Why are we fortifying our bread with iodine?
Iodine is one of the essential nutrients which our bodies need in order to function properly. It’s most well-known for
being an important constituent of our thyroid hormones, which regulate metabolism and, in children, normal growth and
It’s also very important for brain development in unborn, and young, children. Indeed, researchers from Otago have shown
that correcting mild iodine deficiency in children improves their intelligence
Iodine is also something in which most New Zealanders, not just our children, are increasingly deficient. There are a
number of reasons for this, including changing diet over the last few years and changing practices in the dairy
industry. In addition, the iodine content of New Zealand soils is low, meaning that our fruits, vegetables and grains
have low iodine content.
To combat this deficiency, the salt used to make bread in New Zealand (excepting organic and salt-free breads, and some
home-bake bread mixes) will be replaced with iodised salt from early next month. The iodisation of bread means that people will not have to increase their salt intake in order to improve their iodine
The move follows a decision by the Government to delay mandatory fortification of folic acid in bread until at least May
2012. Across the Tasman, Australian bakers were required to add folate to bread from this week
in a bid to cut spina bifida rates.
Food Standards Australia New Zealand has concluded that any risk from iodine fortification is very small across all
groups. A fact sheet containing more information can be found here
The Science Media Centre gathered comment from local experts on the mandatory fortification.
Professor Christine Thomson, of the Department of Human Nutrition at the University of Otago, comments:
“Researchers in the Department of Human Nutrition at University of Otago identified the re-emergence of mild iodine
deficiency in New Zealand in the early 1990s, in spite of adequate iodine status reported during the 1960s-1980s. The
low iodine content of our soils was the reason for the high incidence of iodine deficiency goitre prior to iodisation of
salt in the early 1940s. The reduction in iodine status (as measured by urinary iodine excretion) during the last two
decades throughout New Zealand is due mainly to the reduction in the use of iodophors as a cleaning agent in the dairy
industry, resulting in lower iodine content of our dairy foods. In other words, much of our iodine intake during the
adequate years was coming from iodine contamination of dairy products rather than iodised salt. A reduction in the use
of iodised salt at the table and in cooking as a result of changes in dietary patterns has also contributed to the
recent re-emergence of mild iodine deficiency. In particular, there has been an increase in the consumption of processed
foods; salt used in manufactured and processed foods is not iodised in New Zealand.
“Subsequent research by us indicated that the low iodine status is being reflected in disturbances in thyroid hormone
metabolism, enlarged thyroid glands (goitre) and more recently a possible impairment in cognitive function of children.
This situation is likely to worsen unless measures are taken to increase our iodine status. The most vulnerable groups
in the population are pregnant and lactating women, as vital foetal mental and physical development occurs during
pregnancy and during early infancy. Young children are also vulnerable to iodine deficiency in terms of cognitive and
“Mandatory fortification of bread will go some way towards safeguarding the population from iodine deficiency and will
increase the iodine status of most of the population to adequate levels. However, it will not be sufficient to meet the
very high requirements for iodine for pregnant women, and iodine supplements are still recommended during pregnancy.
“Universal salt iodisation (ie iodisation of all salt used in processed food and table salt) is the recommended method
for eliminating iodine deficiency around the world, but has not been adopted in New Zealand and Australia because of the
perceived resistance from the food industry. Bread was chosen as a convenient and relatively easy first step as the salt
already in bread will simply be replaced with iodised salt.
“Iodine fortification is necessary in New Zealand ultimately because of our low soil content resulting in low iodine
concentrations of food. Folic acid fortification is the replacement of a nutrient removed during processing of cereals.
For both there is good evidence for beneficial effects of fortification on health. Iodine fortification is not
controversial probably because we already have iodised salt and so is not a new issue for the public.
“Consumption of iodine-rich foods such as fish, sushi, eggs and dairy products is still a sensible option for improving
iodine status and also provides many other essential nutrients.”
