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Went from too little to harmful levels of iodine

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Foto: Shutterstock

The prevalence of goitre used to be high in the mountainous country of Nepal, and children were born with brain damage because of serious iodine deficiency. Now, Norwegian research shows, on the contrary, that many Nepalese people have a too high iodine intake. What happened?

Iodine deficiency is the most important cause of preventable brain damage. If a mother is iodine deficient during pregnancy and the breastfeeding phase, the child can suffer serious brain damage and mental retardation. It is therefore very important that women get enough iodine.

Iodine is unevenly distributed in the world

Worldwide, almost two billion people consume too little iodine. The mineral is unevenly distributed in the soil, and most of it is found in the sea. The best natural source of iodine is fish, which is the reason why iodine deficiency is a problem in countries where people eat very little fish.

Nepal is situated high up in the mountains, and the people there eat very little fish and other seafood, so iodine deficiency used to be endemic. A large part of the population suffered from goitre, and many children were born with brain damage. In the 1970s, the authorities chose to follow the World Health Organization’s (WHO) guidelines and started adding iodine to salt.

May disrupt the metabolism

Nepal managed to overcome the problem of iodine deficiency, but they may have a new problem on their hands. An extensive study of mothers and children in Nepal shows that the Nepalese now consume too much rather than too little iodine. The researchers collected urine samples and breastmilk samples from around 500 breastfeeding women, and found that a relatively substantial proportion of them had too much iodine in their bodies. The study did not investigate whether the high iodine intake had harmed the women and children, but a high iodine intake is unfortunate, according to Sigrun Henjum of Oslo and Akershus University College of Applied Sciences (HIOA).

‘Excess iodine can disrupt the metabolism in newborn babies. Infants and young children are less able to adapt to a too high iodine intake from breastmilk, and they are therefore at a higher risk of disruptions in the metabolism.’

A teaspoon of iodine lasts a lifetime

The biggest problem associated with adding iodine to food is that the window between too much and too little iodine is very narrow. When it comes to iodine, we are talking about very small quantities, and a teaspoon is all a person needs in a lifetime.

‘It is difficult to get the message across to large groups of people about the recommended intake of iodine. Because the window is so narrow, it is important to regularly measure the level of iodine in the most vulnerable groups. This type of monitoring is needed to ensure that the measure is effective.’ So says Marian Kjellevold, scientist at the National Institute of Nutrition and Seafood Research (NIFES).

Considering adding iodine to industrial salt in Norway

Nepal is not the only country where iodine is added to salt and other foodstuff. WHO has issued guidelines on iodisation, and many countries add iodine to animal feed, for example. In Norway, 60% of people’s iodine intake comes from milk and dairy products, because iodine is added to the feed for milk cows, while 20% comes from fish and seafood. Some table salt in Norway also contains added iodine, but, until now, industrial salt has not been iodised. Now, the Norwegian Nutrition Council has proposed iodising industrial salt as well.

The example from Nepal shows that close follow-up is important when iodine is added to salt or other foodstuff. In a poor country like Nepal, it is difficult to find the resources to monitor whether iodisation of salt has the desired effect, which can lead to a situation like the one we see now.

‘This is a classic problem that can easily arise if iodisation is left up to the industry and the authorities do not monitor people’s iodine status. Too much or too little iodine can easily be the result,’ says Henjum.



The article Iodine Concentration in Breastmilk and Urine among Lactating Women of Bhaktapur, Nepal was written in collaboration between, among others, Innlandet Hospital Trust (Tor A Strand), HiOA (Sigrun Henjum) and NIFES (Marian Kjellevold)