People with thyroid cancer may be prescribed a treatment called radioactive iodine (RAI or I-131). Thyroid cells (cancerous or not) "feed" on iodine. By cutting out most iodine from your diet, you "starve" these cells. When you have RAI treatment, these starved cells are more likely to feast on the RAI and then be destroyed by the radioactivity. This increases the effectiveness of treatment.

A smaller dose of RAI may also be used prior to a whole body scan (WBS) to determine if the thyroid cancer cells have spread; a low-iodine diet is usually prescribed before this study.

The amount of time necessary to be on the low-iodine diet may vary, but 7-10 days is typical. Follow your doctor’s specific orders, including any diet guidelines provided.

The low-iodine diet is only temporary, but it does require careful planning. This diet often eliminates eating out and using pre-prepared foods. Low iodine does not mean salt-free, so know that you can enjoy some tasty foods while on the diet. Try these tips for following a low-iodine diet:

Avoid:

  • Iodized salt and sea salt
  • Products containing iodized salt and sea salt
  • Dairy products such as milk, cheese, ice cream, yogurt, butter, and sour cream
  • Seafood such as fish and shellfish
  • Other products from the ocean such as agar, seaweed, and carrageenan
  • Baked goods made with iodized salt (most grocery store breads)
  • Eggs yolks and whole eggs (egg whites are okay)
  • Red Dye #3
  • Milk chocolate (cocoa powder and dark chocolate are usually okay)
  • Soybean and soy products (soy milk and tofu)
  • Navy, lima, pinto, cowpeas, and red kidney beans
  • Rhubarb
  • Potato skins
  • Molasses (sulfured, such as blackstrap molasses)
  • Foods processed with iodized salt (look for salt-free canned goods)
  • Vitamins or supplements containing iodine

What You Can Eat:

  • Kosher salt (check label to make sure no iodine has been added)
  • Fruits (except rhubarb and maraschino cherries)
  • Raw or frozen vegetables without salt
  • Unsalted nuts and unsalted nut butters
  • Egg whites
  • Fresh meats (usually no more than 6 oz. per day, as meats contain some naturally occurring iodine)
  • Grains, oatmeal, and cereals with no iodized salt
  • Pasta
  • Sugar, jelly, jam, honey, and maple syrup
  • Black pepper, fresh or dried herbs, and spices
  • Oils
  • Brewed coffee, brewed tea, lemonade, and fruit juices

Check Food Labels

The most important thing to do while following a low-iodine diet is to read food labels. When in doubt, do not eat the food. Iodine is not typically listed in the nutrition facts, so read the ingredient list. If the ingredients include salt, it is probably iodized and you should avoid that while on a low-iodine diet.

Visit ThyCa: Thyroid Cancer Survivors’ Association, Inc. for many low-iodine recipes to help you prepare for your RAI treatment.

Realated Resources

General Information About Thyroid Cancer

Cancer Side Effects: Tips for Managing Hypothyroidism