Lyn Gillanders, Senior Clinical Dietitian at the NZ Dietetic Association comments:
“Worldwide iodine deficiency is the biggest single cause of preventable brain damage and mental retardation. In NZ
evidence from the 2002 National Children’s Nutrition Survey was that NZ children had urinary iodine excretion rates
consistent with mild iodine deficiency (this is best way of measuring iodine status).
“It’s an issue in NZ because the consequences might be that children do not learn and develop as well as they might do.
The effects of deficiency are seen at all stages of development but the other vulnerable time would be foetal
development and when being breast fed.
“The impact of iodine fortification we would hope would lead to the most vulnerable groups becoming iodine sufficient
but fortification might still not be enough. I believe that the Ministry of Health is developing a proposal for a 150
microgram iodine tab (like the folic acid tab) but when I looked on their website I could not find a reference for this.
However, they do have some quite good iodine notes
“Bread was chosen after the FSANZ modelling research which showed that this was most likely to be the most consumed
food. Historically NZ had a relatively high rate of iodine deficiency because our soils are poor in iodine (soil leached
by glaciation or high rainfall contains little iodine) and therefore food grown in these soils contains very little
iodine. We have had iodised table salt in NZ for almost 100 years now as a public health measure to prevent iodine
deficiency. However salt used in manufactured food had to be just ordinary salt. The new measure is that salt used in
breadmaking now will contain iodised salt, i.e. iodine fortification. Previously, over perhaps the last 50 years or so,
use of iodophors as sanitisers in the dairy industry gave us all a little extra iodine from the residues in dairy
products but these are not used very much nowadays.
“It’s really not all that different from folic acid fortification but maybe New Zealanders have had almost 100 years to
get used to the idea that we need a little extra iodine because they are familiar with seeing iodised salt on the
supermarket shelves. Maybe people think salt is more “natural”. It is perhaps worth mentioning that it would be a bad
idea to encourage New Zealanders to have more iodised salt as table salt because salt intake is one of the biggest
factors driving up our collective blood pressure and consequent strokes and heart disease. So we hope that this is a
Dr Sheila Skeaff, Senior Lecturer at the Department of Human Nutrition, University of Otago, comments:
“There are low levels of iodine in New Zealand soils, and it common in New Zealand for our diets to be lacking in
iodine. In the past most of our iodine came from dairy foods such as milk and cheese, and iodised salt used at the table
or in cooking. But today people are adding less salt to food or are replacing iodised salt with rock or sea salt that
contains virtually no iodine. Changes in the dairy industry has meant that the amount of iodine in dairy foods is much
lower than it used to be. Many people are not aware that the salt used to make foods bought in the supermarket (i.e.
processed foods), is not iodised. And although fish and seafoods are rich in iodine, most New Zealanders do not eat
enough of these foods to get much iodine from them. At present, most children and adults, especially pregnant and
lactating women, are iodine deficient. Iodine is an essential element needed for normal growth and development,
particularly of the brain. Growing brains need iodine and that is why pregnant women and children need a good supply of
iodine in their diets.
“A recent study has found that giving New Zealand children extra iodine helped them do better on cognitive tests than
children who were iodine deficient. The mandatory fortification of bread with iodised salt should increase the iodine
intakes of New Zealand children and adults so they are getting enough iodine from foods, however, pregnant and lactating
women will still not obtain enough iodine in this way and should take a supplement containing 150 ug of iodine each day.
People who do not eat commercial breads should ensure that they obtain additional iodine from consuming more iodine-rich
foods or taking an iodine-containing supplement. The use of kelp tablets, however, is not recommended as these tablets
often contain variable and very high amounts of iodine. In contrast to folic acid, which is recommended for one group of
the population (i.e. pregnant women), iodine is needed for all groups of the population and the replacement of
non-iodised salt with iodised salt is relatively simple for food manufacturers; this may explain why the mandatory
fortification of bread with iodised salt is less controversial than mandatory folic acid fortification. Nonetheless, the
lack of iodine in the New Zealand diet for almost two decades has received little attention in the media, despite the
possible implications this may have on brain development, both for individuals and society. In 2008 the Copenhagen
Consensus, a panel of 8 top-economists including 5 Nobel Laureates, identified the iodisation of salt as the world’s
third best investment to improve the state of the planet.”
