Why is iodine deficiency increasing? Unpacking the causes behind a global health trend

December 30, 2025 •

4 min read

Despite decades of successful salt iodization programs, which drastically reduced deficiency rates, a significant portion of the global population still struggles with adequate iodine intake. The recent resurgence and increase in iodine deficiency, even in developed nations, is a complex issue driven by a combination of evolving dietary patterns and shifts in food production and consumer habits.

Quick Summary

Modern iodine deficiency is driven by shifts toward plant-based diets, reduced iodized salt use, and reliance on processed foods made with non-iodized salt.

Key Points

Dietary Shifts: The rising popularity of vegan diets, which exclude major iodine sources like dairy and seafood, contributes to lower intake.
Reduced Iodized Salt Use: Public health campaigns for lower sodium and consumer preference for non-iodized gourmet salts have decreased a primary iodine source.
Processed Food Reliance: Processed and convenience foods, a staple for many, are typically made with non-iodized salt, providing no iodine benefit.
Agricultural Changes: Variations in farming practices, such as changes in animal feed and sanitation methods, have led to decreased iodine content in dairy products.
Goitrogen Interaction: For those with marginal intake, consuming foods with goitrogens (like soy or cabbage) can further inhibit the body's ability to use iodine.
Environmental Impact: People living in regions with iodine-poor soil, far from coastal areas, are naturally at a higher risk of deficiency.

Shifts in Modern Diets and Consumer Choices

One of the most significant factors contributing to the rise in iodine deficiency is the widespread change in dietary habits across many populations. Public health messages encouraging lower salt intake to combat hypertension, coupled with the increasing popularity of certain restrictive diets, have inadvertently depleted dietary iodine sources.

The Move Away from Iodized Salt

For nearly a century, universal salt iodization (USI) has been the cornerstone of iodine deficiency prevention worldwide. However, the landscape has changed dramatically:

Health-Conscious Choices: Growing awareness of the link between high sodium and cardiovascular disease has led many to consciously reduce their salt consumption. While this is beneficial for heart health, it removes a primary source of iodine if not replaced by other dietary sources.
The Rise of Specialty Salts: Consumers are increasingly opting for gourmet salts like Himalayan pink salt, sea salt, and kosher salt, which are often not iodized. This choice, often seen as healthier or more natural, directly contributes to lower iodine intake.

Popularity of Plant-Based Diets

Vegan and plant-based diets have grown in popularity for ethical, environmental, and health reasons. While nutrient-dense, these diets can be naturally low in iodine because they exclude some of the most iodine-rich foods. Major sources of iodine that are typically cut from vegan diets include:

Fish and seafood (including seaweed, although some seaweeds contain variable and potentially excessive amounts)
Dairy products (milk, yogurt, cheese)
Eggs

Since many plant-based milk alternatives (like almond or soy milk) are not fortified with iodine, individuals need to be very intentional about supplementing or seeking out other sources.

Changes in Food Production and Processing

Beyond individual dietary choices, changes in the food supply chain have also had a major impact on iodine availability. The iodine content of milk, a significant source of the mineral in many countries, can fluctuate based on agricultural practices. Furthermore, the processed foods that dominate many modern diets are typically made with non-iodized salt.

Decreased Iodine in Processed Foods

Processed and pre-made convenience foods account for a substantial portion of the salt intake for many people. However, manufacturers predominantly use non-iodized salt for cost and stability reasons. This means that a high intake of these foods does not contribute to iodine sufficiency, exacerbating the problem for those who rely on them heavily.

Shifts in Dairy Farming and Bread Production

Dairy: Iodine levels in dairy products have seen a decline due to changes in farming practices, such as reduced use of iodine-containing feed supplements and iodophor sanitizing agents in dairy equipment. This affects countries that traditionally rely on dairy as a key iodine source.
Bread: In some countries, iodate conditioners, which once contributed to dietary iodine, have been removed from store-bought bread.

Environmental Factors and Dietary Competitors

Some factors influencing iodine status are environmental, while others involve competition from other substances in food. Goitrogens, for example, are compounds that interfere with iodine uptake by the thyroid gland and are found in many common foods.

Goitrogens and Antagonists

For individuals with marginal iodine intake, consuming large quantities of goitrogenic foods can worsen deficiency.

