Iodine is regarded as one of the most important trace minerals for human health and it plays a vital biochemical function in the regulation of hormone levels in the body. Iodine is essential in the bio-synthesis of the hormone thyroxin, also known as the thyroid hormone. The metabolic rate of the human body is regulated by thyroxin and the secretion of this hormone in the body is directly dependant on the availability of iodine in the body. An iodine deficiency is often compensated for in the human body, by a sudden increase in the secretion of thyroxin hormone. This sudden increase in the secretion of thyroid hormone can cause the gland to become enlarged and swollen, it can become congested and results in the condition called goiter - this disorder is typically seen in individuals affected by a deficient intake of iodine. Physical and mental retardation, also known as cretinism can affect a developing fetus, if the mother's diet is lacking sufficient iodine. Regions or areas around the world where iodine is present in low levels or is lacking in the dietary sources, tend to have a lot of people affected by goiter and cretinism. Iodine deficiency goiter - also called endemic goiter - has been all but eliminated in some countries of the world, such as the United States by fortifying common table salt with iodide. This salt is called iodized salt. The disorders related to Iodine deficiency still affects nearly 200 million people across the world mostly in the poorest of countries. The levels of iodine present in the diet have brought attention for two main reasons. One, in areas of the world where breast, uterine and ovarian cancer seem to be low, the iodine intake is generally high. The causation of these forms of cancer could be linked to the stimulation of hormone production by low levels of iodine present in the diet. These relation between iodine and certain cancers is a generalization and can be considered just a theory based on the clinical studies of cancer between iodine intake and death rates across the world. The causative factors behind cancer necessarily and obviously include other causes besides iodine levels. Therefore, for this theory to be clinically verified and authenticated by scientists there must be further experimentation and the exact relationship between iodine and cancer rates has to be outlined. Iodine has a RDA of about 150 micrograms or a dose of 0.15 mg per person daily. This amount can be obtained on consuming 2 grams of iodized salt in the meal. Iodine supplements administered in excess amounts have often induced cases of thyroid toxicity - known as thyrotoxicosis. The physiological effect of a deficiency of iodine is apparently similar to the effects of an excess amount of iodine - both can induce hyperthyroidism in the affected person. Levels of iodine in the body which are safe for some people may induce adverse effects in many other persons, this suggests that such people are affected by some metabolic defects which can directly interfere with the regulation of the iodine thyroid system inside the body. Excessive amounts of iodine in the body can also cause acne, in addition to speeding up the metabolism and inducing hyperthyroidism and thyrotoxicosis. Iodine is found abundantly in sea foods, such as fish and seaweeds of all kinds. Iodine supplementation is normally not required by a person on a diet with plenty of fish and seaweeds. Iodine is also found in milk and baked goods - these are not necessarily reliable sources for dietary iodine as they are not natural foods. Iodine may not be available in the same levels in all milk and baked goods, for example, the local bakery may not use iodine compounds as a part of dough conditioners, the dairy may not give iodine salt licks and disinfectants to their cows - the results will be low or insignificant iodine in the baked goods and the milk. As far as humans are concerned, the mineral iodine is considered an essential mineral whether the intake is from supplements or from natural foods rich in iodine. Eating plenty of seafood is the ideal way to ensure that sufficient iodine is being consumed; this is also the best way of supplementing iodine without the need to increase the intake of iodized salt. Iodine is found abundantly in all kinds of seafood, in iodized salt and in sea weeds such as for kelp. Iodized salt is also found in many types of processed foods. Dairy products also frequently contain significant amounts of iodine. This essential mineral is also found in abundance in vegetables grown in iodine rich soils around the world. A deficiency of iodine can develop in people who avoid all dairy products, seafood, processed food, and iodized salt. The functional state of the thyroid is lowered if iodine levels are low in the body, this deficiency can also induce goiter and cretinism in such individuals. These days, most western countries do not have iodine deficiencies as a health concern in a significant way, and such deficiencies are rare.
Most people do not need iodine supplements and such supplemental use of iodine is needless ever since iodized salt was introduced in packaged salt. Iodine at a supplemental rate of 150 mcg daily is more than sufficient for the supplemental needs of strict vegetarians who do not consume salt and sea vegetables.
Iodine consumed at very high doses - several milligrams daily - might interfere with the normal functioning of the thyroid gland and supplements of iodine at high doses may be used only following approval from a nutritionally oriented doctor experienced in iodine supplementation. Iodine is found at approximately four times the recommended amount in the average diet - this factor can induce health problems in the person. High iodine intake has in fact been linked to cases of goiter in recent times - goiter paradoxically is a disease traditionally linked to iodine deficiency. Thyroid cancer has also been speculatively linked to iodine in clinical reports. Supplemental iodine may also induce side effects of a mild nature in some; the initial physical symptom is typically a rash resembling acne.