Your thyroid gland, located just above the middle of your collarbone, needs iodine to make thyroid hormone, which maintains normal metabolism in all cells of the body. Principally found in sea water, dietary iodine can be scarce in many inland areas, and deficiencies were common before iodine was added to table salt. Iodine deficiency causes enlargement of the thyroid, a condition known as goiter. However, if you are not deficient in iodine, taking extra iodine will not help your thyroid work better, and it might even cause problems.

For reasons that are not clear, supplementary iodine might also be helpful for cyclic mastalgia.

The official US recommendations for daily intake of iodine are as follows:

  • Infants
    • 0-6 months: 110 mcg
    • 7-12 months: 130 mcg
  • Children
    • 1-8 years: 90 mcg
  • Males and females
    • 9-13 years: 120 mcg
    • 14 years and older: 150 mcg
  • Pregnant women: 220 mcg
  • Nursing women: 290 mcg

Iodine deficiency is rare in developed countries today because of the use of iodized salt.

Seafood and kelp contain very high levels of iodine, as do salty processed foods that use iodized salt.

Most iodine is in the form of iodide, but a few studies suggest that a special form of iodine called molecular iodine may be better than iodide.