Your guide to iodine

Many developed nations are currently experiencing significant levels of iodine deficiency. Australia was not considered to be at high risk of iodine deficiency until about 20 years ago when changes in dairy industry regulations saw a significant drop in the iodine present in dairy products. Several studies have now shown that Australians are at a significant risk of iodine deficiency. This is also the case for several European countries and New Zealand, among others. Pregnant women, infants and the elderly are at particular risk of deficiency but optimal iodine levels are imperative throughout life.

Iodine in food

Part of the reason why iodine deficiency is a problem in developed nations as well as developing nations is the fact that the highest concentrations of iodine in the food chain are marine-based. The iodine content of land-based food, such as meat, fruit and vegetables, is dependent on the iodine content of the soil. The iodine present in the upper crust of the earth is very susceptible to leaching through heavy rains and flooding and being washed into the oceans. This process inevitably leads to lower iodine levels on land and higher iodine levels in our oceans.

Interestingly, seaweeds near coral reefs have an inherent capacity to concentrate iodine and hence the reef fish that feed on this seaweed are also rich in iodine, so it flows through the food chain. Many Western countries eat very little seaweed and seafood, hence our susceptibility to iodine deficiency despite our perceived high access to a diverse and healthy diet.

Iodine is found in foods and many supplements in the inorganic iodide form and is easily absorbed in the stomach and small intestine. It is worth noting that certain foods can act to block the functioning of iodine once in it is absorbed in the body. Goitrogens are one such food component and can act to block the synthesis of thyroid hormones through blocking the correct binding of iodine. Food containing goitrogens include the brassica vegies, such as cabbage, broccoli, cauliflower and Brussels sprouts. Foods such as sweet potato and maize contain cyanoglucosides, which can block the uptake of iodine to the thyroid. These are all healthy foods and should not to be removed from a general healthy diet but are of particular interest for people with known thyroid disorders such as hypothyroidism.

The thyroid link

Iodine is actually a trace element (meaning it is needed in very small amounts) and was one of the first trace elements found to be essential for optimal health. Being a component of thyroid hormones, iodine plays a role in normal growth and development of the central nervous system, energy production and metabolic rate. Thyroid hormones are involved in carbohydrate, fat, protein, vitamin and mineral metabolism. In a nutshell, iodine deficiency can flow into a cascade of health issues, some of which are particularly significant.

Pregnancy

Maintaining optimal iodine levels throughout pregnancy is imperative for healthy development of the foetus. We now know that iodine deficiency can affect the development of the foetal brain and possibly cause permanent birth defects, learning difficulties, impairment of motor skills and deficits in hearing. The World Health Organization considers iodine deficiency to be the most common worldwide cause of preventable mental deficiency. Supplements are crucial in achieving optimal iodine levels throughout pregnancy.

Ms Beverly Garside, President of the Australian Thyroid Foundation, stated in 2010, “Pregnant and breastfeeding women cannot possibly get the recommended daily intake of iodine from food alone, so it is essential that they take a supplement during this time.” Studies back up this statement. A study in Rome conducted after implementing an iodised salt program found 92 per cent of pregnant women were still iodine-deficient. Another study closer to home found that after the implementation of bread fortification with iodised salt in Tasmania, the study group of pregnant women had iodine levels at less than half the recommended minimum level.

Yet another study found that iodised salt programs may correct low iodine levels in non-pregnant women but not in pregnant women due to the higher demands during pregnancy. Australian studies have found that approximately half of pregnant women in NSW, Victoria and Tasmania are iodine-deficient. If iodine deficiency exists from week 15 of gestation through to the age of three, the result can be derangement in the development of the brain and central nervous system. These derangements, if they occur, are irreversible with the most serious form being cretinism.

Taking iodine

There are a few ways to assess your iodine status. The most commonly used tools for evaluation include a urinary iodine test, which gives an idea of iodine levels over that past few days, and thyroid hormone levels, which indicate thyroid nutrition over the previous weeks and months.

The recommended daily intake changes depending on age and stage of life. Please consider that taking a recommended daily intake may not be adequate if a frank deficiency is discovered. If you are found to be deficient in iodine an appropriate dose needs to be discussed with your practitioner and usually follow-up testing will be performed after three months to check progress.