Iodine and its compounds are primarily used in nutrition, and industrially in the production of acetic acid and certain polymers. Iodine's relatively high atomic number, low toxicity, and ease of attachment to organic compounds have made it a part of many X-ray contrast materials in modern medicine.
In the universe and on Earth, iodine's high atomic number makes it a relatively rare element. However, its presence in ocean water has given it a role in biology. It is the heaviest essential element utilized widely by life in biological functions (only tungsten, employed in enzymes by a few species of bacteria, is heavier).
Iodine deficiency affects about two billion people and is the leading preventable cause of intellectual disabilities.
Most of the iodine in nature is found in marine sediment in the form of iodine salts.
Functions:
Iodine is an element that is needed for the production of thyroid hormones thyroxine (T4) and triiodothyronine(T3).Receptors binding T3 and T4 have been found in the cell nucleus and in mitochondria.These hormones are involved in the maintenance of metabolic rate, cellular metabolism and integrity of connective tissue. Thyroid hormones are necessary for the development of the nervous system in the foetus and infant.
Iodine is an essential trace element.
The human body contains 15-20 mg of iodine with 70-80% being located in the thyroid gland.
Thyroid hormones are essential for life as they regulate key biochemical reactions, especially protein synthesis and enzymatic activities, in target organs such as are the developing brain, muscle, heart, pituitary and kidney.
Iodine is claimed to assist with weight loss, rheumatism, ulcers, hair loss and the maintenance of healthy arteries, nervous tissue and nails.
What food Iodine is found in:
Natural sources of dietary iodine include seafood, such as fish, kelp and shellfish, dairy products such as milk, cheese, eggs and plants grown on iodine-rich soil.
Iodized salt is fortified with iodine. Ice Cream, seaweed (including kelp, dulce, nori), soy milk, soy sauce, yogurt.
What symptoms and disorders Iodine deficiency may cause:
Iodine insufficiency induces an increase in thyroid-stimulating hormone (TSH) in response to decreased production of thyroid hormone. Goitre develops as a consequence of the stimulation action of TSH. Serious iodine deficiency also leads to functional and developmental abnormalities such as hypothyroidism. Hypothyroidism causes physical and mental retardation in infants and children. In neonate, iodine deficiency causes perinatal mortality, infant mortality and low birth weight. Severe iodine deficiency in the fetal and neonatal period may lead to cretinism, which is characterized by stunted growth, mental and other neurological retardation, and delay in development of secondary sex characteristics. In adults, it causes reduction in mental function and lethargy (FAO/WHO, 2002). This diverse array of iodine deficiency problems in different age groups is described as Iodine Deficiency Disorder (IDD). IDD thus includes mental retardation, hypothyroidism, goitre, cretinism and varying degrees of other growth and developmental abnormalities as a result of iodine insufficiency (IOM, 2001).
Goiter
A low amount of thyroxine (one of the two thyroid hormones) in the blood, due to lack of dietary iodine to make it, gives rise to high levels of thyroid stimulating hormone (TSH), which stimulates the thyroid gland to increase many biochemical processes; the cellular growth and proliferation can result in the characteristic swelling or hyperplasia of the thyroid gland, or goiter.Cretinism
Iodine deficiency is one of the leading causes of preventable mental handicaps worldwide, producing typical reductions in IQ of 10 to 15 IQ points. It has been speculated that deficiency of iodine and other micronutrients may be a possible factor in observed differences in IQ between ethnic groups.Cretinism is a condition associated with iodine deficiency and goiter, commonly characterised by mental deficiency, deaf-mutism, squint, disorders of stance and gait, stunted growth and hypothyroidism.
In areas where there is little iodine in the diet, typically remote inland areas and semi-arid equatorial climates where no marine foods are eaten, iodine deficiency gives rise to hypothyroidism, symptoms of which are extreme fatigue, goiter, mental slowing, depression, weight gain, and low basal body temperatures.
Other possible health effects being investigated as being related to deficiency include:
Breast cancer.
The breast strongly and actively concentrates iodine into breast-milk for the benefit of the developing infant, and may develop a goiter-like hyperplasia, sometimes manifesting as fibrocystic breast disease, when iodine levels are low.Stomach cancer. Some researchers have found an epidemiologic correlation between iodine deficiency, iodine-deficient goitre and gastric cancer. A decrease of the incidence of death rate from stomach cancer after implementation of the effective iodine-prophylaxis has been reported also.
Autism.
Although there is not a definitive answer for the cause of autism in children, research has shown that mothers with low levels of iodine are more likely to have an autistic child.Problems related to excessive doses:
Administration of large amounts of iodine through medications, radiology procedures (iodinated intravenous dye) and dietary excess can cause or worsen hyperthyroidism and hypothyroidism.
In addition, individuals who move from an iodine-deficient region (for example, parts of Europe) to a region with adequate iodine intake (for example, the United States) may also develop thyroid problems since their thyroids have become very good at taking up and using small amounts of iodine. In particular, these patients may develop iodine-induced hyperthyroidism.
Elemental iodine is toxic if taken orally. The lethal dose for an adult human is 30 mg/kg, which is about 2.1–2.4 grams (even if experiments on rats demonstrated that these animals could survive after eating a 14000 mg/kg dose).
Excess iodine can be more cytotoxic in the presence of selenium deficiency. Iodine supplementation in selenium-deficient populations is, in theory, problematic, partly for this reason. Its toxicity derives from its oxidizing properties, which make it able to denaturate proteins (including enzymes).
Elemental iodine is also a skin irritant, and direct contact with skin can cause damage, so iodine crystals should be handled with care.
Solutions with high elemental iodine concentration such as tincture of iodine and Lugol's solution are capable of causing tissue damage if their use for cleaning and antisepsis is prolonged; similarly, cases have been reported where liquid Povidone-iodine (Betadine) trapped against the skin resulted in chemical burns
Recommended doses for people in th UK:
COMA established a Lower Reference Nutrient Intake (LRNI) and a RNI for iodine of 0.07 and 0.14 mg/day, respectively (COMA, 1991).
Accordind to the British Nutrition Foundation no adverse effects have been reported for excess iodine intakes up to 2mg iodine/day.