Cruciferous Vegetables: Foods like broccoli, kale, cabbage, and cauliflower contain goitrogens, but a high intake is only a concern in areas with low iodine status.
Soy and Cassava: High consumption of soy and cassava, particularly in endemic areas, can also interfere with iodine metabolism.
Halogens: Other elements from the halogen family, such as bromide and fluoride, can compete with iodine for absorption and binding in the body.

Table: Iodized Salt vs. Specialty Salts


Feature	Iodized Table Salt	Specialty Salts (e.g., Sea, Himalayan, Kosher)
Iodine Content	Fortified with potassium iodide or iodate.	Typically not fortified and contain only trace amounts, if any.
Primary Function	Public health tool to prevent iodine deficiency.	Culinary appeal, unique flavor profiles, and perceived natural status.
Consumer Use	Traditionally used for all cooking and seasoning.	Often preferred for finishing dishes or specific recipes.
Public Perception	Seen by some as less 'natural' or overly processed.	Often marketed as healthier, pure, or artisan.
Cost	Generally low-cost and widely available.	Can be significantly more expensive.

Identifying and Addressing the Deficiency

As iodine deficiency becomes a renewed concern, particularly for vulnerable groups like pregnant women and those on restricted diets, it's critical to have a clear strategy. Public health organizations emphasize the need for continued monitoring and targeted intervention. For many people, a varied diet that includes fish, dairy, or iodized salt can provide sufficient iodine. For those with dietary restrictions, supplementation under medical guidance may be necessary. Regular testing, especially for at-risk individuals, helps ensure adequate levels are maintained.

Who is Most at Risk?

Pregnant and Lactating Women: Iodine requirements increase significantly during these periods to support fetal brain development.
Vegans and Individuals Avoiding Dairy: Restricted diets, particularly those free of seafood and dairy, are often low in iodine.
People with Iodine-Poor Soil Exposure: Individuals in inland or mountainous regions often consume local produce and water with low iodine content.
Those on Salt-Restricted Diets: People actively reducing salt for health reasons or opting for non-iodized salts may have insufficient intake.

NIH Office of Dietary Supplements Fact Sheet on Iodine

Conclusion

While global iodine deficiency rates have decreased overall, the emergence of new risk factors—such as changing dietary preferences, reliance on processed foods, and shifts in agricultural practices—means the problem is far from eliminated. The reasons why iodine deficiency is increasing are rooted in complex modern trends. Sustained monitoring, robust public health education, and appropriate supplementation for vulnerable populations are vital to prevent a reversal of the progress made in combating this major preventable cause of brain damage and intellectual disability worldwide.

Frequently Asked Questions

Early signs of iodine deficiency can include an enlarged thyroid gland, known as a goiter, which causes swelling in the neck. Other symptoms may include fatigue, weight gain, and feeling sensitive to cold.

Yes, vegans and vegetarians are at a higher risk of iodine deficiency because their diets typically exclude the most iodine-rich foods like seafood, dairy, and eggs. They must consciously seek out fortified foods or supplements to meet their needs.

For ensuring adequate iodine intake, it is better to use iodized salt, as specialty salts like sea salt contain only trace amounts of iodine, if any. However, limiting total salt intake is recommended for heart health.

During pregnancy, iodine requirements increase significantly to support the mother's metabolism and the fetus's brain development. Severe deficiency can lead to developmental delays and intellectual disabilities in the child.

No, most processed and packaged foods, such as canned soups and ready meals, are made using non-iodized salt. This is because manufacturers often use non-iodized salt for cost and shelf-stability reasons.

Goitrogens are natural substances in foods like cruciferous vegetables (broccoli, cabbage) and soy that can interfere with iodine uptake by the thyroid. They do not cause deficiency in most people, but can exacerbate it in those with a marginal iodine intake.

Preventing iodine deficiency involves consuming a diet rich in iodine sources, such as seafood, dairy, and eggs. Using iodized table salt when cooking is also an effective strategy. In some cases, a supplement may be necessary, especially for pregnant women or those with dietary restrictions.

Yes, iodine deficiency can be treated by increasing your intake of iodine through diet or supplements. However, severe complications like cretinism, resulting from extreme deficiency during fetal development, are irreversible.

Diagnosis of iodine deficiency can be made through a combination of tests, including measuring iodine levels in the urine (urinary iodine concentration), and assessing thyroid hormone levels (TSH, T3, T4) in the blood.

Yes, people living in inland or mountainous regions, where soil iodine levels are naturally low, are at a higher risk of deficiency because the crops and produce grown there also contain less iodine.