The incidence of breast cancer in North America has been decreasing since 2000 but it is still the second-most common cancer in women next to lung cancer.
Approximately one in eight American women will develop breast cancer during their lifetimes. (1) While the U.S. and Canada represent only five percent of the world’s population, new breast cancer cases in these countries account for fifteen percent globally on an annual basis. (2)
Worldwide, the numbers of women diagnosed with breast cancer is increasing in developing countries. (3) Risk factors include:
- hormone imbalance
- diet and lifestyle
- certain medications
- exposure to radiation (X-rays)
- heavy alcohol consumption
- some personal care products
- exposure to environmental chemicals
- early menstruation, late childbirth, and late menopause (4)
- mammograms (yes, you read that right)
The Impact of Iodine on Breast Cancer Risk
Studies have found that Japanese women have a significantly lower risk of breast cancer than Caucasian women. (5,6)
“In general, 1 out of 8 women in the U.S. will be diagnosed with breast cancer in their lifetime. In Japan, that is 1 out of every 38, but it was even less a decade ago,” says Kazuki Takabe, MD, Clinical Chief of Breast Surgery at Roswell Park Comprehensive Cancer Center. (7)
This corroborates the extensive research by Bernard Eskin, MD, a renowned scientist and member of the faculty at Drexel University College of Medicine in Philadelphia. As early as the 1960s, Eskin found a correlation between iodine deficiency and the risk of breast cancer.
Iodine is an element found in Earth’s crust and is present in foods we eat. It is essential for proper thyroid and endocrine function and is actively involved in the development and health of breast tissue. Iodine deficiency often manifests in the formation of a goiter, when the thyroid tries to retain as much iodine as it can and thereby swells.
We sometimes forget that breasts are not just sweater pillows but are important glands (especially for women) that are part of the body’s endocrine system.
Breast tissues transport molecular iodine and it’s as important to the breasts as it is to the thyroid. (8) Indeed, there is a link between thyroid disorders and breast cancer; iodine deficiency may be the reason why. (9)
Iodine is essential for the development of healthy breast tissue during puberty. (10) It is an important nutrient for the cognitive development of fetuses and infants; the breasts contain iodine so it can be passed to infants from their mothers’ milk. It then follows that inadequate iodine is linked to the development of cancer in breast tissue.
“Ultimately, the etiology of all cancers is multifactorial with benefit assumed in the reduction of modifiable risk factors. There is substantial evidence that iodine deficiency is a modifiable risk factor in cancers of the stomach and breast.” (11)
Dr. Eskin found that iodine-deficient breast tissue is more susceptible to lesions and the formation of cancerous cells earlier and in greater amounts than tissue with adequate iodine. (12)
Furthermore, iodine inhibits breast cancer cell growth and up-regulates the genes responsible for controlling their expression in the first place. (13)
The Difference in Japanese Women
The typical diet of Japanese women includes lots of iodine-rich seaweed. It’s hypothesized that the higher iodine intake accounts for the decreased incidence of breast cancer in this demographic when compared with North American women.
Supporting this argument is the fact that when Japanese and other Southeast Asian women emigrate to Western countries and adopt the local diet, their incidence of breast cancer increases. (14)
In the early part of the twentieth century, food manufacturers started to add iodine to salt in an effort to add this important mineral to North American diets and prevent goiter. (15) We now know that too much salt (an easily-acquired taste) can raise blood pressure, with implications for cardiovascular illness and stroke risk.
Iodized salt is therefore not the best source for ensuring adequate iodine. The better option is to eat foods that naturally contain iodine; pregnant and lactating women should be especially vigilant to get enough. (16)
Iodine is found in trace amounts in many foods. If you eat a variety, you should be able to meet your daily requirement of sufficient iodine.
Recommended daily intake of iodine for adults and about twice that for pregnant and nursing women.
- Birth to 6 months: 110 mcg
- 7-12 months: 130 mcg
- 1-3 years: 90 mcg
- 4-8 years: 90 mcg
- 9-13 years: 120 mcg
- 14+ years: 150 mcg
Pregnant women: 220 mcg
Lactating women: 290mcg
Topping the list of iodine-rich foods is seaweed-you can add it to whatever you’re eating, raw or cooked. Others:
- cheese and other dairy
- saltwater fish and shellfish
- beans and legumes
- Himalayan salt
- unpeeled potatoes
What to Avoid
A class of chemicals called halides (of which iodine is one), found almost universally in the Western world, is known to interfere with hormone metabolism.
Other halides include fluorine, chlorine, and bromine. These chemicals all compete with iodine receptors in the body; over-exposure to other halides hinders the body’s absorption of iodine from the foods we eat.
Halides can be found in plastics, processed foods, soft drinks, fire retardants, medications, pesticides, fabrics, commercially baked foods, and swimming pools. Look for ingredients that contain “fluor-” (e.g., fluoridated water), “chlor-” (e.g., chlorine bleach), and “brom-” (e.g., brominated vegetable oil, potassium bromate) to keep these out of your diet.
If you are at risk for breast cancer (and for long-term breast health), you may benefit from adding a little more iodine to your diet. If you have a thyroid condition, consult your healthcare provider to discuss how to naturally regulate iodine levels.