Our Greatest Accidental Health Triumph: Eliminating Iodine Deficiency (Until Now)
In the UK we have never directly addressed iodine deficiency. Eradicating it was an ‘accidental public health triumph’. This relied on the fact that milk consumption by UK consumers increased rapidly in the 1950s and 60s.
On February 17th, 1869, Russian chemist Dmitri Mendeleev did something rather clever (and he hadn’t been drinking Red Bull). Like many scientific colleagues of his day he was looking for ways to organise all the known elements in the universe into some sort of order.
Without ‘The Times’ crosswords, Netflix or TikTok (nod to my son) what else was there to do in 1869? At this point in time there were 70 elements known to man and they were begging to be organised.
What Mendeleev did was fundamentally quite simple as well as being touched by a stroke of genius. He arranged elements in order of increasing atomic mass and in doing so he also noticed that certain groups had similar properties (maybe he did need to go out more often). Currently there are 118 elements in the periodic table, 94 of which occur in nature and another 24 which are radioactive, artificial and only synthesised in a laboratory.
All 94 natural elements are products of the lifecycle of ancient stars. The stars forged the elements, but it took the unimaginable pressure and temperature created by the sheer mass of bigger stars to forge and fuse the heavier elements in the periodic table.
Larger stars evolve to form supernovas which burn at incredible temperatures that are 6000 times hotter than our sun (at temperatures measured in billions of degrees Kelvin). Supernovas, depending on their mass, eventually evolve to form either a black hole or a neutrino when they collapse and implode.
It is in supernovas or neutrino stars where many of the heavier elements (such as iron, iodine, uranium and gold) in our periodic table are fused by the extreme limits of physics and chemistry.
Our world (including ourselves) is quite literally made up of elements formed deep within the cores of stars now long dead. As Britain’s Astronomer Royal Sir Martin Rees said, ‘We are literally the ashes of long dead stars.’ Our bodies contain 20 different elements, the heaviest of which is iodine (the 53rd element in the periodic table), and this is the subject of today’s health article.
Iodine deficiency in the UK
In the UK we have never directly addressed iodine deficiency despite it being a wide-ranging national issue until as recently as the 1960’s. This was because it appeared to magically resolve itself more through serendipity than intention. Eradicating it was an ‘accidental public health triumph’. This relied on the fact that milk consumption by UK consumers increased rapidly as it became more freely available in the 1950s and 60s.
Milk is our chief source of iodine in the UK. Unfortunately, as consumer trends turn away from cow’s milk and towards alternatives there are worrying indications that iodine deficiency is once again on the rise. Iodine is important for our health even though it is present in only trace amounts. I am 80 kg, and I would comprise only 0.0128g of the stuff.
Why Iodine is not Spread Evenly Across the Globe
On a global basis iodine is widely available, but unfortunately it is unevenly distributed. Most iodine exists in seawater where it naturally exists as iodide (or iodide ions). The concentration of iodide in sea water is approximately 50 µg per litre (or roughly 0.05 parts per million or ppm).
Iodide ions in seawater fundamentally begin a cycle whereby they evaporate into the atmosphere and are returned to surface soil by rain. However, this cycle is not uniformly distributed across the world leaving some regions in deficit.
Well known regions short of iodine historically are Switzerland, the Midwest in North America, southern Australia and inland areas of western England and Wales. Switzerland was one of the worst possible examples.
Here iodine deficiency was so conspicuous in the 19th century that in certain regions roughly 0.5% of the inhabitants suffered from cretinism (this evolves because of lack of foetal development caused by iodine deficiency). Almost 100% of schoolchildren had large goitres (enlarged thyroid) and up to 30% of young men were unfit for military service owing to a large goitre. Things were not much better in the UK.
A 1924 survey from England and Wales reported visible goitre in up to 30% of 12-year-old children. Similarly, during the Second World War years, visible goitre was noted in 50% of adult females and 26%–43% of schoolgirls in Oxfordshire and Dorset. Iodine deficiency also has an unfortunate local historical legacy in Derbyshire and the Yorkshire Dales.
Limestone soils are alkali which chemically binds iodine thus decreasing its bioavailability. The effects of iodine deficiency were surprisingly common in Derbyshire even up until the 1960’s. A vivid and compelling account of the disastrous effects of iodine deficiency was outlined in British Parliamentary Papers from 1968. This shocking statement was given by Rev. D. Vawdrey, Rector of Darley Dale and vice-chairman of Bakewell Union.
He reported, ‘Goitre is an evil incident to this locality, so extensive and so mischievous that no report of the districts of Derbyshire would be complete without some reference to it. There is a great deal of it in this parish. In one family six daughters were deaf and dumb, one son a maniac, and another imbecile.
In another family four daughters were deaf and dumb. There are many other cases of imbecility and imperfect development either of bodily or mental power or both, all in this parish. Goitre chiefly prevails among the aboriginal inhabitants.’
Endemic regions of goitre: England and Wales 1960.
Why Iodine is So Essential for Us
Even in the 1980’s the first global estimate from WHO on iodine deficiency suggested that 20–60% of the world’s population were iodine deficient and/or goitrous, with most of the burden falling in developing countries.
As many of us know, iodine is essential for all animals and humans where it is actively concentrated in the thyroid gland. Here it is key for the biosynthesis of thyroid hormones. The thyroid manufactures two hormones which it secretes into the bloodstream.
One hormone is called thyroxine; this hormone contains four atoms of iodine and is also known as T4. The other is called triiodothyronine, which contains three atoms of iodine and is called T3. These hormones influence the activity of all cells and tissues in our bodies. They regulate cell growth and differentiation, and even influence our protein, fat and carbohydrate metabolism.
