Understanding Historical Nutrition: How did people get iodine before iodized salt?

According to historical public health records, severe iodine deficiency was once a global problem, manifesting as endemic goiter in millions of people. This widespread issue before the 1920s begs the question: how did people get iodine before iodized salt became a standard fixture in our kitchens?

Quick Summary

Before iodized salt, communities relied on naturally occurring iodine in their environment and diet. Sources varied significantly by geography, with coastal populations having a distinct advantage due to seafood and seaweed consumption. This led to endemic deficiency issues, like goiter, in inland and mountainous regions.

Key Points

• Geographical Determinants: Before iodized salt, iodine intake was heavily dependent on where a person lived, with coastal areas being naturally rich and inland regions often deficient.

• Marine Sources Were Key: Seafood, including fish, shellfish, and seaweed, was the most consistent and potent natural source of iodine for people in coastal communities.

• Soil Dictated Inland Intake: For those in non-coastal areas, iodine levels in produce and dairy relied on the mineral content of the soil, which was often insufficient, especially in mountainous regions.

• Goiter Was a Common Ailment: Widespread goiter (swollen thyroid) and more severe conditions like cretinism were clear signs of endemic iodine deficiency in inland populations before fortification began.

• Ancient Remedies Used Iodine-Rich Foods: Traditional medical practices, particularly in Asia, used iodine-rich remedies like seaweed and burnt sea sponge to treat goiter centuries before the element itself was isolated.

• A Public Health Success Story: The introduction of iodized salt in the 1920s transformed public health by providing a cheap, effective, and universal way to prevent iodine deficiency disorders.

The Geographical Lottery of Iodine Distribution

Before the 20th century, access to iodine was a matter of geographic luck. The natural distribution of this essential trace mineral is highly uneven across the Earth's surface. As a result, iodine deficiency was most prevalent in regions with iodine-poor soil and water, particularly in mountainous areas such as the Alps, Andes, and the Great Lakes region of North America. Conversely, populations living near coastal areas generally had sufficient access to iodine through marine food sources.

The uneven distribution meant that dietary patterns and the resulting health outcomes diverged dramatically. Coastal communities, with diets rich in seafood, rarely suffered from iodine deficiency disorders, while inland populations were plagued by them. This environmental reality shaped historical health for millennia, with historical texts documenting attempts to treat endemic goiter with iodine-rich remedies long before iodine was even discovered.

Natural Dietary Sources of Iodine

Before the advent of iodized salt, people relied on a variety of foods whose iodine content was dependent on their source. Marine life was, and remains, the most reliable source, but other foods contributed to the diet in varying amounts.

Here are some of the primary ways people obtained iodine historically:

• Seafood and Seaweed: For coastal dwellers, this was the most dependable source. The ocean is rich in iodine, and marine organisms, especially seaweed and fatty fish like cod and tuna, absorb it. Ancient Chinese texts as far back as 3600 B.C. document the use of seaweed remedies to treat goiter. Seaweed varieties such as kombu and wakame are particularly potent sources.
• Dairy Products: Milk, cheese, and other dairy could be sources of iodine, but the amount was highly variable. Historically, the iodine content depended on the iodine levels in the soil where the cows grazed and the feed they were given. In modern times, the use of iodine-containing disinfectants in the milking process has made dairy a more consistent source, but this was not a factor in pre-industrial history.
• Eggs: Similar to dairy, the iodine content of eggs depended on the chicken's diet. If the hens were fed iodine-rich food, their eggs would contain the mineral. The yolk holds the majority of the iodine.
• Vegetables and Fruits: The iodine in plant-based foods is directly tied to the mineral content of the soil in which they are grown. In iodine-poor regions, crops would contain very low levels, while crops from iodine-rich coastal soils would be higher. This is why certain areas became known as 'goiter belts' despite a diet rich in local produce.
• Natural Salt Deposits: Some natural rock salt, especially from sources near ancient marine environments, contained trace amounts of iodine along with other minerals. However, this was an inconsistent source and often an expensive commodity, available only to a few. The practice of using naturally occurring iodized salt was advocated by the chemist Jean Baptiste Boussingault in the 1830s after observing its effects in the Andes.

