Pregnant or planning to be? Is Iodine on your radar?

It really should be!

Given iodine’s glaring lack of PR, you would be forgiven for thinking that it’s sole purpose is for making a yellowy black, highly staining liquid for putting on grazed knees.
The reality is that it does a whole lot more than that and, if pregnancy is on the cards, you might want to delve a bit deeper.
Iodine is a micronutrient, sometimes referred to as a trace element, since we only need to ingest it in very small amounts to be replete. Plus, it is stored in the body, so we can get away with a low intake for a short period of time.
In spite of this, an iodine deficiency persists in many countries and this is of particular concern among women who are planning a pregnancy, are already pregnant or are breastfeeding. And that’s because their iodine requirements are raised.
In 2009, the iodine status of 100 pregnant women from Surrey was analysed. For those of you not familiar with UK geography, Surrey is a County in the South East of England known for its relative affluence and hence, one would assume, perfectly well-nourished residents. However, the median iodine level of these women was mild to moderately low. You may be equally shocked to hear that a study carried out in 2011, which looked into the iodine status of girls aged 14-15, found the UK to be in the top ten iodine deficient countries of the world, falling between Angola and Mozambique. Spain, my present country of residence does a little better. What’s more, I’m very taken with the word for iodine in Spanish – ‘yodo’ – and I’m not even a big Star Wars fan! (Yes, I know it’s ‘Yoda’)
In this post, I will reveal why some countries are persistently behind in the iodine stakes. But first off, let’s look at why this matters and why I would urge all women who may one day hope to be mothers to review their intake of this somehow overlooked nutrient, especially if they follow a vegetarian or vegan diet.
What’s so important about iodine?
It’s funny how some things stick in your head (usually the not very useful ones) and others just drift away. Well, ‘Derbyshire Neck’, is a term that somehow lodged in my brain from my days at Kings College London where I studied Nutrition and Dietetics.
The term, ‘Derbyshire Neck’, emerged from the fact that Derbyshire was one of a number of areas of the UK where iodine deficiency was found to prevail in the 1930’s and, consequently, many locals developed large swellings in their necks, called goitres. These swellings were enlarged thyroid glands which had grown in an attempt to increase their production of a hormone that you will no doubt have heard of, thyroxine. In order to make thyroxine they require, you guessed it, iodine. The severe lack of iodine in the Derbyshire folks’ diet meant that the thyroid gland was struggling and trying to overcompensate by growing bigger. I hasten to add that this was happening all over the UK and I believe that the people of Derbyshire now have perfectly beautiful necks. But that doesn’t mean that everyone in the UK gets enough iodine, they’re perhaps just far less severely deficient.
Whilst the population’s iodine status in the UK might be especially worrying, that doesn’t mean that elsewhere in the developed world we needn’t focus our attention on how much we’re consuming. In fact, studies show that whilst many people now appear to have iodine levels within the normal range to fulfill their own needs, the iodine level of many women of child-bearing age is not adequate to meet the increased needs of pregnancy and a developing baby.
And this is a big problem because iodine is vital for mental and physical development.
The WHO cited iodine deficiency as ‘the single most important preventable cause of brain damage worldwide’. Yep! Worldwide malnutrition.
Why do women need more iodine in pregnancy?
Iodine regulates the development of the baby’s brain and its nervous system. It is also involved in the development of bones, especially the long ones. It does have a number of other roles, in addition to the antibacterial role we’re familiar with, but I’ve just listed the crucial ones here.
So, if mum, and therefore baby, receive insufficient iodine from mum’s diet the infant’s development can be affected. I must emphasise though that the effect on bone development has only been documented in severe iodine deficiency. Furthermore, there have been no robust randomised controlled trials to assess the benefit of maternal iodine supplementation on their child’s development. This is when two very similar groups of pregnant women would be given either an iodine supplement or a placebo and the effect on the child’s development then assessed in the future.
That said, there have been some observational studies which suggest a link between an expectant mother’s iodine status and the development of her child. A study carried out in 2011-2012 in Norway showed a relationship between low iodine levels in pregnant women and reduced language skills among their infants at 18 months. A relationship doesn’t necessarily mean that one directly causes the other, of course, but the researchers seem to have tried to take into account other possible parental and socio-economic factors which might have muddied the waters.
