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Trace Minerals

Many people associate iodine with the topical antiseptic their mothers swabbed on their childhood scrapes and bruises.  But the real value of this trace mineral lies in the role it plays in thyroid health.  Without iodine, the vitally important thyroid gland can't function properly.

What it is?

Although the body needs only tiny amounts, iodine is so crucial to overall health that, beginning in the 1920s in New Zealand and in the 1930s in Australia, the government allowed manufacturers voluntarily to add iodine to table salt, mainly as a safeguard against thyroid enlargement (goiter) and the severe form of mental retardation called cretinism, which is caused by iodine deficiency (although the condition was rare in these countries).  Despite the recognized importance of this vital mineral, however, about 1.6 billion people in the world, mostly in underdeveloped countries, still suffer from iodine deficiency.

What it does?

Uniquely among minerals, iodine has only one main function in the body: it enables the thyroid gland to manufacture thyroxine, a vitally important hormone that regulates metabolism in all the body's cells.

By getting enough iodine, pregnant women can prevent cretinism (a type of mental retardation) in their developing fetus.

Additional Benefits 
Unlike many other minerals, iodine doesn't seem to help in the treatment of specific disorders.  It does, however, play a fundamental role in ensuring the health of the thyroid, the butterfly-shaped gland that surrounds the windpipe (trachea).  When your iodine intake is adequate, your body contains about 20-50 g of it, and 75% of that amount is stored in the thyroid.  This organ controls the body's overall metabolism, which determines how quickly and efficiently kilo joules are burned up.  It also regulates growth and development in children; reproduction, nerve and muscle function,; the breakdown of proteins and fats; the growth of nails and hair; and the use of oxygen by every cell in the body.  There is some evidence that iodine derived from an organic source may be effective in reducing the pain of cyclic breast disorder, but patients should discuss this type of supplementation with their practitioner first.

Common Uses

  • Corrects iodine deficiency.
  • Ensures proper functioning of the thyroid gland.
  • May help to treat cyclic breast disorder.


  • Tablet.
  • Capsule.
  • Liquid.


  • Because iodine deficiency is rare in developed countries, take iodine supplements only if prescribed by your doctor.
  • Reminder:  If you have a medical or psychiatric condition, talk to your doctor before taking supplements.

How much you need?

The RDI for iodine is 150 mcg daily for adult men and 120 mcg for women.  Many Australians and New Zealanders meet or exceed this amount by using iodised salt.  (One teaspoon of iodised salt exceeds the RDI for iodine).

If you get too little: 
Among the first signs of iodine deficiency, now rarely seen in developed countries, is an enlarged thyroid gland, known as a goiter.  Lack of iodine can cause the gland to expand in an attempt to trap as much of the iodine in the bloodstream as possible.  If your iodine intake is low, your thyroid hormone level may well be low, too.  This condition can lead to fatigue, dry skin, constipation, a rise in blood fats, a hoarse voice, delayed reflexes and some impairment of mental function.  See your doctor if you have these symptoms.

If you get too much: 
There is very little risk of iodine overdose, even at levels 10-20 times the RDI.  However, if you ingest 30 times the RDI, you are likely to experience a metallic taste, mouth sources, swollen salivary glands, diarrhoea, vomiting, headache, acne and difficulty in breathing.  Ironically, a goiter can also develop if you consistently take extremely large amounts of iodine, as an excess can also repress thyroid function.

How to take it?

If you use iodised salt – or, better, eat seafood frequently – you're probably getting all the iodine you need.  Iodine is also a standard ingredient in many multivitamin and mineral supplements.  Even if you're on a very low-salt diet for high blood pressure, you probably don't require extra iodine, though you can safely take 150 mcg a day.  People on a thyroid drug should always discuss their condition with a doctor before taking individual iodine supplements.

Guidelines for use: 
When prescribed, iodine supplements can be taken at any time of the day, with or without food.

Other Sources

The richest natural sources of iodine are kelp and wakame.  (Tasmanian wakame is a high-quality seaweed with very low levels of contamination).  Soil in coastal areas is often iodine-rich, as are the diary products produced by cows grazing there.  The same is true for fruits and vegetables grown in soil high in iodine.  Fish is also a major source of iodine.

Facts and Tips

  • Iodised salt has helped to relieve many of the problems associated with iodine deficiency, such as goiter, but it's best to obtain your dietary requirements from natural sources of iodine, such as fish.
  • Health-food shops frequently promote sea salt as a healthier alternative to table salt – but make sure you buy the genuine article: dried, unprocessed sea salt.
  • A small amount (1/4 teaspoon) of wakame sprinkled on food makes a good salt substitute and also provides iodine.

Latest Findings

An analysis of 10 studies performed in countries where iodine deficiency is common found evidence that an iodine deficiency can affect motor skills, decreasing reaction time, manual dexterity, coordination and muscle strength.  The analysis, headed by UNICEF researchers, also revealed that the IQ of people who were iodine-deficient was some 13 points below that of those with adequate iodine.