Iodine is an essential nutrient that your body requires for the synthesis of thyroid hormone. Thyroid hormone is responsible for the regulation of your metabolism, or the rate at which your body uses and produces energy. Most Americans can easily get enough iodine through a healthy diet alone.
Recommended Dietary Allowance
The recommended dietary allowance, RDA, for iodine is established by the Food and Nutrition Board and is the average daily intake necessary to sustain the nutritional needs of healthy persons. For healthy adult males and females over the age of 18, the RDA for iodine is 150 micrograms, or mcg, a day. Pregnant and lactating women should consume 220 and 290 mcg a day, respectively. Needs for children vary according to age but range from 90 to 150 mcg a day.
Tolerable Upper Limit
The tolerable upper intake level, or UL, for iodine is the maximum quantity of iodine you can consume in one day without the risk of unwanted side effects. For most healthy individuals, exceeding the UL is not common. For adult males and females, the UL is 1,100 mcg a day. Signs of toxicity from excessive iodine intake may include fever, weak pulses, vomiting, nausea, diarrhea, abdominal pain, burning sensation of the throat or stomach, and coma. Sustained high intakes of iodine may lead to a condition known as hyperthyroidism, in which the level of thyroid hormone in your body is elevated.
Iodine is present in a number of foods. Seaweed is one of the richest sources of iodine, with 1 g providing 11 percent to 1,989 percent of your RDA. Cod is another excellent source, which provides 66 percent of your RDA per serving. Other good sources include dairy products, iodized salt, fish sticks, shrimp, bread, milk and fruit cocktail.
Iodine deficiency can sometimes lead to a reduced level of thyroid hormone in your body, a condition known as hypothyroidism. However, iodine deficiency is an uncommon cause of hypothyroidism in the United States, especially since the introduction of iodized salt in the 1920s has drastically reduced the rates of iodine deficiency. Today, the Americas have the lowest rate of iodine deficiency in the world, with an estimated 10.1 percent of schoolage children deficient, according to a 2003 survey conducted by the World Health Organization. For this reason, Dr. Todd B. Nippoldt of the Mayo Clinic recommends avoiding iodine supplements if you have hypothyroidism.