In a UK study published in 2013, iodine levels and child development data from the Avon Longitudinal Study of Parents and Children collected in 1991-2 was analysed. The study had measured the iodine status of almost 1000 women in their first trimester of pregnancy. In this analysis they split them into two groups: those with adequate iodine levels and those with low levels (based on WHO cut offs). They wanted to see whether the children’s IQ and their reading ability at age 8 and 9 respectively might be affected by the mother’s iodine level. A massive 67% of mothers were found to be deficient in iodine. But how did this affect their children? Well, they fell into the lowest quartile (lowest 25% of scores) for Verbal IQ, reading accuracy and reading comprehension. The study revealed a linear effect i.e. the lower the iodine status, the greater the effect.
You might be thinking that 1992 was a lifetime away and that, surely, things have improved since then. It would appear not. I’ll explain why later.
As is the case with many nutritional deficiencies, it’s impossible to be precise. We can’t say that below a certain maternal iodine level the child’s development will necessarily be impaired. The classification of ’mild, ‘moderate’ and ‘severe’ deficiency are essentially arbitrary numerical ranges, albeit based on the best evidence available.
What I mean is that iodine deficiency doesn’t just fit neatly into three categories. It exists on a continuum and at some point it will begin to have a negative impact on baby’s development. With mild deficiency the impact may be barely perceptible. In reality, we can’t predict someone’s full intellectual potential and so can’t assess whether they ever actually achieve it.
However, if mums (and partners) were made aware of the importance of iodine and, furthermore, that their diet was likely to be low in it, they could make an informed decision as to whether to do something about it and give their child the best chance possible. I think I can guess what most parents would do.
Many pregnancies are unplanned and, even those that are planned are rarely confirmed for a few weeks. Given that the foetus’s thyroid is developed at 10–12 weeks gestation and can function and produce thyroxine at 16-20 weeks, iodine is something that women ideally would be thinking about as soon as they hit child-bearing age.
The need for additional iodine in pregnancy is not just to meet the growing foetus’s requirements, it is because pregnant women lose more iodine in their urine and, when breastfeeding, they pass iodine on to baby.
As with all things nutritional in pregnancy, of course, baby tends to get what they need before mum gets a look in. So, if you’re reading this as an already pregnant woman, please don’t panic. How many women do you know who have had perfectly healthy pregnancies and healthy babies and have probably never considered their iodine intake? The majority, I would guess. This post is certainly not designed to cause alarm just to raise awareness. And, it’s never too late to improve your iodine levels.
Why on earth is it so difficult to get enough iodine and why might a pregnant woman’s intake suddenly drop?
Iodine comes from the sea and the earth. However, it is one of the rarest elements needed for life and, whilst the sea is by far the largest reserve of iodine, the concentration is too low to extract.
If we live in areas where the iodine has been leached from the ground over years by rain, the vegetables grown in that area contain less iodine. In turn, animals grazing in the fields will take in less iodine which means that their meat and milk are lower in this nutrient. This was the problem in Derbyshire (and other parts of the UK and no doubt the world).
In the UK, sometime after the Second World War, iodine was added to the winter feed of cattle as well as being used as a disinfectant in dairies, hence milk and cheese became a rich source of iodine for the UK population. All was well until, in 1971, a certain Secretary of State for Education, Margaret Thatcher, decided that school milk for the over 7’s was an unnecessary expense, hence the ‘Thatcher Thatcher Milk Snatcher’ nickname. Children’s intake of iodine was compromised overnight.
A more recent food movement might be reducing our iodine intake further. Whilst thoroughly positive in many other ways, the desire to eat ‘organic’ might be fueling the fire. Organic milk tends to be far lower in iodine due to differing farming practices. Milk alternatives such as soya, almond and oat milks are often not supplemented with iodine. And if women aren’t aware of the importance of iodine, why on earth would they
bother checking the labels anyway?
