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According to the World Health Organization, 1.9 billion people globally are affected by iodine deficiency. The consequences of this deficiency are far-reaching and the myth that iodine is to be consumed with caution must be put to rest.
Iodine is a trace element, necessary for human health. As with many other nutrients, differences in opinions and approaches exist in terms of iodine recommendations. Health professionals regard iodine as an essential nutrient and, based on latest research, pregnant and lactating women are urged to supplement iodine in support of infant brain development. Health authorities worldwide implement iodine fortification to increase dietary intakes to combat deficiency.
At the same time, iodine is sometimes regarded as a nutrient to use with caution, as it has been mistakenly labelled as an allergen and excess intakes have been linked to health problems. Iodine fortification of table salt has placed iodine in an ironic position, where the negative aspects of excess salt intake is presumed to be associated with iodine, confusing its role and effects on human health.
IODINE FACT FILEWhat is it? Iodine is a trace mineral element that needs to be ingested through the diet as the body cannot manufacture it.
Benefits and functionsIodine plays a vital role in brain development and cognitive function. It is required for the production of two of the thyroid hormones, notably thyroxine and triiodothyronine. As it forms part of the thyroid hormones, it is therefore essential for the functioning of the thyroid gland, which controls the body’s energy metabolism.
SourcesIodine is scarcely represented in food in general, which explains why there is such a large risk of iodine deficiency. Seaweed is one of nature’s richest sources of iodine, followed by fish, other seafood and dairy products. Small quantities are found in plant foods, depending on the soil quality and iodine content that those foods were grown in. Other dietary sources include iodised table salt, which is the result of a worldwide fortification programme commissioned by the World Health Organization (WHO) since 1954, to address a worldwide iodine deficiency. Kelp tablets are often used as an iodine supplement as kelp is a concentrated source of this trace mineral.
How much do we need?The Nutrient Reference Value (NRV) for individuals over the age of four years is 150 micrograms (mcg) per day. More specific recommendations exist for pregnancy and lactation where requirements are increased to support foetal and infant brain development:■ NRV for individuals four years and older: 150 mcg per day■ RDA during pregnancy: 220 mcg per day■ RDA during lactation: 290 mcg per day.
Signs of deficiency ■ Cretinism: One of the biggest risks with iodine deficiency is irreversible mental retardation that results from a maternal iodine deficiency. Since iodine is essential for brain and cognitive development, an iodine deficiency can result in impaired cognitive development and intellectual disability. Cretinism is a congenital disorder characterised by severe physical stunting and mental disability, caused by a deficiency in thyroid hormones, often linked to hypothyroidism (underactive thyroid) during pregnancy. The leading cause of cretinism worldwide is iodine deficiency.■ Goiter: Goiter is characterised by a visible swelling in the neck area, caused by an enlarged thyroid gland and can be linked to either hypothyroidism or hyperthyroidism (overactive thyroid). Goiter is the best indicator of an advanced deficiency in iodine, but can also result from excess iodine intake. Symptoms of goiter include weight gain, lethargy and poor appetite in cases of an underactive thyroid. In cases of an overactive thyroid, symptoms include weight loss, heart palpitations, nervousness, heat intolerance and increased blood pressure.
Upper safe limitHow much is too much? The tolerable upper safe intake level for iodine is 1 100 mcg per day.
Signs of excessHigh intakes of iodine can result in sensitivity or a burning sensation inside the mouth, metallic taste, sensitive gums, increased saliva production and digestive upsets including diarrhoea. Excessive iodine intake affects the thyroid gland and can lead to thyroid disorders.
Signs of sensitivityIndividuals who are sensitive to iodine may experience bleeding and bruising, swelling of the lips and/or face, fever, joint pain, swelling of the lymph glands, and skin reactions such as hives or a rash.
IODINE DURING PREGNANCY AND LACTATIONInsufficient iodine in the mother during pregnancy and lactation can result in damage during the foetal stage and for the first few months after birth, exactly when the infant is dependent on the mother’s nutritional resources.
A recent survey identified iodine deficiency to be a pressing matter among teenage and pregnant women in the UK. This is believed to be linked to insufficient iodine intakes due to low intake of iodised salt and dairy products. As a result, health authorities and health practitioners have urged women to supplement with iodine during pregnancy. Recommendations indicate 200 to 300 mcg per day to support normal foetal brain development, which compares well to the WHO recommendation of 250 mcg of iodine per day during lactation.
