What is the most common cause of iodine deficiency?

November 15, 2025 •

4 min read

According to the World Health Organization, insufficient dietary intake is the single most common cause of iodine deficiency worldwide. This happens because iodine is not produced by the body and must be acquired through food or supplements. Certain geographical regions and dietary patterns contribute significantly to this widespread mineral shortage.

Quick Summary

The most prevalent cause of iodine deficiency is insufficient dietary intake, often due to living in areas with iodine-poor soil or avoiding iodized salt. This can lead to serious thyroid disorders and developmental problems, especially in vulnerable populations. Prevention focuses on diet and public health initiatives like salt iodization.

Key Points

Inadequate Dietary Intake: The most prevalent reason for iodine deficiency is simply not getting enough of the mineral through food and drink.
Iodine-Poor Soil: Soil quality, particularly in inland and mountainous regions, directly affects the iodine content of local crops and animal products.
Non-Iodized Salt: Failure to use iodized salt, whether due to lack of access or preference for specialty salts, significantly increases the risk of deficiency.
Increased Needs: Pregnancy and lactation dramatically increase the body's iodine requirements, making these populations highly vulnerable to deficiency.
Restricted Diets: Vegans and those avoiding seafood and dairy are at higher risk due to the elimination of major natural iodine sources from their diet.
Goitrogen Consumption: A high intake of goitrogenic foods, like certain cruciferous vegetables and soy, can interfere with iodine absorption, especially when iodine intake is already low.

Geographical Factors and Iodine-Deficient Soil

The earth’s soil is the primary source of naturally occurring iodine that finds its way into the food supply, but its distribution is uneven. For large, landlocked geographical regions and mountainous areas, the natural iodine levels in the soil can be significantly depleted. Over time, processes like glaciation and flooding have leached this essential mineral from the soil, leaving crops and the animals that graze on them with very low iodine content. This has historically led to endemic iodine deficiency disorders (IDD) in populations far from coastal regions, where seafood is not a staple part of the diet. This geographical reality is a fundamental reason why dietary intake becomes inadequate for millions of people globally.

Why Soil Quality Matters for Your Diet

The quality of soil directly impacts the nutritional value of the food grown within it. For example, a potato grown in iodine-rich soil will contain significantly more iodine than one grown in iodine-poor soil. In fact, the iodine content of many plant-based foods is highly variable depending on their origin. This makes it difficult for populations relying heavily on local produce from iodine-deficient regions to obtain adequate amounts of the mineral from their diet alone. This environmental factor underscores the importance of a diverse food source or fortified products to prevent deficiency.

The Crucial Role of Iodized Salt

One of the most effective and widespread public health interventions to combat iodine deficiency has been universal salt iodization (USI). This process involves adding a small, safe amount of iodine to table salt during its production. For many decades, this initiative has dramatically reduced the incidence of IDD in numerous countries. However, the global effort is not yet complete, and several factors contribute to a continued lack of access or avoidance of iodized salt.

Factors Influencing Salt Choice

Lack of Access: In many developing regions, particularly in rural areas, distribution of adequately iodized salt remains a challenge, leaving populations at risk.
Dietary Trends: Modern health trends promoting a reduction in salt intake or the use of non-iodized specialty salts (such as kosher, sea, and Himalayan salt) can inadvertently lower a person's iodine consumption.
Processed Foods: A significant portion of daily salt intake often comes from processed and canned foods, which typically use non-iodized salt.

Increased Needs During Pregnancy and Lactation

Certain life stages, such as pregnancy and breastfeeding, increase the body's iodine requirements significantly. During pregnancy, a woman's needs increase by approximately 50% to ensure proper thyroid hormone production for both herself and the developing fetus. The fetus relies entirely on the mother for its iodine supply, and insufficient levels can lead to irreversible neurological and developmental damage. Similarly, lactating women need a higher iodine intake to pass adequate amounts through breast milk to the infant. Failure to meet these heightened needs during this critical period is a serious risk factor for iodine deficiency in both mother and child.

