Iodine deficiency What everyone should know

Transcription

1 What everyone should know

2 what everyone should know You have heard of iodine, of course. But do you really know how important iodine is for your health? Whether we feel fit, our babies are born healthy or our children have normal learning ability - iodine plays a crucial role throughout. Iodine is essential for healthy thyroid hormone production. The amount of iodine needed by your thyroid day to-day is small, but if not available, it will harm your health. According to the World Health Organization (WHO; 1994) insufficient iodine intake is recognized as the most common preventable cause of mental retardation in the world. International efforts to eliminate iodine deficiency - primarily by the WHO, United Nations Children s Fund (UNICEF) and the International Council for the Control of Iodine Deficiency Disorders (ICCIDD) - have dramatically reduced the population at risk since the early 1990s. Nevertheless, around the world approximately 2 billion people including 266 million children of school age (31.5 %) still suffer from iodine deficiency. 1 What is iodine? Iodine is a natural chemical element, like oxygen, hydrogen and iron. Iodine is present in some foods naturally, added to others, and available as a dietary supplement. Due to its important role in thyroid hormone production, fetal and infant development; iodine is a crucial nutrient for proper health at all stages of life. Iodine is the key component in thyroid hormone production. When iodine enters the blood stream, the thyroid gland takes appropriate amounts and converts them into thyroid hormones: thyroxine (also known as T4) and triiodothyronine (also known as T3). The T3 and T4 are then released into the blood and are transported throughout the body. Thyroid hormones are needed in every single cell of all tissue and organs. For example, thyroid hormones help the body use energy, stay warm, and keep the brain, heart, muscles, and other organs working as they should. 2 This guide has been developed to provide you with all the important information you need to know about iodine. Split into helpful sections, it contains specific information on iodine deficiency and its consequences, tips and recommendations for women who are pregnant, parents with young children, and lifestyle related iodine deficiency. Each section contains a list of useful frequently asked questions which can be used for quick reference. A helpful list of additional references is also included. A teaspoon in a lifetime A teaspoon of iodine is all you need in your lifetime, however, as the body cannot store iodine for long periods, tiny amounts are needed regularly. 3 The iodine requirements will change over one s life depending on age, growth and special metabolic needs such as pregnancy and lactation. Several international groups have made recommendations, which are fairly similar. Recommended daily intake of iodine 4 Age Male Female Pregnancy Lactation Birth to 6 months 110 mcg* 110 mcg* 7 12 months 130 mcg* 130 mcg* 1 3 years 90 mcg 90 mcg 4 8 years 90 mcg 90 mcg 9 13 years 120 mcg 120 mcg years 150 mcg 150 mcg 220 mcg 290 mcg 19+ years 150 mcg 150 mcg 220 mcg 290 mcg When reading this material, please remember that the information contained herein is intended for general reference only. As a result of ongoing medical advances and developments, the information herein may not always be completely up to date and, for this reason, such information is provided on an as is and as available basis. Thyroid Federation International and Merck Serono make no warranties, representations or You must consult a suitably qualified health care professional on any problem or matter which is covered by any information in this material before taking any action. gives any undertakings either express or implied about any of the content of this material. It may refer to pharmaceutical products, therapeutics or indications not yet registered or approved in a given country. This information should not be used to diagnose, treat, cure or prevent any disease without the advice of a qualified medical professional, and does not replace medical advice or a medical examination. * Adequate Intake (AI): established when evidence is insufficient to develop a RDA (Recommended Dietary Allowance) and is set at a level assumed to ensure nutritional adequacy. The World Health Organization (WHO), United Nations Children s Fund (UNICEF), and the International Council for the Control of Iodine Deficiency Disorders (ICCIDD) recommend a slightly lower iodine intake for pregnant and lactating women of 200 micrograms per day. 5 occurs when iodine intake falls below recommended levels and the thyroid gland is no longer able to synthesize sufficient amounts of thyroid hormone.

