Iodine deficiency is becoming increasingly recognised in populations previously thought to be replete, such as those of Australia and the UK. In Australia, there is a common belief that iodine deficiency is not an important public health issue. However, recent research has shown that the dietary intake of iodine is declining.
Iodine is found in seafood, iodised salt and some vegetables. It is important for essential hormone development in the human body. Inadequate intake of dietary iodine can lead to an enlarged thyroid gland (goitre) or other iodine deficiency disorders. Iodine deficiency is the world's leading cause of mental retardation in children.
Symptoms of hypothyroidism - which can be related to low iodine levels or other forms of "underactive" thyroid disease - include:
- lethargy and tiredness, muscular weakness and constant fatigue
- feeling cold (even on warm days)
- difficulty concentrating, slowed mental processes and poor memory
- unusual weight gain
- thick puffy skin or puffiness of the face
- hair loss
- dry skin
- weak slow heart beat
- enlarged thyroid or goitre
To develop normally, the brain needs thyroid hormone. If there's not enough iodine, the mother (or the infant) can't make enough thyroid hormone to keep up with the needs of the growing brain. If the deficiency is severe the child may get a condition called iodine-deficiency disorder (IDD). Kids with this condition may have poor control of body movements, hearing problems, an IQ 10 to 15 points below normal, and a greater incidence of attention deficit hyperactivity disorder (ADHD).
Iodine deficiency affects the whole community and can lead to increasing rates of thyroid disease amongst the general population, and higher rates of intellectual impairment in children. Based on overseas studies, it is also estimated that thyroid disease causes about $250 million loss in productivity in Australia each year.
The Earth's crust has very little iodine, so there is very little in the soil. Ocean's have a higher amount of iodine; so fish, seaweed and shellfish are all good sources of iodine. There may also be some levels of iodine found in eggs, dairy, meat and iodised salt. Iodised salt is not a good source as it doesn't contain iodine, only iodide and due to the 'lifelessness' of table salt it has only 10% bio-availability, plus table salt has been bleached and the chlorine competes with iodine for absorption.
Halides compete with iodine for absorption and uptake in the body. The halide group consists of: bromides (found in pools, spa's, some asthma inhalers, carbonated drinks, some vegetable oil and fluor), chlorine (water and bleached products) and fluoride (water and toothpaste).
In 1924 iodine was added to table salt to increase iodine in people's diets as goitre was very common. Deficiency is re-emerging recently due to consumption of commercially prepared food (lacking in iodine and high in bromides), reduced dietary salts and lack of iodine used in tank sanitiser by the dairy industry (bromides are now used).
Iodine deficiency is linked to hypo-thyroidism, fibrocystic breast disease, breast cancer, oestrogen excess, hypertension, infertility, miscarriage, low birth weight and premature babies in women.