Laura Pole, RN, MSN, OCNS, BCCT Senior Researcher

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Nancy Hepp, MS, BCCT Project Manager

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Last updated November 18, 2020.

Key Points

  • Before using this therapy, consult your oncology team about interactions with other treatments and therapies. Also make sure this therapy is safe for use with any other medical conditions you may have.
  • Iodine, a mineral found in some foods, is used by your body to make thyroid hormones.
  • Some foods can inhibit your body’s use of iodine. Those diagnosed with thyroid cancer or at high risk of thyroid cancer should avoid soy, cassava, and cruciferous vegetables.
  • Some clinical evidence shows usefulness in treating breast cancer, but no definitive studies support the use of iodine supplements to enhance the effectiveness of chemotherapy or decrease heart toxicity.
  • Iodine deficiency is a risk factor in breast cancers and thyroid cancer. Excess iodine absorption may promote cancer cell growth in some types of breast cancer.
  • Iodine is an antioxidant and antiproliferative agent and an immune response activator.
  • Iodine can interact with many medications, and excessive iodine intake can cause health risks.

Iodine, a mineral found in some foods, is used by your body to make thyroid hormones. These hormones control your body’s metabolism and many other important functions. Getting enough iodine is important for everyone, especially infants and women who are pregnant.1 Read more about the role of thyroid hormones on our Thyroid Hormones and Cancer page.

Forms of Iodine

Iodine in food, including iodized salt, has several chemical forms. The elemental form of iodine is rarely found, usually taking the form of iodide in a salt, such as potassium iodide or sodium iodide. Other forms include inorganic iodine and iodate. 

Your gastrointestinal tract absorbs iodide from food and iodized salt, or it converts iodate into iodide and then absorbs it. The thyroid gland concentrates iodide to use in making thyroid hormones. Excess iodide is excreted in the urine. A small study found that potassium iodide is almost completely (96.4 percent) absorbed in humans.2

Treating the Cancer

Working against cancer growth or spread, improving survival, or working with other treatments or therapies to improve their anticancer action

Clinical Evidence

Breast Cancer

  • No definitive human studies support recommending iodine supplements for increasing sensitivity to chemotherapy drugs, decreasing resistance to chemotherapy drugs or decreasing heart toxicity with breast cancer.
  • Increased five-year disease-free survival in patients treated with a molecular iodine supplement before and after surgery, compared to those receiving it only after surgery3
  • Suppressed development and size of both benign and cancerous neoplasias (abnormal growths) in humans and animals4

Lab and Animal Evidence

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Food and Iodine

A diet without enough iodine and other key nutrients can contribute to illnesses associated with the thyroid, including cancer. The National Institutes of Health lists the following dietary sources of iodine:

  • Fish (including cod and tuna), seaweed, shrimp and other seafood, which are generally rich in iodine
  • Dairy products (such as milk, yogurt and cheese) and products made from grains (like breads and cereals), which are the major sources of iodine in American diets
  • Fruits and vegetables which contain iodine, although the amount depends on the iodine in the soil where they grew and in any fertilizer that was used
  • Iodized salt, which is readily available in the United States and many other countries; processed foods, however, such as canned soups, almost never contain iodized salt9

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Managing Side Effects and Promoting Wellness

Managing or relieving side effects or symptoms, reducing treatment toxicity, supporting quality of life or promoting general well-being

Clinical Evidence

  • Reduced levels of heart distress enzymes during epirubicin chemotherapy for breast cancer13
  • Reduced fibrocystic breast symptoms14

Lab and Animal Evidence

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Reducing Risk

Reducing the risk of developing cancer or the risk of recurrence

Clinical Evidence

Breast Cancer

  • Deficiency is a risk factor in breast cancers16
  • Excess iodine absorption (such as from antiseptic use during breast surgery) may stimulate estrogen receptor signaling and promote cancer cell growth in some types of breast cancer.17
  • No definitive human studies support recommending iodine supplements to prevent breast cancer

Thyroid Cancer

Lab and Animal Evidence

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Optimizing Your Terrain

Creating an environment within your body that does not support cancer development, growth or spread

  • Antioxidant and antiproliferative agent20
  • Immune response activator21


Food sources of iodine and iodized salt are readily available (see highlight box at right). Many multivitamin/mineral supplements contain iodine in the forms of potassium iodide or sodium iodide. Dietary supplements of iodine or iodine-containing kelp (a seaweed) are also available. 


Iodine can interact with many medications. Before taking an iodine supplement, consult your physician regarding safe use. Consult your pharmacist to check if you are taking any medications or supplements that may interact with iodine.

Excessive iodine intake can cause health risks (hyperthyroidism, goiter, thyroiditis, thyroid cancer). Overdose can result in acute poisoning symptoms. People with autoimmune thyroid disease and iodine deficiency may have side effects when taking iodine doses considered safe for the general population.22

Some people are intolerant of, or sensitive to, iodine in chemical agents such as radiocontrast agents (for x-rays), in iodine-containing disinfectants like Betadine, or even in foods. If people suspect they have an iodine allergy, their doctor can run tests to confirm. An individual should make sure that all medical professionals are aware of an iodine allergy before medical treatment.23

Radioactive iodine (RAI) treatment for patients with thyroid cancer does not appear to increase the risk or recurrence of breast cancer.24


BCCT does not recommend therapies or doses, but only provides information for patients and providers to consider as part of a complete treatment plan. Patients should discuss therapies with their physicians to evaluate contraindications, interactions and side effects. 

Levels of active ingredients of natural products can vary widely between and even within products. See Quality and Sources of Herbs, Supplements and Other Natural Products.

Dosage recommendations for iodine deficiency are available from these sources:

Integrative Programs, Protocols and Medical Systems

For more information about programs and protocols, see our Integrative Programs and Protocols page.
  • Programs and protocols
    • Alschuler & Gazella complementary approaches25
    • McKinney protocols26


From naturopathic oncologist and BCCT advisor Lise Alschuler, ND, FABNO: Iodine should be supplemented only when there is confirmed deficiency.

View All References

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