The importance of iodine
Iodine is an essential nutrient needed throughout life. Its primary role involves the synthesis of thyroid hormones, thyroxine (T4) and tri-iodothyronine (T3), which regulate central nervous system function, oxygen transport, growth, cell maturation, and metabolism. Ensuring sufficient iodine intake is particularly critical during conception, pregnancy, and infancy, supporting optimal foetal and infant neurological development and overall growth.
How much iodine do we need?
Iodine needs vary significantly over the lifespan, increasing substantially during pregnancy and lactation. During pregnancy, iodine requirements rise by approximately 65% to support foetal growth and compensate for increased iodine clearance. This is particularly important during the first trimester, as the foetus relies entirely on maternal iodine for thyroid hormone production. Lactation further elevates iodine demands to ensure breast milk adequately meets an infant’s needs during their first year.
Is there a risk of getting too much iodine?
Exceeding recommended iodine intake through diet alone is uncommon; however, excessive iodine consumption can occur through supplementation, medical treatments, or frequent consumption of iodine-rich foods such as seafood or seaweed. Symptoms of iodine toxicity can include nausea, vomiting, diarrhoea, delirium, and even shock. Excess iodine may also trigger thyroid dysfunction, such as hyperthyroidism, hypothyroidism, or goiter formation, emphasising the importance of moderation and medical guidance in supplementation.
Understanding iodine deficiency
While iodine deficiency is rare in Australia due to mandatory iodine fortification in bread, insufficient iodine intake can still pose health risks. Deficiency can result in clinical symptoms like hypothyroidism—fatigue, cold sensitivity, constipation, bradycardia, and goiter—or hyperthyroidism, marked by warm, moist skin, diarrhoea, and tachycardia. Chronic iodine deficiency can severely impact health, leading to impaired growth, infertility, altered metabolism, and neurological issues. Factors contributing to deficiency include increased iodine demands during pregnancy and lactation, inadequate dietary iodine, exposure to goitrogens (compounds that interfere with iodine uptake), and geographical variation in soil iodine content. Additionally, deficiencies in selenium, iron, or vitamin A can exacerbate iodine deficiency by impairing thyroid hormone synthesis and iodine uptake.
Dietary sources of iodine
In Australia, iodised table salt is the most concentrated dietary iodine source, with half a teaspoon meeting the recommended daily adult intake of 150 micrograms (µg). Other iodine-rich foods include seafood and seaweed, making them beneficial additions to a balanced diet.
Understanding iodine's role and maintaining adequate intake through informed dietary choices ensures robust thyroid function and supports lifelong health and development.
References:
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