Can Iodine Deficiency Cause Cancer?

Iodine is essential for the production of two key hormones which regulate energy in the body T3 (triiodothyronine) and T4 (thyroxine). These two hormones are produced in the thyroid gland and have far reaching effects on the bodys’ metabolism, affecting digestion, mental function, cholesterol regulation and sleep.  Iodine is also essential for the necessary function of the immune system, as it contains potent anti-bacterial, anti-parasitic, anti-viral and anti-cancer properties. See our previous article to learn more about iodine requirements and testing.

Iodine deficiency is rapidly emerging as a major risk factor for breast cancer.

Human breast tissue and breast milk contain some of the highest concentrations of iodine. Breast tissue is rich in the same iodine-transporting proteins used by the thyroid gland to take up iodine from the blood. The evolutionary reasons for this are clear: iodine is essential to the developing newborn brain, so the mother’s body must have a direct means of supplying iodine to the nursing infant.

Iodine plays an important role in the health of women’s breast tissue.  In the presence of chemicals and enzymes found in breast tissue, iodine has been shown to exert a powerful antioxidant effect equivalent to vitamin C. Iodine-deficient breast tissue exhibits chemical markers of elevated lipid peroxidation, one of the earliest factors in cancer development.
Iodine-deficient breast tissue also shows alterations in DNA and increases in estrogen receptor proteins. Coupled with iodine deficiency-induced increases in circulating estrogen levels, these changes can substantially increase the risk of breast cancer in women with low iodine levels.

Iodine also helps regulate levels of the stress hormone cortisol and contributes to normal immune function. Abnormal cortisol levels and deficient immune function are significant contributors to the risks of breast cancer; women with fibrocystic breast disease may also suffer from elevated cortisol levels.

Studies of iodine therapy for breast cancer prevention are encouraging.
Continuous iodine given to cancer-prone rats cut mammary tumor rates nearly 2.5-fold. Breast cancer cells avidly absorb iodine, which in turn suppresses tumor growth and causes cancer cell death

Added dietary iodine reduces the size of both benign and malignant breast tumors, it is an effect credited in part to iodine’s direct reduction of lipid peroxidation levels. Although the doses of iodine used in these studies are substantial, equivalent to 5,000 mcg daily, no toxic effects of iodine were observed, either on thyroid function or in other tissues. Further benefits may be obtained by supplementing with selenium in addition to iodine; selenium is an essential cofactor in the enzymes used in thyroid and breast tissue to make optimal use of dietary iodine.

In addition to its obvious role in preventing breast cancer, increased iodine intake may be important in mitigating another common, if less lethal, breast disorder—fibrocystic breast disease or FBD.

While harmless, fibrocystic breast disease is extremely common. It is found in at least 9% of all women who undergo biopsies, though the actual rate is probably much higher. Animal studies have shown that fibrocystic breast disease can be induced by depriving breast tissue of iodine. These changes can be reversed by iodine doses equivalent to 5,000 mcg per day in humans.

Women with fibrocystic breast disease obtain substantial relief from oral administration of iodine at doses of 3,000-6,000 mcg, with 65% achieving improvements according to their own and their physicians’ assessments. In those studies, only 33% of placebo recipients reported any benefit. No side effects were detected at any of the doses used.

It appears Iodine has a clinical role to play in supporting breast, immune and gastro-intestinal health. Its role goes a lot further than just supporting the thyroid gland. To assess its clinical application to supporting your health, an iodine loading test is encouraged to identify the exact dosage requirements. This relatively simple test is conducted with a urine sample.


For more information regarding iodine, its role in health, and the iodine loading test, please contact clinical Nutritionist, Miles Price on 2881 8131, or


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