Iodine
Iodine is an essential element that enables the thyroid gland to produce thyroid hormones. One needs the proper amount of iodine for optimal thyroid function. (See article: Thyroid Disease).
A severe iodine deficiency can cause hypothyroidism, and even developmental brain disorders and severe goiter. Less severe iodine deficiency is linked to hypothyroidism, thyroid enlargement (goiter) and hyperthyroidism. At the other end of the spectrum, excessive iodine intake -- both severe and moderate -- is also associated with hypothyroidism and goiter.
In the United States, iodine has been voluntarily supplemented in table salt. Other major sources of dietary iodine in the United States are egg yolks, milk, and milk products because of iodine supplementation in chicken feed and the treatment of milk cows and cattle with iodine to prevent hoof rot and increase fertility. Lobster, shrimp and bread also contain iodized salt. Both seafood and seaweed are great sources of iodine.
But did you know... Iodine intake has dropped approximately 50 percent in the last 20 years? Blame that decrease on popular "designer" salt blends and Kosher and sea salts that usually do not contain iodine. In fact, a recent study found that more than half of iodized table salts didn't meet the U.S. Food and Drug Administration's recommendations for iodine levels. That's a big deal, says a Harvard Institute of Medicine researcher, Robert Utiger, PhD. Iodine is an essential componenet of thyroid hormone, as noted above.
Iodine, primarily obtained through the diet as stated, is also a component of some medications.
Normal dietary iodine intake is 100-150 mcg/d. The US Food and Drug Administration (FDA) recommended dietary allowance (RDA) and World Health Organization (WHO) recommendations are 150 mcg/d of iodine for adults and adolescents.
Doctor Approved. Kelp contains nearly 30 minerals and is especially high in iodine. In addition, kelp contains vitamins C, D, E, K and B-complex making it a good source for people with vitamin or mineral deficiencies. The high iodine content of kelp is beneficial in the production of thyroid hormones. Thyroid hormones are essential for maintaining normal metabolism. Kelp, therefore, may help boost the metabolism, which in turn can help you maintain normal weight. 
