Iodine

What does it do? Iodine is needed to make thyroid hormones, which are necessary for maintaining normal metabolism in all cells of the body. Reports suggest that iodine may have a number of important functions in the body unrelated to thyroid function that might help people with a wide variety of conditions;¹ these other uses for iodine are only supported by minimal research.

Where is it found? Seafood, iodized salt, and sea vegetables—for example, kelp—are high in iodine. Processed food may contain added iodized salt. Iodine is frequently found in dairy products. Vegetables grown in iodine-rich soil also contain this mineral.

Who is likely to be deficient? People who avoid dairy, seafood, processed food, and iodized salt can become deficient. Iodine deficiency can cause low thyroid function, goiter, and cretinism; however, iodine deficiencies are now uncommon in Western societies.

How much is usually taken? Since the introduction of iodized salt, iodine supplements are unnecessary and not recommended for most people. For strict vegetarians who avoid salt and sea vegetables, 150 mcg per day is more than adequate.

Are there any side effects or interactions? High doses (several milligrams per day) can interfere with normal thyroid function and should not be taken without consulting a nutritionally oriented doctor.² The average diet provides about four times the recommended amount of iodine, which may result in health problems.³ In fact, goiter, traditionally a disease of iodine deficiency, is now linked sometimes to high iodine intake.⁴ Also, speculations of an iodine link to thyroid cancer have been reported.⁵ Some people react to supplemental iodine, the first symptom of which is usually an acnelike rash.