Proper name Iodine
Category Mineral
Functions Iodine is required to form the hormone thyroxine. Thyroxine increases metobolic rate by increasing cellular oxygen uptake and the burning of glucose to make energy.
RDA 150 mcg per day for adults age 11 and above. 175 mcg per day in pregnancy. 200 mcg during lactation.
Therapeutic dose Some studies have used iodine up to 3-6 gms per day.
Deficiency symptoms Goiter is the classic severe iodine deficiency symptom. Goiter is characterized by enlargement of the thyroid gland. The thyroid enlarges because the pituitary hormone TSH (thyroid stimulating hormone) continues to stimulate the thyroid to make more thyroxine when thyroxine levels are low. The thyroid cannot make more thyroxine without iodine but it can continue to make the protein component of thryoxine, thyroglobulin. With continued stimulation from TSH, the thyroid overproduces thyroglobulin which accumulates in the thyroid follicles. This accumulation of thyroglobulin causes the thyroid gland to swell. Some 800,000,000 people worldwide suffer from iodine deficiency and goiter. Goiter may be cured by administration of iodine. Iodine deficiency may result in hypothyroidism. Prolonged hypothyroidism may develop into myxedema, a condition characterized by fatigue, low body temperature, thinning and loss of head hair - especially the loss of the lateral two thirds of the eyebrows, apathy, drowsiness, slow speech, puffiness of the hands and face, enlarged tongue and anemia. Iodine deficiency during pregnancy may result in a form of physical and mental retardation known as cretinism in the child. Iodine supplementation has produced relief of symptoms in some women with fibrocystic breasts. Food sources Seafood including kelp and other sea vegetables. Iodized salt. Lab tests Plasma iodine (by neutron activation analysis, Urinary iodine
Toxicity There is a wide margin of safety for the use of iodine. Dosages of 10 to 20 times normal have not produced ill effects though it is possible to produce a form of enlarged thyroid gland from excessive iodine. Excessive iodine intake inhibits the formation of thyroxine (thyroid hormone) because the feedback mechanism to stimulate the production of thyroxine is a lack of circulating iodine in the blood.
Best forms  Seafood.
Food sources Seafood. Iodized salt is the major source in the United States.
Lab tests None
Drug interactions None noted
Nutrient interactions Works synergistically with the amino acid Tyrosine in forming thyroxine. There are some plants that contain substances that inhibit the function of thyroxine. These plants are called goitrogens. Some common foods containing these substances are raw soybeans, peanuts, cabbage, cauliflower and turnips. Cooking destroys goitrogens.

Iodine is absorbed primarily from seafood and iodized salt. Dietary iodine is converted to iodides and absorbed in the small intestine. The iodine transported through the blood stream to the thyroid gland is bound with a protein complex containing a large amount of the amino acid tyrosine. This complex is called thyroglobulin. Approximately half the total body iodine is stored in the muscles, 20% is contained in the thyroid gland, 10% in the skin, 6% in the bones and the rest is distributed throughout the other endocrine glands, nervous system and blood. About a third of the iodine is retained by the body. The rest is excreted in the urine within 2-3 days. The retained iodine is converted to thyroxine by the thyroid gland. Iodine is bound with plasma protein and transported to the cells as needed. The hormone is eventually degraded in the liver and excreted in the bile.

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