June 22, 2009
By Tammy Russell, Contributing Writer
As vegetarians and vegans, we may be continually pondering our nutritional intake and associating it with our current state of wellness. We share the burden of new "epidemics" such as vitamin D deficiency and gluten intolerance with the rest of the population.
With all of the recent fuss over hypothyroidism, it is time to take a closer look at iodine. Iodine has long been known for its role as an essential component of thyroid hormones. Beyond this, however, research now shows the benefits of iodine in maintaining the integrity of the mammary gland and strengthening the immune system; it also has anti-tumor properties and participates in detoxification (1).
Regarding breast health, the mammary gland favors iodine, and a lactating mammary gland will take up as much iodine as the thyroid (2). Studies of cancerous breast tissue show significantly lower levels of iodine than iodine levels in surrounding breast tissue (3). Also, the incidence of breast cancer is three times greater in people with goiters (enlarged thyroid) resulting from iodine deficiency (1).
The Japanese consume ten times more iodine than Americans do, and Japanese women have the lowest rate of breast cancer mortality, whereas U.S. women have the highest. Although Japanese women have some of the highest intakes of iodine in the world, they succumb to higher rates of breast cancer when adopting a Western-style diet (1). In terms of anti-tumor activity, iodine has also been shown to potentiate cellular death (apoptosis) in cancer cells in both the body and the test tube. Human breast cell cancer and lung cell lines that were genetically modified died in the presence of iodine (1, 4).
Iodine's potential role in detoxification is just beginning to be known. A recent study showed that women supplemented with 12.5 mg of elemental iodine daily excreted higher levels of mercury, lead, and cadmium after the first day of the study (5). Even though as a population we consume an average of 240 mcg of iodine each day, those consuming non-Western style diets consume one hundred times more than this (1).
The National Health and Nutrition Examination Survey (NHANES) data from 1971 through 1994 show a decrease in iodine intake complemented by an increase in iodine deficiency by 8.1 percent in men and 15.1 percent in women (6). Most Americans typically got their iodine from iodized salt; however, salt consumption has decreased by 65 percent over the last 25 years (1). Also noteworthy is that iodine is lost in sweat during exercise but research has only addressed replacing electrolytes (7).
What's the bottom line in terms of recommended intakes? Although the current RDA of 150 mcg per day may prevent clinical hypothyroidism, goiter and mental retardation, really getting enough iodine may mean reaching for milligram (as opposed to microgram) doses. Adults may want to consider having amounts closer to 10 milligrams per day. It's possible that this amount could provide benefits such as a reduction in gastric and breast cancer risk, improvement in fibrocystic breast disease as well as numerous antioxidant and anti-proliferative effects in the body. Nonetheless, anyone considering taking iodine supplements in the milligram dosage should first be screened for sub-clinical hyperthyroidism. Also, this dose is not appropriate for children younger than 18 years of age (2).
- Miller WD. Extrathyroidal benefits of iodine. J Am Physicians Surgeons. 2006;11: 106-110
- Rhealt S, Olmestead S MD, Ralston J and Dennis Meiss, PhD. Iodine and Iodide: Functions and Benefits Beyond the Thyroid. Townsend Letter. 2008; 12
- Kilbane MT, Aijan RA, Weetman AP, et al. Tissue iodine content and serum-mediated 1251 uptake blocking activity in breast cancer. J Clin Endocrinol Metab. 2000;85:1245-50
- Zhang L, Sharma S, Zhu XL, Kogai T, Hershman JM, Brent GA, Dubinett SM, Huang M. Nonradioactive iodide effectively induces apoptosis in genetically modified lung cancer cells. Cancer Research. 2003;63:5065-72.
- Abraham GE. The historical background of the iodine project. The Original Internist. 2005;12:57-66
- Lee K, Bradley R, Dwyer J, Lee S. Too much versus too little: the implications of current iodine intake in the United States. Nutrition Reviews. 1999;57:177-81
- Smyth PPA, Duntas LH. Iodine uptake and loss – can frequent strenuous exercise induce iodine deficiency? Horm Metab Res. 2005;37: 555-8