If we have insufficient iodine most conditions occur because of a subsequent lack of thyroid hormone production. Goitres initially develop when iodine intake is low. This occurs because of hyperplasia (increased number of cells) as the thyroid tries to respond to low iodine intake by increasing its size in its effort to trap more iodine.
Severe iodine deficiency unfortunately causes a lack of neurological development in children and, at its worst causes ‘cretinism’. Neurological cretinism is characterised by mental retardation, deaf mutism, spastic diplegia (a form of cerebral palsy), and disorders of stance and gait and dwarfism. All these unpleasant side effects were observed by Rev. D. Vawdrey in his report to government in 1968.
Cretinism typically evolves if iodine intake is insufficient during pregnancy. The lack of iodine in the diets of pregnant women in the first trimester appears to be a common factor in cretinism, suggesting that maternal hypothyroidism is responsible for irreversible damage to the foetal brain.
Iodine is essential to produce both maternal and foetal thyroid hormones that regulate the development of the foetal brain and nervous system. A mother’s iodine requirements therefore increase significantly during pregnancy. So how did iodine deficiency become a thing of the past?
How Iodine Deficiency was Resolved in Europe (but not the UK)
In 1917 it was shown that thyroid enlargement (or goitre) was caused by iodine deficiency and could be prevented by iodine supplementation. On a global basis iodization of salt was introduced in 1922, although it was first introduced in the USA and Switzerland.
By 1988, 92% of retail salt and 76% of all salt for human consumption was iodized, even though its use is voluntary. In Switzerland for example there are no documented cases of cretinism after 1930 and the frequency of goitres subsequently diminished rapidly. Iodization of salt has proved a highly cost-effective preventive measure in Switzerland as it did elsewhere.
One of the few countries that did not endorse a roll out of iodized salt was the UK. In the UK, semi-skimmed milk is by far the primary source of dietary iodine for children and adults alike with other dairy products also making important contributions. Indeed, it was the increased milk consumption in the UK that led to improvement in our iodine status from the 1930s onwards.
This has been described as an ‘accidental public health triumph’ despite the lack of any official iodine fortification programme. Unfortunately, iodine deficiency in the UK has re-emerged in certain vulnerable groups. This is likely due to a combination of changing farming practices, our changing dietary preferences and changing public health priorities. For example, free milk provision in primary and secondary schools lasted for more than 20 years, but was gradually withdrawn from 1968 to 1977.
Environmental issues are one of the reasons behind our behavioural shifts. These are used as drivers in marketing strategies for alternative milk companies. Farming research has also focused on reducing greenhouse gas production especially in the dairy industry.
The UK National Farmers Union has set a target for farming to become net carbon zero by 2040. This is part of an effort to improve messaging about milk and the environment. National television campaigns by the Milk Marketing Board finished when it was dissolved in 2002 and since then any marketing has been very low key.
Clever and memorable slogans once included straplines such as ‘full of natural goodness’, ‘milk’s gotta lotta bottle’ and ‘drinka pinta milka day’ . These have been replaced by the alternative milk industry’s call to join the ‘Post Milk Generation’ and slogans of ‘Wow! No cow’.
Organic milk is becoming increasingly popular, but it is lower in iodine content than conventional milk by ~25%–40% and iodine status has been shown to be lower in those consuming organic milk. In general cow’s milk intake has been in decline over the last 50 years in the UK and intake amongst women, children and teenagers is now low.
The WHO recommends an intake of 250 µg iodine per day in pregnancy, and one pint of cow’s milk (560 ml) equates to approximately 140–224 µg of iodine. Alternative milks such as soya, almond, rice, coconut and oat are increasingly visible in supermarkets and UK coffee chains. A recent UK study demonstrated that iodine concentration of milk-alternative drinks was very low, at ~7 μg/L, <2% of the value for winter conventional cows’ milk.
In population surveys, those who drank milk alternatives were found to have a low iodine status compared with those who consumed cow milk. The number of vegans in Britain has reportedly quadrupled between 2014 and 2018 to 600,000.
Although this is still only ~1% of the population, vegan compatible milks have increased in popularity to 2% market share by volume and global sales are only set to increase from 17 to 30 billion US Dollars from 2018 to 2023.
Even as recently as 2016 a review of data from the recent UK National Diet and Nutrition Survey showed that many sections of our population are still not consuming adequate amounts of iodine. This review highlighted that 22% of girls aged 11–18 years old and 10% of women aged 19–64 have iodine intakes below the lower reference nutrient intake (70 μg iodine/d). Other studies in the UK have shown 51% of schoolgirls to be mildly iodine deficient.
As we mentioned iodization of salt has proved a cheap and highly cost-effective treatment but perhaps it is time that we addressed this issue. Last year on May 25th, representatives from the Food and Drink Federation, the Vegan Society and the BDA (British Dietetic Association) convened to discuss iodine food fortification.
This is on the back of a campaign to enhance public awareness of the essential role of iodine in the diet. This campaign would also promote foods that provide iodine and ask manufacturers that all staple alternative products sold in the UK are fortified with iodine equivalent to the amount available in cows’ milk (25-59 µg per 100ml)
One other issue is also to promote knowledge for those who switch wholly from cows’ milk to plant-based alternatives. Many vegans are aware of issues such as Vitamin B12 deficiency but are unaware of the significance of iodine. Iodine deserves special attention particularly as it is not a requirement for the growth of many plants and hence plant-based diets tend to be low in iodine. Many people in the UK have general awareness of important nutrients such as iron and calcium, however, iodine is less well-known.
If you know anyone who has a plant-based diet, please forward this article to them!