Dietary Restrictions and Goitrogens

Certain dietary choices and the presence of goitrogens in some foods can also impact iodine status. Vegans and those who avoid dairy and seafood are at a higher risk of deficiency because these food groups are among the richest sources of dietary iodine. Plant-based milk alternatives, unless fortified, can also lack sufficient iodine. Goitrogens are naturally occurring substances that can interfere with the thyroid gland's ability to use iodine effectively. Foods like cabbage, broccoli, cauliflower, and soy contain goitrogens, and consuming them in very large quantities without adequate iodine intake can further exacerbate a deficiency.

Comparison of Iodine Sources and Risk Factors


Feature	Iodine-Deficient Soil Regions	Iodized Salt Avoidance	Vegan/Restricted Diets	Pregnancy/Lactation
Primary Cause	Inherently low natural iodine levels in crops	Deliberate or unknowing exclusion of iodine from the diet	Exclusion of major iodine food sources (seafood, dairy)	Significantly increased physiological demand for iodine
Vulnerable Populations	Rural, inland, and mountainous communities	Individuals using specialty or non-iodized salts; consumers of primarily processed foods	Vegans, those with dairy or seafood allergies	Pregnant and breastfeeding women, and their infants
Global Prevalence	Widespread in specific regions, especially in developing countries	Varies by country based on USI program effectiveness and local dietary habits	A growing concern in developed nations due to popular dietary trends	Critical and ongoing concern globally, requiring targeted supplementation
Consequences	Endemic goiter, cretinism, intellectual disability	Hypothyroidism, goiter, metabolic issues, fatigue, weight gain	Same as general deficiency, potential long-term issues if not addressed	Severe developmental issues in the fetus/infant, cretinism, miscarriage

Conclusion: Combating a Preventable Condition

In conclusion, the most common cause of iodine deficiency remains insufficient dietary intake, largely influenced by geographical factors, the inconsistent use of iodized salt, and specific dietary patterns. While USI programs have made significant progress globally, millions still lack adequate iodine, especially in vulnerable populations like pregnant women. Preventing iodine deficiency requires a multifaceted approach that includes promoting the use of iodized salt, educating the public about iodine-rich foods, and ensuring targeted supplementation for high-risk groups. Continuous monitoring of iodine levels in salt and the general population is vital to address this preventable global health issue effectively. Continued global focus on this issue is essential to protect cognitive development and overall health, especially in children and expectant mothers.

For more information on the World Health Organization's efforts, refer to the document on salt iodization [https://www.who.int/tools/elena/interventions/salt-iodization].

Frequently Asked Questions

When the body is iodine deficient, the thyroid gland may enlarge to try and absorb more iodine, a condition known as a goiter. It can also lead to hypothyroidism, causing fatigue, weight gain, cold sensitivity, and dry skin.

Yes, individuals following vegan or vegetarian diets are at a higher risk because they typically avoid seafood and dairy products, which are among the most reliable sources of iodine.

No, while iodized salt is a very effective and common source, iodine can also be found in foods like seafood, dairy products, and eggs. Some plant-based milks and certain vegetables may also be fortified or contain iodine, depending on the soil.

Pregnant women can prevent iodine deficiency by consuming iodine-rich foods, using iodized salt, and, most importantly, taking a prenatal vitamin that contains adequate iodine, as recommended by their doctor.

No, processed foods are generally not a good source of iodine. The salt used in most processed and canned foods is typically not iodized, so relying on these products will not meet your daily iodine needs.

Goitrogens are substances found in certain foods, such as cruciferous vegetables and soy, that can interfere with the thyroid's ability to absorb and utilize iodine. Consuming large amounts of these foods, especially with a low iodine intake, can worsen deficiency.

A doctor can diagnose iodine deficiency through a physical examination, particularly looking for an enlarged thyroid (goiter). Urine tests and thyroid-stimulating hormone (TSH) blood tests can also be used to assess iodine status and thyroid function.

Severe, untreated iodine deficiency during pregnancy can lead to cretinism in infants, a condition characterized by permanent and severe intellectual disability and physical developmental delays.

Yes, while rare, excessive iodine intake can cause thyroid problems, including inflammation or dysfunction. It is important to adhere to recommended daily intake levels, especially with supplements.