UK: Expert Group on Vitamins & Minerals

and mineral supplements (providing up to 0.49 mg iodine/day) and is a component of kelp products. It is also present in licensed medicines, topical antiseptics and radiographic contrast agents."

"Iodine is claimed to assist with weight loss, rheumatism, ulcers, hair loss and the maintenance of healthy arteries, nervous tissue and nails."

"A variety of mechanisms exist to compensate for low levels of iodine intake. These include enlargement of the thyroid gland (goitre). Only when these mechanisms fail do the clinical signs of hypothyroidism (also known as myxoedema) develop. Symptoms and signs of hypothyroidism include lethargy, weakness, weight gain, poor concentration, oedema, myalgia, dry skin, delayed tendon reflexes and slow heart rate. In pregnancy, iodine deficiency is associated with an increased risk of miscarriage, stillbirth and congenital abnormality. Cretinism is the result of iodine deficiency in the developing foetus, and is characterised by mental retardation, deaf mutism, and spastic diplegia. A less common form of cretinism is the myxoedematous type, which is characterised by hypothyroidism and dwarfism."

"Iodine interacts with selenium and possibly with vanadium."

"Inorganic iodine (generally in the form of iodide) is readily absorbed, largely from the small intestine. It can also be absorbed through the skin, absorption being increased when the skin is damaged."

"Once absorbed, iodine is distributed rapidly throughout the extracellular fluid, secreted into saliva, and enters the gastrointestinal system, from where it is reabsorbed. Iodine can cross the placenta and is secreted into human breast milk."

"Iodine is largely excreted in the urine, mainly in the form of iodine. Very small amounts of iodine may be excreted in sweat, feces and exhaled air."

"Several biological mechanisms protect against iodine toxicity; these include reduced iodine uptake and preferential production of the more heavily iodinated thyroid hormones. Not all exposed subjects will react to excess iodine.

"Clinical features of acute iodine toxicity that have been produced following accidental or deliberate ingestion, or medical procedures such as wound irrigation, include gastrointestinal disturbance (vomiting and diarrhea), metabolic acidosis, seizure, stupor, delirium and collapse. Sensitivity reactions, such as iodide mumps, iododerma and iodide fever may also occur following treatment with iodine-containing drugs, or the use of radiographic contrast media. Chronic and sub-chronic toxicity have also been identified.

"Excess iodine or iodide intake may disrupt thyroid function, resulting in the induction of hypothyroidism with or without goitre, hyperthyroidism (thyrotoxicosis) and changes in the incidence and types of thyroid malignancies. Responses of this type frequently occur where there is general high iodine intake or where intervention has taken place to correct iodine deficiency. The pattern of effects changes over time as iodine exposure in the population changes. For example, in the UK, the possibility of iodine induced hyperthyroidism associated with prior iodine deficiency appears to be less common due to recent increases in the iodine intake of the population as a whole.

183. Iodine is a halogen. At room temperature it is a blue-black solid which sublimes into a gaseous form. Iodine is present in seaweed, igneous rocks and some soils.

184. In the diet, iodine is naturally present in marine fish, shell fish and sea salt. Levels in cereals and grains vary depending on the soil content. The food colour erythrosine is also rich in iodine. In the UK, iodine is also present in cows’ milk probably as a result of the use of supplemented cattle feeds and iodophors as  sterilants. Iodine is present in food supplements both in its elemental from and as a component of kelp products. It is also present in licensed medicines, topical antiseptics and radiographic contrast agents.

186. Iodine interacts with selenium and possibly vanadium. Natural goitrogens in the diet derived from plants such as cassava, maize, potato, cauliflower and broccoli as well as ions present in drinking water interfere with iodine metabolism.