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 certain thyroid patients who require radioactive iodine treatment, a low-iodine diet is necessary to increase the effectiveness of the therapy because iodine in the diet can prevent the thyroid gland from taking up the radioactive iodine.

Therefore, it may be necessary to be on a low-iodine diet for one to two weeks prior to receiving a radioactive iodine treatment.

Dr. Kenneth B. Ain of the University of Kentucky Medical Center has provided the following information to help you follow a low-iodine diet, if needed.

General Information About the Low-Iodine Diet

  • Low iodine has nothing to do with sodium. Sodium in any form is OK, as long as it is not provided as iodized salt. Non-iodized salt is OK for the diet.
  • No milk or milk products are permissible because milk is an intrinsic site for the biological concentration of iodine. In addition, commercial milking machines are often cleansed with iodine solutions, as are containers and cows' teats.
  • Most commercial vitamin preparations have iodine added as an essential nutrient. The only preparation which I have found to be fine for the diet is Vicon Forte=AE.
  • The problem with food colors is specific to Red dye FD&C #3 (erythrosine) only. FD&C Red #40 is OK. The problem is that most food labels do not specify which red dyes are used, and it is better to be safe than sorry. For medications, the best source is the Physician's Desk Reference (PDR), which clearly states the ingredients. For example, Rocaltrol 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 diet (you can combine two of them to get to the 0.5 microgram dose). Please always check with your physician.

    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 (on-iodized salt may be used).
    • Dairy products (milk, cheese, cream, yogurt, butter, ice cream)
    • 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)

    Additional Guidelines

    • Avoid restaurant foods since there is no reasonable way to determine which restaurants use iodized salt.
    • Non-iodized salt may be used as desired.

    Important Note

    Food prepared from any fresh meats, fresh poultry, fresh or frozen vegetables, and fresh fruits should be fine for this diet, provided that you do not add any of the ingredients listed above to avoid.

    Learn more about thyroid disease and your diet.

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