Iodine is a trace mineral your body needs to make the thyroid hormones triiodothyronine, or T3, and thyroxine, or T4. The phrase "trace mineral" refers to minerals your body needs only in small amounts. However, even though the requirement is small, it is still vital to health. Infants and children require iodine for normal brain development and physical growth, while adults need it for a healthy brain and thyroid.
Iodine and Thyroid Gland
When the thyroid gland enlarges in an attempt to produce thyroid hormones in the absence of enough iodine, a condition known as goiter can occur. It can be recognized through a swelling of the neck, but sometimes the swelling is small. After a deficiency lasting many months, the thyroid can no longer compensate and stops producing normal levels of thyroid hormones, a condition known as hypothyroidism.
Symptoms of Hypothyroidism
Symptoms of hypothyroidism include fatigue, weight gain, depression, intolerance of cold, excessive sleepiness, constipation, dry skin and hair, muscle cramps, difficulty concentrating, aches and pains, leg swelling and increased cholesterol. Severe hypothyroidism can lead to a slow heart rate, a drop in body temperature, an enlarged heart, heart failure, fluid around the lungs and even coma. Your doctor can confirm suspected hypothyroidism with a blood test.
Fetal and Infant Development
An iodine deficiency during pregnancy increases the risk of miscarriage, stillbirth and birth defects, including permanent mental retardation, deafness and stunted physical growth. A deficiency in a baby can result in infant mortality or impaired brain development. Normal brain development requires adequate levels of thyroid hormones, which depend on adequate iodine. Infants should get iodine only through breast milk or formula.
Brain Damage
Internationally, iodine deficiency is the most common cause of brain damage, according to the World Health Organization. Iodine is present naturally in soil and ocean water, but in inland areas, where soil has eroded, iodine content might be negligible. Estimates are that nearly a third of the world's school-age children are iodine deficient, resulting in lower IQ scores, learning disabilities and poor school performance. An adult who does not suffer a deficiency until adulthood can still suffer neurological effects, including slower response times and poor mental function.
Recommended Amounts By Age
From birth to 6 months, babies need 110 mcg of iodine daily and from 7 to 12 months, they need 130 mcg. Children from 1 to 8 need 90 mcg; from 9 to 13, they need 120 mcg. Teens and adults need 150 mcg. A female should increase her intake to 220 mcg per day when pregnant and 290 when breast-feeding.
Dietary Sources of Iodine
Iodized salt is the most common source of iodine in the United States, with 1 g -- approximately 1/5 tsp. -- containing 77 mcg of iodine. Other good sources are cod, at 99 mcg in a 3 oz. serving, and cow's milk, at 56 mcg per 8 oz. glass. While iodine deficiency is rare in the U.S., people who do not eat iodized salt, seafood or sea plants might not get enough iodine through diet.
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