Supplementation should however still be within safety limits, the safe upper limit being 1 100 mcg per day. A recent case study showed the risks of excessive supplementation, with three women who consumed 12 500 mcg per day, which represented more than 10 times the upper safe limit. This unusual case of excessive iodine intakes resulted in hypothyroidism of their babies.1
IODINE SUPPLEMENTATION According to recommendations by the British Dietetic Association,2 iodine supplementation should be highlighted to correct iodine deficiencies and support iodine intake. Iodine intake was thought to be more than adequate but recent research has shown iodine deficiencies, notably in schoolgirls and pregnant women. This is believed to be linked to a decrease in the intake of iodised salt and dairy products, which contribute to dietary iodine intake. There is now concern that many adult women may not be getting enough iodine, particularly in pregnancy.
In cases of thyroid gland disorders, iodine supplementation should be under practitioner supervision due to the complex role iodine plays in these conditions. Kelp tablets rich in iodine are often used for slimming benefits. Taking extra iodine will only assist with weight problems truly linked to an iodine deficiency and a subsequent underactive thyroid gland. Iodine supplementation can in some cases aggravate thyroid problems, practitioner supervision and the assessment of iodine status is therefore recommended.
IODINE IN THE DIETDietary iodine supplementation is often taken in the form of seaweed products, which can include seaweed tablets, capsules, tinctures or actual seaweed or sea grass that is either used as a health food, or included as a culinary ingredient. With the increased popularity of sea grasses and kelp as a superfood, the iodine intake from natural sources is likely to increase in the communities of health conscious individuals who consume these marine plant foods.
IODISED SALTDue to the worldwide deficiency in iodine, the WHO implemented a strategy of fortifying salt with iodine to ensure daily intake of this essential nutrient. Salt was chosen as a household item that was likely to be used on a daily basis. Mandatory iodisation of table salt in South Africa has resulted in good progress in eradicating iodine deficiency. In fact, by 1998, a survey showed that 86.4% of South African households used iodised salt, supporting the plan to achieve adequate iodine intake.3
However, a recent focus on the contribution of dietary salt to hypertension and the consumer-targeted campaigns to reduce salt intake, is likely to affect iodine intakes in South Africa. Because table salt is specifically identified as a negative, the association with iodine has also resulted in confusion about the role of iodine in our diets.
IODINE ALLERGYContrary to popular belief, iodine is not an allergen. Iodine is a mineral element that belongs to the group of nutritional elements including magnesium, zinc, iron and selenium. Allergies relating to fish and shellfish have mistakenly been linked to iodine, simply due to a lack of scientific and clinical information. Fish and seafood allergies are most often linked to protein components within those foods. Many people still perceive iodine to be an allergen, which is infactual. Regrettably this results in dietary restrictions with regard to the consumption of iodine-rich foods and supplements that contain iodine.4
RECOMMENDATIONS It is clear that iodine recommendations should be specific to need states and recommendations should be based on, and take into consideration, all possible benefits and risks. This basically forces the approach to iodine intake to individualisation, a global trend in the approach to optimum nutrition.
References1. Connelly KJ, et al. Congenital hypothyroidism caused by excess prenatal maternal iodine ingestion. J Pediatr. 2012 Oct; 161(4): 760-762.2. The UK Association of Dietitians. BDA Iodine Factsheet. Available from: https://www.bda.uk.com/foodfacts/Iodine.pdf 3. Jooste PL, Zimmermann MB. Progress towards eliminating iodine deficiency in South Africa. SA J Clin Nutr. 2008; 21(1):08-14.4. Schabelman E, Witting M. The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed. J Emerg Med. 2010 Nov; 39(5):701-707. doi: 10.1016/j.jemermed.2009.10.014. Epub 2010 Jan 4.
ANDREA DU PLESSIS, BSC (Dietetics), MPHIL (Exercise Science)
She is a registered dietician with a passion for healthcare through nutrition, natural remedies and a healthy lifestyle. As head of customer care at Vital Health Foods, she regularly presents talks and educational workshops on nutritional supplements and natural healthcare.
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