Why Iodine and Selenium Are Useful For Breast Cancer
One of the things I always recommend for women after they have been through the gamut of treatments for breast cancer is that they go and get their thyroid checked out by their doctor, and the reason I make this recommendation is that there is almost always an issue with the thyroid for breast cancer patients. It is important to note that having hyperthyroidism (an overactive thyroid) can increase your breast cancer risk. Interestingly, however, a person who has had breast cancer already can often find themselves with a hypothyroid (underactive thyroid) condition. How can this be? Iodine and selenium are part of this equation and play an important role.
Hyperthyroidism Increases Breast Cancer Risk
In 2010, the results of a 20-year study that followed over 2600 women were reported in Breast Cancer Research. The women were divided into four groups based on their thyroid hormone levels and the study found that the higher the levels of thyroid hormone, the greater their risk for breast cancer, a nearly 7 times higher risk. Those with the lowest thyroid hormone levels had the lowest risk. The women in the intermediate level groups had 3 and 5 times the risk of those with low to normal levels. (Tosovic A, Bondeson AG, Bondeson L, Ericsson UB, Malm J, Manjer J. Prospectively measured triiodothyronine levels are positively associated with breast cancer risk in postmenopausal women. Breast Cancer Res. 2010;12(3):R33. Epub 2010 Jun 11)
Some of the symptoms of an overactive thyroid include sudden weight loss, rapid heartbeat, increased appetite, nervousness and anxiety, tremors, sweating, changes in bowel patterns, fatigue, difficulty sleeping, skin thinning and fine, brittle hair. If you are experiencing a lot of these symptoms, best to go and get your thyroid checked out.
Those With Breast Cancer Often Have Hypothyroid Condition After Treatments
Conversely, it has been discovered that people who have gone through the treatments for breast cancer often find themselves with a hypothyroid (underactive thyroid) condition and at first it was thought that the actual treatments had caused the problem – radiation was particularly suspected.
In 2008, however, a large study completed by MD Anderson discovered that radiation treatments did not increase rates of hypothyroidism, but just having breast cancer did – those who had breast cancer had a 21% higher risk of being hypothyroid compared to the control group. (Smith GL, Smith BD, Giordano SH, Shih YC, Woodward WA, Strom EA, et al. Risk of hypothyroidism in older breast cancer patients treated with radiation. Cancer. 2008 Mar 15; 112(6): 1371-9)
The naturopath so often quoted in this website, Dr Jacob Schor, says that “… nutritional deficiencies, in particular iodine and possibly selenium deficiency may be to blame. The second theory getting attention is that the breast cancer triggers an autoimmune reaction leading to hypothyroidism.”
Dr Schor further stated recently “The immune system may accidentally attack the thyroid gland after being provoked by the cancer. Perhaps patients with breast cancer experience an immune response to the breast tumor that is also directed against the thyroid gland. Both breast and thyroid tissue share the same sodium-iodide symporter and the immune system may simply target an antigen the two have in common.”
Interesting observation, is it not? Dr Schor feels that some patients may be deficient in iodine, while others may have autoimmune thyroid disease triggered by their cancer. His thinking is that we should be testing breast cancer patients both for iodine deficiency and for thyroid antibodies. He goes on to say “Iodine is the greatest common denominator linking both breast and thyroid health.”
Iodine’s Role in Breast Health
Your breasts contain one of the highest concentrations of iodine in your body. Most natural therapists know that an iodine deficiency is associated with cyst formation. Many women develop fibrocystic breast disease, with cysts turning into small lumps called nodules. In prolonged iodine deficiency, these nodules become hyperplastic, meaning that cells are multiplying abnormally. And hyperplasticity is a precursor to cancer. Thus, long-term iodine deficiency can lead to breast cancer.
Both animal and human studies indicate that iodine suppresses breast cancer development. Some researchers have felt that iodine should be used for breast cancer therapy because of its antiproliferative properties in the mammary gland. (Aceves C, Anguiano B, Delgado G. Is iodine a gatekeeper of the integrity of the mammary gland? J Mammary Gland Biol Neoplasia. 2005 Apr;10(2):189-96)
An interesting study done on rats pretreated with iodine demonstrated that the iodine protected them from developing breast cancer after they were exposed to a strong carcinogen normally used to trigger breast cancer (Funahashi H: Wakame seaweed suppresses the proliferation of 7,12-dimethylbenz(a)-
An even more interesting study done on rats by the same researchers found that an iodine-rich solution made from a combination of seaweed and water suppressed carcinogenesis in rats, and in test tubes it induced apoptosis (programmed cell death) more efficiently than the chemotherapy drug fluorouracil. (Funahashi H, Imai T, Mase T, Sekiya M, Yokoi K, Hayashi H, Shibata A, Hayashi T, Nishikawa M, Suda N, Hibi Y, Mizuno Y, Tsukamura K, Hayakawa A, Tanuma S: Seaweed prevents breast cancer? Jpn J Cancer Res 2001, 92:483-487)
It isn’t just the thyroid and breasts that need iodine, however. Other tissues that absorb and use large amounts of iodine include salivary glands, pancreas, cerebrospinal fluid, skin, stomach, brain and thymus.
Seaweed To The Rescue
Seaweed has a long history of being a rich source of iodine. In places like Japan where dietary seaweed intake is high, there is a much lower incidence of breast cancer – only 6.6 people out of 100,000 get breast cancer in Japan. The rate in the UK is 27 per 100,000 and 22 per 100,000 in the USA. I read today that it’s much worse in Australia, the rate is closer to 113.5 per 100,000.
Dietary sea vegetables provide 25 times more dietary iodine than is found in the standard American diet and it is thought that this high iodine intake may be part of what accounts for the low risk of breast cancer among Japanese women. In particular wakame and mekabu seaweed are good sources of iodine and can generally be purchased from health food shops and purveyors of Asian foods.
Why not iodized salt? It would initially seem this might be an easier (and possibly more palatable) source of iodine. The problem is that common table salt is actually toxic and bad for your health! See my article The Salt That Can Improve Your Health for more information.
The recommended daily dose for iodine has traditionally been 150 micrograms for adults but it should be noted that this was the dose responsible for decreasing the incidence of goiter. Researchers are now finding that much higher dosages are required and 12.5 milligrams per day has been well tolerated and considered to be a therapeutic dose. For a more involved discussion, see my article How Much Iodine to Take.
The Selenium Link
Dr Schor taught me way back in 1997 when my mother was seeing him for her breast cancer that selenium is an important nutrient for those with breast cancer. Selenium deficiency is also considered to be a link between hypothyroid conditions and breast cancer. The thyroid gland contains more selenium by weight than any other organ in the body. Recent studies confirm that the lower a person’s selenium levels are, the greater their risk of cancer.
Selenium is a known protective mineral against breast cancer, it alters the genes to make the body less susceptible to getting cancer. (El-Bayoumy K, Sinha R. Molecular chemoprevention by selenium: a genomic approach. Mutat Res. 2005 Dec 11;591(1-2):224-36) .
In addition, selenium compounds also act as natural aromatase inhibitors (and we are always on the lookout for natural aromatase inhibitors!). (Gao R, Zhao L, Liu X, Rowan BG, Wabitsch M, Edwards DP, Nishi Y, et al. Methylseleninic acid is a novel suppressor of aromatase expression. J Endocrinol. 2012 Feb;212(2):199-205)
A big thank you to Dr Schor for providing me with these last two research studies.
Some forms of selenium are better than others, I have found this Life Extension article to be useful for explaining which forms of selenium are the most protective: Selenium: What Forms Protect Against Cancer?
Other Resources Not Cited Above:
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