Historical Consequences of Uneven Iodine Access

Without reliable sources, iodine deficiency disorders (IDD) were rampant in many parts of the world. The most visible manifestation was endemic goiter—a swollen thyroid gland that forms a large lump in the neck. While often harmless, large goiters could cause difficulty breathing or swallowing. Far more devastating were the effects of severe iodine deficiency, particularly on pregnant women and infants, which could lead to cretinism, characterized by severe intellectual disability and stunted growth.

The connection between goiter and environmental factors was noted for centuries, but the underlying cause remained a mystery. It wasn't until the 19th and early 20th centuries that scientific discoveries, including the isolation of the element iodine in 1811 and its detection in the thyroid gland in 1896, confirmed the link. Landmark studies in the early 1920s demonstrated that supplementing with iodine could effectively prevent goiter. This paved the way for the widespread public health intervention of universal salt iodization, first implemented in Switzerland in 1922 and the United States in 1924.

Historical Dietary Iodine Sources vs. Modern Intake

While historical diets offered varied and often insufficient iodine, modern intake relies heavily on fortification and consistent sources.

Aspect	Pre-Iodization Era (Before 1920s)	Modern Era (With Iodized Salt)
Main Sources	Dependent on geography (seafood for coastal, local crops/water for inland); inconsistent natural salt deposits	Iodized table salt, dairy products (often fortified indirectly), seafood, fortified breads in some countries
Consistency	Highly inconsistent; large regional disparities	Highly consistent in countries with universal salt iodization programs
Prevalence of Deficiency	High prevalence of endemic goiter and cretinism in inland regions	Very low prevalence in regions with effective iodization programs; some risk for specific groups (vegans, low-salt diets)
Public Health Strategy	Traditional remedies (seaweed, burnt sponge), reliance on local food access	Universal salt iodization, targeted supplementation for at-risk groups (e.g., pregnant women)

Conclusion

Before the widespread adoption of iodized salt, securing adequate iodine was a precarious nutritional undertaking. For those living near the ocean, iodine came naturally and reliably through seafood and seaweed. However, for inland communities, especially those in mountainous regions, dietary iodine was scarce and inconsistent, leading to widespread goiter and other severe iodine deficiency disorders. The introduction of iodized salt, based on a century of scientific discovery, stands as one of the most successful public health initiatives in history, effectively eliminating endemic iodine deficiency in many parts of the world by providing a simple, inexpensive, and consistent source of this vital nutrient. It transformed iodine acquisition from a geographical lottery into a universal guarantee, profoundly impacting global health and cognitive development.

For more detailed information on the history of iodine fortification, see this resource from the National Institutes of Health: History of U.S. Iodine Fortification and Supplementation - PMC

Frequently Asked Questions

What is endemic goiter and how was it linked to iodine?

Endemic goiter is the enlargement of the thyroid gland due to insufficient iodine intake. Before the discovery and isolation of iodine in the 19th century, it was a common and geographically localized condition, especially in inland and mountainous regions.

Did people in coastal areas suffer from iodine deficiency?

Historically, coastal residents had consistent and reliable sources of iodine from marine life like fish and seaweed. As a result, they were much less likely to suffer from goiter and other iodine deficiency disorders than their inland counterparts.

Were all natural salts a good source of iodine?

No. While some natural salt deposits contained trace amounts of iodine, this was highly inconsistent and unreliable. Many parts of the world had naturally iodine-poor salt or limited access to it, necessitating modern fortification.

What role did dairy play in pre-iodized salt diets?

In the past, the iodine content of dairy products was highly dependent on the soil where the cows grazed and the feed they were given, which varied widely. It was not a reliable source of iodine for many populations.

What were historical remedies for goiter?

For centuries, traditional medicine used iodine-rich items to treat goiter, including burnt sea sponge and seaweed. However, the dosage and efficacy were inconsistent, and the treatments were not always safe or effective.

Why did iodized salt become the preferred method for iodine supplementation?

Universal salt iodization is a simple, inexpensive, and effective strategy. Salt is a staple consumed by most populations, making it an ideal vehicle for mass fortification. This approach ensured consistent intake across large, diverse populations.

Are we still at risk of iodine deficiency today?

In countries with successful iodized salt programs, iodine deficiency is uncommon, but certain subgroups can be at risk. These include pregnant women, vegans, and those who significantly limit their salt intake or consume a lot of processed foods made with non-iodized salt.