In most countries now, iodine is routinely added to table salt and hence most of the salt sold in shops will be iodised. That said, sea salt is unlikely to be iodised. The UK is, for some reason, resisting the iodisation of salt, one of only 25 countries worldwide to make this decision (as of 2018). I’m not sure why this is. Perhaps they fear it will spark a sudden increase in salt intake. However, by simply replacing current intakes of non-iodised salt with iodised salt, some improvement of iodine status of the population would presumably ensue. Iodised salt sourced from abroad can be found in UK shops, you just need to check the labels.
There is no requirement in any country, however, for iodised salt to be used in processed foods and, since it is more expensive than standard salt, I wouldn’t rely on it as a significant source. In Australia and New Zealand, flour is fortified with iodine. Again, organic versions are excluded from this requirement.
I wouldn’t want you to think, however, that iodised salt is a panacea. Unless taken in amounts that would be discouraged from a sodium point of view, it can’t meet our full requirements. We need to look to other sources too.
Where else can we get a decent amount of iodine in our diet and how much do we need?
The WHO estimates daily iodine requirements for an adult to be 150mcg (140mcg in UK).
For a pregnant woman, the WHO recommends 250mcg whilst the European Food Safety Association recommend 200mcg.
Here is a link to the British Dietetic Association’s leaflet on Iodine. You’ll find a list of good iodine sources.
You may be surprised to see how high in iodine certain white fish are. In many populations, fish is a key source of iodine which explains why, for some women, their iodine intake drops when they fall pregnant. This comes from an understandable desire to avoid consuming excessive amounts of mercury which is known to accumulate in certain fish.
The great news is that white fish such as haddock, cod, skate, hake and plaice do not contain high levels of mercury. The main culprits are those at the top of the food chain and which live the longest and so have had more time to accumulate mercury from their prey. These are shark, marlin and swordfish. Tuna can also contain relatively high levels of mercury but needn’t be avoided entirely. A couple of fresh tuna steaks (170g raw or 140g cooked) or 4 medium-sized tins (140g drained) per week are quite safe and you’ll get a decent dose of iodine with it.
Oily fish tends to store more toxic pollutants than white fish but they are excellent sources of omega 3 fatty acids and iodine, both of which are essential for brain development, so it is recommended to have a portion or two of these a week. We’re talking about salmon, trout, herring, sardines, pilchards and mackerel
Other fish which aren’t classed as ‘oily’ but which may also contain higher pollutant levels are sea bass, sea bream, turbot, halibut and crab. However, these could be included in your 2 portions.
So, pregnant women can still enjoy fish and the wonderful iodine that they bring and are encouraged to eat them at least twice a week.
A word about seafood. Some expectant mums may also avoid seafood to reduce their risk of food poisoning and, consequently, they miss out on the iodine they bring. In reality, if seafood is well-cooked the risk is very low, but mums have to do what feels right for them and I’d certainly never argue with a pregnant woman!
Can I have too much iodine?
You may have noticed that seaweed such as kelp, even in supplement form, is omitted from the list. This isn’t because it can’t be an excellent source of iodine; it can. But, as with vegetables, levels vary enormously dependent on where they’re grown. Whilst the low levels of iodine in the soil means that vegetables pose little risk, the much higher levels in the sea could lead to some seaweed containing excessive amounts of iodine. And you can have too much of a good thing when it comes to many nutrients, iodine included.
Excessive levels of iodine can, dependent on how the body reacts, lead to a low or high thyroid production, neither of which are good for our wellbeing. We certainly wouldn’t want to be passing a large amount through to baby. So, seaweed avoidance in pregnancy is advisable.
What does this mean for you if you are planning a pregnancy or already pregnant?
I hope it means that you now feel informed and able to assess whether you could do with adding a few more good sources of iodine to your diet.
You may decide to look for a pregnancy specific mineral and vitamin supplement which contains iodine. A word of warning though; please ensure they don’t contain more than 150mcg per day or you might overdo it.
I am very concerned that the importance of adequate iodine in pregnancy doesn’t appear to get the press it deserves. Furthermore, with more people adopting vegetarian or vegan diets or choosing to buy organic products for entirely valid reasons, intakes may drop further.
I hope this post gives you the tools to make your own decision, in particular if having a family is in your plans, even if some time off.

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