What is a major source of iodine in the North American diet?

January 1, 2026 •

4 min read

According to the Iodine Global Network, North America is currently considered iodine-sufficient, thanks largely to widespread public health initiatives. These programs, which began in the 1920s to combat widespread iodine deficiency, introduced a staple food fortification that has become a major source of the essential mineral.

Quick Summary

The primary source of iodine in the North American diet is fortified table salt, with significant contributions also coming from dairy products and seafood. Iodization of salt was a public health measure implemented in the 1920s to prevent deficiency disorders like goiter.

Key Points

Iodized Salt is the primary source: The fortification of table salt with iodine, introduced in the 1920s, remains the most significant and consistent source of dietary iodine for most North Americans.
Dairy contributes significantly: Due to the use of iodine in cattle feed and sanitizers on dairy farms, milk and other dairy products are major contributors to iodine intake.
Seafood is a powerful natural source: Fish, shellfish, and especially seaweed are naturally rich in iodine, but they are not the primary source for the general population due to consumption patterns.
Processed foods often lack iodized salt: The reliance on processed foods, which are typically made with non-iodized salt, can lead to lower iodine intake if not balanced by other sources.
Dietary shifts can affect intake: Decreased salt consumption and avoidance of dairy or seafood by certain dietary groups, like vegans, can put individuals at risk of iodine inadequacy.
Iodine balance is key: Both insufficient and excessive iodine intake can cause health problems, especially thyroid issues, making dietary awareness crucial.

The Dominance of Iodized Salt

For most North Americans, the single most reliable source of iodine is iodized table salt. This public health initiative began in the 1920s to prevent endemic iodine deficiency in the "goiter belt" regions of the United States and Canada, where iodine levels in the soil and food were historically low. By adding a small, controlled amount of iodine to table salt, governments could effectively and inexpensively ensure a consistent intake of this vital mineral across a wide population. A quarter-teaspoon of iodized salt can provide a significant portion of an adult's daily recommended iodine intake.

The Rise of Processed Food and Its Impact

While iodized salt is widely available for use in home cooking, a modern dietary trend complicates its role as the sole primary source. The increasing consumption of pre-made and processed foods, which frequently use non-iodized salt, means that a significant portion of the population's salt intake may not be contributing to their iodine levels. Furthermore, many people are encouraged to limit their salt intake for cardiovascular health, which can unintentionally reduce their iodine consumption if they do not seek out alternative sources. This shift in eating habits has led to some concern, particularly for vulnerable populations like pregnant women who require higher iodine intake for fetal development.

Dairy Products as an Unintentional Source

Beyond fortified salt, dairy products—including milk, cheese, and yogurt—are a major source of iodine in the North American diet. This is often an indirect result of dairy farm practices. The iodine content in milk is influenced by several factors related to farm management:

Iodine in cattle feed: Dairy cows are often given iodine-enriched feed supplements.
Sanitation practices: Iodine-containing disinfectants, known as iodophors, are routinely used to sanitize udders and milking equipment, with trace amounts ending up in the milk supply.

Studies have shown that conventional milk typically has higher iodine concentrations than organic milk, with some seasonal variation, but both remain excellent sources. In fact, research indicates that dairy food consumption is beneficially linked with higher iodine status in US children and adults.

Seafood: The Natural Powerhouse

For those who regularly consume seafood, fish and shellfish provide a potent natural source of iodine. Saltwater fish like cod and haddock are particularly rich, and seaweed varieties are among the most concentrated sources of the mineral found in nature. However, seaweed consumption is not widespread enough in the general North American population to be considered a major source for most people. Furthermore, the iodine content of seaweed can vary dramatically depending on the species and growing conditions, and excessive intake can lead to potential health concerns.

Comparison of Iodine Sources


Source	Primary Benefit	Considerations	Role in North American Diet
Iodized Salt	Fortified, consistent, and widely accessible source.	Decreased use in processed foods and general salt reduction efforts may impact intake.	Primary, reliable source for home cooking.
Dairy Products	Significant, incidental source due to farm practices.	Iodine content can vary based on farming methods and season.	Major, often overlooked, source for many.
Seafood	Naturally high concentration, especially in saltwater varieties.	Less frequent consumption for many North Americans; potential for excessive intake with some seaweed.	Excellent, but less consistent, source depending on diet.
Eggs	Good source, with higher iodine from hens on iodine-fortified feed.	Intake levels are generally lower than for milk or iodized salt.	Contributes to overall intake, but less significant than other sources.

Potential for Iodine Imbalance

While the public health effort to iodize salt has been a resounding success, dietary shifts mean that both insufficient and excessive iodine intake can be potential concerns for certain groups. On one hand, individuals who avoid dairy, seafood, and iodized salt (such as those on a vegan diet or a salt-restricted diet) are at a higher risk of deficiency. On the other hand, the combination of multiple sources—such as regular consumption of dairy, some seafood, and certain supplements—can lead to excessive intake, especially when combined with high-iodine seaweed. The narrow margin of safety for iodine intake highlights the importance of dietary awareness and, in specific cases, medical monitoring.

Conclusion

In summary, the major source of iodine for most North Americans is fortified table salt, a legacy of a successful 20th-century public health campaign. However, dairy products also play a substantial, if often unnoticed, role due to modern farming practices. While seafood, particularly seaweed, provides some of the highest concentrations of naturally occurring iodine, it is not a primary source for the majority of the population. Modern dietary trends require consumers to be more mindful of their iodine sources, as relying solely on processed foods may reduce intake, while overconsumption of supplements or specific seaweed types could lead to excess levels. Overall, maintaining a balanced diet rich in varied sources is the most effective strategy for ensuring adequate iodine intake. https://ods.od.nih.gov/factsheets/Iodine-Consumer/

Frequently Asked Questions

North America began adding iodine to table salt in the 1920s as a public health measure to combat widespread iodine deficiency, particularly in inland areas like the Great Lakes region, which was known as the "goiter belt".

No, sea salt is generally not a reliable source of iodine. Unless it is specifically labeled as 'iodized,' it does not contain the added iodine found in fortified table salt.

While trace amounts can occur naturally, the significant iodine content in most dairy products is an incidental result of modern farming practices, such as iodine-fortified feed for cows and iodine-based sanitizers used on equipment.

Yes, people on a vegan diet who avoid dairy and seafood are at a higher risk of inadequate iodine intake. They need to be mindful of incorporating other iodine-rich foods, supplements, or iodized salt.

It is possible to consume too much iodine, which can cause health issues, especially related to the thyroid. High intake can be a risk for people who consume large amounts of high-iodine foods like some seaweeds or take supplements without monitoring.

Studies have shown that organic milk often has lower iodine concentrations than conventional milk, although both can be good sources. The difference is primarily due to variations in feeding practices and sanitizers used on organic versus conventional farms.

Yes, public health organizations monitor population-wide iodine status using surveys like the National Health and Nutrition Examination Survey (NHANES). While the general population is sufficient, some subgroups like pregnant women may still have inadequate levels.