Understanding iodine deficiency

Iodine is a crucial mineral needed for thyroid hormone production. A deficiency can lead to serious health issues, including hypothyroidism. Approximately 2 billion people suffer from iodine deficiency (ID). Moreover, some 50 million people present with clinical signs, making it the leading cause of preventable brain damage. Research shows an excess of iodine, as well as a deficiency, can instigate hypothyroidism.

Symptoms of iodine deficiency

Common symptoms include:
– Fatigue and weakness
– Weight gain
– Depression
– Cold intolerance
– Cognitive impairment (brain fog, forgetfulness)
– Dry skin and hair loss
– Goitre (enlarged thyroid gland)

The connection between iodine and hypothyroidism

Hypothyroidism is an endocrine disorder that occurs when the thyroid gland does not produce enough hormones. The most common causes include iodine deficiency and Hashimoto’s thyroiditis. In iodine-deficient areas, hypothyroidism is primarily due to low iodine intake. In iodine-replete areas, autoimmune thyroid disease is more prevalent.

How iodine deficiency affects thyroid function

The thyroid gland regulates growth, development and metabolism. It needs iodine to produce the thyroid hormones triiodothyronine (T3) and thyroxine (T4). Thyroid stimulating hormone (TSH) is produced by the pituitary gland. When T3 and T4 levels are low TSH signals the thyroid to produce more T3 and T4.  If iodine levels are deficient, the thyroid gland becomes overstimulated and enlarged in an attempt to capture more iodine. The thyroid gland can compensate for mild to moderate deficiency, however, prolonged iodine deficiency can cause goitre, impair metabolism and lead to hypothyroidism.

Sources of iodine in the diet

Iodine is naturally found in:
– Seaweed and seafood (highest iodine levels)
– Fortified bread and iodised salt
– Dairy products like milk and cheese
– Eggs and some fruits/vegetables, depending on soil iodine levels

Table 1. Approximate iodine content of various foods

Iodine fortification programs

Many countries have implemented iodine fortification programs to combat iodine deficiency. The most common approach is iodised salt, but some nations also fortify bread and milk.

In Australia, mandatory bread fortification with iodised salt began in 2009. Research shows that eating three slices of fortified bread daily can significantly improve iodine levels. Even with iodine fortification, there are still countries where iodine deficiency remains a problem, including Australia. Australian soil is naturally low in iodine, leading to lower levels in many locally grown foods.

Table 2. Iodine deficiency table

Goitrogens: substances that block iodine absorption

Goitrogens are compounds that interfere with iodine absorption and thyroid function, leading to iodine deficiency. These include:
– Thiocyanates from cruciferous vegetables such as broccoli, cauliflower, and cabbage
– Phytoestrogens from soy products such as tofu, soy milk, and tempeh
– Smoking and environmental toxins such as chlorine, bromine, fluoride
– Certain medications, such as lithium
– Perchlorate, an environmental toxin found in water supplies and cow’s milk
– Nitrates found in drinking water, leafy vegetables, root vegetables and processed meats

If iodine intake is sufficient, goitrogens are unlikely to cause major issues. However, in iodine-deficient individuals, they can worsen hypothyroidism.

The risks of excess iodine

While iodine deficiency is harmful, excess iodine can also disrupt thyroid function. The Wolff-Chaikoff effect occurs when high iodine intake temporarily suppresses thyroid hormone production. This can potentially lead to hypothyroidism.

Current iodine recommendations

The recommended daily intake of iodine is 150 µg for adults. Pregnant and breastfeeding women need higher amounts (250 µg daily) to support fetal brain development.

Table 3. Recommended daily intake

Does iodine supplementation improve hypothyroidism?

Studies show mixed results. In mild to moderate iodine deficiency, increasing iodine intake can normalise thyroid function. However, in severe deficiency, excessive iodine intake can trigger thyroid dysfunction.

Conclusion

Balancing iodine intake is crucial. While fortification programs have improved iodine status worldwide, some groups—especially pregnant women and children—remain at risk. Ensuring adequate iodine intake through diet, supplementation, or fortified foods can help prevent hypothyroidism and maintain optimal thyroid health.

If you’re experiencing iodine deficiency symptoms or hypothyroidism, speak to All Naturopath today and live your best life! We can help you optimise your iodine levels and improve thyroid function.

Call us today at 0402 926 675 for an appointment!

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