The Low-Iodine Diet for Radioactive Iodine Treatment

If you are going to have radioactive iodine treatment for your thyroid disease, you will have to prepare in advance by following a low-iodine diet. Doing so for at least two weeks prior to receiving your treatment makes your thyroid more receptive to the radioactive iodine, increasing its effectiveness. You'll need to continue to maintain this diet until your iodized radiation treatment is complete.

Radioactive iodine is taken as a pill to permanently reduce your thyroid gland activity. There are a few different thyroid conditions that may be treated with radioactive iodine therapy, including several types of thyroid cancer as well as some kinds of benign (non-cancerous) hyperthyroidism.
What to Avoid

There are certain restrictions when you are on a low-iodine diet. Some foods either contain iodine or increase your absorption of iodine.

Foods to avoid while you are on a low-iodine diet include:

• Iodized salt
• Dairy products—cheese, cream, yogurt, butter, ice cream
• Egg yolks, whole eggs, and foods containing whole eggs
• Seafood fish, shellfish, seaweed, kelp
• Foods that contain the additives: carrageen, agar-agar, algin, alginates
• Cured and corned foods—ham, lox, corned beef, sauerkraut
• Bread products that contain iodate dough conditioners
• Milk chocolate
• Soy products — sauce, soy milk, tofu
• Any supplements that contain iodine, especially seaweed, kelp, and dulse
• Blackstrap molasses (unsulfured molasses is fine)

Special Considerations

Foods and medications may be processed with iodine-containing Red Dye #3 (erythrosine). Your doctor or pharmacist can tell you if any of your regular medications contain iodine, in which case you may need to change to a different prescription before and throughout your radioactive iodine treatment.

You can find information about the iodine content in any of your over-the-counter pills by checking the manufacturer's website or by asking your pharmacist. Be sure to consult with your doctor before discontinuing any red-colored medicines.

Most commercial vitamin preparations have iodine added as an essential nutrient. Read labels carefully and ensure that you are taking an iodine-free vitamin while following the low-iodine diet.

Eliminating the above foods may seem quite limiting, but there are many foods that you can eat while on a low-iodine diet. Many lament about the need to cut out salt, but know that it's fine to use non-iodized salt if you desire.

Foods you can eat while on a low-iodine diet include:

• Non-iodized salt
• Fresh, canned, and frozen vegetables in cooked or raw form
• Unprocessed meats, including beef, pork, and poultry
• Pasta and rice
• Some bread
• Matzo
• Egg whites
• Fresh or canned fruit in cooked or raw form
• Unsalted nuts
• Unsalted nut butters such as peanut butter and almond butter
• Popcorn with non-iodized salt
• Dark, non-dairy chocolate
• Iodine-free spices
• Vegetable oils 
• Soft drinks, coffee, tea

Even if you pick up a prepared dish or order something off a menu that seems to be made from foods that are fine for a low-iodine diet, you need to exercise some caution.

While some ingredients in a dish may be quite obvious, others—like those in a "special sauce"—may not be. Ask questions of your server. You may also be able to request some restaurant or catered foods without salt or with non-iodized salt.

Baked goods are often made with iodized salt, salted butter, egg yolks, and/or dairy products. Seek out specialty grocery stores and bakeries that sell items prepared with low iodine. Preparing these items yourself, however, may be easier.

A Word From Verywell 

Radioactive iodine treatment can be a very effective method of addressing thyroid disease. The process requires a good deal of planning and preparation on your part, between following a low-iodine diet, adjusting some of your medications ahead of time, and so on. Be sure you are clear on the instructions you need to follow to ensure that you get the most out of your treatment.