The iodine content of most foods depends on the iodine content of the soil. Seafood is rich in iodine because marine animals can concentrate the iodine from seawater. Certain types of seaweed (e.g., wakame) are also very rich in iodine. Processed foods may contain slightly higher levels of iodine due to the addition of iodized salt or food additives, such as calcium iodate and potassium iodate. Dairy products are relatively good sources of iodine because iodine is commonly added to animal feed in the U.S. In the U.K. and northern Europe, iodine levels in dairy products tend to be lower in summer when cattle are allowed to graze in pastures with low soil iodine content (6). The table below lists the iodine content of some iodine-rich foods in micrograms (mcg). Because the iodine content of foods can vary considerably, these values should be considered approximate (30).
*A three-ounce serving of meat is about the size of a deck of cards.
|Salt (iodized)||1 gram||77|
|Fish sticks||2 fish sticks||35|
|Tuna, canned in oil||3 ounces (1/2 can)||17|
|Milk (cow's)||1 cup (8 fluid ounces)||56|
|Egg, boiled||1 large||12|
|Navy beans, cooked||1/2 cup||32|
|Potato with peel, baked||1 medium||60|
|Turkey breast, baked||3 ounces||34|
|Seaweed||1/4 ounce, dried||Variable; may be greater than 4,500 mcg (4.5 mg)|
Potassium iodide is available as a nutritional supplement, typically in combination products, such as multivitamin/multimineral supplements. Iodine makes up approximately 77% of the total weight of potassium iodide (15). A multivitamin-mineral supplement that contains 100% of the daily value (DV) for iodine provides 150 mcg of iodine. Although most people in the U.S. consume sufficient iodine in their diets from iodized salt and food additives, an additional 150 mcg/day is unlikely to result in excessive iodine intake (see Safety).
Potassium iodide as well as potassium iodate may be used to iodize salt. In the U.S. and Canada, iodized salt contains 77 mcg of iodine per gram of salt. In other countries, salt commonly contains 20-40 mcg of iodine/gram of salt; the iodization level depends on variables such as iodine intake from other sources and daily salt consumption. Annual doses of iodized vegetable oil are also used in some countries as an iodine source (2, 15).