The Thyroid

The thyroid gland is the “master controller” of metabolism.

Impact of Iodine Deficiency

Thyroid disorders are some of the most frequent diseases in the world, with about 1.6 billion people worldwide at risk.1 Iodine is an integral part of thyroid hormones and is therefore an important factor in the development of hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid).1 Without sufficient iodine, hypothyroidism, cretinism and other iodine deficiency disorders can develop. Conversely, excessive iodine intake can lead to hyperthyroidism.1

Why is iodine important?

Iodine is essential for thyroid hormone production, for fetal and infant development, and it is a crucial nutrient for proper health at all stages of life.2 As our bodies cannot produce iodine, it should be supplied regularly through a healthy diet.2 Iodine deficiency exists in about 54 countries around the world, according to a report by the World Health Organization (WHO).3

Iodine is the key component in the production of the thyroid hormones thyroxine (T4) and triiodothyronine (T3).4 Thyroid hormones help the body to optimally use energy, stay warm, and keep the brain, heart, muscles and other organs working as they should.5 Thyroid hormones and therefore iodine are essential for fetal growth, bone maturation and brain development.2 According to the WHO, insufficient iodine intake is the most common preventable cause of mental retardation.3

A global campaign to iodize the salt supply in almost all countries has led to an estimated 68% of households now using iodized salt.6 Prior to this campaign, an estimated 2 billion people showed iodine definiency by way of having a goiter in 2005 whereas the actual number was 700 million, sparing 1.3 billion people from this disorder.6 Despite this, approximately 40% of the global population remains at risk for iodine deficiency.7

How much iodine do you need?

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.2 Most people can tolerate large amounts of iodine without adverse effects. An intake of more than 1,000 micrograms per day may be harmful.2

The daily iodine requirement changes over a person’s life:4

  • Infants: 110–130 micrograms
  • Children (1–8 years): 90 micrograms
  • Children (9–13 years): 120 micrograms
  • Adolescents and adults: 150 micrograms
  • Pregnant women: 220 micrograms
  • Breastfeeding women: 290 micrograms

Note: Infants are at high risk for iodine deficiency because their need for iodine and thyroid hormones in relation to their weight is much higher than at any other time of life.8 It is not recommended to give babies extra salt and thus babies depend greatly on their mother for their source of iodine. Therefore, the American Thyroid Association (ATA) recommends that all breastfeeding women take a supplement containing at least 150 micrograms of iodine per day, alongside other sources of iodine, to ensure both mother and child reach their respective daily idione requirement, as mentioned above.9

When you are planning for a baby, iodine comes first

When you are planning for a baby or are pregnant or breastfeeding, you need to top up your dietary iodine intake. 2,4 Even a mild iodine shortage during pregnancy can have effects on the development and delivery of the baby. Serious iodine deficiency during pregnancy can lead to spontaneous abortion or stillbirth.3 It can also lead to congenital abnormalities such as cretinism, which is a serious, irreversible form of mental retardation.3 The more pervasive, but less visible, effect of iodine deficiency is a reduction in intelligence that may affect home life, schooling and work.3

Talk to your doctor about whether supplements would benefit you, and what iodine supplements you might need.

How to meet your need for iodine

Seafood is a good source because the oceans are rich in iodine.2 Although less high in iodine than most seafood, eggs, meat and dairy products are richer than most foods of plant origin.2 Any salt used at home should be iodized.2 To ensure sufficient intake for babies in the weaning period, the iodine content of homemade or commercial complementary formula/foods should be considered.8

Common sources of dietary iodine:7

  • Some breads
  • Iodized table salt
  • Cheese
  • Saltwater fish
  • Cow’s milk
  • Seaweed (including kelp, dulse and nori)
  • Eggs
  • Shellfish
  • Frozen yogurt
  • Soy milk
  • Ice cream
  • Soy sauce
  • Iodine-containing multivitamins
  • Yogurt

The best method to prevent iodine deficiency is long-term dietary supplementation with iodized salt, the strategy recommended by the WHO. The WHO recommends a salt intake of less than 5 grams per day (equivalent to about 1 teaspoon of salt per day) to prevent cardiovascular disease.10 One teaspoon of iodized salt contains about 400 micrograms of iodine.7 To meet the total demand of iodine you should not eat more salt, but consume other iodine-rich foods.2

Iodine deficiency and its health consequences

Chronic iodine deficiency can be detrimental to your health.7 A shortage of iodine leads to decreased thyroid hormone and is the most common cause of an underactive thyroid (hypothyroidism).1,7 The visible and unmistakable effect of iodine deficiency is the enlargement of the thyroid, known as goiter.7 To prevent serious health consequences it is important to recognize the early signs of iodine deficiency.

Here, you can read more and find out how goiter and nodules form — and also how to recognize and treat them.

The following symptoms may indicate a lack of iodine:5,7

  • Swallowing and breathing problems
  • Greater neck circumference
  • Fatigue
  • Sensitivity to cold
  • Constipation
  • Dry skin
  • Depression

In children:

  • Mental and physical retardation2
  • Decline in Intelligence (iodine deficiency depresses IQ by 15 points)11
  • Reduced school performance12

The most serious consequences of iodine deficiency occur in women who are pregnant or breastfeeding and in children. Sufficient iodine, and hence enough thyroid hormone, is essential for the normal development of the brain and nervous system. The most serious disorder caused by severe iodine deficiency during pregnancy is cretinism, a condition of stunted physical and mental growth.7 But even mild iodine deficiency during pregnancy can be associated with low intelligence in children.7

Sufficient iodine is the best way to prevent these complications, as well as others such as stillbirth, miscarriage or poor growth.7

Useful 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 ATA

  1. Khan A, Khan MM, Akhtar S. Thyroid disorders, etiology and prevalence. J Med Sci 2002; 2: 89–94. Last accessed February 2022
  2. Nutrition Australia. Nutrition fact sheet: iodine. Available at h . Last accessed February 2022
  3. World Health Organization. Micronutrient deficiencies. Available at Last accessed February 2022
  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, 2001.
  5. American Thyroid Association. Hypothyroidism. Available at Last accessed February 2022
  6. United Nations. Sixth report on the world nutrition situation. Available at Last accessed February 2022
  7. American Thyroid Association. Iodine deficiency. Available at Last accessed February 2022
  8. Zimmermann M. Low iodine intakes in weaning infants. IDD Newsletter 2010; 38: 1–3. Available at Last accessed February 2022
  9. American Thyroid Association. American Thyroid Association (ATA) issues statement on the potential risks of excess iodine ingestion and exposure. Available at Last accessed February 2022
  10. World Health Organization. Unhealthy diet. Available at Last accessed February 2022
  11. World Health Organization. Is it true that lack of iodine really causes brain damage? Available at Last accessed February 2022
  12. Qian M, Wang D, Watkins WE et al. The effects of iodine on intelligence in children: a meta-analysis of studies conducted in China. Asia Pac J Clin Nutr 2005; 14: 32–42


Date of preparation: February 2022