David Roberts, Programme Manager for Nutrition at the New Zealand Food Safety Authority, comments:
“Why is it an issue in New Zealand?
“• Iodine is an essential nutrient for growth and development. Iodine occurs naturally in most foods, but usually in
small amounts. Because iodine can’t be made in the body we need to get it from the food we eat.
• Iodine is important for our thyroid hormones. These hormones support normal growth and development in children and
help to maintain the body’s metabolic rate. As iodine is essential for brain development, it is particularly important
that unborn babies (foetus), infants and young children have enough iodine.
• Recent studies have indicated that the iodine status of New Zealanders is declining to the point where the New Zealand
Government has decided to replace non-iodised salt with iodised salt in most bread. This will contribute to helping to
reduce the risk of iodine deficiency disorders affecting the New Zealand population. Low iodine status may be due to:
• people eating more commercially prepared foods (which tend to be made with non-iodised salt)
• a reduction in the use of iodine-containing sanitisers by the dairy industry. Cows’ milk and foods made from cows’
milk had higher levels of iodine when the dairy industry used disinfectants containing iodine during milk processing
• less salt being used in home prepared foods because of health messages encouraging consumers to reduce their salt
“What are the symptoms/health implications of such deficiency?
“• Low iodine levels in our diet may lead to health issues often referred to as iodine deficiency disorders. This might
include poor growth and development in infants and children, including reduced intellectual quotient (IQ), thyroid
diseases, and goitre (swelling of the thyroid gland in the neck).
“Who is the most vulnerable?
“• Iodine deficiency is associated with a wide range of adverse health effects; with the most detrimental involving the
developing brain, especially during foetal growth and infancy periods. Hence the iodine status of pregnant and
breastfeeding women is of particular importance.
• As substantial brain and nervous system development continues into the first two to three years of life, this period
is also critical with respect to iodine nutrition.
• In adults, long periods of iodine deficiency increase the risk of thyroid dysfunction, predominantly hyperthyroidism
and associated serious health consequences in later life.
• Further, both adults and children are at risk of developing goitre from iodine deficiency. Thus, iodine deficiency
represents a significant threat to the health and wellbeing of the New Zealand community now and in the future.
“What will the impact of fortification be?
• In the general population aged 15 years and older, the proposed fortification is predicted to reduce the prevalence of
inadequate iodine intakes from 51% to less than 1% overall. In children aged 5-14 years, a large improvement in status
would also be achieved. In all age groups, those who do not use iodised table salt are more likely to have inadequate
intakes than those who do use iodised table salt.
• The absence of New Zealand dietary survey data for young children (< 5 years) makes estimating current and post fortification intakes difficult. However, it is apparent that the proposed
fortification would increase the iodine intakes of young children.
• Although the proposed mandatory fortification will increase the iodine intakes of pregnant and lactating women by an
important and useful amount, it is likely that a high proportion of these groups will still have inadequate intakes. For
these women, it is recommended to regularly choose foods that are naturally important sources of iodine, such as low-fat
milk and milk products, eggs and seafood. Iodised salt will provide some iodine in their diet, if used instead of
non-iodised salt in cooking or at the table.
• The Ministry of Health has been working to secure a subsidised iodine-only tablet to help pregnant and breastfeeding
women meet their extra iodine requirements. The Ministry of Health has indicated that a daily 150 microgram iodine-only
tablet will be available later this year. Once the iodine-only tablet has been assessed and approved for supply it will
be available to all pregnant and breastfeeding women as an over-the-counter pharmacy product.
“• One of the reasons bread was chosen is because it is eaten widely by New Zealanders. Bread manufacturers will replace
non-iodised salt with iodised salt in most bread.
• Replacing non-iodised salt with iodised salt, to most bread, is a simple and low cost way of helping to increase the
iodine intake of most New Zealanders, and reduce the number of people who aren’t getting enough iodine.”