Iodine is a trace mineral most of which is converted into iodide in the body. Iodine aids in the development and functioning of the thyroid gland and is an integral part of thyroxine, a principal hormone produced by the thyroid gland. It is estimated that the body contains 25 milligrams of iodine, about 0.0004 percent of the total weight.
Iodine plays an important role in regulating the body's production of energy, promotes growth and development, and stimulates the rate of metabolism, helping the body burn excess fat. Mentality; speech; and the condition of hair, nails, skin, and teeth are dependent upon a well-functioning thyroid gland. The conversion of carotene to vitamin A, the synthesis of protein by ribosomes, the absorption of carbohydrates from the intestine all work more efficiently when thyroxine production is normal. The synthesis of cholesterol is stimulated by thyroxine levels.
Both types of sea life, plant and animal, absorb iodine from seawater and are excellent sources of this mineral. Mushrooms and Irish moss are good sources, too, but only if they are grown in soil rich in iodine.
Iodine is readily absorbed from the gastrointestinal tract and is transported via the bloodstream to the thyroid gland, where it is oxidized and converted to thyroxine. About 30 percent of the iodide in the blood is absorbed by the thyroid gland; the rest is absorbed by the kidneys and excreted in the urine.
The National Research Council has suggested that an intake of 1 microgram of iodine per kilogram of body weight is adequate for most adults. They recommend a daily intake of 150 micrograms for men and 150 micrograms for women, 175 micrograms during pregnancy, and 200 micrograms during lactation.
There have been no reported cases of toxicity resulting from too much iodine as it naturally occurs in food or water. However, iodine prepared as a drug or medicine must be carefully prescribed, because an overdose can be serious.75 Sudden large doses of iodine administered to humans with a normal thyroid may impair the synthesis of thyroid homones. For individuals on low-salt therapeutic diets, iodine supplements may be desirable.
Deficiency Effects and Symptoms
An iodine deficiency results in simple goiter, characterized by thyroid enlargement and hypothyroidism (an
abnormally low rate of secretion of thyroid hormones, including thyroxine).
Iodine deficiency may lead to hardening of the arteries, obesity, sluggish metabolism, slowed mental reactions, dry hair, rapid pulse, heart palpitation, tremor, nervousness, restlessness, and irritability. An iodine deficiency may also result in cretinism, which is a congenital disease characterized by physical and mental retardation in children born to mothers who have had a limited iodine intake during adolescence and pregnancy. Polio has also been associated with iodine deficiency. The higher rate of occurrence of polio cases in the summer may be caused in part by higher losses of iodine through perspiration.
An iodine deficiency may be caused by certain compounds present in some raw foods, such as cabbage and nuts, which may interfere with the utilization of iodine in thyroid-hormone production. This will not occur unless excessive amounts of these raw foods are eaten and the intake of iodine is low to begin with.
Beneficial Effect on Ailments
Iodine therapy has been used successfully in the treatment and prevention of simple goiter.
Hardening of the arteries occurs when a disturbance in normal fat metabolism allows cholesterol to collect in the arteries instead of being used or expelled. Iodine is needed to prevent this metabolic malfunction. Sufficient dietary iodine will also reduce the danger of radioactive iodine collecting in the thyroid gland.
Iodine is beneficial to children suffering from cretinism, if treatment is started soon after birth. Many of the symptoms are reversible, but if conditions persist beyond childbirth or possibly early infancy, the mental and physical retardation will be permanent.