Iodine deficiency: causes, effects, prevention and public‑health significance

Causes and geographic distribution

The principal cause is low dietary iodine. Regions far from the sea, especially mountainous inland areas and some floodplains, often have soils and crops poor in iodine, so locally produced foods contain little of the element. Dietary habits that exclude seafood or iodine-rich foods increase risk. Iodine losses from soil and food can also follow heavy rainfall and glaciation. Populations at particular risk include pregnant and breastfeeding women, infants and young children, because requirements are higher during fetal and early brain development.

Clinical features and consequences

The body’s response to low iodine varies with age and severity. A common visible sign is enlargement of the thyroid gland (goiter) as the organ enlarges to capture more iodine. In severe or prolonged deficiency, especially when it occurs during pregnancy or early life, neurological impairments and developmental delays can result; historically the most severe form has been called cretinism. Less severe deficiency contributes to reduced cognitive performance in populations and can increase rates of miscarriage and stillbirth. Symptoms in adults may include fatigue, sensitivity to cold, weight gain and slowed heart rate due to reduced thyroid hormone levels.

Prevention and control measures

Population-wide prevention is typically achieved by fortifying widely consumed foods with iodine. The most successful and cost-effective strategy has been iodization of table salt. Common iodine compounds used in fortification programs include sodium iodide, potassium iodide and potassium iodate. Other vehicles used where appropriate include addition to flour, drinking water supplies, and milk or animal feed to raise iodine levels in dairy products. Natural dietary sources such as seafood and seaweed are iodine-rich, but access and cultural practices vary, so fortification remains central to public-health efforts.

Implementation, monitoring and notable facts

Successful programs combine legislation, production standards, monitoring of salt iodine content and periodic assessment of population iodine status (for example by urinary iodine concentration surveys). Iodine programs illustrate how small changes in the food supply can prevent large-scale developmental harm. While fortification is effective, monitoring is necessary to avoid both deficiency and excessive intake. Iodine status interacts with other factors—such as selenium and overall thyroid health—so broader nutritional context matters. For further resources and guidance on iodine nutrition and program design, authoritative agencies and reviews are recommended (WHO, The Lancet).