Iodine deficiency, until recently thought to still be a problem only in developing countries (where it is typically over 50%), is now widespread in the U.S. and Canada.
According to 2001-2002 National Health and Nutrition Survey (NHANES) data, iodine intake has dropped 50% since 1971-1974. Analysis of iodine levels in the breast milk of lactating mothers in Boston found that less than half (only 47%) contained sufficient amounts of iodine to meet infant requirements. The situation is made worse by increasing levels of inhibitors of iodine absorption–perchlorate, nitrate and thiocynate–in our food supply.
Although mostly recognized for its essential role in thyroid hormone production (iodine is a required component of both thyroid hormones, T3 and T4) and normal brain development, iodine is now known to be involved in a wide variety of physiological processes. Only about 30% of the body’s iodine is found in the thyroid itself and in thyroid hormones. The body concentrates the rest in the liver, salivary glands, breasts, lining of the stomach and brain. Iodine deficiency is contributing not only to the increase in sub-clinical hypothyroidism seen in the U.S., but also to fibrocystic breast disease, psychiatric disorders and fibromyalgia. For a comprehensive review of the research relating to why Americans are at risk for iodine deficiency and iodine’s many roles in the body, see Iodine: the next vitamin D?
What can you do? Don’t rely on processed or restaurant food for your iodine. The salt they use is not iodized. Sea salt contains very little iodine. You can buy iodized salt and use a teaspoon daily, but not all iodized salt contains the iodine it says it does on the label. Your best bet: buy dulse granules (a type of seaweed rich in iodine that is dried, powdered and sold in small “salt-shaker” containers) and use as a seasoning instead of salt.