3 When you are planning for a baby Iodine comes first When you are planning for a baby, are pregnant or breastfeeding you need to top up your dietary iodine intake to produce enough thyroid hormones for you and your baby. Thyroid hormones, and therefore iodine, are vital to ensure the normal development of the brain and nervous system. 6 Even a mild iodine shortage during pregnancy can have effects on the delivery and development of a baby, including hypothyroidism. Adverse effects on early brain and nervous system development are generally irreversible and can have serious implications for mental capacity in later life. 7 Therefore it is recommended that all pregnant and breastfeeding women should take a nutritional supplement containing iodine every day. 8 Are you at risk of iodine deficiency? The only effective prevention of iodine deficiency is adequate iodine intake. But that s not always easy with the normal diet. The last ice age washed iodine out of the soil and into the sea. Therefore, most natural foods are low in iodine and most commonly consumed foods Women of childbearing age should have an average iodine intake of 150 micrograms per day, which should be increased to approximately 250 micrograms during pregnancy and breastfeeding. 9 You should take iodine supplements from the point of planning pregnancy through the full duration of pregnancy and breastfeeding. If pregnancy is not planned, you should start taking an iodine supplement of the recommended amount as soon as possible after finding out. Because of the potential for side effects and interactions with medications, you should take dietary supplements only under the supervision of a knowledgeable health care provider. provide merely 3 to 75 micrograms per serving 4 - except for seafood, saltwater fish and algae. Seaweed is one of the best food sources of iodine, but it is highly variable in its content 10 Frequently Asked Questions How much iodine do I need? The iodine requirements will change over one s life depending on age, growth and special metabolic needs such as pregnancy and lactation. Women of childbearing age should have an intake of 150 micrograms a day. 4 This should increase to approximately 250 micrograms during pregnancy and breastfeeding. 13 As your body cannot store iodine for long periods, it should be supplied regularly through a healthy diet and the use of iodized salt. Why is iodine intake in pregnancy so important? Iodine is essential to make thyroid hormones which ensure that our bodies run properly. In the first weeks of pregnancy the baby is completely dependent on the mother for the production of thyroid hormone. After this time the baby is able to produce thyroid hormones on its own. However, the unborn child remains dependent on the mother to keep her iodine levels adequate. 11 Should I generally take iodine tablets? No, it is only necessary in certain situations: During pregnancy and lactation, on low-salt diet, allergies to fish or when you are on vegetarian or vegan diets. You should take iodine tablets only after and in consultation with your physician. What foods are made with iodized salt for? Often bread and bakery products are prepared with iodized salt. Even sausage and meat products may contain iodized salt. On packaged food, depending on the country, the iodine content is declared. You can find the appropriate reference in the ingredients list. When it comes to non-packaged food, your baker or butcher can provide information. Does sea salt contain iodine? Sea salts and so-called reform salts contain, if they are not iodized, only small amounts of iodine or even none. To meet the iodine requirements, they do not contribute significantly. How much iodized salt? The WHO recommends a salt intake of less than 5 grams per day (equivalent to about one teaspoon of salt per day) to prevent cardiovascular disease grams of iodized salt contain about 100 micrograms of iodine. To meet the total demand of iodine, you should not eat more iodized salt, but iodine-rich foods. Common Sources of Dietary Iodine 8 To know exactly how much iodine you are getting can be difficult because the amounts can vary significantly and are rarely listed on food packaging. But if you don t eat a lot of fish and don t use iodized salt, you could suffer from iodine deficiency. Bread Cheese Cow s milk Eggs Frozen yogurt Ice cream Iodine-containing multivitamins Iodized table salt Saltwater fish Seaweed (including kelp, dulce, nori) Shellfish Soy milk Soy sauce Yogurt How is iodine deficiency diagnosed? Since more than 90 % of iodine is excreted in the urine, the determination of urinary iodine concentration (UIC) is the most commonly used tool to determine iodine intake in a population. But it is not a reliable indicator of an individual s iodine status; instead, your doctor will determine your thyroid-stimulating hormone (TSH) and thyroid hormone (T4) concentrations, and probably make an ultrasound examination of your thyroid gland.

