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26-09-2016

Scientists call for iodine supplementation for all pregnant women and nursing mothers

Iode pregnancyIt’s finally happened! A group of British scientists have publicly come out in favour of universal iodine supplementation during pregnancy and breastfeeding.1”common problem” which leads to “delayed development in children” .

What convinced these scientists of the need for such iodine supplementation? Quite simply, they studied the data available in previously-published studies. This showed that the benefits of iodine supplementation by the mother equated, on average, to an additional 1.22 IQ points for the child. “Even a slight deficiency in iodine during pregnancy is associated with a lower IQ in the child” confirmed one of the study’s authors, Kate Jolly. In addition to the health aspect, such supplementation could, the authors say, produce b>savings of £4476 per pregnancy for society.

However, they’re not the first to arrive at this conclusion: respected bodies such as the World Health Organisation have for several years advocated daily iodine supplementation during pregnancy . Which begs the question: why has no government yet made recommendations along these lines?

Iodine deficiency: mental disorders and lower IQ in children

Though previously widespread, deficiency in iodine has admittedly all but disappeared in Western societies, due mainly to the addition of iodine to commercially-available salt. However, it is far from uncommon to see mild deficiency, especially in pregnant women.

A number of studies suggest that these slight deficiencies could be responsible for problems with neurological development in children. A recent British study 2 showed that even a minor deficiency in iodine during pregnancy affected brain development in the unborn child. The study’s authors were indeed surprised at how few scientists seemed interested in the impact of mild iodine deficiency, even though the very harmful effects of severe iodine deficiency are well-established.

While excluding the risk of major neurological problems, these same slight deficiencies do affect a child’s IQ 3, as do a number of other factors such as household income, and parents’ educational status and mental health. So the long-term effects of iodine supplementation during pregnancy in this specific context are hugely significant. A year ago, an Australian research team showed that nine years after a child’s birth iodine supplementation had positive effects on their learning! As a result of this discovery, the researchers advised expectant mothers to eat foods rich in iodine such as fish (haddock, salmon and cod) , butter, and eggs. Had they somehow ‘forgotten’ that several organisations such as France’s National Agency for Health & Food Safety (l’Agence nationale de sécurité sanitaire de l'alimentation) recommend pregnant women eat fish no more than twice a week? Why not instead recommend iodine supplementation, which is now well-documented?

Why supplement with iodine?

Iodine is primarily involved in producing two thyroid hormones – T3 and T4. Almost 80% of the iodine absorbed by the body is captured by the thyroid gland. In the absence of sufficient iodine, the thyroid becomes enlarged, reflecting the body’s attempt to trap more iodine. This manifests as a goitre – an unsightly swelling at the front of the neck.

Such cases of severe iodine deficiency used to be extremely common and were responsible for serious mental defects associated with the syndrome cretinism, the name of which is more familiar to us as a modern insult. Affected children failed to grow and suffered significant cognitive problems. As it tended to occur in locations far from the sea and at high altitudes, the expression ‘Cretin of the Alps’ came into being. An estimated 90% of the population of the high valleys of the Swiss Alps had goitres and 2% of them suffered from cretinism 4. While the syndrome has now completely disappeared in the West, it’s thought that throughout the rest of the world, 2 million children a year may still be affected by it5,6.
Over the years, the decreasing incidence of goitres and cretinism has drawn attention away from the link that nevertheless exists between mild iodine deficiency and mental disorders.

Why is it so difficult to obtain iodine from the environment?

The vast majority of the iodine present in the environment is found in sea water (and thus in the animals and plants which live in it), although a tiny amount passes into the atmosphere and land close to the sea via rainfall. This is why the iodine intake of people living far from the coast, is likely to be insufficient for their needs – and even more so at high altitudes. Indeed, in the Western countries concerned, severe deficiency (an intake of below 20 μg/day) only became a rarity when it was decided to add iodine to salt. While this move was undoubtedly effective, it did not lead to the eradication of mild to moderate deficiency, because salt is simply not a food you would recommend freely to everyone. Some people need to avoid it for health reasons, while others choose to avoid it to prevent cardiovascular problems.

What is the right iodine dose?

