Patient education: Low-iodine diet (The Basics)

What is iodine? — Iodine is a mineral found in some foods. Your thyroid gland needs iodine to work properly. The thyroid is a gland in your neck that makes thyroid hormone (figure 1). This hormone controls how the body uses and stores energy.

In people with a condition called "hyperthyroidism," the thyroid gland is overactive. This means that it makes too much thyroid hormone. Some people with hyperthyroidism get treatment with something called "radioiodine." This comes in a pill or liquid you swallow. It destroys the overactive parts of the thyroid gland. Radioiodine is also used to treat thyroid cancer.

Why do I need a low-iodine diet? — If you plan to have treatment with radioiodine, your doctor might recommend following a low-iodine diet for a short time. This is because if you have a lot of iodine in your body, the radioiodine might not work as well. The diet is often followed for 7 to 10 days before treatment, plus 1 to 2 days after.

Table salt is a main source of iodine for most people. Any salt that is labeled "iodized" has iodine added to it. Iodine is also found in a few other foods, including dairy products, egg yolks, and some fish.

A low-iodine diet generally means getting less than 50 micrograms or iodine each day.

What can I eat and drink on a low-iodine diet?

●Grains – Homemade breads made with non-iodized salt and without eggs or milk. Grains and pastas without added iodine or iodine-containing ingredients.

●Fruits – Fresh, canned, or frozen fruits.

●Vegetables – Fresh vegetables with no salt added. Potatoes without the skin.

●Meats, poultry, and proteins – Small amounts of fresh beef, chicken, or pork. Egg whites, and unsalted nuts and nut butters.

●Other foods and drinks – Salt that says "non-iodized" on the label. Vegetable oil and condiments, spices, and seasonings other than salt. Chocolate that does not contain milk, soy, or salt. Tea, coffee, juice, and other drinks without red dye.

What foods and drinks should I avoid or limit on a low-iodine diet?

●Grains to avoid or limit – Store-bought breads, pastries, and cereals that contain iodine. Read the ingredient list on all packaged foods. Avoid foods that list "potassium iodate" or "calcium iodate."

●Fruits to avoid or limit – Maraschino cherries with red dye.

●Vegetables to avoid or limit – Canned vegetables (which often contain iodized salt), potato skins, frozen vegetables with added salt, and canned soups with beans or lentils. Canned, fresh, or dried beans and lentils.

●Dairy to avoid or limit – Milk and other dairy products including butter, cheese, yogurt, and ice cream.

●Meats, poultry, seafood, and proteins to avoid or limit – Fish from the ocean (including shellfish), sushi, and egg yolks. Cured meats like ham, sausage, and deli meats.

●Other foods and drinks to avoid or limit – Salt that says "iodized" on the label, products with red food dye, seaweed, kelp, chocolate, mayonnaise, lard, bouillon, and nutritional supplement drinks (sample brand names: Boost, Ensure). Soy products including soybeans, soybean oil, soy milk, and tofu. Packaged foods, sauces, and seasonings that contain added salt. Any products that contain iodate, iodides, iodate bread conditioners, algin, alginates, agar-agar, or carrageenan.

What else do I need to know? — You might also need to avoid taking certain supplements that contain iodine. This includes most multivitamins. Ask your doctor, nurse, or dietitian if you have questions about any foods, drinks, or supplements. They can also help you make a specific meal plan. It's important to make sure that you get all of the nutrients your body needs, even while you are limiting iodine.

After radioiodine treatment:

●Your doctor will do blood tests to check your thyroid hormone levels. You might need to repeat these tests every 4 to 6 weeks to see how the levels are changing.

●Your doctor might prescribe thyroid hormone medicines. This will give your body the right level of hormone that it cannot make on its own. Follow all of your doctor's instructions about taking your medicines.

More on this topic

Patient education: Thyroid cancer (The Basics)
Patient education: Hyperthyroidism (overactive thyroid) (The Basics)

Patient education: Hyperthyroidism (overactive thyroid) (Beyond the Basics)