4 : A public health problem throughout the world In 54 countries the population has insufficient iodine intake, according to the WHO. 13 Mountainous areas such as the Alps, Andes, Atlas, and Himalayan ranges and river valley prone to frequent flooding, especially in South and Southeast Asia are among the most iodine-deficient regions in the world. Many inland areas, including central Asia and Africa, central and Eastern Europe, are iodine deficient. 17 is defined as a median urinary iodine concentration (UIC) less than 50 micrograms/l in a population. Median urinary iodine (mcg/l) iodine intake iodine status < 20 insufficient severe iodine deficiency insufficient moderate iodine deficiency insufficient mild iodine deficiency adequate adequate iodine nutrition From WHO, ICCIDD, UNICEF 14 ; based on median urinary iodine concentrations of school-age children ( 6 years); applies to adults, but not to pregnant and lactating women. How much iodine your baby needs? Infants are at high risk for iodine deficiency because their need for iodine and thyroid hormone in relation to their weight is much higher than at any other time in the life. 16 When a baby is exclusively breastfed its iodine intake depends solely of the iodine concentration of the breast milk, which in turn depends on the mother s iodine status. Therefore, the American Thyroid Association recommends that all breastfeeding women take a supplement containing at least 150 micrograms of iodine per day. 8 Infants may be at particularly high risk for iodine deficiency during the weaning period when iodine intake depends on homemade, age adjusted foods or commercial complementary formula/foods. 16 Iodine-rich mineral water to cover the daily requirement is not suitable for infants, because most of these waters contain relatively large amounts of sodium, fluoride, sulfate, or other unwanted substances. Suitable mineral waters for babies usually contain only little amounts of iodine and therefore contribute little to iodine supply. What are the symptoms of iodine deficiency? The wide ranging adverse effects of iodine deficiency, termed Iodine Deficiency Disorders (IDD) are related to its effect on the thyroid. The most known and unmistakable effect of iodine deficiency is goiter, and wherever 15 iodine deficiency is common, goiter will be common, too. This is because the thyroid tries to keep up with the demand for hormone production stimulated by the TSH (thyroid stimulating hormone). Like a fisherman who catches all the more fish, the larger his fishing net becomes; the thyroid enlarges to filter out as much iodine as possible from the blood. A goiter is diagnosed by neck inspection and palpation, and thyroid ultrasonography. Iodine supplementation by tablets will reduce the size of the goiter, but often the goiter will not completely dissolve. 15 With insufficient iodine levels hypothyroidism may occur because iodine is essential for thyroid hormone production. is the most common cause of hypothyroidism worldwide. 8 Hypothyroidism and goiter can occur at any stage of life, but the most serious consequences of iodine deficiency occur in women who are pregnant or nursing their infants, and in children. 8 That s because thyroid hormones and therefore iodine are essential for normal development of the brain and the nervous system. When you are pregnant or lactating, you must get the recommended amounts of iodine to protect your health and the health of your baby. The most severe disorder due to severe iodine deficiency during pregnancy is cretinism, a condition of severely stunted physical and mental growth. But even mild iodine deficiency during pregnancy can be associated with low intelligence in children. 8 Sufficient iodine is the best prevention from this potential complication as well as others, such as stillbirth, miscarriages or poor growth. 8 Too few fish: Iodine deficiency in children The favorite foods of children and adolescents are rarely found in the oceans. Fast food and soft drinks instead of sea fish and milk, however, do not provide an adequate iodine intake. Two-thirds of teenagers in the UK are deficient in the trace mineral, says a new study, partly because consumption of milk has plummeted in recent years. 17 In children and adolescents, insufficient iodine and in consequence insufficient thyroid hormones is particularly serious, because the thyroid hormones have a decisive influence on the age-appropriate physical development and maturation processes of the brain. depresses IQ by points. 18 Even moderate iodine deficiency can have consequences such as sudden learning difficulties, and poor concentration. In cases of severe deficiency there may be slower growth and premature puberty. The good news: Even severe disorders are improved when the iodine deficiency in children and adolescents is corrected. 19

