Iodine Deficiency and Breast Cancer:
Is a Deficiency in This Vital Mineral the Cause?

The number of women diagnosed with breast cancer has been increasing dramatically in recent years. According to the Centers for Disease Control and Prevention, breast cancer is now the second most common cancer found in U.S. women and is the number one cause of cancer-related death in Hispanic women.

One in every eight U.S. women will be diagnosed with breast cancer; arming yourself with the latest prevention information, including the important role of iodine, may help reduce your risk.

One out of every eight women is diagnosed with the disease, with a staggering 4,000 new cases diagnosed weekly. Every year in the United States, more than 186,000 women are diagnosed with breast cancer and more than 41,000 die as a result of the disease. With all of the research and effort dedicated to cancer research, women want answers to prevent, treat and gain remission from the grip of breast cancer. Informed women are aware of the actions they can take to minimize their risk of developing breast cancer, including eating healthy, exercising on a regular basis, maintaining a healthy weight and attending regular screening appointments with their physician.

However, there is one secret weapon that many women are not aware of: the essential mineral known as iodine. Yes, the same iodine found in regular table salt may hold the key to breast cancer prevention. In 1924, iodine was added to table salt as part of a national program to prevent thyroid enlargement, known as goiter. Iodine has very well known topical antiseptic and microbial properties, but it has so many more functions that keep your body in a near-perfect running state.

The Basics of Iodine

Iodine is one of the most important minerals found in your body and it is essential for human life. Every single cell inside your body uses iodine in some form. Iodine is needed for proper brain development and cognitive processes, making it a key mineral during fetal gestation as cognitive potential begins formation. Iodine is also found in very high concentrations within the ovaries. It is involved in the metabolism of estrogen and acts as a buffer to the growth effect that is produced by estrogen.

Iodine also helps your hormone receptors to function properly, giving your hormones the ability to communicate with ease and allowing your moods to be regulated. The breast tissue also requires iodine in order to remain healthy. Without the proper amount of iodine, breast tissue can become fibrocystic or develop precancerous and cancerous lesions.

Iodine also plays a role in helping to regulate blood pressure and blood sugar, prevention and treatment of diabetes, and helping to maintain normal heart rhythms. Additionally, iodine found in the gastric mucosa helps protect your stomach from the abnormal growth of bacteria and can deactivate many chemical or biological poisons inside the stomach.

The largest amount of iodine in your body is found within the glandular (endocrine) system. Iodine is necessary for the production of several hormones. One of the best-known roles for iodine is in your thyroid gland, an endocrine organ located in your neck. Iodine is necessary for your body to produce thyroid hormones, which are secreted into your blood and then transported to every tissue in your body. Thyroid hormone is needed to help the cells of organs and tissues to function properly. It helps your body use energy, to stay warm, and allows your heart, brain and other organs to work at peak performance.

Thyroid hormone also helps regulate the formation of other hormones and affects sexual function. If your levels of thyroid hormone drop below normal, every major system in your body is affected, including: your heart, liver, kidneys and endocrine system. A shortage of iodine causes changes to your thyroid gland leading to decreased function of metabolism and the immune response.

Dr. James Wilson (a leading expert on thyroid function) states: “The largest amounts of iodine are stored in the palatine tonsils, located in the back of the throat, conveniently located about an inch or so from the thyroid gland, the largest user of iodine. People who have had their tonsils removed are much more likely to eventually have low thyroid function” resulting in many varying health issues. Next to the thyroid gland, breasts are the body’s second largest storage site for iodine. Iodine is needed for proper breast development, structure, shape and function. Without iodine, your body simply could not function.

Dr. Wilson further states: “In addition to the indirect relationship to iodine to breast cancer through its relationship with the thyroid and low thyroid being associated with a decreased immune response (to fight cancer), there is also a direct relationship between iodine and dbreast cancer.” Several studies have shown at least a correlation of low iodine reserves to breast cancer in demographic, clinical and laboratory studies. “Unfortunately, some areas of the United States and Canada, including and around The Great Lakes area are severly deficient in iodine in the water and soil, leaving the populations of this area vulnerable to low iodine. Furthermore, the US diet is severely lacking in iodine sources because food choices made by most Americans do not feature food containing much iodine.”

Luckily there are easy ways for us to get an abundance of iodine in our foods. Be sure to read the next part of this article on how to help yourself add iodine to your daily eating regiment.

Iodine and Your Diet – Are You Getting Enough?

