Does All Milk Have Iodine in It? A Comprehensive Look

October 30, 2025 •

3 min read

According to a study published in Thyroid, milk alternatives contain an average of just 3.1 µg of iodine per 250 mL serving, significantly less than cow's milk. This stark difference raises the question: does all milk have iodine in it, or is the iodine content highly dependent on the source?

Quick Summary

The iodine content in milk depends heavily on the source. Conventional cow's milk is typically a significant source, primarily due to fortified feed and sanitizing practices, while plant-based alternatives naturally contain very little unless fortified. Factors like farming method and season also cause variation in cow's milk.

Key Points

Iodine is not inherent to all milk: While conventional cow's milk is a significant source of iodine, the mineral is largely absent in most plant-based alternatives and present at lower levels in organic milk.
Sources of iodine in cow's milk: The iodine in conventional cow's milk comes primarily from fortified feed and iodine-based sanitizers used on milking equipment and cow teats.
Organic milk has lower iodine levels: Due to farming regulations, organic cow's milk typically contains less iodine than its conventional counterpart.
Plant-based milks lack natural iodine: Alternatives like almond, soy, and oat milk contain only trace amounts of iodine unless they are specifically fortified.
Season and farming affect iodine content: In cow's milk, iodine concentrations can vary by season, with winter milk often having higher levels due to changes in diet and feed.
Alternative sources are crucial: Individuals who avoid conventional dairy should rely on other sources like seafood, iodized salt, or supplements to meet their dietary iodine needs.

Why Conventional Cow's Milk Contains Iodine

Iodine in cow's milk is largely a result of modern dairy farming. Its concentration can vary due to several factors.

Iodine Fortification in Cattle Feed

Dairy cows often receive iodine supplements in their feed to improve their health and increase iodine in their milk. This supplementation is a key reason for the consistent presence of notable iodine levels in conventional milk.

Iodine-Containing Sanitizers

Iodine-based disinfectants (iodophors) are commonly used to sanitize cow teats and milking equipment. Some iodine is absorbed through the cow's skin into the milk, contributing to the final iodine concentration.

Other Contributing Factors

Seasonal changes and farming methods also influence iodine levels. Winter milk is often higher in iodine due to cows relying more on supplemented feed, while summer milk may be lower if cows graze on pastures with naturally low iodine.

The Low Iodine Content of Organic and Plant-Based Milks

Those choosing organic or plant-based options should be aware of significant differences in iodine levels compared to conventional dairy.

Organic Cow's Milk

Organic farming regulations often restrict iodine supplementation in feed, resulting in lower iodine concentrations than conventional milk. Some research suggests organic milk may have only about a third of the iodine found in conventional milk.

Plant-Based Milk Alternatives

Plant-based milks like almond, soy, oat, and rice milk naturally contain very little to no iodine. Studies show minimal or trace amounts. While fortification is possible, some manufacturers avoid adding iodine as it can affect flavor. Individuals depending on these milks, especially those at risk of iodine deficiency, need alternative sources.

Comparison of Iodine Levels in Different Milk Types

The table below compares typical iodine content across milk types. These are averages, and actual levels can vary.


Milk Type	Typical Iodine Content (µg per 250mL)	Primary Sources of Iodine	Typical Variation Factors
Conventional Cow's Milk	~85-110 µg	Fortified feed, iodophor sanitizers	Season, diet, farming practices
Organic Cow's Milk	~30-50 µg (lower than conventional)	Natural feed, limited supplements	Season, specific farming regulations
Plant-Based Milks (Almond, Soy, Oat)	Trace amounts (<5 µg)	None naturally; requires fortification	Only present if specifically fortified
Lactose-Free Milk	Similar to conventional cow's milk	Fortified feed, iodophor sanitizers	Same factors as conventional milk

Health Implications of Varying Iodine Intake

Iodine is essential for thyroid function, and imbalances can impact health. Milk choice can influence iodine intake.

Importance of Adequate Iodine

The thyroid needs sufficient iodine for hormone production, regulating metabolism, growth, and development. Deficiency can cause goiter and hypothyroidism and is particularly harmful during pregnancy and lactation.

Risks of Insufficient Intake

Vegans or those primarily consuming plant-based milks may be at higher risk of low iodine if they don't get it from other sources. This is especially important for pregnant and nursing women with higher iodine needs.

The Role of Alternative Iodine Sources

If you don't consume dairy, or drink organic milk, other options can ensure adequate iodine intake.

Seafood and Seaweed: Excellent natural sources like cod, tuna, or kelp provide a significant amount.
Iodized Salt: A historical solution for deficiency, using iodized table salt at home is a reliable source.
Eggs: Provide a moderate amount of iodine, though content varies.
Supplements: A healthcare provider may recommend iodine supplements for those with restrictive diets or health concerns.

Addressing Public Health Trends

Trends like reducing sodium can lower iodine intake since iodized salt is a major source. As dairy consumption patterns change, understanding alternative iodine sources becomes crucial. The NIH Office of Dietary Supplements provides resources on iodine.

Conclusion

Not all milk contains iodine, and levels vary significantly by source. Conventional cow's milk is a key source due to fortified feed and sanitizers, while organic milk has less and plant-based milks have minimal amounts unless fortified. Being aware of these differences helps individuals ensure adequate iodine intake through alternative sources if needed for proper thyroid function and overall health.

Frequently Asked Questions

Conventional cow's milk contains iodine primarily because dairy cows' diets are supplemented with iodine and because iodine-based disinfectants are used for sanitation in milking facilities.

Yes, organic milk generally has a lower iodine concentration than conventional milk. This is often attributed to stricter regulations on mineral supplementation in organic cattle feed.

Plant-based milks, such as almond, soy, and oat milk, do not naturally contain significant amounts of iodine. They only contain iodine if the manufacturer has specifically chosen to fortify the product.

While cow's milk is a significant source of iodine for many people, especially in industrialized countries, it is not the only source. A balanced diet should include various iodine-rich foods, including seafood and iodized salt, to ensure adequate intake.

Iodine levels in cow's milk tend to be higher in the winter. This is because cows consume more supplemented indoor feed during colder months, whereas in summer they may graze on pastures with lower iodine content.

If you cannot consume dairy due to an allergy, intolerance, or dietary choice, you should seek other sources of iodine. These can include iodized salt, seafood, or a dietary supplement, especially if you are pregnant or breastfeeding.

Some studies suggest that processing, like UHT treatment or pasteurization, might reduce iodine levels, but other research shows no significant effect. Iodine can also be lost in the whey during cheese-making, though some remains in the curd.