General Info


Iodine is easily absorbed from the intestines.

Dietary Origins

Iodized salt is the most common source of iodine in the United States. Iodine-rich foods include kelp, seafood, seaweed, and vegetables grown on iodine-rich soils.


Iodine’s main known function is the role it plays in the various thyroid hormones, which regulate numerous bodily functions. Dietary iodine is converted to iodide in the gastrointestinal tract where it is easily absorbed and transported to the thyroid gland. Iodine is stored in the thyroid gland. Iodine metabolism and thyroid hormone production are regulated by a negative feedback hormonal control system. A decline in blood thyroid hormone triggers the brain to release more hormones. If the thyroid gland is damaged or absent, the basal metabolic rate can decline to as low as 55 percent of normal, resulting in impaired growth and development. When the thyroid gland is hyperactive, the basal metabolic rate can go up as high as 160 percent of normal, causing a fast heart beat resulting in, nervousness, and excitability.

Toxicities & Precautions


Iodine is a relatively mild trace element that is nontoxic at dosages 10 to 20 times above normal daily needs. The thyroid gland absorbs iodine, but thyroid synthesis remains normal.

Side Effects

Excessive intake of iodine can cause an enlargement of the thyroid gland.

Functions in the Body


Involved in the activity and function of the thyroid hormone. The iodine-dependent thyroid hormone regulates, basal metabolism, cellular oxygen consumption, and energy production throughout the body. As a result, the thyroid hormone controls a variety of biological and physiological activities including body temperature, neuromuscular function physical growth, reproduction, the synthesis of proteins, and the growth of skin and hair.

Symptoms & Causes of Deficiency

A deficiency of iodine results in the enlargement of the thyroid gland, a condition known as goiter. Deficiency may also cause impaired growth, stunted fetal and infant brain development, and infant brain development, decreased productivity and intelligence in populations with symptomatic hypothyroidism, and impose reproductive complications in women. The introduction of iodized salt has made iodine deficiency uncommon in the United States and other developed countries.