Seaweed is one of the richest dietary sources of iodine. However, because seaweed bioaccumulates toxins from the waters in which it’s grown, look for varieties that come from non-polluted areas.

One of the most common misconceptions that people including even Doctors have been told is that table salt provides you with all of the iodine that your body needs to remain healthy. This could not be further from the truth. With only 10 percent of iodized salt being bioavailable, it is hardly enough to supply your body with the necessary amounts of iodine.

Despite all the data showing the importance of iodine in the body, many people are still unaware of the need to maintain their iodine levels. Resent research shows that iodine levels in humans over the last 30 years have plummeted by an average of 50 percent. This decline is thought to be one of the most logical reasons for the increased number of many serious chronic health problems, including breast cancer.

One researcher who has studied this issue in depth is David Brownstein, MD, author of Iodine: Why You Need It. Why You Can’t Live Without It. Dr Brownstein, who practices in the Great Lakes area, tested over 4,000 people, checking their iodine levels. He found that 96 percent of the people studied had below normal levels of iodine. What was even worse, most of them had levels that were so low, they were below any detectable limits. It is for this reason that eating a diet rich in iodine is so important for your overall health. Some suggestions for eating a well-balanced diet while boosting iodine include:

  • Seafood – Eating seafood just two times a week will provide most adults with enough iodine to meet their average iodine requirement. Make sure to choose only wild-caught seafood from non-polluted areas.
  • Dairy Products – milk and cheese are great sources of iodine, with one cup of milk having around 55/mcg.
  • Organic Yogurt – a natural probiotic, yogurt is a great food full of iodine and is easy to add to your diet. Look for natural varieties that do not contain excess sugar or artificial flavors.
  • Seaweed (kelp) and eggs – provide additional dietary sources of iodine.
  • Some vegetables – may contain iodine, but only if they are grown in iodine-rich soils.

Iodine Deficiency, Hypothyroidism and Breast Cancer

Recent research shows that prolonged deficiencies of iodine can exacerbate or be a contributing factor in the development of breast cancer. Animal studies conducted over 40 years ago showed that breast tissue of animals with iodine deficiency developed cancer when the deficiency was not corrected. The same study showed that the risk of breast cancer was directly related to the length of time the iodine deficiency was present.

Iodine deficiency is also known to cause a condition known as fibrocystic breast disease. It is a pre-cancerous condition of the breast tissue, which makes the breast very painful and fibrous. Due to the fibrous and dense nature of breast tissue in a fibrocystic state, it is very hard for doctors to detect the presence of breast cancer. Several studies have shown that supplementation of iodine significantly decreased breast pain, tenderness and nodules of women with fibrocystic breast disease. This makes it easier to evaluate breast tissue properly when testing for the presence of cancer. Other studies have shown that women with breast cancer tend to develop an enlarged thyroid more often than women who do not develop breast cancer. It is especially true among women who have swelling of the thyroid gland, known as goiter. Given the fact that the breasts and the thyroid glands must compete for iodine in the body when a deficiency is present, it makes sense that these conditions would both develop in the absence of proper iodine levels.

Additional studies show that women with breast cancer are more likely to develop hypothyroidism, or low thyroid function, than are women who are healthy. The researchers believe an association between hypothyroidism and breast cancer may be due to the biological effects that the thyroid hormones have on the cells of breast tissue. It is believed that iodine deficiency leads to excess estrogen, which then leads to breast cancer or fibrocystic breast disease. The ovaries normally concentrate iodine, but when iodine is deficient in the body, the ovaries simply produce more estrogen. This makes the breasts increase in sensitivity to the estrogens, which makes the risk of fibrocystic breasts and breast cancer much higher.

Iodine is thought to suppress the growth of tumors, induce the death of tumor cells and regulate the genes that influence hormone metabolism, the life cycle of cells growth and differentiation.

Hypothyroidism and Iodine Supplements

It is always very important to realize that if you have been diagnosed with hypothyroidism and are taking iodine supplements, your doctor needs to monitor your situation closely. You can also monitor your signs and symptoms for thyroid as well, by taking your basal body temperature and monitoring for signs and symptoms of low thyroid. As the iodine supplements begin to increase the efficiency of your thyroid function, you may require adjustments in the dosage amount of your thyroid medication. If your doctor does not monitor your medication dosage and thyroid function, when your thyroid begins to function normally, you put yourself at risk for experiencing symptoms of hyperthyroidism because with your thyroid now functioning normally, the added thyroid hormone from your medication can make you hyperthyroid. Some of the common signs and symptoms of hypo and hyperthyroidism are covered in our related article “How to Avoid Foods That Are Harmful to Your Thyroid”

  • Palpitations
  • Heat Intolerance
  • Nervousness
  • Insomnia
  • Breathlessness
  • Increased Bowel Movements
  • Light/Absent Menstrual Periods
  • Fatigue
  • Increased Heart Rate
  • Trembling Hands
  • Weight Loss
  • Muscle Weakness
  • Warm, Moist Skin
  • Hair Loss

If you notice any of these symptoms while taking iodine supplements, talk to your doctor right away about adjusting your dosage.


