Iodine is an essential element - our body needs it,
but cannot make it on its own.
It has to come from our diet and although only small amounts are needed, iodine levels in food are generally very low, so it can be a challenge to get enough. Dietary sources of iodine include vegetables, seafood, milk and eggs. The iodine content of vegetables, fruits and grains reflects the iodine content of the soil that they were grown in and as New Zealand soils are low in iodine, levels in these foods are low. A normal diet would not give us sufficient iodine. However this is mitigated by fortifying foods with iodine and so many vegetables have iodine added. Salt often has iodine added to it. Commercially prepared bread has to be made with iodised salt making this where most people get the bulk of their iodine.
Low iodine levels used to be a common and important problem that was mostly solved with the use of iodised salt. Unfortunately there appears to be a re-emergence in iodine deficiency with the main reasons being an increased consumption of commercially-prepared foods that are often manufactured with non-iodised salt, and less salt being used generally as a result of health promotion campaigns to reduce salt intake.
There are two main problems that can arise from iodine deficiency, and it also has two other therapeutic uses:
Thyroid disease - iodine assists the thyroid gland to make hormones which maintain the body’s metabolic state. Without iodine, thyroid hormone production is reduced and hypothyroidism occurs. Possible symptoms include fatigue, weakness, weight gain or increased difficulty losing weight, hair loss, constipation, depression, memory loss and infertility. One of the earliest signs may be goiter, an enlargement of the thyroid gland which can be visible in the neck area region.
Pregnancy and Breastfeeding - thyroid hormones are particularly important for normal growth and brain development in foetuses and children. If pregnant women are iodine deficient this can cause major neurodevelopmental deficits and growth retardation in the foetus, as well as miscarriage and stillbirth.
This condition in children is called cretinism and is characterised by mental retardation, deafness, spasticity, stunted growth and many other physical and neurological abnormalities. Less severe iodine deficiency can also cause neurodevelopmental deficits such as lower-than-average intelligence as measured by IQ. Women who are pregnant or breastfeeding are recommended to take an iodine supplement (which may be part of a multivitamin preparation) and/or choose high iodine foods.
The recommended daily intake for iodine varies according to age. For children 1 to 8 years it is 90mcg a day, for 9 to 13 years, 120mcg a day and for people aged over 14 years, 150mcg a day. The RDI is higher still for breastfeeding or pregnant women, with around 250mcg a day recommended for those who are pregnant or who are breastfeeding.