Iodine deficiency causes problems at all stages of life. Iodine is needed in the diet so that the body can produce thyroid hormones. Thyroid hormones help develop the nervous system by aiding the formation of the myelin sheath of certain nerves in the central nervous system. These nerve sheaths form before and shortly after birth.
Iodine deficiency can cause brain damage, especially in the children of pregnant women after the first trimester and in children of up to three years of age. Iodine is critical for the growth and development of the brain and central nervous system.
The damage to the brain caused by iodine deficiency is irreversible. If the deficiency is severe during pregnancy, it may result in cretinism in the child. Cretinism is a state of stunted growth and extreme mental retardation, resulting in intelligence quotients as low as 20. Pregnant and breastfeeding women can ensure adequate iodine by taking a daily prenatal supplement providing 150 mcg of iodine.
Brain Damage from Iodine Deficiency
Iodine deficiency is the most common cause of preventable brain damage in the world. Diets that do not include seaweed, fish, iodized salt, or other iodized food have been found to contain very little iodine. Iodine deficiency disorders affect three-quarters of a billion people worldwide. It is estimated that 50 million people have some brain damage resulting from iodine deficiency.
Goiter and Hypothyroidism
One of the earliest signs of iodine deficiency is goiter, an enlargement of the thyroid gland. In older children and adults, goiter may be reversed with adequate intake of iodine. The incidence of goiter is more common in adolescent girls. Children who are deficient in iodine have poorer school performance, more learning disabilities, and lower intelligence quotients than normal children. Childhood iodine deficiency can cause an average lowering of intelligence quotients by 13 points.
More severe iodine deficiency can result in hypothyroidism. Symptoms of hypothyroidism (low levels of thyroid hormones in the blood) include dry skin, swellings around the lips and nose, mental deterioration, and a slow basal metabolic rate.
Summary for Iodine
Main functions: thyroid functions.
RDA: adults, 150 mcg.
Toxicity: low toxicity, excesses may cause a rise in thyroid stimulating hormone.
Tolerable upper intake level is 1100 mcg for adults.
Deficiency can cause goiter, cretinism, and brain damage to fetuses.
Sources: iodized salt, seaweed, fish.
Forms in the body: thyroxine (T4) and the more active form, triiodothyronine (T3).
Causes of Iodine Deficiency
One cause of iodine deficiency is the over-consumption of certain plants that reduce thyroid hormones even if dietary iodine is adequate. Over-consumption of plants in the cabbage family and certain other plants can also cause goiter. These plants are known as goitrogens because they promote goiter.
Radiation and Iodine
Iodine deficiency can result in an increased susceptibility to thyroid cancer in populations exposed to radiation. Deficiency results in an increased uptake of iodide by the thyroid gland. The thyroid gland is also capable of storing ions of the radioactive form of iodide (iodine I-131).
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