The subject of what constitutes an ideal dose and tolerable upper intake level is a controversial one. A few studies have shown that ingesting more than 1.1mg a day produced symptoms of chronic toxicity in some people. These studies have also indicated that excess iodine may paradoxically inhibit thyroid hormone synthesis and so produce the opposite result of that desired. Nonetheless, side effects may be minimised by increasing the dose very gradually 7. Several studies show that doses even above the presumed upper intake level may be perfectly safe when given under medical supervision8,9.

A number of scientists who are convinced of the benefits of higher-dose iodine are actually calling for the upper intake level to be increased. In some parts of the world such as Japan, daily iodine intake is somewhere between 5000 and 13,000 μg with no side-effects whatsoever 10, that’s almost 13 times the limit supposedly acceptable for the human body … Intakes such as these, particularly in a country boasting one of the oldest populations in the world, have led physicians such as Dr David Brownstein to publish books recommending iodine supplementation.
France’s National Institute of Medicine has set adequate intakes for iodine at 110 μg a day for new-borns, and 130 μg for babies between 7 and 12 months. For older individuals, the figure ranges from 150 μg (over 14s), to 209 μg (pregnant women) and up to 290 μg (nursing mothers).

Again, a number of scientists question these daily recommended intakes, which are based on the amount the thyroid needs to prevent goitres. Should they not instead be based on the overall health benefits to be gained? All the body’s glands need iodine to function optimally which is why many experts believe we should be ingesting 1000-3000 μg a day. Perhaps the doses may be adjusted upwards in the years to come: since the start of the 20th century, recommended doses have continued to increase as have the amounts added to salt.

Increasing iodine intake safely

Since increasing our iodine intake by consuming more salt is obviously out of the question, and since we do not all have access to fresh seafood, iodine supplementation, by means of Lugol’s iodine solution, for example, appears to be the sensible option. A dose of one drop a day (2.5mg) would seem to suffice - but it can be increased very gradually under medical supervision. Pregnant women and nursing mothers are not the only groups of people who should consider supplementation: certain diets and lifestyles can increase the likelihood of developing mild or moderate iodine deficiency. Vegetarians and vegans, those who dislike seafood or avoid salt, and those who eat a lot of bromine-rich foods such as bakery products, would do well to try it. Though in reality, we may all be at risk of iodine deficiency. Recommended daily intakes, considered much too low in relation to our actual requirements, have certainly contributed to this …


Références

1. Monahan, Mark et al. Costs and benefits of iodine supplementation for pregnant women in a mildly to moderately iodine-deficient population: a modelling analysis, The Lancet Diabetes & Endocrinology , Volume 3 , Issue 9 , 715-722
2. Bath S et al. Effect of inadequate iodine status in UK pregnant women on cognitive outcomes in their children: results from the Avon Longitudinal Study of Parents and Children (ALSPAC) The Lancet , Volume 382 , Issue 9889 , 331 – 337, 2013
3. Trumpff C. et coll. : Thyroid-Stimulating Hormone (TSH) Concentration at Birth in Belgian Neonates and Cognitive Development at Preschool Age. Nutrients 2015, 7 : 9018-9032
4. H. Bircher, Der endemische Kropf und seine Beziehungen zur Taubstummheit und zum Cretinismus, 1883
5. Sana Syed, Iodine and the “Near” Eradication of Cretinism, Pediatrics, April 2015, VOLUME 135 / ISSUE 4.
6. Stanbury JB. The Iodine Trail: Exploring Iodine Deficiency and Its Prevention Around the World. Jackson, MS: Farber Public Relations; 2008
7. Sterling JB, Heymann WR. Potassium iodide in dermatology: a 19th century drug for the 21st century-uses, pharmacology, adverse effects, and contraindications. J Am Acad Dermatol 2000;43:691-7.
8. Ghent WR, Eskin BA, Low DA, Hill LP. Iodine replacement in fibrocystic disease of the breast. Can J Surg 1993;36:453-60.
9. Potassium iodide for nuclear exposure. Pharmacist's Letter/Prescriber's Letter 2001;17(12):171214.
10. Patrick L. Iodine: Deficiency and therapeutic considerations. Altern Med Rev 2008
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