The Low Iodine Diet for Radioactive Iodine Treatment

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Iodine is a mineral that plays an important role in several bodily processes, one of which is the production of the hormone thyroxine in the thyroid gland. For optimal health, adults need about 150 mcg of iodine a day. Found naturally in certain foods, most iodine is in our diet comes from iodized salt, dairy products, and breads.

However, for many thyroid patients who require radioactive iodine treatment, a low-iodine diet prior to treatment is necessary. The low-iodine diet increases the effectiveness of the therapy because iodine in your diet can prevent your thyroid gland from taking up the radioactive iodine. Following a low-iodine diet for one to two weeks prior to receiving a radioactive iodine treatment makes your thyroid more receptive to the iodine.

General Information About the Low-Iodine Diet

Here is some important information to keep in mind regarding the low-iodine diet. 

  • Low iodine has nothing to do with sodium. Sodium in any form is fine, as long as it is not in the form of iodized salt. Non-iodized salt is fine for the low-iodine diet.
  • No milk or milk products are permissible because milk concentrates iiodine, and there is no way to get iodine-free milk. addition, commercial milking machines are often cleaned with iodine solutions, as are containers and cows' teats.
  • 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
  • You need to avoid foods with red dyes. The problem is specific to Red Dye FD&C #3 (erythrosine) but most food labels do not specify which red dyes are used, so it's better to avoid all red dyes.
  • Make sure other medications do not contain iodine, usually from red dye. For medications, the best source is the Physician's Desk Reference (PDR), which clearly states the ingredients. For example, Rocaltrol brand calcitriol in the 0.5 microgram size is not good for the diet because it contains FD&C Red #3; however, the 0.25 microgram size does not contain that dye and is safe for the low-iodine diet. also has a list of drugs with Red Dye #3. Always check with your physician and pharmacist.

    The Low-Iodine Diet

    Avoid the following foods, starting when instructed prior to your radioactive iodine test, and continue until after your radioactive iodine treatment is completed.

    • Iodized salt, sea salt (non-iodized salt may be used).
    • Dairy products (milk, 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 (usually small bakery breads are safe; it's best to bake it yourself or substitute with Matzo)
    • Foods and medications that contain red food dyes (consult your doctor before discontinuing any red-colored medicines). The specific bad red dye is Red Dye #3 (erythrosine). The problem is that most ingredient lists do not tell you which red dye is used.
    • Chocolate (for its milk content)
    • Molasses
    • Soy products (soy sauce, soy milk, tofu)
    • Any vitamins or supplements that contain iodine (especially seaweed, kelp and dulse)
    • Milk chocolate (due to dairy content)
    • Blackstrap molasses (unsulfured molasses is fine)

    What to Eat

    A key to success on the low-iodine diet is preparing your own food. You can make breads and baked goods with non-iodized salt and eggs, and prepare meats, vegetables, and poultry without added iodine for a healthy, delicious diet. 

    Other foods you can eat include:

    • All fresh and unprocessed meats, vegetables, and poultry
    • Egg whites
    • Canned fruit
    • Unsalted nuts and nut butters (peanut, almond, etc)
    • Popcorn with non-iodized salt
    • All spices and vegetable oils 

    The Thyroid Cancer Survivor's Association has some helpful guidelines on the low-iodine diet, as well as a free downloadable "Low-Iodine Cookbook" with over 400 recipes. 

    A Word From Verywell 

    Avoid restaurant foods since there is no reasonable way to determine which restaurants use iodized salt. But food prepared from any fresh meats, fresh poultry, fresh or frozen vegetables, and fresh fruits should be fine for the low-iodine diet, provided that you do add iodine-containing ingredients. 

    Also, a helpful read is the blog "Our Two Week Low Iodine Diet Adventure," which includes helpful tips and recipes. 

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