen the symptoms of hyperthyroidism.

Below, we discuss some of the nutrients that can affect thyroid function and note which foods contain them.

The following foods can have benefits for people with an overactive thyroid:

Low iodine foods

If a person is planning to receive radioactive iodine treatment for hyperthyroidism, their doctor may ask them to follow a low iodine diet. A low-iodine diet is a diet with less than 50 micrograms (mcg) of iodine per day.’

Foods and drinks that are low in iodine include:

  • noniodized salt
  • egg whites
  • fresh or frozen vegetables
  • herbs and spices
  • vegetable oils
  • sugar, honey, or maple syrup (up to 2 tbsp.)
  • jams or jellies
  • unsalted nuts and nut butter
  • lemonade
  • beer and wine
  • moderate portions of beef, chicken, turkey, veal, and lamb
  • fruit and fruit juices

The American Thyroid Association offers tips on how to follow a low iodine diet.

Cruciferous vegetables

Some cruciferous vegetables contain compounds that decrease thyroid hormone production and may reduce iodine uptake by the thyroid. Both of these effects may be beneficial for a person with hyperthyroidism.

These cruciferous vegetables include:

  • Brussels sprouts and cabbage
  • collard greens, mustard greens, and turnip roots and greens
  • kale and arugula
  • radishes and rutabagas
  • bok choy
  • cauliflower
  • broccoli and broccoli rabe

Foods containing selenium

Selenium is a micronutrient that the body requires for the metabolism of thyroid hormones. Research suggests that selenium can help improve some of the symptoms of autoimmune thyroid disease, such as thyroid eye disease.

Among people using anti-thyroid medications, those who take selenium supplements may achieve normal thyroid levels more quickly than those who do not.

Foods rich in selenium include:

  • Brazil nuts
  • fortified pasta and cereals
  • rice
  • egg whites
  • baked beans
  • oatmeal
  • spinach

Other selenium-rich foods, including tuna, halibut, shrimp, ham, egg yolks, and cottage cheese are also high in iodine which may affect iodine therapy. Eat fortified pasta and cereals, and rice made without ingredients that contain a lot of iodine. Eat limited amounts of beef, chicken, and turkey.

Foods containing iron

Iron is a nutrient that is important for normal bodily processes, including thyroid health. Iron helps the red blood cells carry oxygen to other cells in the body.

Researchers have linked low levels of iron to hyperthyroidism.

People can maintain an adequate intake of iron by including these foods in their diet:

  • fortified cereals
  • raisins
  • dark chocolate
  • beef, chicken, turkey, and pork
  • spinach

Some iron-rich foods are also high in iodine, which may affect iodine therapy. Make sure your total iodine intake is less than 50 mcg per day:

  • oysters and fish
  • white beans, kidney beans, and black beans
  • lentils
  • sardines
  • chickpeas
  • canned beef, chicken or turkey
  • cured pork products (bacon, sausages, or hot dogs)

Look for fortified cereals made without ingredients that contain a lot of iodine.

Foods containing calcium and vitamin D

There is an association between longstanding hyperthyroidism and decreased bone mineral density, which can lead to osteoporosis.

Calcium and vitamin D are both nutrients that are important for bone health.

Foods rich in calcium include:

  • milk (no more than once a day)
  • broccoli
  • fortified orange juice
  • kale
  • bok choy

Many people with hyperthyroidism have vitamin D deficiency. The primary source of vitamin D is the sun hitting the skin so that the body can make its own. However, due to concerns about sun exposure and increased risk of skin cancer, many people actively limit their time in the sun or use sunscreen.

Not many foods are good sources of vitamin D, but the following foods contain some of this vitamin:

  • salmon and tuna
  • milk and some fortified dairy products (check the labels)
  • fortified cereals

These foods are also high in iodine, which may affect iodine therapy, so you may have to limit these foods or make sure your total iodine intake is less than 50 mcg. Look for fortified pasta and cereals, and rice made without ingredients that contain a lot of iodine.

Spices

Studies have linked certain spices, including turmeric and green chilis, to a reduced frequency of thyroid disease, including hyperthyroidism.

Turmeric also has anti-inflammatory properties.

People can use different spices, such as turmeric, to add flavor to their food.

Below, we look at the foods that can be harmful to people with hyperthyroidism if they eat them in large quantities:

Iodine-rich foods

Too much iodine can make hyperthyroidism worse by leading the thyroid gland to produce too much thyroid hormone.

A person with hyperthyroidism should avoid eating excessive amounts of iodine-rich foods, such as:

  • iodized salt
  • fish and shellfish
  • seaweed or kelp
  • dairy products
  • iodine supplements
  • food products containing red dye
  • egg yolks
  • blackstrap molasses
  • carrageenan, which is an additive
  • baked goods with iodate dough conditioners

Soy

Animal studies have shown that soy ingestion can interfere with radioactive iodine uptake for the treatment of hyperthyroidism.

Sources of soy include:

  • soy milk
  • soy sauce
  • tofu
  • edamame beans
  • soybean oil

Gluten

Research suggests that autoimmune thyroid disease, including Graves’ disease, is more common among people who have celiac disease than among those who do not.

The reason for this is not apparent, but genetics may play a role. Having celiac disease can also make a person more likely to develop other autoimmune disorders.

Celiac disease causes damage to the small intestine as a result of the ingestion of gluten. Gluten is a protein in wheat, barley, oats, and rye.

People with celiac disease need to follow a gluten free diet. Some research suggests that following a gluten-free diet may facilitate better absorption of thyroid medications by the intestine and decrease inflammation.

Caffeine

Caffeine can worsen some symptoms of hyperthyroidism, including palpitations, tremors, anxiety, and insomnia.

Where possible, a person with hyperthyroidism should try to avoid foods and drinks containing caffeine. These include:

  • regular coffee
  • black tea
  • chocolate
  • regular soda
  • energy drinks

Hyperthyroidism is a condition in which the thyroid gland is overactive and produces excess thyroid hormone. People should follow their treatment plan and any dietary recommendations from their doctor.

Changing the diet might improve symptoms of hyperthyroidism. Certain nutrients may help support healthy thyroid function or decrease hyperthyroidism symptoms.

A doctor or dietitian will be able to provide more information about dietary changes for hyperthyroidism.