• By Deanna Segrave-Daly
  • In 2018
  • January 24, 2018

The Low Iodine Diet for Thyroid Cancer Diagnosis

by Zachari Breeding, MS, RDN, LDN, FAND

Thyroid Cancer is a type of cancer usually found in women (3 out of every 4 diagnoses compared to men) and is commonly diagnosed at a younger age than other adult cancers. Though mortality remains steady and low compared to other types of cancers, living with a partial or lack of thyroid tissue carries its own innate health concerns.

Most cases of thyroid cancer are known as papillary or mixed papillary-follicular subtype. The naming of these types has to do with the location of the cancer cells. Prognosis for these types are positive, with little risk of spreading to other areas of the body. When caught and treated early enough, lymph tissue is usually unaffected as well. Treatment typically includes a partial or total thyroidectomy and treatment with thyroid replacement therapy.

A partial or total thyroid resection (or thyroidectomy) may be performed if a person suffers from goiter, thyroid cancer, or hyperthyroidism. Because the thyroid gland produces hormones that regulate your metabolism, its removal can make it difficult to attain a healthy weight. Specifically, during initial management of thyroid replacement therapy (i.e. levothyroxine), weight and other nutrition markers can fluctuate. If there is little to no thyroid tissue left after resection, certain nutrition markers should receive extra attention. Of most note are calcium and vitamin D due to increased risk of hypocalcemia (from chronic hypothyroidism) and bone loss (from chronic hyperthyroidism). Because the body is no longer able to produce thyroid hormones post thyroidectomy, they run the risk of being chronically hypothyroid. This could also be related to inadequate management of levothyroxine or from endocrinologists’ recommendations to keep thyroid hormone slightly low to prevent regrowth of tissue. Furthermore, hyperthyroidism could also occur due to inadequate management of levothyroxine and poor adherence to follow-up protocol; if left untreated, osteoporosis could occur.  

Regardless of how much thyroid tissue is removed, interventions for papillary or follicular types usually include radioactive iodine treatment. During this treatment, a low iodine diet is recommended for the 14 days prior to treatment. When less than 50 micrograms of iodine are consumed daily (standard for the low iodine diet), the thyroid tissue cells (including thyroid cancer cells) become “starved” for iodine. Thus, when the radioactive iodine is administered, these cells are more likely to be destroyed at a higher rate than without adherence to the diet regimen.  

The low iodine diet is one that most dietitians are not educated on, since the prevalence of thyroid cancer is relatively low and is typically monitored closely by an endocrinologist. As the multidisciplinary approach to care becomes more popular, however, it is essential for the dietitian to be aware of the specifics of this dietary protocol. Of note, the most essential foods to avoid contain notable levels of iodine and include the following:

  • Cured, packaged, processed, and canned foods and meats
  • Foods containing red food dyes
  • Seafood or sea products (including seaweed, fish, carrageenan, Fish Oil, etc.)
  • Dairy products and eggs
  • Most commercial bakery products and chocolates
  • Soybeans and soy-based products; Legumes including red kidney beans, lima beans, navy and pinto beans
  • Skins of root vegetables (especially potatoes)

The recommended diet for those undergoing radioactive iodine treatment should include:

  • Kosher salt (check ingredients to ensure no iodine has been added)
  • Fresh fruits and vegetables
  • Fresh animal protein up to 6 ounces daily
  • Unsalted nuts and nut butters
  • Grains, cereals, and pasta up to 4 (1/2 cup) servings daily, provided it has no high-iodine ingredients
  • Fresh and dried herbs, spices, and vegetable oils
  • Jams, jellies, honey, real maple syrup

Zach Breeding, MS, RDN, LDN, FAND, is a Philadelphia-based registered dietitian nutritionist, professional chef and clinical dietitian at The Cancer Treatment Centers of America. He is the author of The Slice Plan: An Integrative Approach to a Healthy Lifestyle and a Better You. Connect with Zach on his website, The-Sage: Nutritious Solutions, and on Facebook and Twitter.


  1. Thyroid Cancer Survivors’ Association. http://www.thyca.org/pap-fol/lowiodinediet. Accessed December 29, 2017.
  2. American Cancer Society. Thyroid Cancer website. https://www.cancer.org/cancer/thyroid-cancer/after-treatment/follow-up.html. Accessed December 29, 2017.