The Link Between Iodine, Breast Cancer, And Thyroid Disease

Health disorders don’t just pile on the medical bills and sick leaves, they also affect one’s quality of life. And, having to spend a good chunk of your life being dictated by pills and hospital visits can be difficult.

Thyroid diseases and breast cancer are a few such health disorders. And, although there are separate treatment options for each of them, the mineral nutrient iodine might have an important role in them all. But, before we go on to look at this connection, it’s important to understand how these disorders are linked.


Linking Breast Cancer And Thyroid Disorders

Thyroid pills increase breast cancer risk.

Although both breast cancer and thyroid disorders seem like separate health conditions, recent research indicates that the lines between them might be blurred. Here are a few factors that they share.

  • Female predominance: The prevalence of both, thyroid diseases and breast cancer is higher in women as compared to men. Additionally, the risk of both is higher around pre-menopause.1
  • Incidence of risk: Research indicates that the incidence of breast cancer is higher in among patients receiving thyroid medicines.2 Inversely, studies also indicate that patients with breast cancer have an increased risk of developing autoimmune and nonautoimmune thyroid diseases.3
  • Growth stimulus: The pattern of tumor growth in breast cancer is similar to that of the enlargement of the thyroid gland.4

Despite the above similarities, experts believe that the most important link between breast cancer and thyroid diseases is iodine.

Iodine For Breast Cancer And Thyroid Diseases

Iodine For Breast Cancer And Thyroid Diseases


Iodine is essential for both breast and thyroid health. Although the breast tissue has a greater concentration of iodine when compared to the thyroid gland, both share the same iodine-transporting proteins.

In women, iodine is crucial for the production of breast milk. Additionally, it is important for mothers to have healthy iodine levels in their bodies, so as to supply it to their infants who depend on the mineral for their brain development.


In the thyroid gland, iodine plays an important role in the synthesis of hormones for the healthy functioning of the organ. And, in both the organs, iodine is believed to offer antioxidant benefits. Hence, its deficiency is bound to come with a few complications.

Iodine deficiency disrupts the formation of thyroid hormones. Improper hormone functioning, in turn, produces oxidative stress which is linked to non-toxic goiter and thyroid cancer. Additionally, hyperthyroidism or Hashimoto’s disease might also worsen due to iodine deficiency.


When it comes to breasts, studies indicate that iodine deficiency alters the structure and function of the mammary glands of rats, making them susceptible to malignant cell growth.5

However, the link between iodine deficiency, breast cancer, and thyroid diseases has been studied in reference to Japanese diets. In Japan, the incidence of breast cancer is 6.6 people per 100,000 people. In comparison, in the U.S., 22 people in 100,000 people are prone to breast cancer. Japan also has significantly lower rates of hypothyroidism, autoimmune thyroid disease, and hypothyroid conditions.


The researchers found the underlying cause for low incidences of each of these diseases in their iodine intake, which is 25 times that of Americans.6

Treating Iodine Deficiency

Seafood is rich in iodine.


It’s important to avoid iodine deficiency to prevent breast cancer and thyroid disorders. This involves meeting the recommended intake of 150 mcg for average adults. Pregnant women need to up this intake to 220 mcg, while lactating mothers need to consume 290 mcg.

Iodine deficiency is generally caused due to poor soil quality, which affects the iodine content of the food that’s grown on it. Besides this, protein-energy malnutrition, contaminated drinking water, and diets that disrupt intestinal absorption also increase the risk of iodine deficiency.7

Although iodized salt is recommended for iodine deficiency, a few experts state that salt reduces the bio-availability (absorbability) of iodine. Additionally, most of the salt intake in the United States comes from processed foods, and food manufacturers almost always use non-iodized salt in processed foods.

In the Japanese, the high intake of iodine is courtesy of seafood, especially seaweed. Other food sources of iodine include dairy products, grain products, and egg. You could also opt for supplements, but be sure to consult a professional before you do.8 9

If you are at risk of breast cancer or suffer from thyroid disorders, do talk to a health professional about your iodine intake. Although researchers are still looking into the effect of adequate iodine on each of these disorders, it might be best to keep up with your intake to ensure you’re doing all that it takes to stay healthy.