Integrative Health Review, The Link Between Iodine Deficiency and Breast Cancer

Global Healing Center — The Health Benefits of Iodine for Thyroid Health

Dr. David Derry Answers Reader Questions Brought to you by Mary Shomon, Your Thyroid Guide. Discussion of Iodine as Breast Cancer Prevention

Iodine: Why You Need It, Why You Can’t Live Without It (2nd Edition) by David Brownstein MD, Book.

Domest. Anim. Endocrinol. 20(I):97-103,

Siiteri, P. Increased availability of serum estrogens in breast cancer, a new hypothesis. In Hormones and Breast Cancer. Banbury Report No. 8. Cold Spring Harbour Laboratories

J Mammary Gland Biol Neoplasia.;10(2):189-96.

Is iodine a gatekeeper of the integrity of the mammary gland?

Aceves C, Anguiano B, Delgado G.


Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla. [email protected]


This paper reviews evidence showing iodine as an antioxidant and antiproliferative agent contributing to the integrity of normal mammary gland. Seaweed is an important dietary component in Asian communities and a rich source of iodine in several chemical forms. The high consumption of this element (25 times more than in Occident) has been associated with the low incidence of benign and cancer breast disease in Japanese women. In animal and human studies, molecular iodine (I(2)) supplementation exerts a suppressive effect on the development and size of both benign and cancer neoplasias. This effect is accompanied by a significant reduction in cellular lipoperoxidation. Iodine, in addition to its incorporation into thyroid hormones, is bound into antiproliferative iodolipids in the thyroid called iodolactones, which may also play a role in the proliferative control of mammary gland. We propose that an I(2) supplement should be considered as an adjuvant in breast cancer therapy.


Is there a role for iodine in breast diseases?

Venturi S.


Servizio di Igiene, ASL n1, Regione Marche, Pennabilli (Pesaro), Italy. [email protected]


It is hypothesized that dietary iodine deficiency is associated with the development of mammary pathology and cancer. A review of the literature on this correlation and of the author’s own work on the antioxidant function of iodide in iodide-concentrating extrathyroidal cells is reported. Mammary gland is embryogenetically derived from primitive iodide-concentrating ectoderm, and alveolar and ductular cells of the breast specialize in uptake and secretion of iodine in milk in order to supply offsprings with this important trace-element. Breast and thyroid share an important iodide-concentrating ability and an efficient peroxidase activity, which transfers electrons from iodide to the oxygen of hydrogen peroxide, forming iodoproteins and iodolipids, and so protects the cells from peroxidative damage. The mammary gland has only a temporary ability to concentrate iodides, almost exclusively during pregnancy and lactation, which are considered protective conditions against breast cancer.


Role of iodine in antioxidant defence in thyroid and breast disease.

Smyth PP.


Iodine Study Unit, Department of Medicine and Therapeutics, and Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Ireland. [email protected]


The role played in thyroid hormonogenesis by iodide oxidation to iodine (organification) is well established. Iodine deficiency may produce conditions of oxidative stress with high TSH producing a level of H_2O_2, which because of lack of iodide is not being used to form thyroid hormones. The cytotoxic actions of excess iodide in thyroid cells may depend on the formation of free radicals and can be attributed to both necrotic and apoptotic mechanisms with necrosis predominating in goiter development and apoptosis during iodide induced involution. These cytotoxic effects appear to depend on the status of antioxidative enzymes and may only be evident in conditions of selenium deficiency where the activity of selenium containing antioxidative enzymes is impaired. Less compelling evidence exists of a role for iodide as an antioxidant in the breast. However the Japanese experience may indicate a protective effect against breast cancer for an iodine rich seaweed containing diet. Similarly thyroid autoimmunity may also be associated with improved prognosis. Whether this phenomenon is breast specific and its possible relationship to iodine or selenium status awaits resolution.