5 Frequently asked questions Can goiter and cretinism be cured? Cretinism is permanent and incurable, but it is preventable by sufficient iodine intake during pregnancy. Certain goiters can be cured in the early stages. Regular intake of iodine, however, prevents goiter and other iodine deficiency disorders. Does iodine deficiency affect my child s performance in school? In cases of mild iodine deficiency, even though your child looks normal, a mild mental retardation may be present. As we know, children living in iodine-deficient areas could have a lower IQ level than those living in iodine sufficient areas; therefore iodine deficiency will affect school performance. Prevention and treatment of iodine deficiency Shortage or lack of iodine is not seen individually but on a population basis. People that live in iodine deficient countries do not get enough iodine. The same is true for animals living there and plants growing there. Therefore food from that region contains little iodine. The best method to cope with iodine deficiency is long-term dietary supplementation with iodized salt, the recommended strategy by WHO. 1 Where this is not possible well water has been enriched with iodine or people have been injected with iodized oil. Thanks to the initiatives by WHO, UNICEF and ICCIDD the number of world households with access to iodized salt increased from less than 20% to 70% over the last two decades. 21 Adding iodine to salt remains the most cost-effective way to control iodine deficiency. As even a mild iodine deficiency can harm the delivery and the development of babies, pregnant and breast-feeding women are advised to take a multivitamin that contains 150 micrograms of iodine per day. 4 Considerable progress has been made ever since the 1990 World Summit for Children has taken action to eliminate iodine deficiency: Each year it is estimated 84 million births are protected against brain damage 22 and nearly 91 million children against learning impairment due to iodine deficiency. 21 What happens if we get too much iodine? Most people can tolerate large amounts of iodine (up to 1000 micrograms a day) without adverse effects. However, too much and too little iodine are undesirable, the consequences of iodine deficiency outweigh by far those of excess iodine. While iodine deficiency can harm human development and cause irreversible brain damage, excess iodine may cause stomach ache, for example. According to ICCIDD properly iodized salt will rarely add more than about 300 micrograms of iodine daily to the diet. Therefore, concern about iodine excess is not a reason to stop or avoid consumption of iodized salt. 20 Checklist Do you get enough iodine? If you eat too little iodine in your diet, your thyroid can become underactive. In the beginning you experience virtually no symptoms. But when iodine deficiency continues to exist you might experience signs and symptoms that correspond to the effect of inadequate iodine uptake on your thyroid. Seafood is rather rare in my diet I rarely use iodized salt I feel tired and sleepy most of the time I have little energy My concentration and memory are poor I feel unmotivated, sometimes depressed I am sensitive to cold I easily catch a cold I have a tight feeling in my throat I have difficulties breathing and swallowing I have a visible swelling at the base of my neck My skin and hair are dry I have brittle nails If you answer 6 of these questions with Yes, you should see your doctor and tell them about your symptoms. There is a possibility that you aren t getting enough iodine and your thyroid is not working as it should. Useful Links If you want to know more about iodine supply and iodine deficiency you can visit the following websites: The International Council for the Control of Iodine Deficiency Disorders (ICCIDD) is a non-profit, non-government organization for the sustainable elimination of iodine deficiency and the promotion of optimal iodine nutrition worldwide) United Nations Children's Fund (UNICEF) publishes Progress for Children, a statistical review that documents progress towards the Millennium Development Goals. Patient information on thyroid health published by the American Thyroid Association (ATA) yes no

6 References 1. WHO. in 2007: Global progress since FNBvol29N3sep08.pdf 2. American Thyroid Association. Thyroid Function Tests International Council for the Control of Iodine Deficiency Disorders. Protecting children 4. Institute of Medicine of the National Academies. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, International Council for the Control of Iodine Deficiency Disorders. How much iodine? 6. Zimmermann MB (2009) in pregnancy and the effects of maternal iodine supplementation on the offspring: a review. The AmericanJournal of Clinical Nutrition: 89; 668S-672S. 7. WHO. Micronutrient deficiencies topics/micronutrient_deficiencies/general_info.htm#idd 8. American Thyroid Association. Iodine Deficiency 9. The Endocrine Society. Management of Thyroid Dysfunction during pregnancy and postpartum final/upload/clinical-guideline-management-of-thyroid-dysfunctionduringpregnancy-postpartum.pdf 10. Zimmermann MB.. Endocr Rev Jun;30(4): American Thyroid Association. Thyroid Disease and Pregnancy broch.pdf Accessed December WHO. Unhealthy diet. unhealthy_diet_text/en/index.html Accessed December WHO. Iodine status worldwide. Geneva int/publications/2004/ pdf 14. WHO, UNICEF, ICCIDD. Progress towards elimination of iodine deficiency disorders. Geneva, World Health Organization, 1999 (unpublished document WHO/NHD/99.4); quoted in WHO, UNICEF, ICCIDD. Assessment of Iodine Deficiency Disorders and Monitoring their Elimination American Thyroid Association. Goiter patient_brochures/goiter.html Accessed December Zimmermann MB. Low iodine intakes in weaning infants Accessed December Vanderpump MP. Iodine status of UK schoolgirls. The Lancet June 11, 2011; Markou KB et al. Treating iodine deficiency: Long term effects of Iodine Repletion on Growth and Pubertal Development in School-Age Children. Thyroid 2008; 18 (4): Tulane University. Most frequently asked Questions. A Brief Non- Technical Guide to Ideal Iodine Nutrition UNICEF. Micronutrients - Iodine, Iron and Vitamin A org/nutrition/index_iodine.html 22. Experts urge complete global access to iodized salt; prevents IQ loss and brain damage in babies news html Useful resources If you would like further information regarding thyroid dysfunction before, during or after pregnancy, please visit: Patient information provided for International Thyroid Awareness Week Patient information by the Thyroid Federation International Patient information on thyroid health published by the American Thyroid Association (ATA) This Booklet has been downloaded from the website and was created in May Please refer to the Privacy and Legal Statement on the aforesaid website when reading this. An initiative supported by