The Collison Newsletter July 2012


                        IODINE  AND  HEALTH*  

Iodine is essential for proper thyroid gland functioning. The thyroid gland and its role in health are described in my June 2011 newsletter Poor Thyroid Function - Signs, Symptoms and Solutions. This newsletter looks at iodine: what it is, how we obtain it in our diet, and how it is relevant to health and good thyroid functioning.


Iodine is a chemical element with the symbol I and atomic number 53. The name is from the Greek ioeides, meaning violet or purple, due to the colour of elemental iodine vapour. Iodine is found on earth mainly as the highly water-soluble iodide which concentrates in oceans and brine pools. Like other halogens, free iodine occurs mainly as a diatomic molecule I2.


Iodine is required by higher animals, which use it to synthesise thyroid hormones. Iodine is relatively rare in many soils, due to its initial low abundance as a crust-element, and also because of the leaching of soluble iodine by rain water. It is estimated that iodine deficiency affects about two billion people world-wide.

Iodine Deficiency Disorders 

“Iodine deficiency disorders” refer to a number of disorders in which iodine deficiency has an effect on growth and development. These include:

  • Goitre. Very low levels of iodine intake (less than 50 micrograms/day) are associated with goitre, which presents as an enlarged thyroid gland. Other symptoms include dry skin, fatigue, hair loss, weight gain and depression which are the characteristics of hypothyroidism. 
  • Cretinism. Severe iodine deficiency (less than 30 micrograms/day) during pregnancy can lead to cretinism in infants. This syndrome is characterised by mental deficiency, Spastic Diplegia, deaf mutism and shortened stature. If diagnosed in its early stages, cretinism can be corrected with iodine supplementation.

Iodine deficiency is the world's leading cause of preventable intellectual disability or mental retardation in children.

Thyroid Hormones 

Iodine is required by the body for the synthesis of the thyroid hormones thyroxine (T4, containing 4 iodine atoms) and triiodothyronine (T3, containing 3 iodine atoms). As such, iodine is essential to human life. Without sufficient iodine, the body is unable to synthesise these hormones, and because the thyroid hormones regulate metabolism in every cell of the body and play a role in virtually all physiological functions, an iodine deficiency can have a devastating impact on health and well-being.


The synthesis of thyroid hormones is under the control of the thyroid-stimulating hormone (TSH) produced by the pituitary gland. When the thyroid hormone level in the blood drops, TSH increases to stimulate the thyroid gland to increase its uptake of iodine from the blood, so that more thyroxine (T4) can be synthesised. When necessary, thyroxine is then converted to the metabolically active triiodothyronine (T3).


15mg-20mg of iodine is concentrated in thyroid tissue and hormones, but some 70% of the body's iodine is distributed in other tissues where its role is essentially unknown.

Food Sources of Iodine

  • Marine sources. Marine foods, including seaweed, regular fish and shell fish are the best sources of iodine.
  • Dairy. Historically, dairy foods contained high levels of iodine due to the sanitisers used in dairy processing which contained iodophors. An iodophor is a preparation containing iodine complexed with a solubilising agent, such as a surfactant. The result is a water-soluble material that releases free iodine when in solution. These sanitisation techniques have been phased out of the processes now involved in the sterilisation of dairy equipment. As a result, dairy today has reduced levels of iodine and is a less reliable iodine source.
  • Salt. In Australia, iodine fortified salt contains high levels of iodine. However the use of iodised salt has been reduced due to an increased awareness of the association between high salt consumption and hypertension.
  • Bread. As of October 2008, Australian bakers are required to replace ordinary salt with iodised salt in the baking of bread.
  • Fruit and Vegetables. The iodine content in vegetarian foods is low and is dependant on the environment and the soil in which they are grown.
Iodine Content of Common Foods 




FoodIodine Content
 (mcg per 100g)
Sushi (containing seaweed)92
Tinned salmon60
Bread (made with iodised salt)46
Steamed snapper40
Cheddar cheese23
Ice cream21
Chocolate milk20
Flavoured yoghurt16
Regular milk13
Tinned tuna10
Bread (without iodised salt)3
Beef, pork, lamb<1.5
Tap water (varies depending on site)0.5-20
Apples, oranges, grapes, bananas<0.5

Iodine Recommendations in Australia



Age and GenderRecommended Daily
 Intake (RDI) mcg
1-8 years boys and girls90
9-13 years boys and girls120
14-18 years boys and girls150
Adult men150
Adult women150

Supplemental Iodine 

Iodine as a supplement can be taken as kelp tablets, Lugol’s iodine or Iosol iodine. Seaweed also has significant amounts of iodine.


The iodine content of kelp is variable, depending on the source of the kelp. On average, one gram of kelp contains 1,500-2,500 mcg of iodine.


Lugol's iodine, also known as Lugol's solution, was first made in 1829. Jean Guillaume August Lugol (1786-1851), a French Physician who studied medicine, formulated a solution of iodine that bears his name. It has been used therapeutically for almost two centuries. As a supplement, 1 drop of Lugol's iodine (6,417mcg of elemental iodine), taken in water, is the recommended daily dose.


Iosol iodine has been in use since 1945. It is said to be a formulation that has high water solubility and thus is more bioavailable. One drop contains 1,830mcg of iodine, the recommended dose.


The above dosages are significantly greater than the Recommended Daily Intake (RDI) suggested by the Australian Government’s National Health and Medical Research Council (NHMRC). This is normal for therapeutic supplements. For example, the NHMRC’s RDI for vitamin C is 45mg/day. Typical supplements for vitamin C range from 500-5,000mg/day.

Iodine Allergy 

Iodine allergy is rare.


The symptoms include nausea and possibly vomiting. External allergy symptoms may occur such as itching, skin rash and hives. Red and watery eyes, runny nose and irritation in the nose are also common symptoms of an iodine allergic reaction. There may be breathing difficulties and, in extremely rare instances, anaphylactic shock.


If any allergic symptoms occur, the supplement of iodine must be ceased immediately.


Iodine is an essential trace element for life. It is important that adequate amounts are part of optimal nutrition.



*Copyright 2012: The Huntly Centre.

Disclaimer: All material in the website is provided for informational or educational purposes only. Consult a health professional regarding the applicability of any opinions or recommendations expressed herein, with respect to your symptoms or medical condition. 


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