PUBLIC HEALTH
IODINE: COMBATTING DEFICIENCY Charlie Cooke Nutritionist and Personal Trainer Nutritionist Charlie Cooke focuses on teaching simple nutrition science, boxing fitness and nutritious home-cooking knowledge to the general/ low-income public. He is now pursuing a writing, reviewing and media career. Charlie runs the website www. knowhownutrition. co.uk/
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Iodine is most probably something that you’re not losing regular sleep over. But, as iodine deficiency is one of the top three public health problems worldwide, affecting two billion people and 245 million school-age children, and being the leading preventable cause of brain damage and mental development issues worldwide (WHO, 2007),1 it perhaps should surely have been eradicated by now. Since 1990, the International Council for Control of Iodine Deficiency Disorder’s (ICCIDD - try saying it 10 times really fast) proposal on Iodine Deficiency Disorders (IDD), as imposed by the United Nations summit in 1992, has been working to make global IDD a distant memory. Yet, the only distant memory is the date which the UN had planned to achieve its target. We are almost two decades away from the year 2000 and, despite 12 countries moving their iodine status to optimal and an overall reduction in iodine deficiency in school-aged children by 5% (among other advances), the UK hasn’t quite seen such gleaming developments, as outlined by Vanderpump and colleagues in 2011, who found 51% of school-age girls to be mildly deficient and 16% to be moderately so.2 CRITIQUE OF METHODS
The typical method of assessing iodine status is by median urinary iodine (UI) levels in school-age children. This is a very easy method, with Vanderpump et al2 being able to assess over 700 samples, though the median must be used in lieu of the mean, due to the large amounts of individual variability. Not only that, but UI levels represent the 90% of iodine consumed because, you guessed it, 90% is excreted. This does mean, however, that we are only measuring the most recent levels of iodine consumption and most especially not measuring levels of thyroid function. Nevertheless, this method followed a similar structure to that used by the WHO in their global assessments and correlates with the guideline methods established by Dr Michael Zimmerman of 44
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the ICCIDD,3 though preferably bloodspot thyroglobulin would be used. WHAT ARE THE RISKS OF IDD?
The very same Dr Zimmerman (2009)4 found that those iodine deficient children suffered an IQ score of 10-15 points lower than their optimally iodised counterparts. This trend has been concordantly correlated in 37 different studies in China, finding an average deficiency of 10 IQ points and thus further correlated by a meta-analysis of another 18 studies demonstrating an average difference of 13.5 IQ points. Reading and writing is hard enough, we need all the help we can get. In the more severe cases of deficiency, more prices are to be paid. Goitre is an excessive enlargement of the thyroid gland which is essentially the processing centre for about 70-80% of our iodine to form the crucially important T3 and T4 hormones. When our iodine levels are at the point of deficiency, the thyroid is no longer able to function properly and is, therefore, underactive (hypothyroidism). If untreated, this condition may progress to a large growth. A foetus is at risk of cretinism when a mother is unable to meet her minimum requirement of iodine during pregnancy. Cretinism is a state of severe mental and developmental retardation due to iodine’s dramatically large role in tissue synthesis (modulation of gene transcription by heterodimerisation with RXR 9-cis-retinoic acid), especially in the brain, spinal cord, liver, kidneys and alike. There are two forms of cretinism:
Figure 1: Iodine Network: Global Map 2014-15
• Myxodematous cretinism - In this form hypothyroidism, stunted growth and mental deficiency are all present. However, as the thyroid is atrophic, this condition cannot be treated with iodine but can observe mild benefit with thyroid hormone treatment. • Neurological/nervous cretinism - This condition brings a more severe condition of mental retardation, stunted growth, stance and gait disorders and hearing and speech disorders, despite hypothyroidism not being present. Now, I am not suggesting that the UK is headed toward widespread cretinism, especially as the current RNI is set at 140ug with small additions if pregnant (slightly more if lactating), which is plenty enough to balance the LRNI of 70ug, but with 40% of pregnant woman in a region of Scotland having insufficient intake,5 a total of 68% of schoolchildren being deficient and our nationwide levels depleting, for the sake of IQ and childhood mental development, there is room for improvement..
iodophores leads to toxicity (despite that this contamination accidently resolved widespread goitre from the 1960s onward6). Less haphazard methods include the use of iodine salts (iodates) which are used inbread manufacture, or the WHO recommended Universal Salt Iodisation (USI) method, which means the addition of potassium iodate to all salts used. This is an area of recent debate. With the UK showing mild levels of deficiency, there comes the stoic debate of free will and autonomy in our dietary practices. Salt iodisation has been found successful not only in New Zealand7 and Australia8 (both countries with poor soil iodide levels), but, it was so successful in China9 that they had to remove it, as levels were going beyond optimum! There is some risk associated with this excess, however, with toxicity not typically occurring beyond 2000ug (2mg) per day and the UK upper limit set at 1mg (below the safe limit of 1100ug/1.1mg per day), it is not very likely that many of us will contract Jod-Basedow syndrome (or iodine-induce thyrotoxicosis, if you prefer) and the associated tremors, high pulse rate, perspiration and weight loss due to a malfunctioning thyroid (which in itself may become underactive from excess rather than deficiency), unless we start consuming our boot-full of seaweed and kelp supplements.
WHAT CAN WE DO ABOUT IT?
DO WE REALLY NEED IT?
Source: www.ign.org/p142000429.html
Dietary iodine is mostly defined by the content in the soil, though as a large amount of the serum iodide not uptaken by the thyroid is sent to the mammary glands in humans and animals alike, dairy is one of our greatest allies. This is especially true in the case of the use of compounds called iodophores which are used for sanitation in the dairy industry, yet slightly too true in cases where contamination with
With UK consumption of iodised salt being less than 5% (compared with the 70% of developing countries with intervention),10 perhaps our free will isn’t doing us that many favours. Luckily, since the reintroduction of free school milk in the mid-2000s for under 5s, levels have started to rise. But is it enough? I’m not one to dictate anything, but I surely am one to listen. www.NHDmag.com July 2018 - Issue 136
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