Hyperthyroidism happens when there’s too much thyroid hormone in your body. This condition is also called thyrotoxicosis. An overactive or enlarged thyroid gland may produce more thyroid hormone.

Your thyroid is a butterfly-shaped gland at the front of your neck. It produces thyroid hormones called T3 and T4. These hormones:

  • help your body use energy
  • help balance body temperature
  • help your brain, heart, and other organs function properly

Some types of hyperthyroidism may be genetic. Graves’ disease is the most common cause of hyperthyroidism in the United States. It’s seven to eight times more common in women than men. In some cases, thyroid cancers may also cause an overactive thyroid.

Hyperthyroidism can be easily confused with other health problems. Its range of symptoms includes:

  • sudden weight loss
  • increased appetite
  • anxiety, irritability and nervousness
  • mood changes
  • difficulty sleeping
  • feeling hot
  • sweating
  • fast heartbeat or pounding heart
  • fatigue or tiredness
  • muscle weakness
  • hand tremor or slight shaking
  • more frequent or other changes in bowel movements
  • skin thinning
  • fine, brittle hair
  • menstruation changes
  • enlarged thyroid gland (goiter)
  • swelling at base of your neck
  • eye changes
  • red, thick skin on upper feet and shins

Treatment is necessary if you have hyperthyroidism. High levels of thyroid hormones in your body can be toxic. Left untreated, hyperthyroidism may lead to heart problems, bone loss, fracture risk, and other issues.

Your doctor may prescribe antithyroid medications. These drugs help to balance an overactive thyroid gland. In some cases, treatment may include radiation therapy or thyroid surgery.

Certain foods can help keep your thyroid healthy and reduce some of the negative effects of this condition. Some minerals, vitamins, and other nutrients are necessary to balance thyroid function.

A low-iodine diet is usually prescribed prior to some treatments for hyperthyroidism. For example, you’ll need to follow a low-iodine diet before having radiation therapy to remove excess or damaged thyroid cells.

After treatment, it’s still important to balance iodine in your diet. Other foods help to protect your thyroid and reduce the long-term effects of hyperthyroidism.

Low-iodine foods

The mineral iodine plays a key role in making thyroid hormones. A low-iodine diet helps to reduce thyroid hormones. Add these foods to your daily diet:

  • non-iodized salt
  • coffee or tea (without milk or dairy- or soy-based creamers)
  • egg whites
  • fresh or canned fruit
  • unsalted nuts and nut butters
  • homemade bread or breads made without salt, dairy, and eggs
  • popcorn with non-iodized salt
  • oats
  • potatoes
  • honey
  • maple syrup

Cruciferous vegetables

Cruciferous vegetables and other types may stop your thyroid from using iodine properly. They may be beneficial for hyperthyroidism:

  • bamboo shoots
  • bok choy
  • broccoli
  • Brussels sprouts
  • cassava
  • cauliflower
  • collard greens
  • kale
  • mustard
  • rutabaga

Vitamins and minerals

Several nutrients are essential for thyroid health and to balance thyroid hormone production.

Iron

Iron is important for many vital bodily functions, including thyroid health. This mineral is needed for blood cells to carry oxygen to every cell in your body. Low levels of iron are linked to hyperthyroidism. Get plenty of iron in your diet with foods such as:

  • dried beans
  • green leafy vegetables
  • lentils
  • nuts
  • poultry, such as chicken and turkey
  • red meat
  • seeds
  • whole grains

Selenium

Selenium-rich foods may help to balance thyroid hormone levels and protect your thyroid from disease. Selenium helps to prevent cell damage and keep your thyroid and other tissues healthy.

Good food sources of selenium include:

  • Brazil nuts
  • couscous
  • chia seeds
  • mushrooms
  • tea
  • meat, such as beef and lamb
  • rice
  • oat bran
  • poultry, such as chicken and turkey
  • sunflower seeds

Zinc

Zinc helps you use food for energy. This mineral also keeps your immune system and thyroid healthy. Food sources of zinc include:

  • beef
  • chickpeas
  • cocoa powder
  • cashews
  • mushrooms
  • pumpkin seeds
  • lamb

Calcium and vitamin D

Hyperthyroidism causes weak and brittle bones. Bone mass may be restored with treatment. Vitamin D and calcium are necessary for building healthy bones.

