Iodine is a nutrient your thyroid gland just can’t function without. Iodine is actively concentrated in your thyroid gland and is used to make thyroid hormones. When iodine is in short supply, so are thyroid hormones.
That’s why it is so alarming to find out that, despite the widespread availability of iodized salt, iodine deficiency has re-emerged as a public health concern in the U.S. Population studies show that more than 11 % of all Americans, and more than 15 % of American women of child-bearing age, presently have urine iodine levels less than 50 micrograms/liter, indicating moderate to severe iodine deficiency. An additional 36 % of reproductive-aged women in the U.S. are considered mildly iodine deficient (less than 100 micrograms/liter of urinary iodine.)
Why the deficiency? Well, for one thing, people are consuming less iodine. Recent reductions in U.S. dietary iodine intake have been ascribed to a reduction in iodine content in dairy products, to the removal of iodate conditioners in store-bought breads, to new recommendations for reduced salt intake for blood pressure control, and to the increasing use of noniodized salt in manufactured or pre-made convenience foods.
People are also being increasingly exposed to environmental toxins that block the action of iodine. These include fluoride, bromide (and bromates) and perchlorates. These chemicals can persist in the environment (and in our bodies) long after exposure to them has stopped.
Maternal iodine deficiency is particularly dangerous to a developing fetus. Even what’s considered a mild iodine deficiency can hamper the growth of children’s brains, reduce their IQ, and cause learning disabilities. Severe iodine deficiency is easily recognized as goiter–an enlarged thyroid. But less severe deficiency can show up as hypothyroidism, slightly enlarged thyroid, nodules on the thyroid, or as slow metabolism (as evidenced by body temperatures that typically average around 97.8 F, or lower). Slow metabolism and low body temperature despite normal thyroid tests is a condition called WIlson’s Temperature Syndrome. (See “How are body temperatures measured” for complete instructions.)
The RDA for iodine is 150 micrograms a day for adults. (It’s 220 mcg during pregnancy and 290 mcg during breastfeeding.) If you suspect your iodine intake is low, you can increase it by eating seaweed such as kelp or shellfish. You can use iodized salt, which has 77 mcg of iodine per gram. Or you can take a daily supplement of iodine. High dose iodine can be very helpful to some patients but is best done under medical supervision (especially if you are pregnant or breast-feeding) since it can rarely have some unwanted effects. You can see a doctor to help you assess your iodine level and help you find an iodine supplement as well, if necessary.
REFERENCES
Becker DV, Braverman LE, Delange F, et al. Iodine supplementation for pregnancy and lactation-United States and Canada: recommendations of the American Thyroid Association. Thyroid. 2006;16(10):949-951.
Caldwell KL, et al. (2008). Iodine status of the U.S. population, National Health and Nutrition Examination Survey 2003-2004. Thyroid 18(11):1207-14.
Dunn JT. What’s happening to our iodine? J Clin Endocrinol Metab. 1998;83(10):3398-3400.
Food and Nutrition Board, Institute of Medicine. Iodine. Dietary reference intakes for vitamin A, vitamin K, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. Washington, D.C.: National Academy Press; 2001:258-289.
Hollowell JG, Staehling NW, Hannon WH, et al. Iodine nutrition in the United States. Trends and public health implications: iodine excretion data from National Health and Nutrition Examination Surveys I and III (1971-1974 and 1988-1994). J Clin Endocrinol Metab. 1998;83(10):3401-3408.
Iodine Level, United States, 2000.
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