Iodine deficiency is the leading global cause of preventable brain damage and mental retardation or neurocognitive disorders. The World Health Organisation (WHO) estimates that about 2 billion people live in regions that are iodine deficient, and are at risk of one or more of the iodine deficiency disorders (IDD).
Iodine deficiency has profound effects on intellectual development with the most extreme being cretinism, which occurs as a result of severe deficiency. This syndrome is characterised by mental deficiency, Spastic Diplegia, deaf-mutism and shortened stature in infants. Alarmingly, 30 to 40 million children are born each year suffering from neurocognitive disorders.
Cause of Iodine Deficiency
Iodine deficiency is not a new phenomenon in Australia (see below) and New Zealand. A national study has shown that Australian children are mildly iodine deficient; however, several smaller studies have shown more that 50% of pregnant Australian women are iodine deficient specially in New South Wales and Victoria.
Pregnancy places a unique demand on the thyroid gland to increase thyroid hormone production by up to 50%. To achieve an optimal outcome requires a combination of adequate thyroidal iodine stores and an increased dietary intake of iodine. Low amounts of thyroid in pregnant women could lead to adverse consequences including miscarriage, gestational hypertension, premature delivery and fetal complications, but especially neuro-cognitive disorders.
Iodine status from the National Iodine Nutrition Survey 2004:
|State Sample size MUIC (μg/L) Population iodine status|
|New South Wales 427 89.0 mild deficiency|
|Victoria 348 73.5 mild deficiency|
|South Australia 317 101.0 borderline optimal|
|Western Australia 323 142.5 optimal|
|Queensland 294 136.5 optimal|
|Total sample (un-weighted) 1709 104.0 borderline optimal|
|Total sample (weighted) 1709 98.0* borderline deficiency|
How Much Iodine Do You Need
A person’s iodine status is considered optimal if the population median urinary iodine concentration (MUIC) falls between 100-200 μg/L(table 2) . Mild iodine deficiency is defined as MUIC between 50 and 100 μg/L. Recent studies on the iodine status of mainland Australian school children showed that about 50% are classified as mildly or moderate iodine deficient. Among that group, 14% of children in NSW, 19% in Victoria and 20% in Tasmania are classified as moderately iodine deficient.
The term ‘mild iodine deficiency’ is potentially misleading as it does not convey the seriousness of the associated health effects. Professor C J Eastman, a consulting endocrinologist at Westmead Hospital who has headed major research and public health projects into the elimination of IDD, emphasizes that even a mild iodine deficiency can result in a reduction in the average IQ and fewer gifted individuals.
Iodine recommendations in Australia and New Zealand
|Age and Gender||RDI|
|1-8yrs boys and girls||90µg/day|
|9-13yrs boys and girls||120 µg/day|
|14-18yrs boys and girls||150µg/day|
Food sources of iodine
It is of paramount importance to obtain iodine through food sources such as seafood, including regular fish, shellfish and iodized table salt (See table 3). The iodine content of plants and vegetables is dependent on the environment and soil in which they are grown.
Pregnant and breast-feeding women may require iodine supplements, though consultation with a doctor is recommended before commencing a supplementation program.