Calcium-rich foods include:

  • spinach
  • collard greens
  • white beans
  • kale
  • okra
  • calcium-fortified orange juice
  • almond milk
  • calcium-fortified cereals

Vitamin D is found in these low-iodine foods:

  • vitamin D–fortified orange juice
  • vitamin D–fortified cereals
  • beef liver
  • mushrooms
  • fatty fish

Healthy fats

Fats that are from whole foods and largely unprocessed may help reduce inflammation. This helps to protect thyroid health and balance thyroid hormones. Nondairy fats are important in a low-iodine diet. These include:

  • flaxseed oil
  • olive oil
  • avocado oil
  • coconut oil
  • sunflower oil
  • safflower oil
  • avocado
  • unsalted nuts and seeds

Spices

Some spices and herbs have anti-inflammatory properties to help protect and balance thyroid function. Add flavor and a dose of antioxidants to your daily meals with:

Excess iodine

Eating too many iodine-rich or iodine-fortified foods may lead to hyperthyroidism or worsen it in some cases.

A teaspoon of iodized salt gives you 284 micrograms of iodine. Seafood has the most iodine. Just 1 gram of seaweed contains 2 milligrams of iodine. The recommend dose of iodine is about 1.1 milligrams per day. A low-iodine diet requires even less.

Avoid the following seafood and seafood additives:

  • fish
  • seaweed
  • prawns
  • crabs
  • lobster
  • sushi
  • carrageen
  • agar-agar
  • algae
  • alginate
  • nori
  • kelp

Avoid other foods high in iodine such as:

  • milk and dairy
  • cheese
  • egg yolks
  • iodized salt
  • iodized water
  • some food colorings

Some medications also contain iodine. These include:

Nitrates

Chemicals called nitrates may cause your thyroid to absorb too much iodine. This can lead to an enlarged thyroid and hyperthyroidism.

Nitrates are found naturally in some foods. Processed foods may contain added nitrates. It may also be found in drinking water. Avoid or limit foods such as:

  • processed meats (sausage, bacon, salami, pepperoni)
  • celery
  • lettuce
  • beets
  • spinach
  • parsley
  • leeks
  • endive
  • cabbage
  • fennel
  • dill
  • turnip
  • broccoli
  • carrots
  • cucumber
  • pumpkin

Gluten

In some people, gluten may harm the thyroid by causing inflammation. Even if you don’t have a gluten allergy or intolerance, it may be beneficial to restrict or limit gluten. Check food labels for gluten-containing ingredients such as:

  • wheat
  • barley
  • brewer’s yeast
  • malt
  • rye
  • triticale

Soy

While soy doesn’t contain iodine, it’s been shown to interfere with some treatments for hyperthyroidism in animals. Avoid or limit foods with soy such as:

  • soy milk
  • soy sauce
  • tofu
  • soy-based creamers

Hyperthyroidism may not always be preventable, but it’s treatable. See your doctor if you have any of the symptoms of hyperthyroidism. Follow your treatment exactly as prescribed, including all dietary recommendations.

Talk with your doctor or dietitian about making short-term and long-term changes to your diet. This can help balance thyroid function and protect your body from the effects of hyperthyroidism.

Enjoy home-cooked whole foods on a low-iodine diet. Avoid restaurant, boxed or processed meals, and prepared sauces and marinades. These may contain added iodine.

If you’re on a low-iodine diet, it can be more difficult to get enough vitamin D and calcium. Talk with your doctor or dietitian about taking supplements for these nutrients.

Seek support from a thyroid support group. Most dietary restrictions will be temporary. Other dietary changes are part of a healthy, balanced lifestyle for better overall health and wellness.