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Iodine and pregnancy

Pregnant Woman holding vitamin tablets in her handThere is now irrefutable evidence that mild to moderate iodine deficiency is widespread in Australia and New Zealand.

Recent research data gathered in both countries (and many other countries in the world for that matter) has opened our eyes to a previously hidden and worsening epidemic of iodine deficiency afflicting more than 50% of pregnant women and their offspring.

The Royal Australasian College of Obstetricians and Gynaecologists (RANCOG) asked the International Council for Control of Iodine Deficiency Disorders (ICCIDD) to provide them with some guidelines on how to prevent and treat iodine deficiency during pregnancy.

So why is iodine so important to us?

What is iodine and why is it essential for good health?

Iodine is such a small chemical molecule we call it a “trace element” or a “micronutrient”. Its sole function in humans is to serve as a building block for the synthesis of thyroid hormones (thyroxine -T4 and triiodothyronine -T3) in the thyroid gland. The thyroid gland is important as it helps lots of different parts of the body to function properly.

Iodine gets into the body from food we eat, and once it is in the blood it is extracted by the thyroid gland to make T3 and T4. Iodine is a good anti-bacterial agent when used in large amounts in antiseptic solutions to kill germs on the skin or in body cavities, but this is not a physiological function.

From the time of conception until very late in the pregnancy, the foetus is almost entirely dependent upon the mother for its supply of thyroid hormones (mainly T4). Only in the very last weeks of gestation, just before birth, is the foetal thyroid gland able to function well enough to make its own T4. We now know that to provide the extra T4 needed to maintain the pregnancy and supply the developing baby, the maternal thyroid gland has to increase its production of T4 by at least 50%. At no other time in life is the thyroid gland challenged like this. If the mother does not get enough iodine in her diet she will fail to meet this challenge.

Unless the developing brain of the foetus receives enough thyroid hormone for its growth and maturation, it can suffer irreversible damage. The child will have a high chance of suffering from a lower IQ, coupled with hearing and learning difficulties, and other forms of neurological impairment. There is even some evidence that iodine deficiency during pregnancy may contribute to the development of ADHD, but we are still uncertain about this. The World Health Organisation (WHO) says that iodine deficiency during pregnancy is the most common cause of preventable intellectual impairment in our world today. The more severe the iodine deficiency, then the greater is the risk of brain damage and intellectual impairment. The level of iodine deficiency in Australia is mild to moderate, but this does not mean that it is insignificant. It can still cause neurological disorders.

Where does iodine come from in the diet?

Iodine is found naturally in soil and water. But, over millions of years, most of the earth has become depleted of iodine so that crops and grazing animals more often than not struggle to get enough iodine. Iodine from the soils has been washed into the oceans to be taken up by seaweeds and ocean creatures, such that seafood is a major source of iodine in our diet. Next to seafood, milk and dairy products are the richest sources of iodine. Of course, if we use salt in our cooking or add it to food at the table we should make sure that it is always iodised salt and not one of the many different “gourmet salts” currently being promoted commercially.

Table:  Food Sources of Iodine (FSANZ Nutritional Tables)

Food Level of Iodine (mcg)
Fruit, 1 serve < 2
 Vegetables, 1 serve < 5
  Ice Cream, 45g 9.6
Cheese, 40g 13.6
 Seaweed (Nori), 1 sheet 16
Egg, poached, 55g 20.1
Oyster, raw, 13g 21
 Swiss Cheese, 40g 23.6
Milk, 200ml 31.8
Yoghurt, low fat fruit, 200g 33.4
Fish, Bream, baked, 100g 35.2
Pink Salmon, tinned, brine drained, 85g 51
Seaweed (Red algae), 5g 174

How much iodine do we need?

The current recommendations by WHO/UNICEF/ICCIDD for daily iodine intake are as follows:

  • younger children (1 to 8 years) – 90 mcg
  • older children (9 to 13 years, boys and girls) – 120 mcg
  • adolescents (14 to 18 years) – 150 mcg
  • men – 150 mcg
  • women – 150 mcg
  • during pregnancy – 220 mcg
  • during breastfeeding – 270 mcg

Any more than 500 mcg intake per day is considered excessive and is unnecessary.  While taking more iodine will not do any good it is unlikely to do any harm until an adult ingests more than 2000 mcg per day. The only exception to this recommendation is the person who suffers from Graves’ disease (overactive thyroid) who should avoid extra iodine as it may make the overactive thyroid worse.

Why are we now iodine deficient in Australia?

Iodine deficiency has re-emerged in Australia for two reasons. Firstly, Australian households do not buy and use iodised salt as they once did. Secondly, and most importantly, the dairy industry has changed its work practices and has discontinued the use of ‘iodophors’ as sanitisers for milking apparatus, containers, tankers, and so on. Iodophors are rich in iodine and leak iodine into milk in significantly large amounts. Until the late 1990s, iodine concentrations in milk were frequently in excess of 300 mcg per litre. It is now less than half this concentration. It is easy to see how those who drank milk and ate other dairy products obtained plenty of iodine in their diets.

What is the government doing about iodine deficiency in Australia?

The Commonwealth Department of Health and Food Standards of Australia and New Zealand (FSANZ) have finally accepted there is a serious and ongoing problem of iodine deficiency in Australia (and New Zealand). FSANZ has responded by mandating that all salt used in the bread industry (organic bread has been excepted) must be iodised from October 2009. While this is a step in the right direction, especially for children, it will still not provide enough iodine to correct the problem in pregnant women.

Why do pregnant and breastfeeding women need to take iodine supplements?

From studies in pregnant women, it has been calculated that the average iodine intake is approximately half the WHO recommended daily intake of 130 mcg per day. Pregnant women should be taking a folic acid supplement and an iodine supplement before conception or right from the beginning of pregnancy. The ideal daily supplement should contain between 150 and 250 mcg iodine per tablet. Once again, the only exception to this advice is the woman who is suffering from Graves’ disease.

 

– this article was kindly supplied by Professor C J Eastman, AM MD, of the Australian Thyroid Foundation

Image credit: evgenyatamanenko/123RF Stock Photo

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