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The importance of iodine during pregnancy and childhood

Are you getting enough iodine in your diet? Recent studies have shown that iodine deficiency has increased dramatically in Australia and this is most concerning for pregnant/breastfeeding women and growing children.

What is iodine and why is it important?

Iodine is an essential mineral required for hormone development, energy and growth. More specifically, it is needed for the production of thyroid hormones, thyroxine (T4) and triiodothyronine (T3). Thyroid hormones play an important role in metabolic processes in particular those involved during general growth and development, with its strongest connection to the brain.

During pregnancy/breastfeeding

Given the role iodine and thyroid hormones play during times of growth and development, it is no surprise that pregnant and breastfeeding mothers require more iodine than any other health groups. The recommended daily intake (RDI) of iodine for adults (both men and women) is 150µg/day. That jumps rapidly during pregnancy (220µg/day) and again for breastfeeding (270µg/day) [1]. This is because during the first two trimesters of pregnancy, the fetus is unable to produce its own thyroid hormones. It relies solely on the mother to increase her production of thyroid hormones by increasing her intake of iodine, so they can be used for fetal brain development and general tissue growth. By the last trimester of pregnancy, the fetus is able to produce its own thyroid hormones, but still relies on an iodine supply from the mother. This is also the case after birth; iodine from breast milk is needed during the crucial stages of growth. Given that iodine deficiency is quite prevalent amongst adults, many women find it extremely difficult to meet the increased demand for iodine during these times and are therefore their babies are most at risk of the problems and disabilities that arise with iodine deficiency (discussed later).

During childhood development

Throughout development, iodine and thyroid hormones play a crucial role to make sure children grow up and develop properly. Thus during these early years, it is important that children maintain a good level of iodine in their diet. The National Iodine Nutrition Study conducted in Australia has shown that an alarming number of children are iodine deficient [2]. The study involving over 1700 students from 88 schools across five states of Australia, discovered that almost half of the children (46.3%) fall in the range of mild to moderate iodine deficiency. This shows that iodine deficiency poses a significant health problem within children across Australia. In reference to the rest of the world, it has been estimated that 31.5% (266 million) of school children around the world do not receive enough iodine [3].

What happens if you don’t get enough iodine?

Iodine deficiency is the number one cause of preventable mental retardation and brain damage in the world. If a pregnant/breastfeeding mother (or the child) is deficient in iodine, it places the newborn child at risk of becoming mentally retarded and prone to severely stunted growth (cretinism). Iodine deficiency disorders (IDD) predominately lead to intellectual disabilities, growth problems and a wide range of neurological and physical disorders. Commonly linked to iodine deficiency is the enlargement of the thyroid gland (goitre) which can reach the size of a football and protrudes out of the neck. If this continues, hypothyroidism can develop which can result in dry skin, hair loss, slow reflexes, reproductive problems and thyroid cancer.

Why is the level of iodine deficiency so high in Australia?

There are several possible reasons why the country’s high rate of iodine deficiency is comparable to developing countries:

  • The increased consumption of processed foods which are manufactured with non-iodised salt
  • Reduced iodine levels in milk because of changes in treatment methods
  • Lower levels of iodine in Australian soils which reduces its levels in vegetables

To combat the growing trends in iodine deficiency, Food Standards Australia & New Zealand have recently made it mandatory that iodised salt replace non-iodised salt in all bread sold in Australia and New Zealand.

How can you prevent iodine deficiency?

The best food sources of iodine are kelp (seaweed), seafood, eggs, dairy, bread (now that it is fortified with iodine salt) and vegetables (though the amount does vary considerably given the levels of iodine in the soil fluctuate). Including these food sources in your diet is a great way to prevent iodine deficiency.

However during pregnancy and breastfeeding, it can be extremely difficult using diet alone to reach the recommended daily requirements. You would have to consume around 9 cans of tuna a day! Given that this is the most crucial stage for iodine requirements (to prevent mental retardation and stunted growth); it is recommended that women during this period take supplements that contain iodine. It is also important that your growing children reach their recommended targets for iodine, thus they can also benefit from supplements containing iodine to ensure they are growing and developing properly.

References

  1. National Health & Medical Research Council (NHMRC) Nutrient Reference Values for Australia and New Zealand, 2005.
  2. Li M, Eastman CJ, Waite KV, Ma G, Zacharin MR, Topliss DJ, Harding PE, Walsh JP, Ward LC, Mortimer RH et al: Are Australian children iodine deficient? Results of the Australian National Iodine Nutrition Study. Med J Aust 2006, 184(4):165-169.
  3. De Benoist B, McLean E, Andersson M, Rogers L: Iodine deficiency in 2007: global progress since 2003. Food Nutr Bull 2008, 29(3):195-202.

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